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This PDF file contains the front matter associated with SPIE Proceedings Volume 9449, including the Title Page, Copyright information, Table of Contents, Authors, Introduction (if any), and Conference Committee listing.
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Focused ring patterns are used for many applications like corneal surgery, micro drilling, optical trapping, etc. The generation of focused ring patterns in the earlier reported cases employed many refractive optical components with different functions. As a result the optics configurations of the ring pattern generation systems are bulkier. In diffractive optics, it is possible to alter a function of an element and also integrate multiple functions in a single element. In this paper, we present the design, fabrication and evaluation of single and composite diffractive optical elements for the generation of focused ring patterns. A diffractive toric Fresnel zone lens was designed for parallel beam illumination. This element is compared with other composite diffractive elements capable of generating focused ring patterns. The toric Fresnel zone lens and composite elements were fabricated using electron beam direct writing. The fabricated elements were found to exhibit interesting properties, with the toric lens out-performing the other elements in several areas such as efficiency, focal depth, and ring thickness.
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Multicore structures based on increased index waveguiding traces are fabricated by ultrafast laser photo inscription in bulk optical glass. A parametric study of the geometry of structure, number of traces and index contrast is discussed with respect to guided modes characteristics. Multicore waveguide present optical designs allowing large mode area light guiding by ultrafast laser photo inscription with coherent mode superposition in near infrared and mid-infrared in fused silica and Chalcogenide glass.
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In this paper, a high-dimensional statistical signal processing is revisited with the aim of introducing the concept of vector signal representation derived from the Riesz transforms, which are the natural extension and generalization of the one-dimensional Hilbert transform. Under the new concepts of vector correlations proposed recently, the statistical properties of the vector signal representation for random signal are presented and some applications to speckle metrology developed recently are reviewed to demonstrate the unique capability of Riesz transforms.
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A phase unwrapping algorithm specially designed for phase-shifting fringe projection profilometry (FPP) is proposed. This algorithm is based on a principle that combines a refined double-frequency fringe projection algorithm and a fringe background based quality guided phase unwrapping algorithm (QGPUA). The phase demodulated from high-frequency fringe images are partially unwrapped by that from the low-frequency ones. This would help to avoid phase order ambiguity in the eventual phase unwrapping while guarantee the phase resolution. The fringe background based QGPUA is adopted to completely unwrap the partially unwrapped phase. The quality map utilized during the phase unwrapping is generated from the fringe background and divided into different subregions. Further unwrapping for the partially unwrapped phase goes on in the order from phase in the highest quality subregion to that in the lowest one gradually. Partially unwrapped phase in each subregion is unwrapped with flood-fill algorithm. Therefore the phase unwrapping speed can be improved. The proposed method can make the phase unwrapping for phase-shifting FPP more robust and faster. Experiment result confirms the effectiveness of the proposed method.
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Detecting angle between target and optical axis in Q-APD is an effective way of fast ATP. It is the key point in this method to acquire the ratio of some parameters. In this paper, a novel method of achieving division of analog electric signal using integral chopper is proposed. This can avoid the problem of high speed acquisition faced in the digital processing solution, that is, MHz level sampling frequency should be used in microsecond level signal. After the target is detected by using Q-APD, the four-channel signals generated by target are amplified by the emitter follower. Then using sample hold and sum difference calculation, background signal and offset signals in azimuth and elevation are generated. Because of using the integral chopper, integration time of offset signal to capacitance is controlled by the background signal, and the output value is just the ratio of the background signal and the offset signal. This value which has is independent of intensity of incident light, represents the angle between the target and optical axis. The optical axis can be driven by servo system based on the angle, therefore realizing the fast ATP.
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Diamagnetic levitation system is studied in detail in this paper. From top to bottom, the diamagnetic levitation system is composed of a lifting magnet, a top pyrolytic graphite sheet, a floating magnet and a bottom pyrolytic graphite sheet. The gravity of the floating magnet is balanced by the attractive force between the lifting magnet and the floating magnet. And the floating magnet is stably levitated between the top and bottom graphite sheets due to their diamagnetism. The force exerted on the floating magnet is analyzed through theoretical and numerical methods, and at the same time the equilibrium position is obtained. Totally 11 groups of magnets are studied by COMSOL, in which the accumulative error is eliminated to improve the accuracy of finite element analysis(FEA). Corresponding experiments are carried out to verify the numerical results, and the error of equilibrium position is less than 10%, which shows that the FEA is precise enough to simulate the diamagnetic system. Motion characteristic is studied for group 6, in which the lifting magnet is a φ3/16”× 1/8” cylinder. For the floating magnet, the horizontal force versus the eccentric displacement and the vertical force versus the vertical displacement are calculated by COMSOL respectively. In the magnetic potential well of the lifting magnet, the floating magnet returns to the vertical central axis automatically, and the frequencies of the vertical and horizontal movements are between 4 and 5 Hz. The frequencies of the two directional movements can be tuned by the magnetic parameters of the lifting and floating magnets and the structure dimensions of the system. The method used to analyze the diamagnetic system is proved effective to design the diamagnetic levitation structure. Because of the contactless levitation of the floating magnet based on diamagnetism, the system is sensitive to very small input. This diamagnetic levitation structure is potential in micro-actuators and sensors.
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Infrared imaging fault detection which is treated as an ideal, non-contact, non-destructive testing method is applied to the circuit board fault detection. Since Infrared images obtained by handheld infrared camera with wide-angle lens have both rigid and non-rigid deformations. To solve this problem, a new demons algorithm based on regional information entropy was proposed. The new method overcame the shortcomings of traditional demons algorithm that was sensitive to the intensity. First, the information entropy image was gotten by computing regional information entropy of the image. Then, the deformation between the two images was calculated that was the same as demons algorithm. Experimental results demonstrated that the proposed algorithm has better robustness in intensity inconsistent images registration compared with the traditional demons algorithm. Achieving accurate registration between intensity inconsistent infrared images provided strong support for the temperature contrast.
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We propose a new concept for an unconventional type of two-color method for interferometry-based length
measurements based on the adjacent pulse repetition interval length (APRIL), which is the physical length associated
with the pulse repetition period. We demonstrate by numerical simulations that if the wavelength-based two-color
method can eliminate the inhomogeneous disturbance of effects caused by the phase refractive index, then the APRIL-based
two-color method can eliminate the air turbulence of errors induced by the group refractive index. We show that
our analysis will benefit the pulse-laser-based two-color method, which secures traceability to the definition of the meter.
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CO2 is the greenhouse gas that influenced by human activities most and has a great impact on the climate change. Monitoring of global CO2 variations on a basis of, high precision has great significance for the study of global climate change and carbon cycle, as well as the understanding of CO2 sources and sinks. This study develops the forward model and inversion software system GF_VRTM-V1.0 for space-borne near-infrared hyperspectral measurements of CO2 into a ground-based observation version. The simulation results are compared with the ground-based data of the column-averaged mole fraction of carbon dioxide measured at Fuling, and showed general agreement.
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Observations are presented of the Volume scattering function (VSF) over the angular interval 20 to 160°, to maximum depth of about 90m in the Northern South China Sea in Case I and Case II waters. The observations were collected by using a self-developed in situ scattering instrument, which synchronously measured the attenuation coefficient, the VSFs in seven angles between 20 to 160° at 650nm, and the sea depths. General, the VSFs show a strong scattering in the forward, a broad scattering minimum in the scattering angular interval 90 to 126° and a weak increase in the rest of backward scattering angles. The analysis of the in situ data also indicates that the magnitude and the shape of the VSF change with areas and profile depths. From Case II to Case I, the forward scattering in 20°, which is mainly due to relatively large suspended particles, varied about three orders magnitude with highest values observed in Case II waters. In Case I waters, form the surface layer to the deeper layer, the magnitude of the VSFs firstly decreased with the depth, and then increased with the depth until reached a maximum scattering layer between 30 to 50m, and then decreased with depth until reached the maximum measurement depth. In Case II waters, the vertical profile distributions of VSF are complex, but in almost all profile, the magnitude of the VSFs firstly decreased with the depth, and then increased with the depth until reached the maximum measurement depth.
The result of analysis also showed that in almost all of these stations, in the surface water, based on the light scattering by bubbles at shallow depths, the angle scattering at 60º-80º has a significant “shoulder”, and the wind plays a key role in the bubble scattering.
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In order to enhance the capability of space-based surveillance, the detailed non-resolved space object characterization with brightness data is described in this paper. Firstly, according to the optical scattering theory, mathematical model for brightness characteristics of space object is established with the bidirectional reflectance distribution function (BRDF) by region classification and grid division. Then, brightness of typical geosynchronous satellites is simulated. Influences of the shape, size and status on brightness are analyzed. Characterization with brightness data is proposed. It shows the shape, size and status of the object can be deduced with brightness data over a range of time-space periods. Finally, the several special fields of non-resolved space object characterization are discussed
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The unresonant procedure of the interaction of atoms with cavity-field by intensity-dependent coupling was analyzed in the union system consisting of multi-atom and multi-cavity using of the complete quantum theory. The results show that through controlling the time of cavity-field interacting with atoms and measuring the atomic states just being out of cavity, the quantum entangled information can be completely exchange between the atomic maximal entangled state and the maximal like-odd-even coherent entangled state. The quantum information can be completely swapping transmit on account of properly confining the detuning value. The process above mentioned display that the evolution is opposite each other in the close system.
