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1Institute of Optics and Electronics, Chinese Academy of Sciences (China) 2Univ. of Electronic Science and Technology of China (China) 3Tianjin Jinhang Institute of Technical Physics (China) 4Zhejiang Univ. (China)
This PDF file contains the front matter associated with SPIE Proceedings Volume 11567, including the Title Page, Copyright information, and Table of Contents.
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In recent years, terahertz imaging system has become more and more mature. There are good detectability for hidden objects on the human body surface, because terahertz waves has certain penetrating characteristics and low electromagnetic radiation in terahertz band. Using terahertz imaging technology has the advantages of high efficiency and non-radiation to carry out human body safety inspection, that makes it more and more widely used in the security security field. In order to achieve the purpose of detecting the hidden objects on the human body surface using terahertz technology, a convolution neural network named ResDeepNet is proposed in this paper. This network is different from the convolution neural networks structure of traditional optical images. According to the terahertz imaging characteristics of human body image, the semantic segmentation network is designed. Through the convolution network, the segmentation algorithm of terahertz image is realized, the target information is enhanced, and the noise is effectively suppressed in the terahertz image. The segmentation network and algorithm achieved the best results in test and practical application.
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Asteroid exploration has become one of the important ways to understand the origin of the universe, exploit the space mineral resources and protect the earth from the asteroid impact. The imaging spectrometer, which can acquire the spatial and spectral information simultaneously, has become one of the most important payloads for the asteroid exploration. In this paper, the optical design of a broadband Offner imaging spectrometer for the asteroid exploration is presented. It covers from 0.4μm to 3μm, and the F/# is 6 and 3 for the VNIR band (0.4μm-1.0μm) and the SWIR band (1.0μm -3.0μm), respectively. The convex grating in the imaging spectrometer is divided into two regions of different groove spacing, and each region is optimized with different blazed angles to improve the spectral response of this imaging spectrometer. The diffraction efficiency is analyzed with the Comsol software and the result is greater than 0.36 in the wavelength range of 0.4μm to 3μm. After optimized with the optical design software, the diameter of the imaging spectrometer's spot diagram is less than one pixel, and the lowest MTF is 0.460 at the Nyquist frequency. The smile and keystone is less than 10% of the pixel.
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Most of the existing defect detectors focus on the size, location, depth and number of defects of the tested components. The instrument is usually large in size and requires high accuracy for the environment and motion devices. In contrast, the direct random bed motion, which aims at finding and locating defects, is highly efficient, low-cost and environmentally practical, while the research on vibration-resistant defect tester is rare.In order to solve this problem, based on the principle of micro-scattering imaging in dark field, a set of optical component surface defect detection device is built, and the influence factors of light intensity, illumination angle, wavelength and other defect detection factors are experimentally studied, in order to provide design basis for the follow-up development of on-line defect detection instrument. The experimental results show that the most important factor affecting the sensitivity is the azimuth angle and pitch angle of the incident light, which is more than 30 degrees between the incident light and the scratch direction. When the pitch angle is between 60 degrees and 70 degrees, the higher detection sensitivity can be obtained. In addition, improving the illumination intensity can help to improve the detection of defects. In the visible range, the wavelength has little effect on the sensitivity.
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In analogy to the velocity decomposition in continuum mechanics, we introduce two new tensors, referred to as the deformation-rate tensor and rotation-rate tensor, to the optical coherence theory for stochastic optical field, and decompose a coherence current vector into its translation, rotation and deformation components to study the optical coherence dynamics. To investigate the optical coherence propagation and evolution, we have conducted an experiment with results given to demonstrate the two newly introduced tensors.
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Through the investigation and analysis of the characteristics of Martian atmosphere, the distribution of solar energy outside the Martian atmosphere is calculated. Using the fast calculation algorithm to calculate Mars surface radiation, a fast calculation mode is established, and a visual software interface is written. The radiation under given conditions can be calculated by directly inputting the location, time, solar zenith angle, surface albedo and light depth. The calculation results of the fast calculation mode are compared with the other two models, which increases the credibility of the calculation results. The calculation results are used to analyze the variation of surface radiation of Mars with solar zenith angle and light depth. This study will help researchers to predict the location and time of landing of Mars detectors, and provide theoretical support for analyzing the solar power generation situation of Mars. To ensure the successful implementation of the Mars exploration program.
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In this paper, the finite element model of the fiber optic plates is established by using the finite element software. The simulation process is basically in line with the actual production process of the fiber optic plates. According to the simulation results, the deformation degree and speed of each part of the fiber optic plates in the process of melting pressure, as well as the changes of stress and strain of each part in the process of forming are analyzed. The results show that the deformation speed and degree of different parts are different in the process of melting pressure of fiber optic plates, especially the upper and lower end faces and side edges of fiber optic plates; and the stress and strain of each part are constantly changing, and the stress and strain values of the upper and lower end faces and side edges of fiber optic plates are larger than others.
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Spinal surgery, such as pedicle screw placement, is difficult and risky due to the complexity of the physiological characteristics of the spine. Although intraoperative image guidance using a C-arm or an O-arm can significantly improve the success rate of the procedure, it is time consuming and the person is exposed to X-ray radiation for a long time. To solve this problem, this paper aims to exploring the application of new real-time 3D imaging technology in spinal surgery. Firstly, a CT scan of the pig's spine bone about 20 cm in length was performed and the accurate 3D data was obtained. Then, the 3D reconstruction was performed using a TOF camera and a light field camera. At last, the accuracy of the results was compared. The experimental results show that although the TOF camera has a good real-time performance, its resolution and accuracy of 3D reconstruction are low. The multi-frame superposition method can improve the data accuracy. The real-time performance of the light field camera is slightly lower. And the point cloud acquired by the bone is sparse because the spine texture feature is not obvious. But the accuracy of the 3D reconstruction can be significantly improved after the aid of structured light illumination. Therefore, the two techniques about 3D imaging proposed in this paper have some certain development potential in real-time navigation for spinal surgery.
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The BaSO4 diffuser and the PTFE diffuser are general reference diffuser in BRDF measurement. However, there are some differences of reflectance charactors between these two diffuser with illumination of narrow laser beam, and it affects the BRDF measurement precision. So the study of the differences of BRDF between the diffusers is necessary. Analysis the BRDF component of the diffusers was made with proposal of a 7-parameter model which including the volume scattering. Fittings of parameter models to the BaSO4 diffuser and PTFE diffuser was made based on Simulated Annealing Algorithm respectively. The results showed that the 7-parameter model decreased the variance and improved the PTFE diffuser’s BRDF fitting results compared with 5-parameter model.
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A bio-inspired Lidar imaging method with a non-uniform curved linear array receiving system is proposed. The receiving system is composed of a curved surface, a microlens array, an aperture array, and an avalanche-photodiode (APD) array. The microlens array and APD array are placed on a curved surface to mimic the large field of view (FOV) feature of the compound eye. The location distribution of the microlens array and APD array on the curved surface is non-uniform to mimic the retina-like property of the human eye. An experimental prototype, which consists of 12 microlenses and APD detectors is built and the effectiveness of the proposed approach has been validated by experiments. The results show that the whole FOV of the proposed system is 25.8° and it has a higher resolution in the central FOV and the lower resolution in the peripheral FOV. Moreover, the results show that the proposed Lidar imaging system has the rotation and scaling invariance property. This method is beneficial for developing a Lidar system with large FOV and high imaging efficiency.
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Aiming at the problem of unclear results and low accuracy of ultra-high speed photographic measurement such as the transient process of glass crack breaking at the end of projectile, a laser source with high power and uniform facula was designed, and the results were verified by software simulation and field test. First, the specific scheme was designed according to the parameters of high-speed camera. High power laser beam was generated by semiconductor laser array, and the compound eye lens was used to divide and superimpose the shaping beam to form uniform rectangular facula. Then, the mathematical model of the facula and the energy model of the facula were established to analyze the homogenization mechanism of the large area rectangular facula. After that, Zemax software simulation proved that the size, uniformity and illumination of the facula could meet the needs of high-speed photography. Finally, the experimental verification proved that the facula could compensate the background light. The final results showed that the designed large area light source had 425 W power and 0.9203 facula uniformity. It basically satisfied the requirements of brightness and uniformity of background light source for high speed photographic detection.
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An in-fibre temperature sensor based on a novel dual-mode fibre is proposed and experimentally characterized. The sensor head uses an in-fibre Mach-Zehnder(MZ) structure to sense the surrounding temperature, which depends on the interference spectrums. The concentric multilayer-core fibre (CMCF), in which only two modes could be propagated, would be easier to fabricate an in-fibre MZI with clean spectrum than many fibres, such as multimode fibres, thin-core fibres, PCFs and et al. And low-loss high-strength splice between CMCF and conventional single-mode fibre can be implemented with a commercial fusion splicer. Both the propagation characteristics and operation principle of such a sensor are demonstrated in detail. A sensitivity of ~50.13 pm/°C within temperature range of 30–70 ℃ are experimentally achieved, respectively.
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Reflectance Transformation Imaging (RTI) is a computational photography technology that allows interactive manipulation of virtual lighting within two-dimensional images to enhance object surface information. RTI is based on the reflection characteristics of the surface of the object characterized by a specific parabolic function, of which the most classic is Polynomial Texture Mapping (PTM) based on biquadratic polynomial. Therefore, RTI is ideal for diffusely reflecting objects, and metal materials with specular reflection are nearly out of consideration before. In this article, several metal samples with different surface topography were selected to explore the potential of RTI for subtle traces on metal surfaces. The results show that, with the cooperation of different image enhancement algorithms, especially Specular Enhancement and Diffuse Gain, RTI can be well applied to the detection of metal, even metal with relatively strong specular reflection. And the No-Reference Structural Sharpness (NRSS) assessment is consistent with subjective perception, confirming that RTI not only helps to explore the 2D or 3D geometric texture of the surface of metal materials, but also plays an important role in understanding and spreading the cultural phenomena implied in the content on metal surfaces. Promisingly, RTI is expected to be extended to a wider range of fields.
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The assembly gap between components is very vital for the evaluation of assembly quality of aircrafts. Due to the limits of gap size and operation space, the assembly gap needs to be indirectly calculated by the measurements of surface of components instead of plug gauge test. However, the surface constituted of point cloud is usually mixed with different types of noise ,which severely affects the evaluation of assembly gap. To remove these different types of noise simultaneously with high efficiency, a classified denoising method combining with an improved bilateral filtering and median filtering was proposed. Firstly, based on the principal component analysis, a new coordinate system was established to achieve the homogeneity of coordinates of point cloud. Then, an improved median filtering method on the basis of region segmentation (RSMF) was used to remove large-scale noise. Next, the fast bilateral filtering method based on threshold segmentation (TSBF) was proposed to remove small-scale noise. Finally, a measurement experiment of aircraft component was performed to verify the effectiveness of the proposed method. Experimental results showed that the proposed method could not only reduce measurement error including RMSE (Root Mean Square Error), but also improve SNR (Signal Noise Ratio) and PSNR (Peak Signal to Noise Ratio) of point cloud data.
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A fiber loop ring-down (FLRD) magnetic field sensing system combined with frequency-shifted interferometry (FSI) was proposed and the effect of temperature on its performance was experimentally demonstrated. The FSI-FLRD technique measures the light intensity decay rate (called the ring-down distance) in the space domain instead of in the time domain. Compared with conventional time domain FLRD scheme, FSI-FLRD technique greatly reduces the cost due to only need of inexpensive continuous-wave laser and slow detection. The tapered single mode fiber surrounded by magnetic fluid (MF) was utilized to construct the sensor head for temperature measurement. Different temperature was generated due to the thermal effect of MF and the temperature was obtained by measuring the ring-down distance. The experimental results indicated that a sensitivity of 0.31 /(mm·°C) was achieved.
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It is a key problem to get the high resolution and large field of view (FOV) of dynamic measurement in the display technique. In this paper, Charge Coupled Device (CCD) was synthesized with seams to be a display unit. A reconstruction method is proposed which combines the principles of synthetic aperture and phase retrieval to detect the 3D particle target with synthetic CCD. In the simulation experiment, the correlation coefficient of surface l is 0.73217 between the reconstructed image and the simulated particles target image. The pictures from the experiment depicts the particle is not only clearly visible at the normal region but also at the seams. The optical information can be recovered well of the high resolution and large field of view (FOV) with this method.
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Previous studies on the use of photoacoustic spectroscopy (PAS) techniques in the measurement of CH4 concentrations have been mainly limited to a single point measurement using only one PAS cell. A single point measurement will not satisfy the detection need, for instance in a natural gas transmission pipeline or an underground coal mine, gas explosion may occur at any point of the pipe or tunnel. Therefore, simultaneous multi-point measurements are required to obtain the gas distribution profile along the tunnel. Here we proposed and demonstrated a multi-point photoacoustic spectroscopy gas detection system based on the power compensation technique and fixed wavelength technique for CH4 detection. In the multi-point photoacoustic spectroscopy gas detection system, the gas absorption of the first PAS cell would make the measurement of the second PAS cell inaccurate. Therefore, we proposed a power compensation technique to compensate the absorbed laser power. In addition, a simple fixed wavelength technique was used in multi-point photoacoustic spectroscopy gas detection system to improve the signal to noise ratio (SNR). Finally, the experiment results showed that the two PAS cells achieved the minimum detection limit of 7.72 ppmv and 5.14 ppmv, respectively.
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It is well known that achieving a robust visual tracking task is quite difficult, since it is easily interfered by scale variation, illumination variation, background clutter, occlusion and so on. Nevertheless, the performance of spatio-temporal context algorithm is remarkable, because the spatial context information of target is effectively employed in this algorithm. However, the capabilities of discriminate target and adjust to scale variation need to promote in complex scene. Furthermore, due to lack of an appropriate target model update strategy, its tracking capability also deteriorates. In the interest of tackling these problems, a multi-scale spatio-temporal context visual tracking algorithm based on target model adaptive update is proposed. Firstly, the histogram of oriented gradient features are adopted to describe the target and its surrounding regions to improve its discriminate ability. Secondly, a multi-scale estimation method is applied to predict the target scale variation. Then, the peak and the average peak to correlation energy of confidence map response are combined to evaluate the visual tracking status. When the status is stable, the current target is expressed in a low rank form and a CUR filter is learned. On the contrary, the CUR filter will be triggered to recapture the target. Finally, the experimental results demonstrate that the robustness of this algorithm is promoted obviously, and its overall performance is better than comparison algorithms.
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Microchannel plate (MCP) is an important compact signal multiplier. The dynamic range of MCP is the key index influencing the detection quality of high flux, high energy and wide output linearity signals, but limited on the bulk resistance of MCP multiplier. Therefore, the problem of the bulk resistance-dependent of dynamic range transition in these devices needs to further continues to be investigated. In this paper, lead silicate glass microchannel plates in three different bismuth contents (0at%, 1at%, 2at%) were present. The bulk resistance decreased exponentially (from 6000MΩ into 15MΩ) with the increase of the content of bismuth in the lead silicate glass from 0at% to 2at%, meanwhile, the dynamic range was increased from 3.3×102 to 2.3×103 . As the bulk resistance of MCP multipliers dropped from 150MΩ into 15 MΩ (dropped about 90%), while the dynamic range of that just extended by seven times, meanwhile, the dark current of that boosted almost ten times (from 1pA to 10pA). It implicated that the dynamic range of MCP multiplier was influenced not only by the charge replenishment abilities involved in the bulk resistance, but also by the joule heating effect-depended dark current variation concerned with the bulk resistance.
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Infrared thermal camera is one of the important sensors in electron optic tracking system (EOTS) of UAV, and its parameters and performance directly affect the reconnaissance and surveillance performance particularly the combat efficiency in night of the UAV system. In this paper, we propose a method for determining the parameters of infrared thermal camera in EOTS of UAV. This method can easily determine parameters of infrared thermal camera from the aspects of working wavelength, sensors, lens size and focal length and so on. It realizes recognition distance of EOTS and can be used to guide the selection and integration of the infrared thermal camera in EOTS of UAV.
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We propose a new optical engine that supresses stray light to address the problems of high stray background light and low star point simulation in traditional star simulators and offer an experimental proof that the new design provides higher contrast. Our design incorporates an optical collimator with a modulation frequency transfer function (MTF) greater than 0.6 at a cut-off frequency of 60 lp/mm that meets star point identification requirements. Experimental results show the background noise of the high contrast star simulator to be well suppressed, providing a 3.16-fold reduction in stray light compared with a traditional system.
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Luminance gain is an important parameter to evaluate the light intensity enhancement ability of the low light level image intensifier assembly. The higher the luminance gain, the easier the receiver is to sense and recognize. However, luminance gain is not a directly measurable physical quantity. Thus, luminance gain measuring devices have non-standard specific properties. Based on the principle of luminance gain measuring specified in the standard, the structure and measurement methods of measurement devices are analyzed, the error and optimization methods of two major measurement methods are compared, and the distribution of the combined uncertainty of measuring luminance gain is studied. Then, an optimized measurement scheme of luminance gain of low light level image intensifier assembly is put forward. Based on this scheme, a comprehensive measurement uncertainty analysis is carried out and the calculated luminance gain measurement extended combined uncertainty is about 6.7% (k=2). The results are of great significance for improving the measurement accuracy of luminance gain of low light level image intensifier assembly.