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The development decoding algorithms of two-dimensional cross strip anodes image readouts for applications in UV astronomy are described. We present results with Monte Carlo simulation by GEANT4 toolkit, the results show that when the cross strip anode period is 0.5mm and the electrode width is 0.4mm, the spatial resolution accuracy is sufficient to reach better than 5 μm, the temporal resolution accuracy of the event detection can be as low as 100 ps. The influences of the cross strip detector parameters, such as the anode period, the width of anode fingers (electrode), the width of the charge footprint at the anode (determined by the distance and the field between the MCP and the anode), the gain of the MCP and equivalent noise charge (ENC) are also discussed. The development decoding algorithms and simulation results can be useful for the designing and performance improvement of future photon counting imaging detectors for UV Astronomy.
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An ordinary space optical remote sensing camera is an optical diffraction-limited system and a low-pass filter from the theory of Fourier Optics, and all the digital imaging sensors, whether the CCD or CMOS, are low-pass filters as well. Therefore, when the optical image with abundant high-frequency components passes through an optical imaging system, the profuse middle-frequency information is attenuated and the rich high-frequency information is lost, which will blur the remote sensing image. In order to overcome this shortcoming of the space optical remote sensing camera, an online compensating approach of the Modulation Transfer Function in the space cameras is designed. The designed method was realized by a hardware analog circuit placed before the A/D converter, which was composed of adjustable low-pass filters with a calculated value of quality factor Q. Through the adjustment of the quality factor Q of the filters, the MTF of the processed image is compensated. The experiment results display that the realized compensating circuit in a space optical camera is capable of improving the MTF of an optical remote sensing imaging system 30% higher than that of no compensation. This quantized principle can efficiently instruct the MTF compensating circuit design in practice.
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A method is presented for generating multiple-channel color-entangled photon pairs simultaneously based on type I quasi-phase-matched spontaneous parametric downconversion pumped in a single periodically poled lithium niobate (PPLN) crystal. It is predicted that one-, and two-channel color-entangled photon pairs can be simultaneously generated just by suitably choosing the PPLN grating period and the pump frequency. We point out that the full width at half maximum (FWHM) of idler and signal light are broadened dramatically due to spontaneous parametric downconversion in case of a pulsed pump. Then this method is applied for generating multiple-channel polarization-entangled photon pairs simultaneously based on type II quasiphase- matched spontaneous parametric downconversion.
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The spectra of O2 A-band (0.76 μm) and CO2 near-infrared emissions (1.6 μm) for Medium-resolution Satellite (SCIAMACHY) are simulated by the SCIATRAN model (V3.1.29), and compared with the ESFT and LBL method, as the inversion accuracy and time consuming. The time consuming of LBL was more than ESFT with the relative error less than 1%, especially for the CO2 band. But for the CO2 (2.0 um) of High-resolution Satellite, the opposite result was found. That is to say, the LBL method was more suitable for High-resolution Satellite. Different wavelength intervals and integral wavelength steps are applied to the LBL to select the most appropriate combination for High-resolution SatelliteO2 A-band (0.76 μm) and CO2 near-infrared band (1.58 μm).
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It is important for particle detection technology to research the polarization properties of particle’s scattered light and explore the relationship between particle size and polarization degree of its scattered light. Particle scattering model was established and polarization properties of spherical particle’s scattered light with different sizes and different scattering angles was simulated using the finite element method. The polarization degree of particle scattered light were explored with different sizes, also were the polarization degree with different scattering angles. Results show that relationship curves between polarization degree and scattering angles can be described as parabolas. Polarization degree increases when scattering angles increase in the range of 0°-90° and reached the maximum value at 90°. Polarization degree decreases when the size of particle increase and this change more obvious gradually. The polarization degree of particle scattered light reached 1 at 90°when the particle size is much smaller than the wavelength and the maximum value of polarization degree decreases gradually when particle size increase further. In order to verify the correctness of the finite element simulation model, the polarization degrees were calculated in different particle sizes and different scattering angles by classical Mie scattering theory. Polarization simulation model of particle scattered light is proved to be correct and effective by making comparisons between simulation results and theoretical calculation results. This model lays a foundation for the further research on polarization characteristics of particle scattered light with different morphology and distribution.
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In order to improve high-speed laser space optical communications terminal receive energy and emission energy, meet the demand of mini-type and light-type for space-based bear platform, based on multiple-reflect coaxial optical receiving antenna structure, while considering the installation difficulty, a high-efficient optical system had been designed, which aperture is off-axial, both signal-receiving sub-optical system and emission sub-optical system share a same primary optical path. By the separating light lens behind the primary optical path, the received light with little energy will be filtered and shaped and then transmitted to each detector, at the same time, by the coupling element, the high-power laser will be coupling into optical antenna, and then emitted to outside. Applied the power-detected optical system evaluate principle, the optimized off-axial optical system's efficiency had been compared with the coaxial optical system. While, analyzed the Gauss beam energy distribution by numerical theory, discussed that whether off-axis optical system can be an emission terminal, verify the feasibility of the theory of the design of the system.
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We introduced a generalized version of the transport of intensity equation from a partially coherent phase-space perspective that relates axial intensity derivative to the transverse divergence of the conditional frequency moment of the Wigner distribution function. This expression provides a powerful analytical tool for the study of phase retrieval and computational imaging under partially coherent illuminations. The correspondence between the Wigner distribution function and the light field in the geometric optics enables extracting phase information from the light field and vice versa for slowly varying specimen under certain simplified illumination conditions.
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It has been a debatable problem that what the essence of light is, and how it is produced. Since the modern times, as James Clerk Maxwell setting the theory of electromagnetic up, the mainstream consciousness was occupied gradually by the wave theory of light. But at the end of 19th century, a series experimental phenomenon weren't precisely explained by the wave theory of light such as photoelectric effect experiment. Then Albert Einstein published his famous paper “On a Heuristic Viewpoint Concerning the Production and Transformation of Light”, which laid the foundation of light quantum hypothesis. While solving these problems perfectly, a new problem was caused that because the wave theory and the quantum theory are both applicable to interpret some of the experiment of light, what is the essence of light. This paper first outlines the history of optical development and current status, and states the difficulties and deficiencies of the study of light. Then we put forward the key concept of the paper called lightstring which consults some points of the theory of modern optics and physics which called the optical frequency comb and the string theory, then presents the essence of light based on the light string concept in order to make the concept of photons specific. And then we put forward the production mechanism of light ---- the String-Light effect based on the concept of light string. In this paper, we attempt to put forward a new idea of the study of the essence of light and the production mechanism of it.
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The number of perspective views limits the viewing zone of a passive, untracked autostereoscopic display. To enhance the freedom of movement in front of the 3D display, the number of views has to increase as well. An improvement of the viewing zone caused by the raising view numbers will result in lower resolution of each single perspective. A few companies have showed 3D displays with more than 8 or 9 views (including Sunny Ocean Studios 64 view display).
The number of effective orthoscopic stereo image pairs is a triangular number on the base of the perspective views n. Using a stereoscopic glass (with only 2 views), the triangular number nΔ is also 2. But in a 5 view display (i.e. techXpert 3D display), nΔ=10. In a theoretical case, each vertical line of a display, represented by a sub-pixel, could consist a single view. On a real display with 7.680 sub pixel columns, the resulting triangular number is more than 29 million.
The display system guides more than one view in the pupil of the observer’s eye. This superposition principle of views leads to a reduction of channel separation and an increase of cross talk.
It will be examined if a multitude of very low-resolution images with a high crosstalk could reproduce a satisfying 3D
image.
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A thermal effect model is presented in this paper, with the background of ground-based laser irradiating moving and rotating target in the air. Firstly, the encounter scene of laser irradiating target is assumed, and the main parameters of laser and target are given. Secondly, the calculation model of irradiating parameters is derived, including irradiating area, power density distribution and convection heat transfer per unit area. Thirdly, the thermal effect model is established to describe heat conduction and thermal ablation during laser irradiating. Finally, the thermal effects are calculated by assuming the parameters in encounter scene of laser irradiating target. As shown in the example, the thermal effect model can minutely describe the temperature field and ablation results of moving and rotating target irradiated by laser.
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Digital holography (DH) is a 3D imaging technique with a theoretical axial accuracy of better than 1-2 nanome-ters. However, practically, the axial error has been quoted to be tens of nanometers which is much larger than the theoretical value. Previous studies of the axial error mainly focused on the phase error introduced by lens. However, it is found that CCD aperture size is also an important contributors to axial error by our group. It is necessary to investigate the reduction approach of such axial error. The most possible connection between the limited CCD aperture size and the axial error is the diffraction effect. Window functions once have been applied to digital holograms for diffraction suppression and improve the lateral resolution of the intensity image. How-ever, their impacts on phase image and the associated axial dimension measurement are still unknown. In this paper, window functions are applied to digital holograms for phase/axial error reduction. Both simulation and experiment are performed. Moreover, the relation between axial error and window functions is also illustrated by the mathematical formulas derived in the theory. And all the results validate that the window functions can reduce the axial error of digital holography.
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Infrared character of aircraft is one important factor to estimate the ability of breaching the defense of enemy, this paper firstly analyzed the method of infrared calibration with collimator and energy factors composing the sky background, propose one method of deleting energy of background within current image; furthermore, the paper points out that the parameters of calibration with collimator can’t be directly applied to computing Infrared character of flying target, and based on that propose the method of deleting energy of background with another background image measured before mission.
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A single-channel color image encryption method is proposed based on iterative phase iterative process in quaternion Fourier transform domain. First, three components of the plain color image is confused respectively by using cat map. Second, the confused components are combined into a pure quaternion image, which is encode to the phase only function by using an iterative phase retrieval process. Finally, the phase only function is encrypted into the gray scale ciphertext with stationary white noise distribution based on the chaotic diffusion, which has camouflage property to some extent. The corresponding plain color image can be recovered from the ciphertext only with correct keys in the decryption process. Simulation results verify the feasibility and effectiveness of the proposed method.
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Known disparity search range is a crucial parameter for many stereo matching algorithms. It is necessary to estimate the disparity search range automatically in real time systems. In this work, we present an approach to estimate disparity search range of each pixel to be matched. A dual-mode camera which can be used to take stereo images or coarse depth maps is developed in our work. Under the constraint of the coarse depth map with the same spatial resolution as the stereo pairs, expected disparity of each pixel is limited within a narrow search range. We demonstrate the effectiveness of the proposed approach on benchmark images with ground truth as well as on images captured in our lab.
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Two wavelength optical signals in the infrared regime were generated in atomic rubidium (Rb) vapor using a Ti:sapphire laser amplifier and competition between the two signals was observed. The effects of Rb number density, pump laser intensity and the chirp of laser pulses on the characteristics of the two signals were investigated. The results show that the two signals were mainly generated by two coupled difference frequency six wave mixings and, in the meantime, two coupled six wave mixing channels were identified. The competition between the two signals is dominantly governed by phase matching conditions in the two six wave mixing processes. The phase matching conditions in the two channels are primarily determined by the Rb number density and, whereas, the phase matching conditions are scarcely related to pump laser intensity and the chirp of pump laser pulses.
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Cabbage growth and health diagnosis are important parts for cabbage fine planting, spectral imaging technology with the advantages of obtaining spectrum and space information of the target at the same time, which has become a research hotspot at home and abroad. The experiment measures the reflection spectrum at different stages using liquid crystal tunable filter (LCTF) and monochromatic CMOS camera composed of spectral imaging system for cabbage leaves damaged by diamondback moth pests, and analyzes its feature bands and the change of spectral parameters. The study shows that the feature bands of cabbage leaves damaged by diamondback moth pests have a tendency to blue light direction, the red edge towards blue shift, and red valley raising in spectral characteristic parameters, which have a good indication in diagnosing the extent of cabbage damaged by pests. Therefore, it has a unique advantage of monitoring the cabbage leaves damaged by diamondback moth pests by combinating feature bands and spectral characteristic parameters in spectral imaging technology.
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In this paper, absolute spectral responsivity and relative spectral responsivity of silicon trap detectors are presented. The absolute spectral responsivity calibrated with absolute cryogenic radiometer at seven wavelengths between 488nm and 1064nm. The absolute spectral responsivity scale is obtained in the spectral range from 400nm to 1100nm. The external quantum efficiency of the silicon trap detector is investigated.
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The paper presents a hardware in loop dynamic IR scene simulation technology for IR hyperspectral imaging system. Along with fleetly development of new type EO detecting, remote sensing and hyperspectral imaging technique, not only static parameters’ calibration of hyperspectral IR imaging system but also dynamic parameters’ testing and evaluation are required, thus hyperspectral dynamic IR simulation and evaluation become more and more important. Hyperspectral dynamic IR scene projector utilizes hyperspectral space and time domain features controlling spectrum and time synchronously to realize hardware in loop simulation. Hyperspectral IR target and background simulating image can be gained by the accomplishment of 3D model and IR characteristic romancing, hyperspectral dynamic IR scene is produced by image converting device. The main parameters of a developed hyperspectral dynamic IR scene projector: wave band range is 3~5μm, 8~12μm; Field of View (FOV) is 8°; spatial resolution is 1024×768; spectrum resolution is 1%~2%. IR source and simulating scene features should be consistent with spectrum characters of target, and different spectrum channel’s images can be gotten from calibration. A hyperspectral imaging system splits light with dispersing type grating, pushbrooms and collects the output signal of dynamic IR scene projector. With hyperspectral scene spectrum modeling, IR features romancing, atmosphere transmission feature modeling and IR scene projecting, target and scene in outfield can be simulated ideally, simulation and evaluation of IR hyperspectral imaging system’s dynamic features are accomplished in laboratory.
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Raman spectrometry was employed to study the characteristics of Raman spectra of aliphatic polyamide fiber and polyethylene terephthalate (PET), which were treated with sodium hydroxide, sulfuric acid and copper sulfate, respectively. Raman spectra under different conditions were obtained and the characteristics of the Raman spectra were analyzed. The results show that Raman peaks beyond 1200 cm-1 appear for aliphatic polyamide fiber processed by sodium hydroxide, while the Raman peaks beyond 1000 cm-1 disappear for aliphatic polyamide fiber processed by sulfuric acid. Raman peaks beyond 1750 cm-1 decrease for polyethylene terephthalate processed by sodium hydroxide, while Raman peaks beyond 1000 cm-1 disappear, except weak peaks around 3000 cm-1 , for polyethylene terephthalate processed by sulfuric acid. The variations of the Raman spectra are primarily related to the changes of chemical bonds and molecular structures.
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Temporally and Spatially Modulated Fourier Transform Imaging Spectrometer (TSMFTIS) is a new imaging spectrometer without moving mirrors and slits. The interferogram of the target point can be consisted by sequentially arranging the interference information extracted from the same target point of the sequential images, and the spectrum can be recovered by using fast Fourier transform. In the practical application, there is nonuniform sampling in the interference data, and many researchers have carried out researches on nonuniform sampling with the fast Fourier transform algorithm. As to the issue of interference data in the nonuniform sampling, the nonuniform sampling degree’s impact on the recovered spectrum precision is currently and mainly analyzed. This paper has adapted several typical nonuniform fast Fourier transform (NUFFT) methods, carried out spectrum recovery precision comparison on the interferogram of the nonuniform sampling point with the above methods, and further analyzed the impact of kernel function type, oversampling ratio and kernel function width’s on spectrum recovery precision in the above mentioned methods. The experiment result indicates that, when the oversampling ratio is 4 and the kernel function width is 4, the spectrum recovery precision with NUFFT based on Blackman type kernel function is optimal, however, the Gaussian kernel function is stable.
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Traditional spectral based color reproduction technologies cannot achieve the faithful reproduction of the object color. There are errors between reconstructed images and original ones. To solve this problem, an error compensation method is researched in this paper after spectral reflectance reconstruction and dimension reduction of spectral data. Experimental data show that the proposed method can significantly improve spectral accuracy, decrease system disturbance and achieve device independent and scene unrelated features.
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In this paper, light-emitting diode (LED) based two-dimensional fluorescence correlation spectroscopy was used to discriminate tea leaves with different grades. The distance between LED and tea samples was changed as an external variable. As the fluorescence spectral data collected through the experiment was large, principal component regression (PCR) was used to extract the important information and analyze the spectral data. The final two-dimensional fluorescence correlation spectra contour maps showed obvious difference between different tea leaves and the predictive results based on the leave-one-out method. It showed the strong ability of this spectral method for tea classification.