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In the process of fast automatic alignment of optical path in the integrated diagnosis system of host laser facility, there are six kinds of different optical target images captured. Because of the different characteristics of optical target, different methods for calculating the center of optical target image must be put forward, which increases the algorithm complexity of calculating the optical target center. In order to improve the efficiency and accuracy of fast automatic alignment of laser beam in the integrated diagnosis system, it is necessary and important to propose a method that can calculate all kinds of optical center of collimating images. In this paper, based on the synthesis of the characteristics of pinhole image, schlieren sphere image and common optical target image, a general method for calculating the optical target center of weak contrast collimating image is proposed. Firstly, multi-dimensional image cubes are constructed by using multi time-sharing images or neighborhood vectors, and the dimension of multi-dimensional data cubes is reduced by using NVPCA transformation to remove the correlation between the various dimensional images, separate and readjust the noise of original image; Secondly, the one-dimensional image data is classified by Kmeans, and the binary image is processed by the mathematical morphology operation to separate the laser target and background respectively; Thirdly, if the optical target image is a schlieren image, it need to obtain the background of schlieren image, the region of schlieren sphere, the edge of schlieren sphere respectively; If the optical target image is a pinhole image, it need to obtain the characteristic points on the circle contour of the pinhole image; Finally, the least square method is used to calculate the circle center of the pinhole image and the schlieren sphere image, and the center of gravity method is used to calculate the center of optical target. The experimental results show that this paper synthesizes the same and different characteristics of all kinds of collimating images, proposes a method to calculate the optical target center of weak contrast collimating images, improves the calculation accuracy of the optical target center of collimating images (less than 1 pixel) effectively, shortens the fast alignment time of the optical path of the integrated diagnosis system, and provides an effective guarantee for the measurement experiment of far-field focal spot of high power laser based on schlieren method.
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It is known there are some problems such as the image suffers from excessive brightness or darkness under non-uniform illumination, loss of detail in the enhanced image, halo effect and so on. In this paper, an adaptive correction algorithm is proposed for these problems. Firstly, based on the illumination-reflection model, the illumination component was extracted by weighted guided filtering integrated with gradient information. Afterwards, the index of 2-d gamma curve is adjusted with the illumination component to realize the adaptive illumination correction. Finally, the output image pixels are produced with their adjacent pixels to enhance the local contrast of the image. The experimental results show three aspects. One is the improved weighted guided filtering can distinguish the edges adaptively and avoid the halo caused by excessive smoothness near the edges. Two is the clarity of enhanced image was improved by over 86.5% on average. At the same time, due to the reduction of color distortion, the ability to enhance image detail was improved by 18.5% on average.
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As a typical atomically thin two-dimensional (2D) crystal, graphene-based photodetector has attracted tremendous attention in recent years due to excellent photoelectric performance of graphene. However, due to the unstable chemical properties of graphene, the guidance is lacking in the design of composites with other materials. The stability and repeatability of the device are also restricted by the material properties. Here, we have established a graphene simulation model and obtained the electrical characteristics of graphene which are consistent with the experimental results by using the method of equivalent design. We simulate the detection capability of graphene-silicon composite photodetector and graphene-germanium photodetector under different doping conditions for visible light (532nm) and near infrared wave (1550nm) respectively. The current-voltage characteristics of the heterojunction are obtained. Through this model, the proposed bottom gate adjustment mechanism makes the carrier transport of graphene/silicon-on-insulator (GSOI) photodetector adjustable. By adjusting the carrier concentration and distribution in the graphene channel and silicon through the bottom gate voltage, an enhanced built-in potential is obtained, which increases the device responsivity by 5-10 times to 106 A/W. This model can be used to simulate the carrier distribution and current density when different gate voltages are applied, and the modulation law of this model is in good agreement with the experimental results. This work will be beneficial to the mechanism analysis and performance optimization of the graphene composite structure photodetector, which has important guiding significance for the experiment.
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A robust multi-focus image fusion method is proposed to generate an all-in-focus image with all objects in focus by merging multiple images. The proposed method first estimates local focus maps using a novel measure of Gaussian model combined with joint bilateral filtering in HSV space. Then, a propagation process is conducted to obtain accurate focus maps based on a traditional natural image matting model that makes full use of the spatial information. The fused all-infocus image is finally generated by a focus-selected strategy. Experimental results demonstrate that the proposed method has state-of-the-art performance for multi-focus image fusion under various situations encountered in practice, even in cases with little edge information.
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Aiming at the problems of target scale change, color similarity and occlusion during target tracking, this paper proposes a single target tracking algorithm based on the fusion feature of color feature (CN) and direction gradient histogram (HOG). Under the relevant filtering and tracking framework, the original RGB color space is mapped to the color attribute space to reduce the target color from being affected by environmental changes during the tracking process. The adaptive component dimensionality reduction through principal component analysis (PCA) method, features The number of channels drops from 10 to 2, and the cost of crossing different feature subspaces is increased by smoothing constraints. At the same time, the direction gradient histogram is extracted, and the feature map is calculated by kernel correlation filtering to obtain the correlation response map, and the maximum response value is found from the response map to determine the target position. 36 groups of color video sequences were selected on the OTB standard data set for experiments. The popular correlation filter tracking algorithm was compared. The experimental results show that the algorithm has high recognition accuracy and can be used in complex environments such as illumination changes, target occlusion and deformation. Stable tracking target.
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By combing the technique of coherent detection with ghost imaging, we establish an experimental system for pulse-compression ghost imaging via coherent detection. The results have experimentally demonstrated for the first time the feasibility of ghost imaging via coherent detection. More importantly, it shows that even when echo power is only 5 pW, which is lower than three orders of magnitude compared with previous ghost imaging via photon intensity detection, an image with a spatial resolution of 0.8 mm can be obtained for the proposed method.
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In order to better characterize the polarization characteristics of reflected light in oil spill monitoring by remote sensing on the sea surface and improve the accuracy of oil spill detection, the quaternion method is introduced into the oil spill detection system, and a kind of oil spill monitoring technology based on quaternion is proposed in this paper. Firstly, the quaternion matrix method for calculating the sea surface reflection polarization information is proposed, and the relationship between the characteristic parameters of quaternion and the refractive index of oil film is discussed. Then, four kinds of oils crude oil, soybean oil, lubricating oil and diesel oil are used as the experimental samples for oily pollution on water surface, and the characteristic quaternion parameters, s and p components of different samples are obtained through the reflection images at different polarization directions, so the identification of different oil products is realized.. The experimental results show that the quaternion polarization characteristics can be used as an important parameter for oil identification.
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The false alarm generated by the background object in the complex sky background is a difficult problem in the detection of infrared small targets. The problem is particularly prominent when the target signal is weak. In order to effectively suppress the false alarm rate and improve the detection rate, a weak target detection algorithm based on infrared polarization map is proposed. Firstly, the data is collected by the infrared polarization detecting device, and then the polarization component map with the best image quality is analyzed. Finally, the filtering algorithm combined with Top- Hat morphological filtering and median filtering is used, and the global component threshold detection method is used to complete the polarization component map. Weak target detection. The experimental results show that the proposed method has higher detection rate and lower false alarm rate than the Top-Hat algorithm, maximum mean filtering algorithm, and LCM algorithm. An effective method for detecting weak targets in the background.
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With the development of infrared surveillance technology, the short focus zoom LWIR lens has been paid to more and more attention. In this paper, dual fields zoom lens with the fields of 20°×25°/8°×10° are designed by two different methods. The main specifications of the lens include: aperture is 1 / 2, detector resolution is 640 × 512, pixel size is 15 μ m, temperature adaptability is -40 ° to + 60 °. And we compare the volume, weight, imaging transmission, transmissivity and economy of the lens by different methods. It is found that the re-imaging method has smaller volume, weight and economy. While another imaging method has better transmittance, so the imaging system can reach higher noise equivalent power at the same image quality
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Different from the traditional mechanical gyroscope, fiber optic gyroscope (FOG) has the characteristics of fast start-up speed, high precision, small volume, and low cost, which has been widely used in the fields of sea, land, air and so on. With the wide application of FOG, the problem of its reliability has gradually emerged. Among all kinds of reliability problems, the problem of degradation of the input axis misalignment angle of high-precision FOG with the time is particularly prominent. If it cannot be solved as soon as possible, this problem will seriously affect the actual use of highprecision FOG In this paper, a fault tree is established, which takes the degradation of the input axis misalignment angle of high-precision FOG with time as the top event. The physical and chemical factors and manufactucoil process parameters that cause the degradation of the misalignment angle are analyzed. Through the study of the degradation mechanism, it is concluded that the change of the size stability of the fiber coil is one of the main factors that cause the degradation of the misalignment angle with time. Then we design and build a special testing system for the misalignment angle of highprecision FOG. The degradation mechanism of the misalignment angle of high-precision FOG is verified by experiments. The theoretical analysis and experimental results show that the stability of the size of fiber-optic coil changes with time, which will have a very bad impact on the reliability of the misalignment angle of FOG. Finally, through the design and process optimization, the reliability of the misalignment angle of gyro can be improved.
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As a new generation of INS products, high-precision FOG has been widely used. High precision fiber coil is the sensitive core of high precision fiber optic gyro. Its performance and reliability index determine the performance and reliability of high precision fiber optic gyro. In this paper, the key process methods and parameters that affect the performance and reliability of optical fiber coil are studied. Firstly, the process flow chart of high-precision fiber optic gyroscope is drawn, and every process link of high-precision fiber optic coil manufacture is deepened. Through theoretical analysis, the key process and process parameters affecting the performance and reliability of high-precision fiber optic coil are identified. Then carry out the corresponding process validation test at the same time, through the analysis of the test results to verify the previous theoretical analysis. Then the optimization design and reliability growth research are carried out for the key process, and the control of the key process is strengthened to improve the performance and reliability index of the coil from the process link.
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Combining support vector machine with infrared spectrum analysis, the infrared spectra analysis model of mixed gas is established. Taken the mixed gas containing hydrocarbon as an example, the selection and optimization of model parameters is researched through experiment. Beginning with the SVM analysis model, infrared spectrometer and spectra data, spectra analysis band and spectrometer scanning interval, the detailed study of how the parameters like the types of kernel function for the SVM analysis model, penalty factor C, method of spectra data preprocessing, spectrometer scanning interval, spectra analysis band, etc. Affect the analysis result are carried out. The experimental results show that under the condition of the SVM analysis model is determined, a reasonable selection and optimization of the SVM analysis model parameter can improve the accuracy of the analysis results, and it has a practical application value.
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Lead sulfide colloidal quantum dots, similar to the nanoscale crystals of most semiconductor crystals, are available in a variety of sizes, shapes, and compositions as well as to make different chemical molecular ligands to modify the surface of the quantum dots and to fabricate functional optoelectronic devices on a variety of substrate materials. The combination of silicon and colloidal quantum dots enables the fabrication of silicon-based compatible quantum dot optoelectronic devices over a wide range of applications. In this paper, the effects of channel doping concentration and channel length on the performance of silicon-based CQD/Si photodetectors are calculated and analyzed from the simulation method. The results show that a suitable doping concentration and a short channel length can improve the performance of the device, which provides a simulation basis for the fabrication of silicon-based compatible arrayed colloidal quantum dot photodetectors.
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The infrared characteristics of the target is very important for target recognition. The infrared radiation characteristics are different between damaged solar panel and normal working solar panel. It is the characteristic position for the solar panels’ nondestructive fault testing. In this paper, the temperature model of solar panels is established, and the numerical calculation is carried out. The calculated results and the measured data matching well verify the correctness of the calculation model. The results also show that the temperature of solar panels which are damaged are higher than the temperature of those who are normal working. On the basis of the temperature calculation, the infrared radiation characteristics of solar panels are calculated .The result shows also that the infrared radiation intensity of those damaged solar panels are higher than the normal working solar panels. This provides the theoretical support for the infrared nondestructive testing of solar panels.
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Based on the principle of compressed sensing, a single-pixel imaging system (single-pixel camera) was built in our laboratory, and our single-pixel camera can successfully acquire the picture of imaging scene of a distant building. However, the process of single-pixel imaging is easily disturbed by noise. In order to reduce the interference of noise in the imaging results as much as possible, we apply the method of adaptive dictionary learning to denoise the reconstructed image in our single-pixel camera. The block-coordinate decent idea and K-SVD algorithm are used to complete the dictionary learning by training on the noisy reconstructed image in the method of block-by-block scanning, which doesn’t require the extra corpus of image patches, so the method of dictionary learning is self-adaptive to the imaging picture that need to be denoised. The overcomplete DWT (discrete wavelet transform) dictionary is applied as the known initial dictionary that will be trained in the adaptive dictionary learning. The effectiveness of the adaptive dictionary learning has been demonstrated by the simulation experiment and the practical imaging experiment, the method of adaptive dictionary learning based on the initialization of overcomplete DWT dictionary effectively reduces the imaging noise and improves the image reconstruction accuracy and imaging quality.
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The traditional operating distance model of infrared imaging system is only valid under the condition that the background is single and invariable. For the sea surface targets, radiation characteristics are affected by the sea-sky-line, specular reflection, sea clutter and so on, resulting in a large calculation error of operating distance if traditional operating distance model was used. In this paper, the operating path of infrared imaging system is divided into chaotic path and methodical path. The chaotic path is the operating path with a certain slant distance from the sea surface target, the infrared radiation propagation characteristics of the target in this path are uncertain, multivalued and volatile, showing certain chaotic characteristics. The methodical path is from observation point of infrared imaging system to the terminal point of chaotic path, the infrared radiation propagation characteristics of the target in this path are certain regularity and linearity, which can be estimated by using the traditional operating distance model. The main work of this paper is to subdivide and characterize the infrared radiation characteristics of the sea surface target in the chaotic path, and finally linearize it in a specific situation, convert the radiation energy of the sea surface target to the starting point of the methodical path, and at last calculate the operating distance according to the traditional operating distance model of infrared imaging system. This method is innovative in theory and can give a reference to the research of infrared system detection range under complex backgrounds.
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The emergence of HTV-2, X-51A and other near space hypersonic vehicles poses a new challenge to radar target tracking. Near space hypersonic vehicle has the characteristics of high speed and high maneuverability, but the tracking performance of conventional tracking algorithm is low, which can not meet the operational requirements. In this paper, the technical difficulties of near space target tracking are described. By analyzing the motion characteristics of near space hypersonic vehicle, the dynamics model of HTV-2 is established, and a tracking method based on interacting multiple model (IMM) for near space vehicle is proposed. At the same time, considering the unscented Kalman filter (UKF) algorithm has a better filtering effect on strong nonlinear object. The simulation results show that, the interact multiple model-unscented Kalman filter (IMM-UKF) algorithm is better than the single model EKF algorithm.
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In the process of crack identification for round logs, conventional edge extraction cannot effectively suppress noise because of the tree's annual ring lines and the similarity between the burr noises during cutting and the gray level of the target. Therefore, it is no easy to extract the target crack. The method of continuous gray-scale transformation enhancement is put forward in this thesis to increase the difference between the gray level of the background pixel and the gray level of the target so that can obtain an ideal pre-processed image. In the process of image preprocessing, the method of continuous gray-scale transformation enhancement is applied, that is to combine the gray-scale transformation enhancement and the non-linear filtering process so that can realize the preprocessing of the original image. The gray level difference between the extraction target and the background is increasing under the premise of preserving the image-extraction features. In the extraction process, the extracted target crack image is obtained through utilizing the localization minimum in mathematical morphology and then the compound morphological algorithm is designed based on the basic algorithm of mathematic morphology so as to obtain the target crack image which is connected by the edge curves. Results The MATLAB image processing algorithm is used to simulate each step of the method. The results show that the extracted target crack images are ideal. The mentioned algorit can not only ensure the integrity of the extraction target, but also can suppress the noise very well so that can satisfy the needs during the extraction of complex background images, especially the images with little difference between the background gray level and the extraction target gray level.
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Optical antenna is an afocal telescope system which used to transmit or receive optical signals in free-space laser communication systems. In designing a high performance optical antenna, the challenging tasks including achieving of very compact and light weight optical configuration, appropriate exit pupil distance, high transmission efficiency, and wide temperature working range. The formulae of Gaussian parameters between the objective and eyepiece are derived by using the ideal imaging process. A first-order optics analysis of the optical antenna is given, which allows optics engineers to pre-define a suitable optical layout before performing design optimization and analysis. Design examples of off-axis reflective optical system are presented.
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With high time resolution and wide coverage, GF-4 camera can achieve high-frequency repeated monitoring over a wide range of areas within a certain period of time. However, there are some problems of its sequence images, such as shaking, non-prominent ship targets and insufficient brightness in sea area, which are not conducive to the detection of moving ships. Thus, a hierarchical registration algorithm combining SURF and SIFT, and an image enhancement algorithm combining wavelet threshold denoising and Top-hat filtering was proposed to solve these problems. Matlab’s experiment proves that the processed image can almost only contain the highlighted target and the black background, which improves the accuracy of subsequent ship monitoring.
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Aiming at the problem of poor detection of slow speed targets in sea surface under complex sea conditions for airborne maritime surveillance radar, this paper first analyzes the distribution characteristics of sea clutter in different sea conditions, studies focus on inter-scanning coherent processing, non-coherent processing and frequency agility processing. Finally, the results of three methods, such as non-coherent accumulation, constant frequency coherent accumulation and fixed frequency non-coherent accumulation, are analyzed and compared under different sea conditions. It is concluded that under low sea conditions, the method of coherent accumulation and increasing the number of pulse accumulation can effectively detect the slow target of the sea surface.
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In order to solve the difficult problem of unmanned air vehicle(UAV) target detection in visible light images under complex sky background, this paper proposes a UAV target detection method based on frequency domain transform. First, the B-channel in the image LAB space is used to extract the sky and cloud boundary images, and then the image feature channel is used to construct a quaternion function. Secondly, Fourier transform is performed on the quaternion function to extract the amplitude spectrum and phase spectrum, then the amplitude spectrum image is subjected to multi-scale decomposition using wavelet transform in the frequency domain, the amplitude spectrum image of each scale and the phase spectrum image are combined by inverse Fourier transform, and the evaluation function is used to obtain the best scale image. Finally, the best-scale image and the boundary image are normalized to make a difference to obtain the final detection result. Experimental results show that the algorithm can effectively detect UAV targets under complex cloud background.