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In this paper, HMME-TiO2 nanocomposites was synthesized and characterized through TEM, Uv-vis spectra, Zeta potential, FTIR spectra. The characterization results show that HMME was successfully conjugated onto the surface of TiO2. It can be seen from the TEM images the average size of HMME-TiO2 conjugation is nearly spherical and the particle size range from 20 to 28 nm. Compared with HMME, the B bands of HMME-TiO2 were much broader and lower while in the region of Q bands the absorption peaks of HMME-TiO2 are higher than that of HMME. Encapsulation efficiency of HMME-loaded TiO2 was assessed and calculated as 45.46%. FTIR spectra show the bonding between TiO2 and HMME was through the hydrogen-bonding between COOH and OH bonds. Fluorescence microscope results demonstrated HMME-TiO2 mainly distributed in the membrane and cytoplasm of SCC cells and its best incubation time is six hours. After treated with HMME-TiO2 plus light irradiation (1.8J/cm2 , 632nm), the viability of SCC cells turned to 32.96% is much lower than that treated with HMME plus light irradiation. It can be concluded that the combination of HMME and TiO2 will enhance the PDT efficiency of HMME. In the process of HMME-TiO2 mediated PDT, as a kind of photosensitizer HMME can induce the death of SCC cells, meanwhile it can transform electron to the conductive band of TiO2 stimulating the photocatalytic activity of TiO2 under visible light. The photocatalytic of TiO2 can also induce the death of SCC cells. The combination of these two effects lead to more SCC cells died.
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Abstract: An instrument was built to measure the output fluorescence response characteristics of a 248nm KrF laser using 4mm-thick fluorescent glass as a screen. Experiments show when irradiated laser intensity is no more than 0.7J/cm2, the fluorescent response is linear. And the fluorescent spot intensity distribution was spatial coherent with the output beam profile distribution of the LPX-150. So we can use high-homogeneity optical glasses as fluorescence wavelength conversion material in beam profile measurements.
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Future space missions may use laser power beaming systems with a high power laser to transmit light to a photovoltaic array receiver. The photovoltaic array receiver can be mounted to a satellite or a spacecraft. To investigate the V-I and P-V characteristics of photovoltaic cells (PV cells) under laser illumination, a mathematical model and simulation model related to the voltage and current of PV cells is studied. Based on the MATLAB simulation tool, the simulated V-I and P-V characteristics of PV cells for various irradiances are presented. To validate the simulated results, three experiments are designed. The results obtained by experimenting are compared with the simulated results, and the difference between them is not apparent.
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Infrared-to-visible upconversion emission intensities are investigated in Li+/Er3+, Li+/Ho3+/Yb3+ and Li+/Tm3+/Yb3+
codoped oxide nanocrystals. By introducing Li+ ion, the upconversion emission intensity of rare-earth ions are
significantly enhanced comparing with that without the Li+ ion. The local structure around Er3+ and Ho3+ ions are studied
by the extended X-ray absorption fine structure spectroscopy. After doping Li+ ion, both the average bond lengths of
Er-O and Ho-O are decreased.
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Total internal reflection diffraction gratings in conical mounting, where the plane of incidence does not contain the grating vector, are investigated in this paper and the relevant conditions and parameters for such gratings are presented. These are then used to design total internal reflection diffraction gratings in conical mounting that the diffraction angle into the first order is equal to the incidence angle. The applications of such gratings in conical mounting to planar optics configurations, which have at least three gratings and one of them is total internal reflection diffraction grating in conical mounting, are discussed in detail. Also, the diffraction properties of all three gratings in this configuration, especially the grating period which is the most important parameter of gratings, are analyzed. The main condition, on which all the gratings in planar display configuration have the same grating periods, is presented based on theoretical analysis: the turning grating should be in 60 deg conical mounting. The configuration can be used to virtual display or wearable display.
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The digital calendar circuits controlled by 80C52 have been designed based on Proteus simulation software. The whole design process is made of three parts: hardware circuits, software programming and software simulation. Finally, it shows that the circuit design of hardware and software is correct through Proteus software simulation. The method of circuit design is systematic and practical, which will provide certain design ideas and reference value for display circuit in the future.
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A humidity sensor based on microfiber Bragg grating is proposed and demonstrated. The microfiber Bragg grating is obtained through chemical etching commercial fiber Bragg grating. The experimental results show that the central wavelength of the microfiber Bragg grating has red shift with humidity increasing, while the power decreases. The relative humidity sensitivity of the microfiber Bragg grating with diameter of 8.9um is 3pm/%RH in the range of 55%-80%RH. Furthermore, the sensor has a linear response to humidity with linear fitting of 0.991. The sensor possesses advantages of easy fabrication and low cost.
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The negative refractive index characteristics of one-dimensional photonic crystal consisted by Fibonacci multi-layer films has been studied by numerical method. The refractive indices for two materials, which are used to construct the Fibonacci multi-layer films, are 0.920 and 0.999, respectively. The calculation result shows that, on one hand, there are several negative refractive index zones for this kind of photonic crystal even if the refractive indices are very small; on the other hand, the difference is very large for the frequency between the zones. As an example, a kind of transmission-type plano-concave lens is designed. The simulation of the electromagnetic field distribution for the lens demonstrates that the lens can focus the incoming X-ray radiation. At the same time, the calculation of the absorption strength and refractive indices for real materials shows that not only there are large differences for the absorption strength with different materials, but also the refractive indices for real materials are different in X-ray band. Obviously, the characteristics above support a kind of transmission-type lens using in X-ray.
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We theoretically investigated the ultrafast thermal excitation behaviors on Au films surface irradiated by polarization-shaped femtosecond laser. The spatio-temporal dynamics of temperature evolution in Au film with polarization-shaped femtosecond laser excitation are obtained based on Finite Element Method (FEM). It is revealed that the phonon temperature fields can be flexibly adjusted by optimizing the polarization state combinations of polarization-shaped double femtosecond laser pulses. The results are attributed to pulse synthetic effect, which closely depends on the polarization state combinations of double femtosecond laser pulses. The study provides the basic for understanding of the thermal excitation dynamics for optimizing laser micro and nano-fabrications via tailoring the polarization state of temporally shaped femtosecond laser.
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The monolayer SiNx optical thin films were prepared by Plasma Enhanced Chemical Vapor Deposition (PECVD) technology on the BK7 glass substrate, the laser-induced damage threshold was measured by laser damage testing equipment, and we also investigated the relations between processing techniques and laser-induced damage properties. The study and analysis to orthogonal experiment results show that PECVD processing techniques have an effect on the laser-induced damage properties. Among them,radio frequency has the biggest effection, temperature is the main factor, working pressure is the unimportant factor, and we also achieve the optimal processing parameters (Temperature is 350℃; RF power is 250W; Working pressure is 60Pa).
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Ordinary inter-satellite optical includes at least three optical paths for acquisition, tracking and communication, the three optical paths work simultaneously and share the received power. An optimal structure of inter-satellite optical communication terminal with single working optical path at each of working stages of acquisition and communication is introduced. A space optical switch based on frustrated total internal reflection effect is applied to switch the received laser power between the acquisition sensor and the communication sensor between the stages of acquisition and communication, this is named as power fusion which means power is transferred for shutting down unused optical path. For the stages of tracking and communication, a multiple cells sensor is used to accomplish the operation of tracking while communication, this is named as function fusion which means accomplishing multiple functions by one device to reduce the redundant optical paths. For optical communication terminal with single working path structure, the total received laser power would be detected by one sensor for each different stages of acquisition, tracking and communication, the link budget would be maximized, and this design would help to enlarge the system tolerance and reduce the acquisition time.
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Surface conduction electron emission device (SED) was fabricated with a back gate electrode. And then the device was electroformed in using continuous triangle wave at vacuum environment. After that we prepare an aluminum back electrode on the back of device. With the back electrode voltage changing, we could observe the change of the emission current. When device voltage and anode are fixed, the device’s emission current and efficiency decrease under positive back voltage of 5V. On the contrary, the device’s emission current and efficiency increase with negative back voltage of -5V. Our results directly proved that the emission electrons were from the field include cool electron emission, but not from the power induced thermal electron emission due to size-effect.
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The bit error rate is raised by the presence of the noise when the quantum key transmits in practice. So both sides of communication can not judge the presence of eavesdropping. For this issue, an improved scheme based on BB84 protocol is proposed by a paper of Luanxin that a matrix transformation is carried out for every quantum of both sides. The advantage of the transformation is that the eavesdropper can be found easily. But the disadvantage is that it leads to a low key generation rate. In this paper, an improvement that a matrix transformation is carried out randomly for the quantum of both sides based on the scheme of Luanxin is proposed. The result shows that not only the presence of eavesdropping can be judged easily, but also the key generation rate is increased significantly.
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Readout circuit is designed for a special retina-like CMOS image sensor. To realize the pixels timing drive and readout of the sensor, the Altera's Cyclone II FPGA is used as a control chip. The voltage of the sensor is supported by a voltage chip initialized by SPI with AVR MCU system. The analog image signal outputted by the sensor is converted to digital image data by 12-bits A/D converter ADS807 and the digital data is memorized in the SRAM. Using the Camera-link image grabber, the data stored in SRAM is transformed to image shown on PC. Experimental results show the circuit works well on retina-like CMOS timing drive and image readout and images can be displayed properly on the PC.
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The complex index of refraction was the fixed characteristic of the target material. In the remote sense field, the complex index of the refraction is a useful parameter for classify and recognize the material. To detect the complex index of the refraction of the opaque material was difficult. A new method of estimating the complex refraction index based on the measured polarization degree of the material according to the different incident angle of reflectance angle was provided. The result showed that the stability and reliability of the acquired complex refraction index was fine.
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Imaging laser radar is a new type radar with vast potentials, that it can provide echo intensity image, range gating image, velocity image and three-dimensional image of the target at the same time. In order to improve its performance, to combine the polarization spectral detection technique with the imaging laser radar technique is worth studying. In this paper, the author studies the characteristics of laser echo using the method of modeling, as well as the theories of Stokes parameters and Mueller matrices. In the first place the author derives a polarized bidirectional reflectance distribution function (polarized BRDF) model that simulates the polarimetric of the laser echo from the basic theory with established scalar BRDF models. Then it makes a simulation of all the process of the model construction and compares the results to the experiment data. With the results of comparison it makes corrections of some parameters in the polarized model and obtains a relatively correct polarized model in the end. At last, the author induces the characteristics of laser echo with some main influence factors.
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A high average power and high beam quality nanosecond laser is presented that is based on CW diode side-pumped Nd:YVO4 grazing-incidence slab amplifier. A TEM00, passively Q-switched diode-pumped Nd:YAG laser as the seed laser, generating a M2 ≈1.3 beam train of 0.25W, 2.3ns pulses with adjustable repetition rate in the range 5-20kHz. After double-pass amplification, more than 20W of output power with a beam quality of M2 ≈1.4 is obtained at an optical-optical efficiency of 35%. The high brightness of this laser system seems ideal for nonlinear optics and laser processing applications.
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The color based on prism dispersion was analyzed and the mathematical model was established in this paper. Firstly, based on Dan Bruton's research, the mapping relationship between visible wavelength and data in color map matrix was created, the geometric data of color after dispersion of the prism was processed with least squares curve fitting, then the mapping relationship between wavelength and the refractive index was built. Secondly, on the basis of the work before, the mapping relationship between wavelength and projection geometry was built. Finally, through the building of color management system, the characterization of spectral lines and colors in LAB color space would be got.
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Framing camera based on gated Micro-channel plate (MCP) was widely used in inertial confinement fusion (ICF) and Z-pinch because of its ultrafast time-resolve. Electrons with imaging information are multiplied when the HV pulse propagating through the MCP strip line. Obviously, the HV pulse was used as a shutter here, then the exposure time of the imagine will be determined by the width of the pulse. Theoretical analysis indicates that thegating pulse(200ps) has a bandwidth of 5GHz, thus, impedance match in the propagating path of the pulse will be very important. Impedance mismatch will cause reflecting of the pulse and decrease the transmission efficiency. This will cause un-uniformity of the dynamic gain of the MCP, and finally resulting in imagedistortion. A new designed impedance matching circuit is developed in this paper. Simulated results showedthatthe newdesignedimpedance matching circuit couldreduce the reflection of thegating pulse significantly, and dynamicgain uniformity of the MCP was increased simultaneously
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Diamond-like carbon (DLC) filmare widely used in the infrared protection window, but their ability of anti-laser damage is insufficient. The common methods to improve the anti-laser ability of DLC films were summarized at first, then a new method which use the external electric field was proposed. Based on the standards ISO11254 of laser damage threshold, the damage morphology of DLC films with and without the bias field were compared. The results show that with the bias field, damage morphologies changes obviously under the same laser energy. According to the physical mechanism analysis, the photogenerated electrons of the films under the action of electric field drift speedy, the drift reduce the heat generated from the laser radiation area, then relayed the graphitization of the DLC films. This after-treated method will be a new method to improve DLC films’ anti-laser damage ability.
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We present evidence that transmission loss in gated x-ray framing cameras can affect relative gains. Transmission loss is caused by a variety of factors including: incident voltage waveform, matched load, width of Au electrode gap, and so on. The transition electrode in MCP (Micro-channel Plate) is continuous gradual change line, and it has good capability of compensation. When continuous gradual change micro-strip line is designed, dielectric loss tangent is one of transmission loss factors too. The model structure is designed based on the analysis of modeling and simulation techniques and experiment data as well as forecast target. The transmission loss is reduced from 50% to 25%, the transmission efficiency is greatly improved.
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The III-V nitride material such as InGaN has many favorable physical properties including a wide direct band-gap (0.7- 3.4eV), high absorption coefficients (105 cm-1), and high radiation resistance. As such, InGaN has been chosen as an excellent material for full-solar-spectrum photovoltaic applications utilizing its wide and tunable band-gap. The refractive index of GaN is about 2.5 in the full-solar-spectrum. According to the Fresnel formula, there is a high reflection of ~18.4% as the sun light entering GaN. Anti-reflection films could be used on InGaN/GaN solar cell to decrease the reflection loss. The photonic crystal structure is a kind of anti-reflection based on the effective medium theory without any limitations, for example the mismatched thermal expansion coefficient. In this paper, we reported our research work on the design and fabrication of photonic crystal structure on the surface of GaN. FDTD Solutions is used to simulate the reflectivity on the surface of GaN with hexagonal close-packed pillar which has different period-a, diameter-d and height-h. When the parameters a is 500nm, d is 300nm, the reflectivity reached the lowest point of 4.18%. The self-assembly method was used to fabricate the photonic crystal structure on the GaN surface and the fabrication process was also researched. The photonic crystal structures on the surface of p-GaN were obtained and their characteristics of the antireflective film will be discussed in detail.
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With the development of lighting technology, high-power white LEDs will become the future mainstream technology. At present, there are still many problems in optical stability, reliability, heat dissipation. This paper focuses on the optical properties of vertical high-power white LEDs. The measurement results of the luminous flux output, correlated color temperature and color coordinates of the white and blue LEDs after 1100 hours of aging life testing under the drive current of 350 mA show us that the color coordinates of the white LED changed from (0.3362,0.3700) to (0.3359,0.3698) and shifts to the blue color coordinates direction. The luminous flux output of the white LED is declined from 95.002lm to 93.046lm. The color temperature declines from 5403k to 5383k. After the rapid temperature changes, the aging speed of white LED is faster than the blue LED’s. Analyzing the results, it can be concluded that phosphor aging rate greatly affects the optical stability of the device, how to improve the stability of phosphor is the key to improve optical stability for the vertical high-power white LED.
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This paper carries out theoretical research and numerical simulation on the temperature characteristics of LPFG magnetic field sensor based on magnetic fluids. The simulation results show that the change of ambient temperature can make coupling resonance wavelength of the long period fiber grating drift, change the refractive index of magnetic fluids, which affects the measurement precision of the magnetic field. Our research has a certain significance for the practical application of LPFG magnetic field sensor based on magnetic fluids.
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According to the sensing principle of FBG, the measurement performance of magnetic field sensor based on the differential group delay (DGD) in FBG is discussed in this article. The influence of external environmental parameters, including temperature, stress and pressure, on magnetic field sensor based on DGD are then analyzed from the aspect of theory and simulated through Matlab. As the simulation results indicates, the magnetic field sensing scheme based on DGD is not sensitive to temperature and stress, the specific performance is that the changing temperature or stress can make the DGD spectrum move along the horizontal axis (the wavelength), with the shape unchanged; when temperature variation or phase axial stress maintains the same, the DGD has a linear relation with the magnetic induction intensity. While the external pressure has serious impact on the magnetic field sensing scheme, which is apparently embodied in nonlinear and irregular change of DGD spectrum with the varying pressure.
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The analysis of the temperature property of sensors based on symmetrical metal-cladding optical waveguide (SMCOW) is focused on analyzing the temperature property of reflectivity of SMCOW sensors, which is theoretically studied with single-factor investigation under spectral and angular interrogation scheme. There are mainly four factors influencing the temperature dependence of reflectivity, it is the temperature dependence of refractive index and thickness of guiding layer, along with the temperature dependence of the metal film thickness and metal-dielectric function. The simulation result shows that the effect of temperature on the reflectivity of SMCOW is mainly attributed to the temperature dependence of refractive index and thickness of guiding layeron the contrary, the temperature properties of metal film hardly contributes to the influence of temperature on the reflectivity. Based on the analysis, the sensitivities of SMCOW with guiding layer of different optical glasses are computed under both spectral and angular interrogation. This paper is supposed to provide direction in designing temperature-sensitive SMCOW structure sensors.
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Back-illuminated near-infrared detectors were designed and fabricated using p-InGaAs/p-InP/i-InGaAs/n-InP p-i-n layer structure. In order to optimize the detector layer structure, the device was simulated by drift-diffusion simulator “SimWindows” first, and then the epitaxy material was grown by metal organic chemical vapor deposition (MOCVD). The current-voltage characteristics of the fabricated detectors with and without light were investigated respectively. The results show that the responsivity of the detectors is around 0.7 A/W, and the dark current is about 1×10-4 A/cm2 at reverse bias 0.1V, both of which are comparable to the simulated results. Our results also show the smaller detector has better dark current density, and the dominated mechanisms of dark current are discussed in the paper.