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The most important part of visible-infrared image characteristic simulation, is the degradation simulation of the image in the actual turbid atmosphere. Aerosols, molecules, turbulence, and imaging devices in the atmosphere are the dominant factors in the image degradation process. These effects occur simultaneously in the real-world atmosphere. According to the equivalence principle, the MTF of molecule can be calculated, whose results show that the absorption and scattering effect of molecule cannot be treated easily as a dampen on image contrast but is as important as that of aerosol. At and near some absorption bands, molecule MTF at high spatial frequency is smaller than aerosol MTF at high spatial frequency; at weak-absorption and strong scattering bands, molecule MTF is comparable to, even bigger than, aerosol MTF at high spatial frequency. In turbulence free atmosphere, the dominant factor that affects the image quality is determined on the dependence of weather and wavelength. At molecular absorption lines, the effect of molecule is dominant, whereas, at visible bands, the effect of aerosol is comparable to, even more important than, that of molecule. When the turbulence is considered, the result is a little complex. If turbulence blurs the image seriously and the cut-off spatial frequency is much smaller than that of overall turbid atmosphere MTF, the image degradation is dominant by the turbulence. In addition, the cut-off spatial frequency of aerosol MTF or molecule MTF is generally smaller than 2 cycles/mrad even 1 cycles/mrad, which means that aerosol MTF or molecule MTF will be dominant factors for imaging degradation when the turbulence is weak enough in atmosphere.
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In this work, a new type of optical fiber pressure sensor based on Frequency Modulated Continuous Wave (FMCW) laser interference technology was designed and produced. The sensor consists of a diaphragm-type Fabry-Perot (F-P) cavity structure, which is made of 316L stainless steel with excellent elastic properties. The deformation of the diaphragm occurs under the gas pressure, which causes the length of the F-P cavity to change. The FMCW laser interference technique was employed to demodulate the change of cavity length. The experimental results show that the linearity of pressure and cavity length can reach 0.99993 whin the range of 0~600 kPa, and also verify that the pressure sensor has good repeatability and stability.
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A mid-infrared TDLAS sensor near 2.5μm was designed for time-resolved measurements of temperature and water vapor partial pressure at the nozzle exit of a laboratory-scale hybrid rocket motor. Several previously used H2O transitions within 2.4-2.9μm were thoroughly investigated, and a line-pair containing three transitions (4029.52 cm-1 , 4030.51 cm-1 and 4030.73 cm-1 ) was selected for the optimal overall properties like strong absorbance, sufficient temperature sensitivity, single laser scan, high immunity from the ambient H2O transitions and low measurement uncertainty affected by temperature over the range of 1500K-2500K. Firing tests were conducted on an oxygen/paraffin-fueled hybrid rocket motor operating at oxygen/fuel ratios (O/Fs) of 3.10, 2.77 and 2.88, corresponding to average combustion pressures of 1.91MPa, 2.09MPa and 2.38MPa. A distributed feedback (DFB) laser tuned repetitively at 2kHz was used as the light source, and simultaneously the transmitted spectra were detected at a 2MHz sampling rate. Finally, a 4.5ms time-scale variations of temperature and H2O partial pressure were captured by TDLAS sensor. Uncertainty analysis was made in detail based on average temperature (1929.8K, 1926.5K, and 1990.7K) and average H2O partial pressure (0.237MPa, 0.253MPa, and 0.285MPa), leading to temperature uncertainty of around 2.24% and partial pressure uncertainties of around 3.80%, 3.79% and 4.04% respectively. The time-resolved measurement results and small measurement uncertaintiesindicate that TDLAS has the potential to evaluate the combustion performance of hybrid rocket motor
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In this paper, a novel optical method is proposed to effectively double the sensitivity of FOGs. Two fiber polarization combiner/splitters (PCS) are added in the traditional FOG optical path, which are able to either combine two orthogonal polarizations transmitting at two different PM fibers into the two orthogonal axes of one PM fiber respectively or split two polarizations transmitting at the two orthogonal axes of one PM fiber into two polarizations to transmit at two different PM fibers respectively. Through the specific placement and coupling of these two fiber polarization combiner/splitters, the incident light can transmit twice along the light path of FOG. The experimental setup is established and the method is verified experimentally. The results show that the proposed method will effectively improve the sensitivity and the signal-to-noise ratio (SNR) of FOG without increasing the length of fiber coil, which is very benefit to improve the technology of FOGs, as well as the miniaturization of FOGs.
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Three-dimensional imaging lidar is a new type of active detection technology, which can obtain target spatial information accurately and quickly. It has a wide application in the fields of target detection and recognition, scientific research detection, mapping and navigation, etc. Three-dimensional imaging lidar has many modulation modes, among which the non-scanning three-dimensional imaging lidar based on polarization modulation has the advantages of long measurement range, high measurement accuracy, fast imaging speed and no motion artifacts, which is one of the hot research directions in this field. In view of this technology, this paper analyzes the principle of polarization modulation imaging by Jones matrix calculation, and obtains the geometric relationship between the imaging illumination values in four polarization directions and the polarization modulation phase delay of Pockels Box. Then, a set of laser radar optical system based on polarization modulation imaging is designed by using optical software. The analysis results show that the designed optical system has good imaging quality, clear target edge imaging and can distinguish independent square targets with a diameter of 1m; The light outside the field of view of the strip light source does not enter the detector, so the system has less stray light and less imaging distortion; At last, the input phase delay δ of the Pockels box in the simulation model is randomly set to different values, and the illumination values of four polarization directions are obtained by imaging simulation, so that the phase delay δ′ of the Pockels box is inverted. The results show that | δ′-δ | ≤ 5.2× 10-6 λ, which proves that the polarization modulation method is correct.
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Laser active imaging uses a pulsed laser to illuminate the target. Through imaging detection of the target's reflected light, more detailed information of the target can be obtained. It can be used in severe weather conditions, at night and in the light of fire or smoke to monitor the target and attitude measurement. This article introduces the working principle and research status of four active laser imaging methods, including commonly used point scanning imaging, continuous light imaging, fringe tube imaging and APD imaging.
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Among pathological images, there are usually some typical patient structures. For these typical images, template matching can be used for diagnosis, thereby the workload of doctors can be reduced. In this paper, pathological images of breast masses are studied in depth. A typical breast masses pathological template is established. Three template matching methods, correlation coefficient matching, correlation matching method as well as square difference matching method are used for experiments separately, and the timeliness and effectiveness of them are evaluated in terms of computing time and matching accuracy. The experimental results show that among these three template matching methods, the accuracy of correlation coefficient matching is the highest, and it is able to overcome the interference of angel rotation and noise. However, it is also consumes the longest time.
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Using the output of the photodiode as a current source, and then introduce an operational amplifier to convert the photo-generated current to voltage becomes a typical photodiode amplifier circuit. The seemingly simple circuit faces a difficult problem when detecting weak photo-generated current: the photosensitive surface of the diode and the resistor using for current-voltage conversion need to be enlarged as much as possible to increase the output amplitude. However, this will result in a reduction in the bandwidth of the photodiode amplifier circuit, a reduction in stability, and an increase in noise. It was therefore decided to introduce software to assist in circuit design for the improving of performances of circuit. To assessing the applicability, the photodiode amplifier circuit was matched with other optoelectronic devices such as laser driver, temperature controller and lock-in amplifier, and employed in wavelength modulation spectroscopy (WMS) for NH3 detection at its P(6) absorption line belonging to the ν3 + ν4 combination band. Under the experimental conditions of room temperature (296 K), normal pressure (1.01e5 Pa) and an effective absorption path length of 10 cm, the experiments were conducted using five samples with their concentrations ranging from 500ppm to 1%, and a 1.3ppm detection limit was deduced from the linear regression analysis. The results not only indicate that the photodiode amplifier circuit has great potential in other trace material detection applications based on absorption spectroscopy, but also reflect from the side that the method of using simulation software to assist circuit design is highly feasible.
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In this paper, based on the collaborative integration and modeling calculation of single-point Laser Doppler Vibrometer (LDV), a 3D oblique non-contact dynamic attitude measurement system is proposed. By using two groups of three-dimensional measurement devices which consist of three LDVs, our system can measure the translation and rotation of the measured object. The experiments are carried out under line vibration environment, and the elicited results are compared to those elicited using fiber optic gyroscope (FOG), which verified the feasibility of our system.
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Schlieren method is an effective method to measure the high dynamic range far-field focal spot of high power laser at present, it has been used in the comprehensive diagnosis system of the host facility of the national large scientific device. However, the background subtraction algorithm is used for denosing process of the main lobe and side lobe images in the experiment, which could not effectively remove the noise under the condition of strong radiation. In order to improve the reconstruction accuracy and reliability of far-field focal spot measurement based on schlieren method, there are two aspects have been proposed and optimized in this paper as follows, the mathematical model for the measurement of high dynamic range far-field focal spot is constructed, the noise of images captured by detected CCD is removed effectively. Firstly, the mathematical model of laser focal spot measurement is constructed, which provided a theoretical basis for the measurement of far-field focal spot based on schlieren method. Secondly, the denoising algorithm based on Convolutional Neural Network (DnCNN) is introduced into the denoising of main lobe and side lobe CCD image, which can effectively remove the noise of different levels (0-75db) of main lobe and side lobe CCD image.The experimental results show that the noise signal of main lobe and side lobe images are removed by using DnCNN algorithm, and the best reconstructed image of far-field focal spot of high power laser is obtained when the influencers of amplified noise of main lobe image is reduced greatly. After the above optimization and improvement, it will meet the requirements for accuracy and efficiency of the measurement of high dynamic range far-field focal spot.
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PS plate (presensitized plate) is a new type of plate used in the fast printing industry. Due to the "squeaking" caused the production process, it will seriously affect the printing quality. This kind of helium detection device is currently entirely monopolized by large foreign companies, the price is expensive, and it is also not suitable for the conditions of domestic enterprises. The development of this device will fill the gap in the domestic field. At present, most domestic companies adopt manual inspection methods for naked eye observation. Because of the subjective nature of human beings, it is impossible to quantitatively analyze. The PS version quality report provided by the device development provides data basis for later-stage sheet and stacking work which can realize Intelligent production.
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In recent years, the number of small unmanned aerial vehicles (UAVs) present in the airspace around us has increased dramatically. Unmanned aerial systems were traditionally associated with military use, however, the increase in drone activity is far from exclusively being generated by increased military use. The increase in micro-UAVs has made it a tough challenge for the detection of UAVs. The demand for measurement and analyze of radar characteristics of UAVs is increasing significantly. This paper focuses on the Radar Micro-Doppler signatures of small UAVs, and experiments were conducted to support the analysis. In this paper, the characteristic of rotor blades were shown, and the doppler signatures of a real micro-drone were measured by a pulse radar system, and the short time Fourier transform was used to analyze the micro-doppler signatures from the data collected.
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Based on basic principle of infrared radiation, aiming at infrared radiation characteristics of aircraft in different altitude, speed and attitude, a dynamic measurement method of infrared radiation characteristics based on flight parameters is proposed, and the infrared radiation intensity of a typical aircraft is simulated and analyzed. A typical aircraft is simulated and analyzed. These conclusions provide a basis for stealth aircraft design and the IR guidance air-defense weapon system design and application.
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Orbit prediction is the premise of consistency transfer calibration of space radiation standard. By using the satellite's orbital elements and the calibration sites information, the time and location of the two satellites are predicted with the joint observation constraints. The orbit prediction process of the consistency transfer calibration of space radiation standard is briefly introduced, and the satellite space position calculation method for orbit prediction is studied. By selecting TERRA and Landsat8 as the radiation reference satellites, GF-1, GF-2, GJ-1, etc. as the satellites to be calibrated and analyzing the constraints such as the observation time interval and the observation angle difference that limit the joint observation cross frequency, the analysis of the cross-matching constraint mechanism is done with the six calibration sites. The simulation and analysis results are helpful for the optimization design of the standard satellite orbit with the cross frequency of twice a month, and could provide technical support for the high-frequency and high-precision in-orbit radiometric calibration for Chinese satellites.
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Super-wide FOV lens has a short focal length, making the detection distance shorter. To suit the need of long detection distance, the inversed telephoto structure is used. In this paper, we designed a super-wide FOV camera system with a negative-positive inversed telephoto structure, whose FOV is 95°×71.25°.And optical aberration were analyzed detailedly, the structure of foreside and backside were made certain respectively, based on these, optical optimum design was accomplished.The result shows that in the entire field of view, the MTF at 60lp/mm is more than 0.4, the diameter RMS of spot diagram dispersion circle is less than 5 microns and the maximum distortion is less than 5%. The result shows that it meets the requirement of system well.
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In recent years, requirements such as over-the-horizon, high resolution, large field of view, wide spectrum and dexterity have pointed out new directions for the development of optical imaging systems. Common optical surfaces such as planes and spherical surfaces have been difficult to meet the requirements of optical indicators. It is often necessary to use multiple high-precision complex optical surfaces such as high-order aspherical surfaces, off-axis aspherical surfaces, non-rotational symmetric curved surfaces, microstructured optical array surfaces and freeform surfaces. This brings processing, testing and adjustment in terms of problems, the monolithic multisurface optics as a new type of optical element are increasingly attracting researchers' attention.
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Images captured from outdoor scenes are usually suffer from the atmospheric scattering and absorption, these natural phenomenon of hazy cause low contrast, poor quality of images, which severely affect their subsequent applications. Despite numerous image dehazing methods have been developed to improve the quality of hazy images, effective image dehazing method remains a challenging problem. In this paper, we propose a new method for retina color perception-based image dehazing, which considers the light response model based on the retina color perception mechanism, and the transmission estimation model combines with the dark channel prior. Specifically, an adaptive light response model is designed based on stimulus perception of retinal ganglion cells and lateral geniculate nucleus (LGN) neurones in the receptive field; and a new transmission estimation model combine with the dark channel prior is developed, thus we propose a retina color perception-based image dehazing method. Moreover, to validate the effectiveness of the proposed dehazing method, we test the method on various synthetic hazy images, and compare with several state-of-the-art image dehazing methods quantitatively. Extensive experimental results shown that the proposed method could improve the clarity of the hazy corrupted images, and the details of dehazed images could be protected moderately.
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As a sort of low-altitude remote sensing technology, UAV remote sensing possesses the advantages that satellite remoting sensing and traditional aerial remote sensing do not have. It can be effectively used as an indispensable supplementary means for obtaining remote sensing images. The paper develops a set of image processing systems basing on the characteristics of UAV remote sensing platform, which can provide digital images with high quality as well as high resolution. In this paper, firstly, a series of preprocessing such as noise reduction and enhancement will be performed on the obtained data. Then, the feature points in the images will be extracted, the potential image matching pairs will be set up and the mosaicking process will be completed. Finally, the UAV remote sensing images will be segmented and the road extraction of UAV remote sensing can be realized. Experiments show that with known camera calibration parameters, the accuracy of image mosaic is high. Also, roads are extracted from the sequence of images taken by the UAV continuously, with an accuracy of more than 90%.
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With the progress of science and the development of society, the study of material composition becomes more and more important, and the identification of material composition is mainly to distinguish the spectral information of different substances. Spectrometer is an important optical instrument, which combines the optical method with modern electronic data processing technology, and accurately analyzes the structure, composition and content of the target substance by obtaining its spectral information. At present, it has been widely used in some important scientific fields such as field exploration, material detection and space-borne analysis. In this paper, a new type of spectrometer based on periodic array structure is proposed. The spectrometer modulates the phase of the incident light by using the small hole array structure with the diameter of sub-wavelength. By using the diffraction effect of light, the light intensity distribution of the incident light is directly recorded by Charge Coupled Device(CCD)according to different wavelengths. After passing through the diffraction aperture array, the light intensity distribution is recorded again, and the transmittance coefficients of the diffraction aperture array for different wavelengths are obtained respectively. Finally, the transmittance matrix of diffraction aperture array for incident light is obtained, and the spectral curves of different incident light can be obtained by data processing algorithm according to the transmittance matrix. The main optical device of the spectrometer is diffraction aperture array, which is a metal film coated on a transparent substrate made of resin material. A series of aperture arrays with diameters of 2-78 microns and 10×10 are processed on the metal film by micro-nano processing technology. Any aperture has different diameters, and the apertures are periodically arranged on the metal film. By using diffraction effect, the incident light with different wavelengths will produce different light intensity distribution on CCD. Combined with data processing method, the incident light can be obtained. Compared with the traditional spectrometer, the new spectrometer has no moving parts in the system, which improves its stability, and has the characteristics of fast data processing, small size, low cost and high spectral resolution. In this paper, the theoretical analysis, simulation and experimental verification of the new spectrometer are carried out. The results show that the new spectrometer has obvious advantages compared with the traditional spectrometer and has broad application prospects.
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In frequency-modulated continuous-wave (FMCW) ladar, researchers usually linearize the output of the ladar’s tunable laser by a reference interferometer for high-accuracy measurement, but the reference interferometer need to be precisely calibrated. The H13C14N cell is a universal tool to complete the calibration. Here, we use the optical frequency comb instead of the traditional HCN gas cell to calibrate the path-length difference of the reference interferometer for higher precision. In this article, we present a detailed introduction of the experiment for path-length difference measurement and data processing method. The finally experimental results show that this method can give a micron precision, the standard deviation is 2.560e-5.
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It is well-known that the synchrotron radiation light source (SRLS) possesses the unparalleled superior characteristic compared with other light sources. Therefore, the investigation and development of the advanced SRLS has always been a major international hotspot. At the same time, there are more and more researcher are actively devoted to construct the new generation of light source in China. For example, the Hefei Advanced Light Facility (HALF) in University of Science and Technology of China (USTC), etc. For HALF, in order to provide machine researchers and users with an intuitive reflection of the quality of the light source, it is necessary to develop a synchrotron light spot measurement system which is employed for real-time and non-destructive monitoring the synchrotron light spot size. According to the pre-designed parameters of HALF, which corresponding to the characteristic wavelength is 0.5 nm. Obviously, the general optical material cannot be satisfied the imaging requirements in this wavelength. Furthermore, the transverse profile of the synchrotron light spot of HALF is need to be less than 10 μm, of which puts forward higher resolution requirement for the synchrotron light imaging measurement system. In view of the above-mentioned characteristics, in this paper, we concentrate on improving a monitor based on Fresnel Zone Plate (FZP) for measuring the synchrotron light spot size. In terms of the numerical simulation and theoretical analysis of the diffraction of the light source, it is shown that the simulated results are in good agreement with the pre-designed values.