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In this study, the fabrication and characterization of AlGaInP-based light-emitting diodes (LEDs) with further improvement by the design of a SiO2 current blocking layer were described. It was found that with the SiO2 CBL, the injected current can be forced to spread outside instead of flowing directly downward under the p-pad electrode. At 20mA, as compared to traditional LEDs, the optical output power for novel LEDs is increased by about 30%. We found that the novel LEDs have better saturation characteristics, this improvement is contributed to more uniform of injection current and less heat generation in the novel LED chips.
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An designed output coupler used for the dispersion compensation in Cr:LiSAF femtosecond lasers is reported. It is composed of 50 alternating Ta2O5 and SiO2 layers whose thicknesses are obtained by computer optimization to provide low transmittance and as little as possible group delay dispersion. The optimized output coupler has continuous low transmittance of 1% and group delay dispersion of 0 ±6fs2 from 750nm to 900nm, which can meet the need of dispersion compensation in Cr:LiSAF lasers.
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An electrically controllable fiber Bragg grating (FBG) for working in the communication band is demonstrated by utilizing holographic polymer-dispersed liquid crystal (HPDLCs). PDLC is infiltrated in hollow-core fibers which are about 2μm and 5μm by means of capillarity. For the purpose of periodically separating polymer and liquid crystal to form an FBG, a two-beam interference system based on an argon laser (wavelength: 364nm) is used. To reduce coupling loss, we directly connect single-mode fibers (SMFs) to input and output ports. A maximum transmission loss dip of approximately 5-dB band rejection is obtained. After the cladding diameter is etched by buffered oxide etchant (BOE) solution to 12μm and a 150V external voltage is applied, a dip shift by ~ 15nm is measured
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In order to reduce the nonlinear effects in optical fiber effectively and make energy output of the light beam much more uniformly, a flat-top beam-shaping device based on micro-structured optical fiber (MOF) has been designed in this paper. Output of flat-top fundamental mode is realized by introducing a low refractive index inner core in the refraction-guiding MOF. Based on this principle, output performance of flat-top MOF is simulated and alayzed with the Rsoft. The structure parameters of the flat-top MOF are obtained after optimization, and the diameter of the corresponding mode field is 10.37 μm and the defect degree is 0.16%. These results show that the flat-top fundamental mode with large mode area can be carried out in the designed MOF, and moreover, they also provide theoretical basis for the fabrication of the flat-top MOF.
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Based on the propagation of Gaussian light, Zemax program is used to simulate the pump light propagating process and absorbing distribution for LDA side-pump laser rod,and the corresponding heat load distribution analysis of the rod is done by using Lascad program.On the basis of simulation results,the pump parameters of LDA side-pump Nd:YAG are optimized which provide valuable guidances for side-pump LDA designing and pump module engineering.
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For imaging equipments, exposure is one of the crucial factors for evaluating the quality of imaging. The correct method of exposure is the key to obtain high-quality image. Traditional calculation of exposure is slow in adaptation under extreme environment. In addition, the object of imaging under extreme light usually cannot achieve suitable gray level. To obtain accurate and effective control of automatic exposure under back light and front light environment, this article divides shoot scenes into different regions, applying the method of fuzzy logic to give each region a different weight number, and finally allowing it to correctly carry out automatic exposure. This method can manage imaging under special light conditions without being affected by the position of the main object. Experiments show that this method can effectively control automatic exposure under all kinds of environments.
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A high-sensitivity Mach-Zehnder(MZ) interferometric refractive index(RI) sensor based on two different ultra-abrupt
tapers is proposed and demonstrated experimentally. The whole fabrication process is relatively simple. One taper is
fabricated by the fusion-splicing method and the ratio of the waist diameter to the taper length is 1:1. The other taper is
fabricated by CO2 laser irradiation with a ratio around 1:10. According to the experimental results, the spectral loss of
the proposed MZ interferometric sensor has a linear response to the external RI change with a ultrahigh sensitivity of
-412.02138 dB/RIU(refractive index unit) in the range of 1.3505-1.3684. The sensor has the potential application for RI
measurement in chemical or biochemical sensing fields due to its low cost, simple structure and extremely high
sensitivity.
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A novel strain sensor based on in-fiber Mach-Zehnder interferometer (MZI) is proposed in this paper. The sensor is with the structure of single mode-thin core-multimode-thin core-single mode (STMTS) fiber structures fabricated by splicing two short sections of thin core fiber (TCF) among lead-in single mode fiber (SMF), multi-mode fiber (MMF) and lead-out SMF. The first section of TCF excites the core mode and high-order modes in the core of MMF and the second section of TCF couples the core mode and high-order modes into lead-out SMF to procedure inter-modes interferences. The sensor with MMF length of 20mm and TCFs length of 1mm is fabricated. The transmission spectrum of the sensor with respect to external strain has been studied by experiment. The result shows that the central wavelength respects to external strain with a good linearity. The strain sensitivity of the sensor is -2 pm/ue; over a strain range of 0 to 4500ue;. The temperature response of the sensor is also studied by experiment. The results indicate that the central wavelength of the transmission spectrum is insensitive to external temperature change. The proposed sensor features the advantages of easy fabrication, low cost and high sensitivity, and it exhibits great potential in single parameter measurement.
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In the system of airborne remote sensing measurement, the optical system should meet the requirements of long focal length, large aperture, light weight and wide waveband due to the particular characteristics of usage environment and observation objects. To meet the special requirements of the optical system structure, an off-axis four-mirror reflective optical system is designed based on an off-axis three-mirror reflective optical system from modern optical design theory. The structure and principle of the off-axis four-mirror reflective system are described and the MTF curve is given in this paper. At the same time, according to the working environmental condition of the system, the temperature adaptability of the system is analyzed and the analysis results are given. Based on the results, the system error is analyzed and discussed in detail applying the precision theory. The system error for each optical component is analyzed and allocated. The qualitative analysis for the influence factors of system error is also given.
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Photoelectric rotary table as the main test tracking measurement platform, widely use in shooting range and aerospace fields. In the range of photoelectric tracking measurement system, in order to meet the photoelectric testing instruments and equipment of laboratory and field application demand, research and design the portable photoelectric rotary table data acquisition and analysis system, and introduces the FPGA device based on Xilinx company Virtex-4 series and its peripheral module of the system hardware design, and the software design of host computer in VC++ 6.0 programming platform and MFC package based on class libraries. The data acquisition and analysis system for data acquisition, display and storage, commission control, analysis, laboratory wave playback, transmission and fault diagnosis, and other functions into an organic whole, has the advantages of small volume, can be embedded, high speed, portable, simple operation, etc. By photoelectric tracking turntable as experimental object, carries on the system software and hardware alignment, the experimental results show that the system can realize the data acquisition, analysis and processing of photoelectric tracking equipment and control of turntable debugging good, and measurement results are accurate, reliable and good maintainability and extensibility. The research design for advancing the photoelectric tracking measurement equipment debugging for diagnosis and condition monitoring and fault analysis as well as the standardization and normalization of the interface and improve the maintainability of equipment is of great significance, and has certain innovative and practical value.
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Photoelectric rotary table is mainly used in the defense industry and military fields, especially in the shooting range, target tracking, target acquisition, aerospace aspects play an important one. For range photoelectric measuring equipment field test application requirements, combined with a portable photoelectric rotary table data acquisition hardware system, software programming platform is presented based on the VC++, using MFC prepared PC interface, the realization of photoelectric turntable data acquisition, analysis and processing and debugging control. The host computer software design of serial communication and protocol, real-time data acquisition and display, real-time data curve drawing, analog acquisition, debugging guide, error analysis program, and gives the specific design method. Finally, through the photoelectric rotary table data acquisition hardware system alignment, the experimental results show that host computer software can better accomplish with lower machine data transmission, data acquisition, control and analysis, and to achieve the desired effect, the entire software system running performance is stable, flexible, strong practicality and reliability, the advantages of good scalability.
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Conformal imaging systems are confronted with dynamic aberration in optical design processing. In classical optical designs, for combination high requirements of field of view, optical speed, environmental adaption and imaging quality, further enhancements can be achieved only by the introduction of increased complexity of aberration corrector. In recent years of computational imaging, the adaptive coded apertures techniques which has several potential advantages over more traditional optical systems is particularly suitable for military infrared imaging systems. The merits of this new concept include low mass, volume and moments of inertia, potentially lower costs, graceful failure modes, steerable fields of regard with no macroscopic moving parts.
Example application for conformal imaging system design where the elements of a set of binary coded aperture masks are applied are optimization designed is presented in this paper, simulation results show that the optical performance is closely related to the mask design and the reconstruction algorithm optimization. As a dynamic aberration corrector, a binary-amplitude mask located at the aperture stop is optimized to mitigate dynamic optical aberrations when the field of regard changes and allow sufficient information to be recorded by the detector for the recovery of a sharp image using digital image restoration in conformal optical system.