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In order to study the temperature distribution characteristics of near-space hypersonic vehicles, the numerical calculation method was adopted to simulate and analyze the aerodynamic heating effect of hypersonic vehicles in this paper. The simulation process consisted of model establishment, mesh division, and CFD numerical calculation. Based on the simulation results, the temperature distribution characteristics of hypersonic vehicles and the influence of flight speed on the body temperature were analyzed. The results show that hypersonic flight will increase the body temperature significantly. The temperature at the stagnation point of the warhead can reach up to 2185K, and the temperature in other areas along the axis of the projectile gradually decreases. As the flight speed increases, the temperature of the vehicle body rises rapidly. When the flight speed is at 6.58Ma, 8Ma, 9Ma, and 10Ma, the temperature at the stagnation point of the missile body can reach 2185K, 3172K, 3792K and 4772K respectively
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Image information for single polarization parameters is weak, low contrast and the common visible light intensity image detail fuzzy problems, in order to further improve the target detection of polarization imaging detection system identification capability, put forward a kind of based on the sampling of shear wave transformation under visible light image fusion algorithms, intensity and polarization parameters can effectively improve the identification of targets in complex background. Polarization degree of the image and visible light intensity image using the sampling shear wave transformation under the decomposed high frequency subband and low-frequency subband, then low frequency subband image fusion rules design based on region distance energy weighted algorithm, and the high frequency subband image fusion rule is designed to combine guide take large filtering area of energy, will eventually high low frequency subband image by the NSST finally fused image is obtained by inverse transformation refactoring. By comparing the fusion results of this algorithm with those of other methods that adopt the same decomposition transformation method but choose different fusion rules, the experiment proves that this algorithm not only has the best visual effect, but also has the advantage in the objective evaluation index value.
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Anomaly detection with visual information by distributed deep learning is proposed in the paper. First, visual anomalies are defined in a special application domain, which are very important and critical for safe operation. Secondly, deep convolutional neural network is chosen as detector for visual anomalies. Thirdly, detection results from different visual sources are fused to get higher accuracies and lower false alarm rate. Experimental results demonstrate that the visual anomaly detection framework proposed can achieve high performance and provide satisfactory security assurance.
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In this paper, a TV component of 16 times visible light continuous zoom lens is presented based on 1280×1024@2.7 micron COMS device. The system adopts 4 groups of 12 lenses to achieve continuous zoom, the former fixed group consists of 1 set of adhesive lenses and 1 single lens, the zoom group use 2 single lenses and 1 set of adhesive lenses, the compensating group use 3 single lenses and 1 set of adhesive lenses, and the latter fixed group consists of 2 sets of adhesive lenses and 1 single lens. After selecting three focal length positions for calculation and simulation, when the focal length are 5mm, 40mm and 80mm, the MTF of each field of view is above 0.3 at 120lp/mm, the total length of the system is less than 200mm, the field Angle is 1.6°×24.1°, F# is 4, and the focal length can be up to 5mm-80mm. The root-mean-square value of the dispersion circle size of each focal length position of the 16-fold visible light continuous zoom TV lens is less than the size of one pixel, so the image quality of each focal length position of the system is better. When the system is in the short focus position, the variable doubling group and the compensation group are at two ends, and the distance between them is the largest. When the system changes from short focus to long focus, the variablesize group and the compensation group approach to the middle, and the distance between them becomes smaller. In the process of system zoom, the image quality is clear, the CAM curve is smooth and suitable for processing. Continuous zoom TV lens all adopt spherical mirror with the characteristic of manufacturing easily, and the glass materials of the system are all taken from Chengdu bright glass library that the materials are easy to obtain. The zoom curve of the continuous zoom lens is smooth and the image is clarity. The distortion of the full view field is less than 3%, which meets the system requirements of the TV lens components.
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A homemade temperature controller, which features with robust and inexpensive, is designed for actively adjust and stabilize the operating temperature of the tunable semiconductor diode laser. The accuracy of this temperature controller is +/- 0.05K, which corresponds to 0.035 cm-1 in wavenumber for our selected laser diode with a center wavenumber of 6045.949 cm-1. This temperature controller uses the STM32H743 (an ARM processor) as the control core, and introduces a capacitive touch screen to realize the visualization of experimental data and the intuitive of human-computer interaction. Through the simulation using software, the performance of conventional PID algorithm and adaptive fuzzy PID algorithm are compared and analyzed. Based on this, the fuzzy PID control strategy is determined and implemented through programming. In order to improve the efficiency and the stability of the ARM processor, the temperature control process is divided into several threads such as temperature acquisition, control quantity calculation, PWM output, temperature data/curve display, and SD card storage. The RTX5 operating system is ported to manage the cooperative operation of the above tasks and the communications between them. Using wavelength modulation spectroscopy, measurements of methane concentration are carried out in a laboratory controlled environment (P ∼ 1 atm, T ∼ 296 K) to validate the proposed temperature controller. In a stainless cell, the experiments are carried out using five samples with their concentrations ranging from 1000ppm to 2%, and a 5ppm detection limit is determined by nonlinear regression analysis, with a regression coefficient as high as 0.9979.
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Microchannel plate (MCP) is two dimensional arrays of microscopic channel electron multipliers. In this study, oxide thin films such as zinc oxide doped with aluminum oxide (AZO) as conductive layer and aluminum oxide (Al2O3) as secondary electron emission (SEE) layer were prepared in the pores of MCP via thermal atomic layer deposition (ALD). The bulk resistance of MCP in the suitable range (about 40~100 MΩ) was obtained by adjusting the percentage of zinc oxide (ZnO) cycles and the nano-oxide thin film thickness. As the tested voltage increased a behavior of negative temperature coefficient of the film was observed. After 5 days of continuous loading with 800 V bias, the resistance nearly doubled and stabilized. For the conduction mechanisms, the I-V curve obeys the ohmic law at low voltage region and the trap-controlled space-charge-limited conduction mechanisms as the applied voltage continue to increase. High gain performance (24000 @ 800 V) can be obtained by depositing only aluminum oxide film on traditional reduced lead glass microchannel plate. Meanwhile after the deposition of aluminum oxide film, the dark current density of the microchannel plate would increase to 1.8 picoampere in 15 minutes at DC 1000 V. Because of blocking effect the dark current density will drop to 0.03 picoampere in 50 minutes by depositing zinc oxide film with thickness of 4 nm before the SEE layer, and the resistance of MCP will reduce when the thickness of zinc oxide exceeds 4 nm.
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For traditional camera calibration methods, the calibration accuracy of camera parameters is highly dependent on the feature extraction of the control points of the calibration target. However, due to problems such as perspective and lens distortion, the commonly used checkerboards, circular dots, and other calibration patterns will inevitably undergo large deformation, resulting in a serious impact on the accuracy of the extraction of control points. To solve this problem, a camera calibration method based on active phase calibration targets is proposed. The method uses the MI Pad that can automatically display the structured light patterns as the calibration target. Compared with the method of using a checkerboard calibration target, this method does not require pattern detection and avoids the process of manual marking. Also, based on the phase information of the structured light gratings, a large number of dense, high-precision control point coordinates can be obtained even in areas where the image edge distortion is severe. Not only is it highly automated, but it is also suitable for defocused cameras. Experimental results show that the reprojection error of our method is only onetenth of the comparison method, and it has better robustness and accuracy.
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Convolution neural network (CNN) has been know as a state-of-the-art technique for hyperspectral image (HSI) classification. However, the basic CNN architecture still has obstacles to deal with the intraclass diversity caused by spatial variability of spectral signature, especially in the case of highly limited training samples. Furthermore, they also have challenges to exploit the relationships between different features of the same object. In this paper, we propose a new network architecture based on matrix capsule network (MatCapNet) to alleviate these problems. To extract spectral-spatial features, the proposed network takes the 3-D neighboring blocks as input data. Specifically, the network consists of two conventional convolution layers, a primary matrix capsule layer, and a convolution matrix capsule layer. The proposed network uses spread loss to maximize the gap of activation values between the target class and other wrong classes. To learn more relevant instantiation parameters of the input data, a decoder network is used to reconstruct the input center spectral signature. Finally, the reconstruction loss and the spread loss are added at a certain ratio to optimize network parameters. Besides, in order to solve the problem of unbalanced sample sizes, the sample weight coefficient is utilized. The proposed approaches are carried out on two well-known HSI data sets. Compared with other state-of-the-art methods, the experiment results exhibit that the proposed network could provide a competitive advantage in terms of classification accuracy.
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As part of investigating the human perception of polarized light, Haidinger’s brushes (HB) is well-known optical phenomena. Although differences in the human polarization perception were well known there was a limited quantifying to them. This paper presents a 3D Stokes model of the human polarized light perception, views the human perception of polarized light as a multivariable applied optics problem to simulation and explored the optical phenomena of Haidinger’s brushes. The images comparison verifies that the simulation patterns and detected images are consistent which proves the model is appropriate for simulating polarization perception of the human eye. Then this paper explored the optical limitations of perception and macula density. The combination of the 3D Stokes model and experimental verification opens up new possibilities to become an early diagnostic method for eye polarization sensitivity and macular degeneration. The objective is to give purpose and new mathematics understanding to the biomedical optical phenomenon.
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The unsharp masking algorithm is an effective method for image spatial domain enhancement. The improved unsharp masking algorithm can achieve the sharpening effect of edge enhancement while suppressing noise. However, it is difficult to implement in real-time image processing systems due to the need to perform multiple spatial domain filtering and a large amount of calculation. In this paper, an improved unsharp masking image enhancement algorithm is implemented on FPGA. Compared with the software implementation, time optimization has been carried out to meet the requirements of real-time processing of video streams, and it can achieve edge enhancement while suppressing noise to meet the performance needs of real-time video processing.
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The spatial resolution of hyperspectral data is low, so there are a large number of mixed pixels, which is also one of the main reasons that reduce the accuracy of hyperspectral image target classification. Hyperspectral unmixing is an important subject in the field of remote sensing. Hyperspectral unmixing generally consists of three steps: reduction, endmember extraction and inversion. As one of the key steps of hyperspectral unmixing, efficient and rapid endmember extraction is an important object in hyperspectral remote sensing. In this paper, the endmember extraction of hyperspectral data is implemented based on PCA and a new SGA algorithm, which solves the dimension limitation of traditional SGA algorithm and the new SGA algorithm without data redundancy caused by data dimensionality reduction.
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The camera control system is the most important part of the space remote sensing camera. Due to the products in the camera of the Marine Satellite or the Meteorological Satellite are easily disturbed by the space environment, it is necessary to develop a high-reliability camera control technology to guarantee the camera reliable and long-life operation in orbit. Firstly, in this paper, a dynamic reconfiguration technology of a serial bus based on multi-node and extensible ways is carried out, and a fault detection and automatic recovery technology based on error detection and correction of hamming code and the periodic automatic refresh technology are applied. Meanwhile, the camera control system not only apply the single event immune memory to storage original program safely, but also carry out on-orbit maintenance technology which include parameter and program on-line reloading for the facilities in the whole camera, including control system itself. Secondly, In order to ensure the safety of infrared detection component, the control technology of early over-temperature warning and self-protection is also applied. Ultimately, The autonomous and interactive control technology of the multi-process imaging is developed for the multichannel camera, it can facilitate user to complete the imaging process to relay on ‘shortcuts’. Within conclusion, in this paper, The camera control technology realized can not only effectively guarantee the camera to cope with the harsh space environment, but also solve the convenience of users of the complex camera system, and it provides a technical guide for future development of space remote sensing camera control system.
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Graphene-based photodetector with ultra-high responsivity is an important research field of low dimensional optoelectronics applications. A number of hybrid graphene/quantum dots photodetectors with high responsivity have been developed. In this paper, the in-situ oxidation of the copper covered by monolayer graphene was studied under the oxygen-rich condition. It is found that the oxidation process first occurs at the grain boundary of graphene and the oxide is Cu2O. The intensity ratio of 2D band and G band of graphene is ~3, and the defect D peak is absent, which indicates that the quality of graphene is not damaged during the oxidation process. The hybrid transfer-free graphene/Cu2O photodetector is fabricated by in-situ copper oxidation. Under 450 nm laser illumination, the responsivity of the photodetector is 3.8×106 A/W at 0.2 V. The gain is up to 1.1×107 , which is due to the modulation of Fermi level of graphene by Cu2O quantum dots. The photodetector exhibits the specific detectivity of 3.6×1011 Jones. This work opens a feasible pathway to develop transfer-free graphene/semiconductor photodetector with high responsivity.
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We theoretically develop a method for maintaining the self-compensated state of a K-Rb21Ne comagnetometer, which is one of the core problems in optimizing the detection sensitivity of the comagnetometer to fundamental interactions and inertial rotation. The result of Rb21Ne coupling dynamics under transverse cosinusoidal magnetic field modulation can present a dispersive response with respect to the varying 21Ne nuclear magnetic field Bn, in which a monotonic interval can be used to monitor the drift of Bn. Furthermore, the result of Rb spin poparization evolution under the constraint of self-compensated-state maintenance exhibits a large enough time scale relative to Rb spin relaxation that it can be regarded as a quasi-static process, thus the adopted time-varying pump light intensity can be obtained using Rb equilibrium polarization. Accordingly, an implementation scheme is given. This method can not only compensate the drifting �", but also promote the system to return back to the original self-compensated state through manipulation of atomic polarization via time-varying pump light, which is useful in stabilizing the system performance.
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With the continuous development of astronomy theory and space exploration technology, searching for extrasolar planets has become one of the most active research topics in astronomy. In recent decades, countries around the world have invested a lot of ground and space projects in this search field and obtained abundant results. Firstly, this paper summarizes the mainstream exoplanet detection methods such as radial velocity, transit and direct imaging method with the outline of the principles and features. Then, several instruments for obtaining the spectrum of exoplanets are introduced, focusing on the optical system parameters of telescopes and spectrometers. Finally, according to the comprehensive discussion above, the future development trend of exploration missions and instrument design in this field is predicted, and it is recognized that these survey missions for detecting and characterizing exoplanets are of great significance for searching biological signals outside the solar system.
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In this paper, the photometric characteristics of passively marked corner-cube-reflector-class cooperative targets are studied. The imaging characteristics of corner cube reflector(CCR) are discussed theoretically, and the influencing factors such as surface accuracy, angle error and diffraction effect are analyzed. The reflection uniformity and diffraction characteristics of CCRs with different positions and different precision are simulated and verified. In addition, the influencing factors and control methods of CCR precision are proposed. To the photometric characteristics of cooperative targets, especially the influence of aperture size of cube-corner prism on comprehensive aberration, the transmission surface (bottom surface) on comprehensive aberration was concerned firstly, besides the three reflection surfaces. The conclusion was been drawn that the transmission surface and the three reflection surfaces had most effect on the parallel of emerging beams, and the minimum error was the minimum algebra sum of above four surfaces. It can provide theoretical support for on-orbit services such as companion flight, autonomous rendezvous and docking (RVD).
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In the process of surface reconstruction, the gradient data inevitably contains noise, which results in poor surface quality. Traditional denoising algorithms have slow processing speed and unsatisfied effects. To realize high precision surface reconstruction, a novel denoising method was presented based on improved curvature filter. The innovative method optimizes the projection operator to enhance the denoising capability of the algorithm. According to the numerical simulation and analysis, the simulation results show that the proposed algorithm can remove noise in the gradient data and contributes to higher accuracy of surface reconstruction.
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Tunable diode laser absorption spectroscopy (TDLAS) technique has been widely investigated for gas concentration measurement in both industry and laboratory. In order to detect different gases within the multi-gas mixture based on TDLAS, different types of schemes have been developed, such as wavelength division multiplexing, time division multiplexing and so on. However, there are many drawbacks of the above methods, and the sensitivity and accuracy of multi-gas detection have been greatly restricted, the effect of cross-talking interferences becomes a technical bottleneck for multi-gas detection. Therefore, a high accuracy synchronous detection technology for multi-gas detection using the least square fitting is reported. The wavenumber of 6380cm-1 has been selected to detect CO and CH4. Because the absorptivity of CH4 and CO is less than 0.1, the least square fitting method can be used to calculate the concentrations of CH4 and CO simultaneously. This novel method has been shown to improve the precision achieved in the detection of multi-gas by 18%, compared with the precision measured at another wavelength. The Allan variance results indicate that the optimal integration time has been improved from 50s to 100s, the minimum measurement precision of CH4 and CO is ~0.45% and ~0.46 10-6 respectively. Meanwhile, the detection cost and response time can be reduced obviously.
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This paper presents a mathematical model which can fit a parameter in an optimal position by measuring data. The model can synchronously correct the measurement error caused by the small rotation about X, Y and Z axes and the small deviation along X, Y and Z directions. The measurement results of the surface show that the model is reliable and effective, which provides loose conditions for placing mirrors and reliable measurement results for contact Coordinate Measuring Machine(CMM) off-axis surface contour measurement. The basic principle of the data analysis is also of high reference value for contour measurement of other non-contact free-form surfaces. The validity of the model is verified by mathematical simulation and practical engineering application, which is of great help to the measurement of high precision contact free-form surface.
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Compared with the image target detection system of single infrared band , the target detection system of double infrared band image fusion has higher performance. However, the target detection of dual band image fusion requires higher real-time and stability of data processing. Aiming at the characteristics of large amount of data and complex algorithm of dual band image fusion target detection system, a dual band infrared image target detection system based on DSP+FPGA architecture is designed. This system has the advantage that DSP is good at realizing complex image processing algorithms and FPGA has high speed parallel processing capacity. This design meets the system's requirements for real time and stability.