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In the process of developing the photoelectric image acquisition equipment, it needs to verify the function and performance. In order to make the photoelectric device recall the image data formerly in the process of debugging and testing, a design scheme of the camera simulator is presented. In this system, with FPGA as the control core, the image data is saved in NAND flash trough USB2.0 bus. Due to the access rate of the NAND, flash is too slow to meet the requirement of the sytsem, to fix the problem, the pipeline technique and the High-Band-Buses technique are applied in the design to improve the storage rate. It reads image data out from flash in the control logic of FPGA and output separately from three different interface of Camera Link, LVDS and PAL, which can provide image data for photoelectric image acquisition equipment’s debugging and algorithm validation. However, because the standard of PAL image resolution is 720*576, the resolution is different between PAL image and input image, so the image can be output after the resolution conversion. The experimental results demonstrate that the camera simulator outputs three format image sequence correctly, which can be captured and displayed by frame gather. And the three-format image data can meet test requirements of the most equipment, shorten debugging time and improve the test efficiency.
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As one of the most significant parts in the development of the next generation infrared detection system, the infrared signal processing system requires the ability of real-time processing and high speed data transmission. A newly developed real-time signal processing system for infrared detecting based on the heterogeneous multiprocessor system on chip (MPSoC) is proposed in this paper. The device follows the architecture of Xilinx Zynq platform, integrating a feature rich dual-core ARM and Xilinx FPGA in a single chip, built on the 28nm high-k metal gate process technology. According to our design, the FPGA fabric portion retains all the programmable flexibility to drive the infrared detector and acquire data from ADC, with registers parallel operations to implement hardware acceleration. Furthermore, the FPGA fabric is connected to the ARM centered processor unit through multiple high performance interfaces, confirming high bandwidth communication and high speed data transmission between the two portions. Finally, the dual core ARM takes charge of the infrared signal processing system in general. One of the CPUs controls separate hardware modules and maintains the GUI for user interaction. The other responds to the dedicated system commands and external interrupts to update system parameters simultaneously. The integration of ARM and FPGA provides levels of performance that two-chip solutions cannot match due to their limited I/O bandwidth, loose coupling and power budgets. Experiments show that the architecture of heterogeneous MPSoC enhances the efficiency of memory controller and increases the speed of data transmission, approaching the theoretical value of the interfaces bandwidth.
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In recent years, the off-axis aspheric surface is widely used in wide coverage and high-resolution space optical systems. In this paper, research on processing technology of high precision and high efficiency off-axis ellipsoid aspheric mirror was studied deeply. With the help of CNC milling and polishing machine, off-axis ellipsoid aspheric mirror with diameter of 58mm was developed, by optimizing the concentration of polish liquid, grinding size, machining direction and other process parameters, based on the disadvantage of traditional processing that off-axis aspheric is easy to generate edge splitting and secondary surface damage, a new processing method "vertical off-axis ellipsoid aspheric surface processing method" was put forward. This method not only ensures the accuracy of work piece of optical axis, surface accuracy and accuracy of the edge, but also reduces secondary surface damage, improves processing efficiency and achieves high precision and high efficiency processing of off-axis ellipsoid aspheric surface, which is conducive to mass production. Through the detection of off-axis ellipsoid aspheric mirror by Taylor Profiler , surface accuracy (PV value) is 0.1981μm, the aspheric surface finish is level II and the optical axis accuracy is 0.01mm that it meets the requirements.
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Laser polishing technique using thermal effect of the interaction of light with matter to achieve removal of material, it is a non contact polishing techniques. In recent years, ultra fast laser polishing techniques got great progress, when ultra fast laser matter interaction, no thermal effect or thermal effect is very small, the removal of material is achieved primarily through momentum transfer. In the material removal process will appear the phenomenon of surface atoms in the redistribution, using this effect, we are likely to achieve the manufacture of the ultra smooth surface of atomic scale magnitude. This article has discussed and analyzed the mechanism of ultra fast laser semiconductor materials, based on this, parameters and their influence on the influence of ultra fast laser polished monocrystalline silicon effects were studied. Used the orthogonal experiment method to optimize the main parameters of the laser polishing, it can reach to a better combination of optimized parameter values. Used self-built picosecond laser polishing system and did monocrystalline silicon polishing experiment, got a good polishing effect.
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A satellite laser communications network structure with two layers and multiple domains has been proposed, which performance has been simulated by OPENT. To simulation, we design several OPNET models of the network’s components based on a satellite constellation with two layers and multiple domains, as network model, node model, MAC layer protocol and optical antenna model. The network model consists of core layer and access layer. The core network consists of four geostationary orbit (GEO) satellites which are uniformly distributed in the geostationary orbit. The access network consists of 6 low Earth orbit (LEO) satellites which is the walker delta (walk-δ) constellation with three orbit planes. In access layer, each plane has two satellites, and the constellation is stably. The satellite constellation presented for space laser network can meet the demand of coverage in the middle and low latitude by a few satellites. Also several terminal device models such as the space laser transmitter, receiver, protocol layer module and optical antenna have been designed according to the inter-satellite links in different orbits t from GEO to LEO or GEO to ground. The influence to network of different transmitting throughput, receiving throughput, network protocol and average time delay are simulated. Simulation results of network coverage, connectivity and traffic load performance in different scenes show that the satellite laser network presented by the paper can be fit for high-speed satellite communications. Such analysis can provide effective reference for the research of satellite laser networking and communication protocol.
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Celestial navigation subsystem of airborne celestial/inertial integrated navigation system periodically correct the positioning error and heading drift of the inertial navigation system, by which the inertial navigation system can greatly improve the accuracy of long-endurance navigation. Thus the navigation accuracy of airborne celestial navigation subsystem directly decides the accuracy of the integrated navigation system if it works for long time. By building the mathematical model of the airborne celestial navigation system based on the inertial navigation system, using the method of linear coordinate transformation, we establish the error transfer equation for the positioning algorithm of airborne celestial system. Based on these we built the positioning error model of the celestial navigation. And then, based on the positioning error model we analyze and simulate the positioning error which are caused by the error of the star tracking platform with the MATLAB software. Finally, the positioning error model is verified by the information of the star obtained from the optical measurement device in range and the device whose location are known. The analysis and simulation results show that the level accuracy and north accuracy of tracking platform are important factors that limit airborne celestial navigation systems to improve the positioning accuracy, and the positioning error have an approximate linear relationship with the level error and north error of tracking platform. The error of the verification results are in 1000m, which shows that the model is correct.
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As the performance of the previous distortion correction methods is not well for the wide-angel lens, we present a two-step correction algorithm for wide-angle distortion by using the Division Model and the coherent detection. In our algorithm, a grid template is used as the calibration target. Firstly, we approximate the distortion characteristic of wide-angle lens with single parameter Division Model, and then fit the distorted straight line with a circular arc to calculate the distortion parameter and distorted center. Secondly, we correct the residually distorted image, which is gotten from the previous step, with coherent detection to compensate the error between Division Model and the distortion characteristics of wide-angle lens. The quantitative assessment and experiment results show that the presented distortion correction algorithm is easy to achieve and has high accuracy.
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For the realization of target detection and monitoring of a wide range with the unmanned aerial vehicle (UAV), an UAV-based reconnaissance and surveillance system was proposed. The main optical system was consisted of visible camera with narrow field of view (FOV), mid-wave infrared camera (MWIR) and long-wave infrared camera (LWIR). The aperture was shared and the spectrum was disparted in the terminal. The diameter of primary mirror was 170mm. The focal length was 880mm and field of view was 0.86º for visible camera with narrow FOV, the focal length was 880mm and field of view was 0.8º for MWIR camera, the focal length was 220mm and field of view was 3.2º for LWIR camera. Considering the influence of temperature on the imaging quality, a kind of material with good thermal property was used as mirror substrate. The athermalization method was introduced to realize a high image quality in a wide temperature range of -40℃~+65℃. Zoom optical system was adopted in the visible camera with middle FOV and wide FOV, the view of it was 3.4º~34º. The operating distance of laser channel was designed to 20km. The results of the design indicated that this set of optical system could be used for ground target detection and monitoring of a wide range, met user’s requirement.