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Fiber optic imaging elements is a general term for optical fiber products including fiber optic plate (FOP), fiber optic inverter (FOI), and fiber optic taper (FOT), which is a light and image transmission array made of optical glass fibers that are drawn, regularly arranged, vacuum melted-pressed, secondary thermal processed and optically processed. They are mainly used in photomultiplier devices for low-light-level night vision and particle detection equipment. Its devices have been widely used in many fields such as low-light night vision, electronics, aerospace, nuclear diagnostics, high-speed photography, etc., especially in the field of military operations at night combat, guidance, early warning, and electro-optical countermeasures. With the continuous development of glass fiber material, preparation technology and performance requirements, the optical fiber imaging element has been significantly improved, and its application field has been continuously expanded. This paper reviews the materials, structures, principles, characteristics, preparation processes and detection technologies of optic fiber imaging elements. It mainly summarizes the development situation, latest technological progress, and several major devices in optical applications. And the bottlenecks in the preparation and detection of fiber-optic imaging elements at present are analyzed. Furthermore, the development trend and challenges of fiber-optic imaging elements evolving to larger size with smaller diameter of fiber, higher contrast, higher resolution, lower distortion, ultra-short and ultra-light are prospected.
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High-power special-shaped infrared radiation sources are usually used for detection systems such as compact photoacoustic spectrometers for gas detection. In this article, the light emitting characteristics of a rod-shaped infrared thermal radiation light source was obtained experimentally. Then, based on the luminous characteristics and the illuminance requirements on the target photoacoustic cell, combined with the basic principle of conservation of light energy during transmission, the shaping system for the special-shaped infrared radiation source for photoacoustic spectroscopy was designed and optimized, aiming to achieve efficient collection and utilization of light source beams.
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The analog signal output by the infrared detector is usually sampled as a 14-bit high-dynamic-range digital infrared image, which is not compatible with most 8-bit display systems and cannot be directly used for imaging display. Therefore, image compression quality is very important for image display .This paper studies and analyzes the mapping technology of the base layer, focusing on the traditional limited contrast histogram equalization method (CLAHE). Considering that the conventional CLAHE method is applied to infrared images, there will be a problem of excessive stretching of some uniform areas. a new algorithm for Contrasted Limited Adaptive Histogram Equalization based on uniform region test (M-CLAHE) is proposed. Based on the traditional CLAHE method, this method introduces a gradient operator to extract the contour boundary of the sub-region image, and quantifies the complexity of the image region to solve the above problems. The experimental results show that compared with the traditional CLAHE infrared image compression method, this method can more than double the visual indicators such as image contrast and average gradient compared with the traditional visualization method. This method has engineering portability, and it can be transplanted to the infrared movement to increase the image quality of most scenes by about twice.
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Space cryogenic infrared remote sensor has a wide range of applications, but there are only a few cases which function well in orbits, especially the domestic related research is still in the preliminary stage. Cryogenic lens is installed and adjusted at room temperature. In low temperature environment, the lens structure will produce thermal stress deformation, which will affect the surface shape and focal plane position of the lens, thus affecting the optical imaging quality. Therefore, the design of cryogenic lens must combine the three physical fields of light, machine and heat. This article is based on an infrared cryogenic lens, low temperature 210k working conditions, cryogenic lens finite element model (FEM) is established, using the simulation analysis software to calculate the lens at low temperature for the thermal deformation and thermal stress, the deformation of the mirror node data export for Zernike polynomial fitting, and translated into changes in surface shape and deformation after the modulation transfer function (MTF). After the installation and adjustment, the cryogenic lens was placed in a vacuum tank, and MTF was tested at room temperature and low temperature. The test results showed that the deviation is less than 0.5%, within the acceptable range, indicating that the cryogenic lens multi-field coupling simulation method used in this paper is reliable and has strong engineering significance.
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In order to obtain reflector supporting structure with high stiffness and thermal stability, a “2-2-1-1” kinematic supporting structure is designed for a 350mm mirror of space remote sensor. Firstly, the kinematic principle of the “2-2-1-1” supporting structure is studied, and the dynamic model of the “2-2-1-1” supporting structure is deduced, the relationship between the supporting stiffness of the mirror assembly and the parameters of the length, diameter and span of the ball-end supporting rod is given. According to the relationship between the supporting stiffness of the mirror assembly and the length and diameter of the supporting rod, a “2-2-1-1” supporting structure of the mirror assembly is designed. The mechanical simulation of the design results is carried out by means of finite element analysis, and then the test of the actual supporting structure is carried out. The experimental results show that the RMS value of the reflector supported by “2-2-1-1” supporting structure is better than λ/40(λ=632.8nm), The fundamental frequencies of the components in three directions are respectively 231Hz, 319Hz and 365Hz, it is close to the results of finite element analysis and theoretical calculation. The rationality of the designing of the “2-2-1-1” supporting structure of the reflector is proved, which meets the imaging requirements of the space remote sensor.
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The photoelectric tracking platform is often installed in various military and civilian equipment such as unmanned aerial vehicles, and has multiple high-precision detection and tracking equipment such as visible light and infrared thermal imaging cameras. In the detection process of various detection imaging systems, because the optical detection equipment is fixed on a carrier aircraft such as an unmanned aerial vehicle, the imaging system often rotates the detection image due to the rolling, pitch and yaw movement of itself and the carrier. In this regard, this article will analyze the principle of the image rotation problem caused by the photoelectric tracking platform in the detection and tracking of the target, and design an algorithm to eliminate the image rotation. First of all, this article clearly understands the purpose and indicators of rotation, carefully analyzes the reasons for the problem of image rotation, improves the definition of the relevant coordinate system and the relationship between them, and finally derives the value of the image rotation angle and performs the operation of eliminating the image rotation. And image post-processing operations. After testing, the designed algorithm can solve the problem of rotation of the image presented by the photoelectric tracking platform, and the processed image is easier to observe and capture manually or by related algorithms.
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Direct detection laser detection and ranging (LADAR) has been widely used in many specific applications such as precision guidance, machine vision, underwater images, landslides investigations, city modeling, and so forth. One of the most promising methods to design, develop, test and validate a LADAR system is hardware-in-the-loop (HWIL) simulation. LADAR target simulator generates return signals of the simulated targets and background according to the test requirements. One of the key technologies of the LADAR target simulator is target modeling. A target modeling method based on data matching and restoring is pdroposed in this paper, which can provide a feasible way for LADAR target simulator to acquire the information of the target. The coordinate transformation is used to transform the target coordinate data under two or more viewpoint coordinate system into the reference point coordinate system to obtain the whole information of the target. Then, the target coordinate data under the reference coordinate system is transformed into a given viewpoint coordinate system. Furthermore, the deley time and the pulse width are calculated arrcording to a return signal mathematical model. Finally, the effects of the incident angle and target distance on target data are analyzed.
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In order to clarify the mechanism on electron multiplication of MCP, it is necessary to study the secondary electron emission properties of inner wall surface. The secondary electron emission is not completely required by materials or devices, and sometimes it can bring bad effects such as noise. In addition to the secondary electron produced by electron colliding with the inner wall, there are additional secondary electrons produced by the ionized cation colliding with the inner wall, which is the key to control the noise of MCP. In this paper, the secondary electron emission produced by the ionized cation colliding with the inner wall of MCP was analyzed after the materials were acid and alkaline treated and hydrogen reduced at high temperature. Time of Flying (ToF) was used to detect secondary electron emission yield (SEEY) of lead silicate glass surface. By comparative analyses, the influence trend of surface treatment process on the secondary electron emission yield of glass surface was acquired. It is expected to provide data supports for parameters optimization of MCP manufacture and preparation of MCP with high signal to noise ratio (SNR).
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Three-dimensional measurement technology is a popular technology in recent years. The traditional binocular vision measurement system has a low image matching accuracy when there are few or many duplicate feature points on the surface of the object to be measured, which affects the work of three-dimensional reconstruction. In this paper, the combination of structured light three-dimensional measurement technology and binocular imaging technology reduces the difficulty of feature point search, increases the accuracy of image matching, and conducts experiments of three-dimensional measurement by building a verification system. The measurement results show that the technology is highly feasible.
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Scene classification shows pivotal role in remote sensing image researches. Since challenges of large similarity between classes, high diversity in each class and huge variations in background, spatial resolution, translation, etc., remote sensing image scene classification still urgently need development. In this paper, we propose a novel method named deep combinative feature learning (DCFL) to extract low-level texture and high-level semantic information from different network layers. First, feature encoder VGGNet-16 is fine-tuned for subsequent multi-scale feature extraction. And two shallow convolutional (Conv) layers are selected for convolutional feature summing maps (CFSM), from which we extract uniform LBP with rotation invariance to excavate detailed texture. Deep semantic features from fully-connected (FC) layer concatenated with shallow detailed features constitute deep combinative features, which are thrown into support vector machine (SVM) classifier for final classification. Extensive experiments are carried out and results prove the comparable advantages and effectiveness of the proposed DCFL contrasting with different state-of-art methods.
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In order to realize the in situ detection of plankton and organic particles in the deep sea, we proposed a dynamic holographic microscopic imaging method based on the principle of parallel phase-shifting. We analyzed the implementation mechanism of the parallel phase-shifting holographic imaging. We designed the implementation scheme of the deep sea in situ detection system, carrying out experimental research on underwater dynamic holography. High resolution images were acquired and reconstructed using the resolution target and several biological samples. Experimental results show that local details of underwater samples can be clearly distinguished. We preliminarily verified the feasibility of the parallel phaseshifting holographic method to achieve underwater high-resolution in situ detection.
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A micro filter array for portable spectrometer was fabricated. Based on the Fabry Perot periodic multilayer dielectric film, a narrow band filter with a central wavelength of 589 nm was designed and fabricated. The bandwidth is about 3.2 nm, the transmittance is more than 60%, and the cutoff is OD3 . The mask is designed based on the selected mobile camera, and the pixel of narrow-band filter is realized by using semiconductor technology such as step lithography and reactive ion etching on the optical film. The optical fiber spectrometer and atomic force microscope (AFM) were used to measure the micro area of the filter array. The results show that the adjustment of the Fabry Perot cavity is accurate and effective. A 4 × 4 filter periodic structure is realized. The filter array with unit size of 3 μm × 3 μm and size of 1280 × 720 is fabricated.
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The surfaces of many ancient relics as murals and oil paintings we can see today appear three-dimensional features to some extent, which poses a challenging problem for line scan imaging to capture the features on these objects. With this goal in mind, a line scan camera-based shape from focus (SFF) method is proposed for obtaining three-dimensional information in planar cultural heritages with three-dimensional features. First, line scan imaging is employed to obtain high-resolution image sequence of objects. Next, spatial frequency (SF) is used to evaluate the focus quality of a specific local area of each image in the image sequence to find out the position of the best focused image. Through analyzing the relationship between this position and the relative movement distance of the camera-object, the three-dimensional shape of the object can be roughly estimated. Then, a fitting method was utilized to refine the local details of the three- dimensional shape of the object. An experimental setup is established to restore the three-dimensional shape of the test sample using the proposed SFF algorithm. Root mean square error (RMSE) was used as the evaluation criteria, and the result demonstrated the effectiveness of the proposed method, which shows the high precision three-dimensional shape recovery and also gains the benefits of high resolution and uniform point cloud distribution. Finally, the factors affecting the results of 3D reconstruction was discussed in detail, which may guide the selection of parameters in practice.
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With the development of the fourier ptychography in microscopy imaging, more and more researchers consider applying fourier ptychography in long-distance imaging. However being different from microscopic imaging, long distance fourier ptychographic imaging will face more challenges, one of which is the source image quality. In this manuscript, the influence of the source image quality on camera scanning FP imaging will be investigated and simulated. In the first part, the calibration aims to solve the influence of unenenly illumination. After that, a poisson-gaussian mixed noise model based denoising is uesd and could effectively suppresses the noise through parameter estimation. Finally, Phase correalation regisitrtion has to be used to correct the mismatch between adjacent images caused by camera scanning mode. The simulation results demonstrate the effectiveness of the preprocessing methods and could make FP more robust.The signal to noise ratio could reach to 40.5dB while obtained 5×improvement in resolution.
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The SPGD (stochastic parallel gradient descent) is a control algorithm widely used in WFSless (wavefront sensorless) AO (adaptive optics) system.The gain is commonly set to a fixed value in the traditional SPGD algorithm.With the increase of the number of DM (deformable mirror) actuators, the optimization space of the algorithm becomes larger, which can easily lead to the slow convergence speed of the algorithm and the rise of the probability of falling into the local optima. Adam(Adaptive Moment Estimation) optimizer is an optimized stochastic gradient descent algorithm commonly used in deep learning with the advantage of achieving adaptive gain. Wavefront aberrations under different turbulence strength as correction objects, WFSless AO systems are built with 32, 61, 97 and 127 elements DM as wavefront corrector respectively. Results show that the optimized algorithm can converge faster than basic SPGD and the probability of falling into local optima decreases. The system’s convergence speed is increased by about 30%. The probability of falling into local optima is decreased by 29.8% , 30.3% , 32.6% and 35.9% respectively under D/r0=5 and by 28.8% , 30.5% , 33.3% and 34.5% respectively under D/r0=15. The advantages of the optimized algorithm are more obvious as the number of DM actuators increases. Above results provide a theoretical basis for the practical application of the SPGD algorithm based on Adam optimization.
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The full-stokes expressions of polarizer direction (PD) and Quarter-wave-plate direction (QWD) was deduced at any angle. The experiments of full-stokes polarization imaging detection were carried out with artificial target under the natural background, and the degree of polarization (DOP) images contrast (DOPIC) with the target and the background were analyzed. This paper mainly research that different angle combination influence between polarizer and quarter-wave plate for the DOPIC of full-stokes polarization imaging detection. It was found that the DOPIC of target and background was obviously higher than intensity image, but also (1)The detection results were related to the angle of PD when changing the angle of QWD only; (2) If three groups of direction angles (α1β1α2β2α3β3) were same and the fourth group of angles (α4β4) was set interval angle 45°between PD and QWD angle, the average detection result of full-stokes polarization imaging was higher than other PD and QWD.
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High-precision phase retrieval is the key step of the fringe projection profilometry, while the traditional multifrequency phase-shifting method is easy to suffer from noise, which leads to a decrease in measurement accuracy. Based on the local similarity of phases, a new phase retrieval method is proposed in order to improve the accuracy of the phaseshifting and reduce the phase order error. The input images are down-sampled to obtain an image pyramid, and the phase of the high-resolution images is recovered from the low-resolution fringe patterns. Simulation and experimental results show that the proposed method can effectively reduce the phase error in the multi-frequency phase-shifting method and has good robustness and high accuracy
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Position sensitive micro-channel plate (MCP ) is a kind of high sensitivity detector with low noise, Combined with advanced time-correlated single photon imaging technique (TCSPC) could make a moderate aperture system be sensitive to only one single arriving photon. In this paper, a theoretical model of photon counting imaging with Position sensitive MCP was established and the factor of laser power affecting the detect possibility was analyzed. the three-dimensional point clouds data are generated using Monte Carlo simulation and the typical space target could be reconstructed three-dimensionally. Through the all-chain simulation model the comprehensive performance of the MCP based active three-dimensional imaging system could be analyzed from viewpoint of detection probability, ranging accuracy and signal to noise ratio etc. The application of the position sensitive MCP based active three-dimensional imaging system for long range space objects is verified in simulation condition. The results shows that only a single pulse energy of tens of mico-Joule is needed for the positive sensitive MCP based active three-dimensional imaging system to image the target at the hundreds of kilometers. the counting rate could reach 106 counts/s. And the ranging accuracy of this active three-dimensional imaging system for the objects at 300 kilometers could reach 0.1228meters by simulating with 50 mico-Joule single pulse power.
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Linear array CCD device has the characteristics of large pixel size, high precision, good resolution, wide spectral response, small volume and so on. It is widely used in image sensing, spectral analysis and non-contact measurement fields such as size, displacement and vibration measurement.In this paper, the general structure and timing control characteristics of linear CCD are analyzed, and the typical CCD chip Toshiba TCD1304 is studied. The CCD is a linear image sensor with high sensitivity and low dark current. The pixel size is 8um × 200um, 3648 pixels in total, and the wavelength response range is 300nm ~ 1100nm.Secondly, the 32-bit flash microcontroller STM32F103 based on the core of arm cortex m3 processor is used as the main control chip, and a set of CCD data acquisition system with flexible integration time adjustment function is designed by combining with the 12 bit high speed A/D converter, 2.8-inch TFT LCD and upper computer software.Finally, the whole system is tested, The test results of the system verify the feasibility of the driving timing design of linear array CCD. The driving timing signal is connected to the CCD device. Under the condition of different light incidence, the CCD works normally and outputs the corresponding video signal driven by the driving signal. The technical indexes of the system can meet the requirements of the system design, and provide a technical reference for similar CCD data acquisition system and lay the foundation for further image recognition and processing.
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Photoelectric stabilization platform is the eye of the aircraft.At present, the two-axis two-gimbal photoelectric platform is widely used in military, commercial and scientific applications due to simple mechanism, low cost and small size. However, the stability performance of the outer gimbal will be reduced at large pitching angle. In this paper the reason was analyzed , the three-axis gyro system was proposed to stabilize the outer gimbal and the mechanism of this method was explained ,then the control system was designed, the outputs of speed loop were compared between the three-axis gyro and the traditional two-axis gyro system, The results showed three-axis gyro system has higher stabilization accuracy than two-axis gyro system.
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The imaging principle and radiometric calibration principle of long linear array TDICCD cameras are analyzed. Calibration work is carried out using the integrating sphere and collimator while developing a more comprehensive radiometric calibration scheme. The study used quantitative analysis to gain insights into the linear responsivity of input radiance, integral time, integral series, and gain to the camera. The least-square method is chosen to fit the experimental data to obtain the corresponding linear regression equation. The correlation coefficient is above 0.99. The results show that the radiation response of TDICCD camera is excellent when other dimming parameters remain constant; the gray value of the image changes linearly with the input radiance value. Fixing the input radiance, the gray value of the image varies linearly with the gain, integral series, or integral time. The results of this research support the study of the automatic dimming of TDICCD camera.
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This paper presents a retractable infrared laser characteristic fusion target design configuration. In this configuration, the folding mechanism provides the retraction and playback function to drive the simulated target to extend in the length direction, and the extension length can be adjusted according to the background and scene requirements. The simulated target has both infrared and laser characteristics, which can provide a fixed laser reflectivity and cross-sectional area of the characteristic body target. At the same time, the characteristic body target has infrared radiation characteristics of 3~5um and 8~12um bands, respectively, for detection and recognition of high-sensitivity infrared detector, and for the verification of laser range finder's ranging ability.
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We develop differential column image motion (DCIM) lidar for monitoring atmosphere refractive structure constant Cn2 profile. It is important to use an appropriate regularization method for DCIM lidar since the ill-posedness of the integral equation between the Cn2 profile and the measured r0 profile. In this paper, three typical regularization methods are studied to retrieve the Cn2 profiles from r0 profiles.The experiments illustrate that the Tikhonov method and truncated SVD method perform good performance, while damped SVD shows poorer inversion accuracy.
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The recognition and tracking ability[1-4] of detection equipment in the process of relative movement with the observed target is always one of the key research contents and important research directions of photoelectric detection technology. Aiming at the relative angular position between the target and the detection equipment, this paper designs a kind of relative motion simulation equipment which can independently control the bearing two axes. The motion range of the platform carrying the measured equipment can reach ± 120° , the positioning accuracy is better than 10 ″ , the maximum angular velocity and angular acceleration can reach 60°/ s and 40°/s2 respectively. The target motion range can reach ± 150° , the positioning accuracy is better than 10 ″ , and the maximum angular velocity and angle acceleration can reach 60°/s and 60°/s2 respectively.
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Based on the contrast thresholdμ function and modulation transfer function theory, the contrast threshold function and the minimum resolvable temperature difference of a typical airborne medium wave imaging system are numerically calculated. Taking typical coastal and inland climate environments as examples, combined with historical meteorological sounding data and meteorological observation data, the atmospheric transmittance, atmospheric radiation and target background scattered radiation brightness in the 3μm-5μm band under different environmental conditions were calculated The relationship between the apparent temperature difference of typical target background and the environmental factors such as visibility, aerosol type, illumination and meteorological conditions. The detection and recognition distance of the mid-wave infrared imaging system under different weather conditions was simulated, and the influence of environmental factors such as illumination and weather conditions on the detection performance of the airborne infrared imaging system was analyzed.
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In this paper a novel way to correct chromatic aberration and remove the color fringe for variable aperture optical system considering the physical causes is proposed. From the perspective of the correlation between chromatic aberration and aperture, we explain why image fusion with different aperture parameters can effectively remove color fringing. Then we propose a specific color fringing detection and image fusion process. First, we detect the overexposed area of the large aperture image, perform grayscale grading on its neighborhood, extract the edges, and expand to obtain the candidate color fringing region. Then the two images are transformed to YCbCr color space to extract the purple fringe area by comparing the color information of the candidate color fringe area. Finally, we use the Cb and Cr channels of the small aperture image to correct the corresponding channels in the color fringing area and retain the brightness of the original image. Through image fusion, we can remove the color fringing caused by axial chromatic aberration and sensor crosstalk, and the residual lateral chromatic aberration can be corrected by simple image warp. Compared with the traditional blind restoration of color fringe regions, our method uses the hue information of small aperture image as a reference and no artifact is introduced. Experimental results show that both the subjective visual effects and objective evaluation have been significantly improved.
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Star trackers measures the attitude of spacecraft by matching the centroid coordinates extracted from star image with the star database. However, dim stars, fake stars, noise and irregularly shaped star spots interfere with star extraction. In order to solve these problems, a new star centroid extraction algorithm based on adjacent branch decision marker is proposed in this paper. The first step is to use labels to encode the pixel of star points which are processed by double threshold segmentation; the second step is to judge the validity of the labels by using the adjacent branch decision marker and output them. Compared with the traditional connected area segmentation method, the algorithm can solve the influence of irregular shape star points on Star Information segmentation, and two kinds of threshold segmentation method can effectively eliminate the influence of background on star point extraction. The experimental results show that the algorithm has high precision and speed of star centroid extraction, and the resource cost is low. Compared with other methods, this method has stronger anti background interference ability and better robustness.
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In the process of the license plate photo recognition process, light and external environment are important factors for the clarity of the photo result. We first add a 400nm filter in front of the camera to carry out the experiment, take pictures with ultraviolet rays light and without ultraviolet rays light source irradiation, then add a 390nm filter in front of the camera to perform the same experiment for comparison. Perform comparative analysis and image processing on the experimental shooting results. First, it can be seen from the comparison of the shooting results that the clarity and recognition of the image under the action of the 400nm filter are significantly improved compared with that of the 390nm filter. Second, the image processing is used to analyze the results, which can effectively identify the license plate information. Finally, the license plate is irradiated with micro-nano filter and ultraviolet light source instead of the monitor fill light, so the strong light stimulation to the driver's eyes is avoided, thereby alleviating the short-term ‘light blindness’ phenomenon of the human eyes and reducing the hidden safety hazards when driving.
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Monocular visual camera measurement can obtain the accurate pose information of 3D objects from a single image, but the pose ambiguity problem will inevitably occur when using the same method to process 2D object images. To solve this problem, this paper proposes a binocular vision method, using two pre-calibrated cameras to shoot the coplanar target from different angles at the same time, and matching the corresponding image points of the coding markers on the coplanar target. After obtaining the 3D coordinates of the coded points, the pose information of the target is calculated by Bundle Adjustment method. The experiment results show that this method can effectively solve the problem of pose ambiguity in monocular vision. Compared with other methods, the pose measurement method proposed is faster and more robust with larger coding capacity , more accurate positioning, and better comprehensive performance.
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In this paper, the properties of transition metal oxide borate glass were studied. It was found that introducing a small amount of CaO and BaO into borate glass could improve the crystal resistance and chemical stability of the glass. The introduction of V2O5, ZnO, Al2O3, SiO2 and other components is beneficial to widen the glass forming range and improve the anti-crystal performance of glass. The introduction of MgO and ZrO2 can improve the acid resistance of glass. The mixed and co-mixing of Fe2O3, MnO2, V2O5 and other transition metal oxides can increase the total doping amount by more than 30%. At the same time, the introduction of multiple components can effectively prevent glass crystallization and improve the anti-crystallization ability. The developed transition metal oxide borate glass has a resistivity up to 5×1010•cm, good chemical stability and anti-crystallization ability, and is suitable for the production of large crucible melting, realizing the preparation of 100×100×1mm glass samples.
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The grating projection phase measurement method can obtain 3D surface profile of an object with a grating projection device and two cameras, which is widely used in reverse engineering, industrial detection, cultural relic digitization and human body measurement due to its simple measuring principle, convenient operation, fast and high-precision data acquisition of 3D point clouds. As one of its calibration processes, binocular vision calibration plays a key role in getting high-precision measurement results, and the accuracy of extracting feature points on the calibration target directly affects the binocular calibration accuracy. In this paper, a sub-pixel corner extraction method based on Shi-Tomasi algorithm was proposed to extract corner points of checkerboard. An experiment is done to compare the extraction effect of the proposed algorithm with the traditional Harris method. The experimental results show that the proposed algorithm can locate the position of corner points more effectively with higher extraction accuracy. The mean square value of the reprojection error is about 0.008 pixels, the rate of corner extraction is 74.6%, and the processing time is shorter, about 0.78 seconds. Therefore, the method used in this paper is reliable and feasible for the feature point extraction in 3D reconstruction of measured objects.
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Due to the harsh working environment and lacking of external information, after a long period of work, the performance of the local reference inertial device will deteriorate, which will cause the navigation information to fail to meet the requirements of user equipment. In this paper, a local reference dynamic calibration method based on hull deformation compensation is proposed. Firstly, eliminate the coordinate system misalignment between the main inertial navigation system (MINS) and the local reference. Furthermore, a Kalman filter is designed to calibrate the bias errors of the local reference laser gyro and accelerometer based on the high-precision navigation information of the MINS. The simulation results show that after accurate hull deformation compensation, the local reference laser gyro bias error estimation accuracy is better than 0.002°/h , accelerometer bias error estimation accuracy is better than 1μg ,which provides an effective solution for local reference marine dynamic calibration
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Dynamic range compression and contrast enhancement are the key steps of infrared imaging. Reasonable dynamic range compression should not destroy the gray distribution relationship between adjacent pixels. Most of the existing dynamic range compression algorithms do not take maintaining the gray distribution relationship between adjacent pixels as the basic principle of algorithm design. After dynamic range compression, the gray distribution of adjacent pixels can not be consistent with that before compression, which may lead to gradient reversal, edge halo, and some algorithms have the problem that the whole image is smooth, but the details are lost seriously. An infrared image dynamic range compression algorithm with the characteristics of neighborhood gra y distribution preservation is proposed based on the principle of keeping the gray distribution of neighboring pixels. The algorithm is based on the commonly used segmented linear transformation algorithm. In order to minimize the loss of image details in dynamic range compression, local factors are introduced into the global transformation to reduce the loss of overall image details. The specific method is to add the description operator of gray distribution of adjacent pixels in the calculation of transformation parameters. The algorithm effectively improves the image details, and can obtain good display effect for the original infrared image with high dynamic range. The experimental results show that the algorithm is better than the segmented linear transformation algorithm in displaying the original infrared image with high dynamic range.
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For bistatic RCS (Radar Cross Section, RCS) measurements, when the target is away from the base line its range resolution and Doppler resolution of radar are close to those of monostatic radar, when the target is in the vicinity of baseline, the shape of bistatic radar ambiguity function is stretched and target resolution is significantly reduced, and the target is at baseline, the resolution will be infinite, and there is no way to distinguish tested target. This paper tries to make an estimate and optimize test condition to ensure the best position resolution take into account transmitting antenna position, receive antenna position, target position and transmission signal bandwidth by simulated annealing algorithm before testing. Meanwhile, two waveform’ optimized result were compared, and the measurement model was found to fit the best parameter to the current bistatic measurement environment to ensure the bistatic RCS measurement accurate.
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The CMM is a good way to measure the shape error of the workpiece after initial machining. IIn order to study the error of measuring workpiece with CMM, this paper introduces the three-dimensional contour measurement theories and methods of measuring optical free-form surface, analyzes the three coordinates measuring instrument error of measuring free-form surface, and by using the basic principle of the least squares method, can set up the free surface correction error data processing model, then particle swarm optimization (pso) with inertial weights are used, solving the error parameters is realized. Matlab programming is used to simulate the free-form surface data. The computer simulation verifies the feasibility of the data processing model and processing software.
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Hull deformation is the fundamental reason that restricts the establishment of a unified attitude reference for large ships. The causes and types of hull deformation are introduced. Hull deformation measurement includes the yawing angle, the pitching angle, and the rolling angle. The rolling angle is more difficult to measure than the pitching angle and the yawing angle. Optical measurement methods and stress measurement methods are introduced to measure the rolling angle. Optical measurement methods mainly include the grating method, camera measurement method, dual light sources, and dual CCD method, polarized light energy measurement method, double-frequency polarized method, large steel reference method, etc. Stress measurement methods mainly include the hydraulic stress method and the strain sensor measurement method. The inertial matching measurement method which can measure the pitching angle, yawing angle, and rolling angle simultaneously is introduced. The urgent problems faced by measuring hull deformation and their developments are discussed.
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Due to the advantages of good monochromatic, high brightness and strong directivity, laser is widely used in ranging and target recognition.However,the laser have a weakness,that is easy to be affected by the natural environment,especially the weather of the fog,which has become a bottleneck restricting the development of laser detection technology.In order to solve the problem that laser detection is affected by fog scattering during laser transmission in the atmosphere, a new method of anti-fog scattering laser detection is proposed by adding the wave-front measurement technology.Firstly, the interaction mechanism of laser and fog is introduced . Secondly, the phase fluctuation difference between the hard target and the fog echo is analyzed. Due to the scattering effect, the echo phase of fog will be seriously distorted. According to the working principle of shack Hartmann detector, the wavefront phase of incident wavefront can be recovered. Finally, a laser fuze test device for wavefront measurement is constructed to test the backscattering phase of hard target and fog.The experimental results show that the phase fluctuation of hard target is slow, and the phase fluctuation of fog is more severe. By comparing the wavefront parameters of hard target and fog, the hard target and fog can be effectively distinguished, which provides a new idea for target recognition and anti-jamming of laser detection.
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In order to realize detection and precise positioning of small-caliber visual optical system targets, according to the "cat eye effect" of photoelectric system, the research based on laser active reconnaissance precision detection technology was carried out. The effects of parameters such as laser emission power, receiving aperture and detection distance on the detection performance are simulated. The experiment has verified the ability to detect small-caliber targets under certain laser power. The experimental results show that the 10mm aperture visual optical system at 700m can be accurately detected under the condition of laser peak power of 1000W and laser divergence angle of 1.5mrad.
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Short arc xenon lamp is a point light source with high brightness, good light color and short start-up time. Short arc xenon lamp is widely used in industrial production, national defense and scientific research. It can be used as standard white light source, continuous ultraviolet radiation source, solar simulation light source, etc. it can also be used in infrared heating imaging furnace to melt refractory metals and materials. The trigger voltage and working voltage of different power short arc xenon lamp are different, so different trigger and working power supply need to be configured. On the basis of meeting the requirements of triggering 10kW short arc xenon lamp, this design optimizes the design idea, can automatically detect the relevant parameters of xenon lamp and power supply, and judge the triggering and working state of short arc xenon lamp according to the test data. If the trigger is not successful, it will be automatically triggered again. After the short arc xenon lamp is lit, it can detect and display working parameters such as electric power. The multi-functional xenon lamp flip-flop has been verified by software simulation, and it completely meets the design requirements. The trigger voltage of the trigger can be adjusted according to the need, and the trigger requirements of different power short arc xenon lamp can be met by replacing the peripheral mutual inductance coil.
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Unmanned aerial vehicles have been widely used in military and civil areas, which requires vision processing in explicit usage scenario. Existence of haze or fog can influence the context awareness capability of the aerial vehicles and makes affectation on target tasks. The captured images in hazy scenes suffer from degradation problems including poor contrast, color distortion, incomplete information, which lead to many difficulties in the follow-up processing. A simple and effective single image dehazing algorithm based on atmospheric scattering model and the optimum of image quality evaluation is proposed in this paper. Three image quality evaluation parameters: image entropy, standard deviation, and Fourier amplitude are combined to establish and the image quality evaluation function. On the basis of quality evaluation function, the image with the optimum of quality evaluation among the potential defogging images is chosen as the best result. Results show that this method has lower computational complexity, simplified operations and improved real-time performance.
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For general power system, the thermal exhaust at the exit of funnel has obvious infrared radiation characteristics. In this paper, funnel exhaust plume about the dynamic system is modeled and analyzed. The 3D flow field of exhaust plumes is calculated based on CFD methods. A calculation method of high temperature exhaust plume's infrared radiation is obtained by spectral band model and calibration with C-G two parameters. And the effect of the detecting azimuth angle on the flow field and the infrared radiation of ship exhaust plumes is analyzed. It can be concluded that with the detection angles’ increasing, the space distribution of the exhaust plume shows a tendency to increase progressively. The difference of the radiation intensity of different detection angles can be up to 32.6%.
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In the laboratory verification test of space plane array camera with wide field of view, the image distortion caused by camera distortion will reduce the ranging accuracy for space camera with on orbit ranging function. In addition to verifying the performance of space camera, the distortion correction in laboratory stage can also verify the validity of distortion calibration results. First of all, a nonlinear distortion mathematical model including radial distortion and tangential distortion is established based on the principle of optical lens distortion. Distortion correction is generally divided into two steps. Firstly, the coordinate conversion relationship between each pixel in the ideal image and the corresponding pixel in the original image with distortion need to be established. The purpose of it is to make the pixel of original fall on the right position. Secondly, assign the gray value of the original image to the corresponding coordinate in the ideal image, and re-determine the gray value of the new pixel. By the bilinear interpolation method, the gray value of the original image with distortion is assigned to the undistorted image. Finally, the undistorted image can be obtained. The distortion correction algorithm is realized by MATLAB and verified on a space plane array camera. The corrected image distortion is less than 0.1 pixel
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This paper investigates the development of robot wheel polishing,the off-axis aspheric polishing technology is studied by combining the technical characteristics of industrial robot and wheeled small polishing head.Firstly, the rasterized machining path for off-axis aspherical mirror is selected,a computer control model based on machining trajectory and dwell time is established,a removal function of off-axis aspheric surface with caliber 72 mm is established by numerical simulation software and the simulation analysis of the machining process, verify the stability and effectiveness of wheel polishing。It shows that the wheel polishing method based on industrial robot has great potential in the polishing of aspheric components.
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In this paper, we propose a method which is based on the dual-focal camera facing the same target to expanse the dynamic range of images. Since the spatial resolution of dual-focal camera in this paper is different, down-sampling, up-sampling, and multi-resolution fusion are required in image fusion processing to obtain an ideal high dynamic range image. The current multi-frame high dynamic range algorithm is mainly for similar resolution images. When there are two images with large resolution differences, The effect of ordinary registration algorithms (For example, optical flow registration algorithm) are limited, and the image may appear ghost and color artifacts after registration. Our method uses a convolutional neural network, which composed of two subnets. An image fusion subnet and a style transfer subnet. Because there is only one exposure image in the surrounding field of view, the central field of view is processed separately from the surrounding field of view. In the central field of view, U-Net is used to register the images layer by layer to increase the registration speed and registration accuracy. After the high dynamic range image in the central field of view, the style transfer network is used to transfer the color distribution of the high dynamic range image to the surrounding field of view. As for result, we performed extensive qualitative and quantitative comparisons to show that our method produces excellent results where ghost and color artifacts are significantly reduced compared to existing general multi-frame high dynamic range methods, and is robust across various inputs.
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The corner reflector is usually realized by fixing the corner cube prism through a specific structure, which is much easier to install and debugin practical application. As we all know, one of the most important uses of the corner reflector is that it can be used as a passive target marker for satellites and aircrafts. At a certain distance, as the angle of incidence increases, the return light efficiency of the corner reflector gradually decreases, and the return light efficiency directly affects the shape and brightness of the target point. Usually when multiple targets are tracked, the better the target direction consistency, the more uniform the light spot can be obtained. This paper introduces the method of drawing the normal direction of the corner cube prism to the mounting surface. The normal direction of the corner cube prism is tested by the self-collimating theodolite and the direction error is within 1′, and the error of return light efficiency is better than 5%, which provides high-precision pointing for the combination of multiple corner reflectors. On this basis, we expand the pointing design of the sub-corner cube prism for the plane array of the corner reflectors. After testing, the direction error of the sub-corner cube prism is within 5′.
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Air-to-ground photoelectric tracking platforms are often installed in unmanned aerial vehicles or various military weapons, and they play a major role in terrain mapping and military investigation. In the course of implementing tasks such as UAV reconnaissance and weapon strikes, the photoelectric tracking platform plays the role of identification and tracking. This paper proposes and compares the methods for calculating the position of the target detected by the platform based on the information of the photoelectric tracking platform attitude, the attitude of the platform carrier, such as the drone or the weapon body attitude, and the target distance. First, a conventional method is proposed, which is to obtain the target's latitude and longitude using coordinate transformation and other methods based on the information such as the target distance, platform and carrier attitude. In order to better meet the needs of rapidity, a method for obtaining the target latitude and longitude according to the distance of the target from the carrier in all directions is proposed. This method has a simple calculation process but a reduced accuracy. To ensure accuracy on the basis of improving real-time performance, consider For the spherical nature of the earth, a method of using spherical triangles to solve the target position is also proposed. Finally, use actual measured data to test and compare the practicability and accuracy of various methods. After testing, the three methods can achieve precise positioning of the target and meet the performance indicators.
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In recent years, Low-Light-Level (LLL) remote -sensing camera has become a novel subject for the development of aerospace optical remote-sensing payloads. LLL remote sensing camera works in ultra-low light conditions, the image signal is very weak and requires image intensified technology to achieve. In order to make better use of LLL remote sensing data, it is necessary to establish the quantitative relationship between the amount of radiation received by the camera and the digital signal output to process the image. That's radiation calibration technology. Therefore, the radiation calibration of the LLL remote sensing camera is particularly important. In this article, first the requirements for calibration of LLL remote sensing cameras are analyzed in theory. After that, a radiation calibration scheme of the LLL remote sensing camera is put forward. Finally, the radiation calibration test is carried out, and the calibration data are analyzed. The results show that the calibration scheme of LLL remote sensing camera is reasonable and feasible.
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Aiming at the problem that the focus range and focus accuracy cannot be balanced during the focusing process of scenes with small targets in a large field of view such as ships in the ocean, this paper proposes a selection of the focusing window based on gradient matrix and an adjustable coverage range autofocus evaluation function in frequency domain. By using gradient operators of different sizes for different search intervals, the gradient matrix of the image can be obtained. This kind of strategy takes both accuracy and detection rate into consideration. Through segmentation, area with rich details could be chosen as the focusing window. In order to solve the problem that the focusing evaluation function don’t works well when the amount of defocus blur is large, this paper proposes a new evaluation function based on an amplitude summation of different frequency component with variable threshold. For the scenes with small target in a large filed of view, more than 100 pictures with continuously changing defocus were established. Experiments indicate that the method proposed in this paper can meet the characteristics of a wide focusing range and high sensitivity at the same time when variable threshold was used. Compared with existing methods, the method above performs better in noise robustness and has a larger coverage range, at the same time, it provides a sharper peak of evaluation function which means higher sensitivity.
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Micro-nano project by studying the micro channel plate surface micro convex particle sizes can produce a phenomenon of point discharge which causes the field emission, and particles on the surface on the micro channel plate mechanism, then through metallographic microscope classification and testing for different particle morphology, finally three kinds of particle preparation is be determined. Through the study, by water to remove the ultrasonic repeatedly can get rid of polishing powder residue. And acid etching process of silica particles by adding alkali ultrasonic frequency and the use of high frequency ultrasound alternately can be completely removed. Then through evaporation before increasing ion bombardment can effectively control the micro convex particles which is produced after evaporation electrod. Through the study, by water to remove the ultrasonic repeatedly can get rid of polishing powder residue. And acid etching process of silica particles by adding alkali ultrasonic frequency and the use of high frequency ultrasound alternately can be completely removed. Then through evaporation before increasing ion bombardment can effectively control the micro convex particles which is produced after evaporation electrod.
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An LED-based integrating sphere light source (LED-ISLS) was designed and fabricated for radiance responsivity calibration of microscopes. The LED-ISLS was composed of a miniaturized integrating sphere, an LED chip, a thin circular aperture, and was successfully applied to calibrate the radiance responsivity of a home-built microscope system. Several issues remain to be discussed. Firstly, the area of the circular aperture, which served as an exit port, was measured by comparing the light flux through an area-certified standard aperture and the circular aperture. The measurement uncertainty was smaller than 0.2%. Secondly, the radiance uniformity on the exit port was discussed. Simulations and experiments were conducted to evaluate the effects of circular aperture edge thickness and integrating sphere internal material reflection parameters on the radiance uniformity. From the simulation it was found out that as the edge thickness increases, the radiance uniformity drops drastically; the Bidirectional Reflectance Distribution Function (BRDF) also has impact on the radiance uniformity of the LED-ISLS. By reducing the BRDF from 0.9 to 0.6, the radiance uniformity at the exit port was reduced by about 63%. The radiance uniformity was also evaluated experimentally by using a 1 mm small aperture to scan the different small areas of the exit port. The radiance non-uniformity across the exit port of the LED-ISLS was about 5% from the scanning results. This work further investigated the radiance non-uniformity of the LED-ISLS and offered ideas of technical optimization of the LED-ISLS for better radiance responsivity calibration performance.
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We propose a new method to detect the orbital angular momentum(OAM) of Bessel vortex beams by an elliptical screen covering the partical azimuth angle. When the diffraction screen is illuminated with a vortex beam, the far-filed diffraction pattern can be used to determine the modulus and sign of topological charges. It was found that the diffraction patterns can best reflect the topological charge information when the angle of initial position is set as 8° and span angle of opaque region of the ellipse aperture is set as 4°. The simulation results show that the number of dark fringes denotes the number of topological charge. The sign of topological charge is determined by the direction of intensity pattern, which flips by 180° for a change in the sign of topological charge. This new method to detect of vortex beam topological charge information is very simple and low-cost.
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For the marine integrated navigation system composed of strapdown inertial navigation system (SINS) and Doppler velocity log (DVL), when the range of DVL is insufficient, it can only output the velocity of carrier relative to ocean current. If the algorithm is not improved, it will cause great navigation and positioning error. In this paper, the Kalman filtering equation is derived by analyzing the error equation of integrated navigation system, and a SINS/DVL integrated navigation algorithm considering ocean current velocity is proposed, and the feasibility of the algorithm is verified by simulation experiments. The simulation results show that the SINS/DVL integrated navigation algorithm considering ocean current information can effectively improve the positioning accuracy when DVL works in water tracking mode.
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Triangle star identification algorithm is the most widely used and most mature star pattern recognition algorithms. When the number of guide star is relatively huge and the capacity of guide star catalog is relatively large, with the result that the complexity of triangle star identification algorithm increases, the time of star pattern recognition becomes longer, and even the storage space occupied by the algorithm becomes larger. So it is difficult to realize the rapid and effective star identification in star map. In order to improve the efficiency of star identification algorithm and shorten the time of star recognition, it is proposed that a star identification algorithm used on the data structure of hash map and based on the triangle algorithm. The first thing is to make the guide star catalog. Then, all the angular distance values d ijm (0 < i < j ≤ N) of the brightest N observed stars in an observed star image and their corresponding star angular distance sets are calculated, and the triangle features, namely angular distance values, are stored in the hash map. In this algorithm, each triangle feature is mapped to an integer, and the hash map of all triangle features is set to reduce the computational complexity of triangle pattern matching, decrease the number of star angular distance matching, and greatly shorten the time of star image recognition. Simulation results show that the star image recognition algorithm based on hash map has better computational complexity and efficiency of performance than traditional triangle algorithm.
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In recent years, sinusoidal Siemens stars have been widely used as a method of measuring spatial frequency response (SFR). Previous researches pointed out that incorrect recognition of the Siemens star center could result in errors in SFR measurement, and these errors are more significant at high frequencies. To reduce the errors, this paper proposed two methods to correct the center of Siemens star. By calibrating various Siemens star centers with the proposed methods, it is found that both the two methods are highly consistent, with a difference of no more than 2 pixels.
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In order to solve the problem of traditional target recognition and tracking algorithms of the multispectral image such as high computation complexity, poor real time performance and low stability under complex scene and great variation of target appearance, a new mosaic image tracking algorithm based on dimension reduction of HOG feature data and multi-scale correlation filter is proposed in this paper. Firstly, in order to reduce the calculation complexity as well as to enhance the detection rate of small target, the 2D multispectral mosaic image data instead of the traditional 3D multispectral image data cubes is used, Then the histogram of oriented gradient (HOG) feature is extracted from the mosaic image data, and the singular value decomposition (SVD) algorithm with improved threshold selection method is adopted to reduce the dimension of the HOG feature matrix. Compared to the method which extracts HOG feature after dimension reduction, the proposed method takes advantage of high recognition precision, simple operation and high real-time performance. Finally, the target tracking is realized based on the dimension-reduced HOG feature with the fast discriminative scale space tracker (fDSST) algorithm which combines the scale filter and the position filter. A multispectral image dataset for target tracking was established, including different target occlusion, motion blur, variation of target scale and target appearance. Target tracking results on the dataset show the proposed algorithm can realize good tracking continuity and stability even if there exist different ground objects, variation in the appearance of the target shape, or target reappearance after occlusion.
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The anti-vignetting glass (AVG) is the key material for super-second and third-generation low-light image intensifiers. With the development of low-light night vision technology, the requirements of high precision and low damage are put forward to AVG. However, traditional measurement methods, such as vernier calipers, micrometers, dial indicators, etc., are all contact measurement, which will inevitably cause damage to AVG during the measurement process. They cannot meet the technical requirements for low damage. Non-contact measurement technology is a non-destructive testing method that realizes the geometric measurement of AVG by writing measurement programs and setting measurement parameters. However, due to the special structure of AVG, the non-contact measurement technology has measurement errors and cannot meet the high-precision measurement requirements. In this paper systematically analyzes the causes of errors in non-contact measurement technology by studying the characteristics of the light source, the difference in light intensity, and the way of grabbing contour edges. Through the error correction technology, the error of the non-contact measurement technology is eliminated, the AVG high-precision and low-damage non-destructive testing is realized.
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In this work, we develop an optimized 4H-SiC U-shaped trench-gate MOSFET structure with a high breakdown voltage. In the optimized structure, a p+ shield is added under the gate oxide and the drift layer is divided into multilayers with different doping concentration. Simulation results reveal that adding a p+ shield and lowering the doping concentration around the corner of U-shape trench can effectively protect the gate oxide, resulting a significant improvement of the breakdown voltage. As a result, the breakdown voltage of the optimized structure increases by 47.7% compared with that of the conventional structure, corresponding to an improvement of 32.2% in figure of merit.
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With the development of optoelectronic imaging technology, remote sensing optical system gradually develops towards super large imaging field of view in order to obtain target characteristic information in a wider space. Concentric multiscale system is a new type of large field of view optical system. At present, most of the schemes studied are multiscale system based on concentric spherical lens. Due to the limitation of optical materials, this optical system is generally only used in visible and near infrared optical bands, and is difficult to be applied in long-wave infrared band. Starting from the structure principle of concentric multi-scale system and considering the application of long-wave infrared band, this paper proposes to use spherical reflector instead of concentric spherical lens to construct a retracted multi-scale system based on spherical reflector. The system can achieve all the features of multi-scale system and can be applied in the infrared band. According to the construction principle of the system and the design idea of off-axis deviation field, a multi-scale system based on spherical reflector is designed. The main parameters of the single channel of the system are: the focal length is 72mm, the system F#=2, the working band is 8-12um, and the imaging field of view is 20°×0.1°. The imaging quality of the system is close to the diffraction limit in the full field of view, and the distortion of the full field of view is less than 5%. The circular field of view imaging of 360°×0.1° can be achieved by extending the spherical reflector and multi-channel splicing.
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In this paper, transparent Er3+/Yb3+/Tm3+ tri-doped tellurite glass samples were prepared by high temperature calcination method and drawn into filaments when in molten state. The tip of each filament selected was melted by flame and subsequently fabricated into a microsphere via the surface tension of liquid. The microsphere resonators were effectively pumped by 976 nm/1550 nm continuous wave (CW) lasers respectively, using the same biconical tapered fiber which acted as a coupler, transmitting the pump light into the microspheres under uniform conditions and collecting the up-conversion (UC) fluorescence from the microspheres at the same time. We obtained blue, green and red UC emission upon both two types of excitation, but with different intensity distributions. The UC luminescence mechanism of the Er3+/Yb3+/Tm3+ tri-doped samples has been investigated in the perspective of the energy level structure of these rare earth (RE) ions. We find that different pump light sources may cause different energy transfer paths among ions, which thus results in the difference on spectral distributions. It is predicted that such kind of multi-color luminescence material has potential to be applied in the white lighting. In addition, we also did some theoretical analyses on the propagation constant matching that greatly influences the coupling between the microsphere and the tapered fiber, and discovered the fact that it may require a pretty small size of the microsphere for effective coupling when there exists a large refractive index difference between them. Besides, it seems that the waist of the fiber has to get thinner when the light has a shorter wavelength. The outcomes from our experiments were in correspondence with the results above. These results will pave the way for the research on further improvement of the coupling efficiency between the microsphere and the tapered fiber.
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In the process of restoring the image of space optical camera, it is necessary to use the standard 24 color card to correct the image. In order to improve the accuracy of the mapping function in the process of color correction and prevent the occurrence of overfitting at the same time, a neural network correction method with comprehensive objective function is proposed. Using the idea of regularization as a reference, a constraint term with smooth performance is added to the objective function of the neural network to improve the generalization ability of the network map to data. The experimental results on the dataset of the real color card of the space camera sho-ore the correction.
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Since laser beam pointing stability affects the quality and accuracy of work in areas such as laser guidance and laser processing, the paper proposes a method for measuring the laser beam pointing stability based on the linearly angle-displacement transformation characteristics of F-theta lens in order to measure the pointing stability accurately and comprehensively and evaluate the performance of the laser. The method linearly converts an angular offset into a displacement offset that can be accurately measured and evaluate the pointing stability by means of finding the minimum envelope circle. Based on this method, a laser beam pointing stability measurement system with CCD camera as image acquisition unit is built for He-Ne laser source. The experimental results show that the pointing stability of the He-Ne laser is 1.500mrad. The result is only 0.186% affected by the error, which verifies the feasibility of the measurement method and the high-precision measurement of laser beam pointing stability by the system.
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High-resolution visible spectral remote sensing images enriches human cognition of the world, also brings challenges to the image storage and transmission. Traditional compression method can reduce the transmission bandwidth, also cause defects such as long computing time, high algorithm complexity, and large errors. Compressed sensing can reconstruct high-quality images which is similar with the original image. It provides a new method for remote sensing image compression and reconstruction. This paper analyzes the advantages of blockbased compressed sensing algorithm, and proves that block-based compressed sensing algorithm is superior to nonblock-based compressed sensing algorithm from the perspective of algorithm complexity. This paper modifies the smoothed projected Landweber (SPL) algorithm to make it suitable for the color image. According to the simulation results, it is obvious that the block-shaped compressed sensing algorithm can effectively reduce the transmission cost and ensure the reconstruction quality of the compressed images.
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The traditional single reference arm swept-source optical coherence tomography (SSOCT) has the ability to image 7mm axial length, however larger depth can not be obtained directly. Conventionally, the extending depth can be obtained via special system design or multi-arm imaging. However, in this paper we design a SSOCT system with large detection depth which only need one reference arm. The difference between this system and the traditional is that the proposed system use a high-speed scanning laser. The large imaging depth range is achieved owing to the increased k-trigger number and the related sample point number in one A-scan period. The sample signal and the reference signal interfere in the optical fiber coupler, and then it is detected by a balanced detector. The digital signal of each A-line goes through spectrum shaping, background removal, mirror image removal, dispersion matching and the Fourier transform, then the A-scan signal can be obtained. 512 A-scan signal comprise the B-scan frame. The imaging depth can reach 54mm, and the axial imaging resolution is 7.5 μm . The frame rate is 5fps of the SSOCT system which can be improved if algorithm is simplified further. The system can be employed in human eye axial-length measurement and dimensional measurement.
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Loss of texture information and color distortion have always been two key issues that plague the quality of fusion images. In recent years, with the development of remote sensing payload technology, the difference between the spectral range of panchromatic and multi-spectral images has become larger and larger, resulting in the problems proposed above becoming more prominent in the process of true color fusion. On one hand, the energy distribution of water areas and vegetation in the near-infrared and visible spectral ranges is very different, therefore, the color distortion is mainly concentrated in the water area and vegetation area, the specific manifestation is that the energy of the vegetation is sufficient and the energy of the water area is very small. On the other hand, multi-spectral devices have poor antisaturation and anti-dispersion characteristics, which often leads to the loss of texture information in images. In addition, the lack of energy of multi-spectral sensor results in limited recognition of textures in the shadow area of the fusion image. Based on the analysis of the shortcomings of the existing fusion methods, we propose a pan-sharpening fusion optimization method based on the pyramid model in this paper. This method first uses the spectral relationship between the spectral image and the panchromatic image to build the basic fusion model, then, in order to prevent the "illconditioned equation" phenomenon appeared during the fusion process, unequal conditional equations are introduced into the basic fusion model to form simultaneous equations to avoid color distortion and invalid data in the fusion results. Secondly, in order to suppress the blurring of the edges of the fused image caused by the saturation overflow in the image, we calculates the ratio of the panchromatic image to the up-sampling multi-spectral images, and replaces the deficiency of the previous fusion model to generate fusion images with high clarity and high spectral fidelity.
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Mueller matrix polarization imaging system (MMPIS) is one of the most prospective tools that can provide a highresolution image of polarization properties for samples or systems. The MMPIS is composed of a laser source, polarization state generator (PSG), the sample, polarization state analyzer (PSA), a high-resolution imaging optics, collimating optics, and a CCD camera. Usually, the traditional eigenvalue calibration method (ECM) can be used to calibrate PSG and PSA. However, the imaging and collimating optics are not calibrated in MMPIS. For the highnumerical-aperture imaging system, the imaging and collimating optics can behave as polarization aberration modifying the tested sample’s polarization properties leading to the erroneous judgment which affects the measurement accuracy of the MMPIS. In this paper, the multi-step eigenvalue calibration method (MECM) is explored to calibrate MMPIS. For the MECM applied to calibrate MMPIS, the calibration samples are required to place in different positions of the light path and the ECM is adopted in each position. In this way, the Mueller matrices of PSG and PSA, as well as the Mueller matrices of imaging optics and collimating optics can be obtained through calculation. To evaluate the measurement accuracy of MMPIS, the sample with known polarization properties such as air is measured. The experimental results show that before calibrating the imaging optics and collimating optics the measurement accuracy of MMPIS is 0.0124, while after the measurement accuracy has been improved to 0.0046, which is 62.90% better than before. The MECM can be used for the requirements of high accuracy measurement.
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The morphology monitoring of the wall surface of the Tokamak is of significance for understanding the erosion and deposition phenomena that occur on the wall surface. Laser speckle interferometry (LSI) is a technique that can measure the three-dimensional morphology of surfaces on-line in-situ, which can achieve real-time non-destructive measurement. In this paper, the influence of continuous white light emitted by plasma discharge on the LSI measurement is investigated off-line. The experimental results show that the existence of white light background is not conducive to the measurement of three-dimensional morphology of the plasma-facing-components (PFCs) by LSI in Tokamak. Therefore, we propose an improved laser speckle interference (ILSI) technology based on frequency domain and spatial domain filters to depress white light background. The experimental results show that the ILSI works well. This lays a theoretical foundation for the future application of LSI technology to Tokamak devices.
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As a method of active laser interference, energy laser interference can be used to interfere with laser fuzes. This paper studies how the energy-type laser interference the pulsed laser fuze. By simulating the transmission characteristics of the fundamental mode Gaussian beam in free space, the energy transmission model of the fundamental mode Gaussian beam is established. The thermal conductivity theory is used to calculate the thermal effect of the fundamental mode Gaussian beam irradiating the photosensitive surface of the Si PIN photodetector, and the related physical processes are discussed. The results show that a monopulse laser with a wavelength of 1064 nm, pulse width of 10 ns, and peak power of 11.5 MW can generate a temperature of about 1800 K in the center of the silicon photosensitive surface,which can cause irreversible damage to the photodetector, and the detection performance of the photodetector is sharply weaked or even unfunctioned. This result provides theoretical basis for the further development of the jammer.
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The optical tracking and measuring on mobile type of large aperture ground-based measurement system can obtain the real-time sequence image information and position information of the target, analyze the motion characteristics of them, monitor and predict the trajectory information of the target in real time. At the same time, it has the characteristics of flexible deployment. In the aspects of in-orbit monitoring and prediction of space debris target, in-orbit live image acquisition and infrared radiation characteristic measurement and analysis of targets, combined with advanced orbit prediction technology, it can be used for real-time trajectory tracking and measurement, and the related physical events in the course of operation can be studied. The detection information is analyzed and processed in real time to obtain he basic conditions for the research of high precision, real environment measurement, multi-state measurement and multi-feature measurement.
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Optical Phase Array - OPA is a fast, flexible and non-mechanical beam pointing technology, which can be regarded as the extension of microwave phased array to the Optical wave frequency band. It has a wide application prospect and research value in target detection, imaging recognition, tracking scanning, laser interference and other fields. Optical phased array system is composed of a number of array elements, the basic idea is through electric scanning technology and modular design method. The beam can be transmitted, received and detected with high precision by using multiple small aperture beam oriental arrays. Based on acoustic-optic and elector-optic devices, the propagation direction of the beam is changed by controlling the initial phase of each element in the optical aperture, thus completed the laser beam array scan. In this paper, the development background and working principle of optical phased array technology are introduced. Based on the typical application of optical phased array technology, that is, laser phased array radar system, this paper summarizes the research progress and key technology breakthrough of this system in domestic and abroad. Finally, by analyzing the outstanding advantages of optical phased array technology, for one hand the research direction and application prospect of this technology in industrial and military fields are put forward, for the other hand the conceptual design and engineering research of this technology are summarized and prospected.
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Hypersonic cruise vehicles emit intense infrared radiation when maneuvering at high speed in the near space, which highlights the practical significance of studying their infrared remote sensing characteristics. This paper makes a survey on the previous research into the infrared radiation characteristics of scramjet plumes, the infrared radiation characteristics of hypersonic cruise vehicle bodies and the infrared remote sensing characteristics of hypersonic cruise vehicles in the near space. Survey results show that, tentative studies have been carried out on infrared remote sensing technologies for hypersonic cruise vehicles, but more thorough and systematic research need to be conducted in depth. Further studies should focus on the infrared remote sensing mechanism of hypersonic cruise vehicles in the near space, and specific research is supposed to be targeted in particular to calculate the total infrared radiation intensity, with not only the infrared radiation of scramjet plumes and vehicle bodies taken into account, but also atmospheric attenuation and background radiation into consideration.
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Through the influence of the temperature, concentration, acid type and acid dissolution time of the acid solution on the acid etching speed of the multi-fiber and the surface quality after acid etching, the acid dissolution mechanism of the acid solution flexible optical fiber image bundle is discussed. The weight loss method was used to test the acid dissolution rate of different acid-soluble glasses, combined with the breakage of the multi-fiber after acid dissolution, to study the effect of acid-soluble glass on the image quality of the flexible optical fiber image bundle. The experimental results show that using a suitable acid solution, a suitable acid solution concentration, a suitable temperature and a reasonable acid dissolution time has obvious effects on reducing the broken wire rate of the flexible optical fiber image bundle and improving the image transmission quality.
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Infrared Search and Track – IRST system as a passive panoramic surveillance device based on infrared features can detect and track air or surface targets. It has many advantages, such as high resolution, strong resistance to electronic interference, good concealment, and strong anti-stealth and so on. Because IRST system and the radar can be complemented by multi-sensor data fusion technology. this paper summarizes the research progress and key technology breakthrough of IRST system in domestic and abroad. Then by analyzing the outstanding advantages of IRST technology for one hand the research direction and application prospect of this technology in industrial and military fields are put forward, for the other hand the conceptual design and engineering research of this technology are summarized and prospected.
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The photon counting detectors have a wide range of applications in different areas, such as quantum communication, linear-optics quantum computing optical metrology and so on. In this work, a fiber-based 16-channel multiplexer with different time delays was designed based on a construction scheme of 1 (1×4) coupler = 4 (1×4) couplers = 16×optical fibers - 4 (4×1) couplers - 1 (4×1) coupler. The lengths (di, i =1, 2, ...16) of the optical fibers were manufactured to be 0 m, 8.0 m, ... 120.0 m, respectively, with a length difference (Δd) of 8 m. The time delay between the optical fibers (Δt) can then be calculated to be 38.8ns. A pulsed 850 nm laser with a repetition rate of 1 MHz and a pulse duration of 10 ns was adopted to test the time-multiplexing capability of the 16-channel fiber coupler. A 1-GHz Si photodetector and a 1-GHz oscilloscope were used to measure the overall insertion loss and relative power through the 16 different channels. The photoelectric pulse count of the pulsed light passing through the fiber bundle will be measured. According to the loss of optical fiber and the photon detection efficiency of detector, we can roughly the photon detection efficiency of the system. If the fiber bundle with 16 entrances instead of only one, the scheme would be used as a detector array, and for imaging. This is what we're going to do in the future.
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The simultaneous acquisition of spatial information, spectral information and polarimetric information can obtain more characteristic information to distinguish targets. The conventional spectral polarization imaging system mainly includes the filter/polarization wheel rotation system, the crystal modulation system and multi-path beam splitting system. The disadvantages of these systems are: unsynchronized spectral polarization detection, requiring dynamic modulation, complex system, etc. To solve these problems, a spectral polarization detection technology based on optical fiber image bundle is proposed, which combines optical fiber imaging spectral technology with pixel level polarization detection technology. The input shape of the optical fiber image bundle is plane, and the output shape is linear. Optical fiber image bundle can transform the information of array target into that of linear array. The linear array information is the input of spectral imaging system. The polarization detection uses a micron level polarization array to match the pixel size of the detector. The technology can synchronously acquire the two-dimensional spatial information, the spectral information and linear polarization information of the target. The technology can be used to image the area target in snapshot mode. The experimental device is set up to obtain the spectral image in the visible light range, as well as the polarization degree image and polarization angle image of each spectral segment. The data acquisition ability of the system is verified. With the improvement of optical fiber manufacturing technology, the integration of optical fiber is getting better, and the scale of optical fiber is getting larger. The technology will have a high application value in astronomical observation, atmospheric detection, target recognition and other fields.
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In order to solve the problems of serious electromagnetic interference, high cost and long detection time of radaroptoelectronic traditional airport runways Foreign Objects Debris Detection(FOD) system, a novel FOD detection algorithm was proposed which based on the improved yolov3. The multi-scale detection and feature extraction network were used to improve the learning ability of object features. Meanwhile, the classical image processing and the deep learning technology was adopt, the algorithm has the ability of target autonomous recognition, besides conventional image restoration. The experimental results show that the algorithm has a strong ability of autonomous recognition and environmental adaptability, the time consumption is better than 0.2s, which can meet the real-time detection of foreign objects debris. It has a guiding significance for the next stage of the engineering of pure-photoelectric foreign object detection system.
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Considering the shortcomings of the traditional security technology system, such as poor stability, limited installation environment, high false alarm and missing report rate, this paper proposes a hanging fiber detector and video monitor system for perimeter security based on Michelson Interference Technology, and carries out functional test in the oil terminal of Petrochina Company Limited. In this system, an ordinary single-mode communication optical cable is arranged along the top of the fence in wavy shape. When the intruder climbs or turns over the fence, the system triggers the alarm event and emits an alarm. Then the high-speed dome camera will be controlled to turn and shoot the location of the invasion through the network video recorder and network switch. In the functional test, the system has realized climbing alarm, knocking the wall alarm, multi-point simultaneous intrusion alarm, false alarm learning, broken fiber alarm and other functions, which has better sensitivity, lower false alarm rate and better learning function compared with the products based on Sagnac principle and double MZ principle.
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High-precision line scale, as the benchmark of the dissemination of quantity in length measurement, is being widely used in processing and calibration of precision instruments. The key for tracing measurement of line scale templates is to achieve high-precision alignment of the linear ruler. In order to perform the traceable measurement of 2-D Line Scale templates, we designed a kind of 2-D dynamic photoelectric microscope that can realize high resolution aim at the crosswire. When the templates moves unidirectionally with uniform speed, the corresponding crosswire will be imaged in the two slits successively. Then the light signal is converted into an identical electrical signal by the photomultiplier tube. Finally using laser interferometer ambient parameter monitor and laser wavelength compensation , the high-precision calibration of 2- D line scale templates can be realized. The measurement uncertainty can reach U=(0.1+0.1L)μm(k=3,L:m).
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Based on the sub-aperture field imaging system which microlens array located at the front of the primary focal plane and the back of the main lens, firstly, the schematic diagram of each microlens re-focus imaging with different aperture information were given in two structures. Then, the coordinate system of the related planes was defined to study the optical field transformation mode among the target point in the scene plane, the microlens array plane, the primary image plane and the detector plane. In addition, the discrete sampling mode of the detector and the schematic diagram of the radiation transmission path were established. Moreover, the determinants of its position and direction resolution were studied. Finally, three same size scene targets were generated by computer simulation, when the microlens array was located in different positions of the optical system, different cases of obtaining images on the detector were obtained. The results show that the position of the microlens array would lead to the change of magnification of the primary image surface and the detector image surface, meanwhile it would lead to the difference overlapping area of the image. At the same time, the number of apertures could be distinguished, but the images could be basically consistent by rearrangement.
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With the development of specific light environment design, people are no longer satisfied with the simple lighting needs of the light source in the traditional sense, and begin to pursue ideal vision in complex light environments. The creation of shadowless spaces has been widely used in various fields, such as medical treatment, photography, dynamic capture, etc. While enjoying the convenience brought by the shadowless space, people are also exploring the most optimized shadowless space design. This article proposes two design methods to achieve shadowless space. One is based on the design concept of traditional shadowless lamps. Light is evenly irradiated to the target object from different directions. By setting the number and position of the light source in the space, shadowless areas are produced within. The second is based on the semi-light principle in the integrating sphere to realize the shadowless space. The reflectivity of the inner surface of the spherical cavity is extremely high. The light emitted by the light source is reflected by the spherical cavity multiple times, and finally evolved into uniform illumination in the space. Diffuse reflection reaches the shadowless space. Based on these two ideas, we proposed two optical design systems and simulated these two systems with Tracepro.
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The SL0 algorithm is a sort of sparse reconstruction algorithm approximate to l0 norm, which has significant applications in the field of deblurring. In the SL0 algorithm, usually a number of important parameters need to be set to obtain deblurred images. This paper first introduces the basic of the SL0 algorithm, then it analyzes the operator, which has higher dipartite degree for blurred images in edge extraction algorithm, and choose the Roberts operator as the standard for judging parameter optimization. Finally, an algorithm for image restoration parameter adaptive selection is designed, and experiments are conducted. The experimental results show that comparing with the traditional SL0 algorithm, the algorithm in this paper has a great improvement in terms of repairing quality. The repairing effect of the algorithm in this paper is more natural, and the PSNR of images can be increased about 1.5dB.
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This paper presents a novel single-pixel imaging (SPI) framework which can produce high-resolution target images with undersampling. Undersampling is used to work around the problem of long imaging time in SPI for real-time applications. However, the reconstruction from undersampled measurements suffers from noise, ringing or pixelated artifacts, and low resolution which complicates target recognition. To improve image quality, deep learning (DL) based approaches have been proposed but the improvement is merely based on noise and artifact removal. In order to improve image resolution, it is necessary to recover fine details from undersampled input which is very challenging due to absence of high-frequency information (during target reconstruction). To achieve this task, we propose to apply a DL model which learns to generate both low and high-frequency representations from an undersampled (10%) 96×96 input, and combines them to produce a high-quality (high-resolution) output. Experimental results show that the proposed model is robust against noise and frequency-based artifacts, and reconstructs high-quality targets by improving resolution (fine details).
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The current semi-physical simulation testing of optoelectronic products requires the simulator to meet the requirements of full band, high accuracy and portability.In response to this demand,a full-band target simulator that can be used on a five-axis turntable was designed.The collimating optical system of the target simulator adopted off-axis reflective structure design, and the radiation simulation source adopted infrared and visible light composite radiation sources; the infrared radiation source and the visible light radiation source adopted the coaxial mode, the structure was compact, and the temperature control accuracy can reach 0.1°C.In order to ensure the imaging quality of optical products, this paper designed the target simulator with exit pupil diameter Φ200mm, exit pupil distance 700mm, parallel difference 8.5", transmittance 0.8@632.8nm. Targeted on different test requirements,designed a variety of shapes such as point hole, four bar, cross and multi-target.Aiming at the problem that the optical axis of the infrared and visible light sensors of the tested photoelectric product is not at the center of rotation of the five-axis turntable, physical translation is used to achieve the connection between the target simulator and the pupil of the sensor optical system of the tested photoelectric product.The target simulator was put into use as soon as the design was completed. After using a variety of optoelectronic products, the feedback was good and met the design requirements.
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At present, airborne optoelectronic products mostly use multi-sensors (visible light, infrared, laser, etc.) to coordinate the detection, recognition and tracking of threatened targets. Therefore, higher requirements are placed on the optical axis consistency of multi-sensors.In response to this demand, the visible light, laser and infrared astigmatism axis detection equipment suitable for a wide temperature range (-55°C~+70°C) are designed.The collimating optical system of the optical axis detection device adopts a common aperture design, and uses an off-axis parabolic mirror to achieve collimation of the light beam.For a wide temperature environment, the optical system adopts passive athermal design.Compared with the previous independent radiation sources, the multi-band composite radiation source is used to integrate infrared, visible and laser radiation sources, saving space, simplifying the operation steps and reducing the difficulty of use.The optical axis detection equipment needs to be used in the temperature box. Compared with the previous manual operation of the temperature box, this solution uses electric means to realize the optical axis measurement, which greatly improves the use efficiency and reduces the risk of personal injury.The optical axis detection equipment designed finally can control the collimation optical system parallel difference within 10″under wide temperature range and within 6″ under 20°C.
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