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With the demand of autonomous precision guidance of air defense missile, the system scheme of the IR imaging/Ladar dual-mode seeker with a common aperture was proposed, and the optical system used in was designed. The system had a common receiving aperture, and its structure was very compact, so it could meet the requirement for the miniaturization of the seeker. Besides, it also could meet the demands of a wide field of view for searching target, and the demands for accurately recognizing and tracking the target at the same time. In order to increase the narrow FOV tracking performance, the dual FOV infrared optical used the zooming mode which some components flip in or out the optical system to firm the target signal. The dual FOV optics are divided into the zooming part, with dual variable focal length, and the reimaging part which was chosen in such a way to minimize the objective lens while maintaining 100% cold shield efficiency. The final infrared optics including 4°×3°(NFOV) and 16°×12°(WFOV) was designed. The NFOV lens composed of two common IR/Ladar lens, three relay lens, a beam splitter and two reflective fold mirrors, while WFOV lens increased two lens such as Germanium and Silicon. The common IR/Ladar lens ZnS and ZnSe could refractive the IR optics and Laser optics. The beam splitter which refractived IR optics and reflected Laser optics was located in the middle of Germanium and Silicon. The designed optical system had good image quality, and fulfilled the performance requirement of seeker system.
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In order to realize the real-time segmentation processing of multi spectral images in practice, a real-time multi-spectral images segmentation system composed of four TMS320C6455 DSPs, two Virtex-4(V4 XC4VLX80)FPGAs and one Virtex-2 Pro(V2 Pro20)FPGA is designed. Through the optimization of the cooperation processing of the multi DSP and multi FPGA, the parallel multitask processing ability of the DSPs and the effective interface coordination ability of the FPGAs in the built system are used fully. In order to display the processing ability, the segmentation test experiments of 10 spectra visible images, with 1024×1024, segmented by the Multi-scale Image Segmentation Method, was done in the built multi spectral images segment system. The experiment results prove that the multi DSP and multi FPGA multi spectral images processing system designed in this paper satisfies the real-time processing requirement in engineering practice.
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According to the requirement of detector, a continuous zooming TV camera with a high resolution and a large zoom ratios used for precision strike was designed. In this paper, basis the selection of continuous zooming optical systems was discussed. Combing with PW method, the incipient structure was computed. Using the CODE V, the optimum design was done. Having analyzed the cam curve of this zooming system, a continuous zooming optical system meeting the technical requirements well was designed, which provided the technical support for the miniaturization of the structure and the stability of the optic axis. This continuous zooming optical system has been checked with image quality testing, real imaging and environment testing and the result showed that the image quality was well, the optic axis was stable and the system meet the requirement of detector well.
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An off-axis reflecting dual-band common optical path optical system is described, which integrating MWIR and VIS band. The front part is an off-axis reflecting afocal telescope, then the collimated light is splitted into MWIR and VIS band. Dual-FOV MWIR and VIS lens zoom in and out by flip in and out two lens. Comparing to other common optical path optical system, this one has the advantage of compact structure, unobstructed pupils, little chromatic aberrations, high transmittance. Good image performance is realized in dual-band optical system by CodeV analysis.
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A new detecting system on color space resolution of imaging system is proposed in this study. We define color space resolution as the just distinguished spatial frequency. It can be detectable to a trained operator on a test image which is a color four-bar pattern of various spatial frequencies. Testing patterns are generated by two light beams produced by the color generator separately going through the four-bar target, the collimating optical system, color imaging system and color management module, finally displayed on the display. Observers obtain the information of the testing pattern on the display, and record the just distinguished spatial frequency. Comparing to the traditional method, by simulation and feasibility analysis, it can be concluded that: this design not only reduces the system error, but also improves the stability and the precision. Additionally, it indicates a new aspect for the application of different color spaces.
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In order to improve the reliability and working performance of the optical window for airborne optoelectronic equipment, we conduct the aerodynamic analysis of airborne optoelectronic equipment under different flight speed, and get the aerodynamic load distribution of optical window under three different typical flight speed. By building the model of the optical window and simulating the model with the method of CFD, the deformation and stress caused by aerodynamic loading under different thickness of the optical window have been got. The results shows that the thickness of the optical window at 10mm could best meet the requirements of structural strength and quality. Then we analysis the impact of the deformation of the optical window on the imaging quality of the optical system. The deformation of the optical window is very tiny, and it is deformed from the flat into a spherical whose radius is very large. The MTF of the optical system after deformation are basically the same as its MTF before deformation. Thus, the impact of the deformation of the optical window on the imaging quality of the optical system can be ignored. The results of the analysis provide important reference for the design of the optical window for airborne optoelectronic equipment.
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The determination of numerical reconstruction distance is key to recover the wavefront at focal plane in digital holography. In this paper, we propose a new autofocus method based on angular spectrum method (ASM). The proposed method takes successive Fourier transform after 1st order spectrum selection, and then calculates the summation. It saves operations compared to classic autofocus functions. When an exhaustive z-axis search is performed, the proposed method obtains unimodality coincided with the results from four classic autofocus functions. Moreover, the proposed method is more time-effective, which is the optimal one for ASM.
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The influence of polarization state and energy distribution of the incident beam on the spot properties of the super-resolution near-field structure (Super-RENS) disc system for various numerical aperture (NA) of the objective lens is analyzed. According to rigorous vector diffraction theory, the spot properties on the recording layer corresponding to linearly, circularly and radially polarized incident beam are analyzed respectively. The simulation results indicate that, wide spot of the incident beam and high NA of the objective lens are beneficial to obtain sharp spot on the recording layer. Furthermore, the circularly polarized incident beam can generate sharper and more symmetrical spot on the recording layer than that of the radially and the linearly polarized beams. However, by introducing annular aperture illumination, the radially polarized incident beam generates the tightest spot if high annulus ratio is applied.
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In this paper, we designed the laser scanning galvanometer system according to our requirements. Based on scanning range of our laser scanning galvanometer system, the design parameters of this system were optimized. During this work, we focused on the design of the f-θ field lens. An optical system of patent lens in the optical manual book, which had three glasses structure, was used in our designs. Combining the aberration theory, the aberration corrections and image quality evaluations were finished using Code V optical design software. An optimum f-θ field lens was designed, which had focal length of 434 mm, pupil diameter of 30 mm, scanning range of 160 mm × 160 mm, and half field angle of 18°×18°. At the last, we studied the influences of temperature changes on our system.
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In order to overcome the problem of low spatial resolution in ordinary optical microscopy, microscopic indirect imaging with super resolution is introduced. This article elaborates three aspects of the status and trends of indirect imaging system: first, the theories in variable optical coupling transmission and the super resolution metrology; second, metrology method and model of multidimensional optical wave vector parameter; third, the theory in super resolution indirect vectorial parameter imaging by modulation and compensative imaging of multi-spatial dimensions and physical parameters.
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Solar blind UV detecting system has many advantages such as strong environmental adaptability, low error rate, small volume and without refrigeration. To in-depth develop UV solar blind detection system research work has important significance for further improving solar blind UV detection technology. The working principle of solar blind UV detection system and the basic components were introduced firstly, and then the key technology of solar blind UV detection system was deeply analyzed. Finally, large coverage solar blind UV optical imaging system was designed according to the actual demand for greater coverage of the solar blind UV detection system. The result shows that the system has good imaging quality, simple and compact structure. This system can be used in various types of solar blind UV detection system, and is of high application value.
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The III-N material system (including alloys of InN, AlN, and GaN) has several characteristics which give it key advantages over the existing solar cell materials, for example, the high absorption coefficient and high carrier mobility, more important, the wide range of band gap energies which spans nearly the entire solar spectrum. In this paper, we fabricated a multiple quantum well (MQW) InGaN/GaN solar cell. The photovoltaic characteristics of the device was demonstrated that, the short circuit current density (JSC) is about 0.43mA/cm2 , the open circuit voltage is about 2.2 eV, and the fill factor is about 81%. But the peak external quantum efficiency (EQE) is not very high, only 30%. And the conversion efficiency is about 0.83%, so more work for device design should be done in the future.
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With the development of the digital airborne photo-grammetry technology, the more performances of the optical system for airborne mapping camera are required, such as the longer focal, the wider field of view (FOV), at the same time, the secondary spectrum correction becomes more important and difficult for the optical system design. A high performance optical system of airborne mapping camera with 200mm focus and2ω=60°FOV is designed in this paper. The range of work wavelength is from 430nm to 885nm. A two-layer HDOE with negative dispersive characteristic is used to eliminate the secondary spectrum in the process of optical system design. The diffraction efficiency of the designed two-layer HDOE is up to 90%. From the result of design, the MTFs in whole fields are over 0.5 at 90lp/mm, which shows that the system has a great image quality. Meantime, the thermal analysis is done at the temperature range between -20°C and 40°C, and the MTF curves of the system at-20°C ~40°C show that a great image quality is kept, which meets the design requirements.
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Based on the principle of capacitor pre-charging, an analog pulse stretch circuit is designed for detecting peak power of narrow laser impulse. Experimental test were carried out. And it could achieve regulation accuracy of 5ps, jitter<600ps. Due to the need of different delay ranges during the practical applications, the analog pulse stretch circuit is optimized. It doesn’t only meet the different adjustment ranges, but also maintains high regulation accuracy.
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In order to solve the problem of the existing single waveband thermal imaging system can’t get precise temperature of object with emissivity unknown, an optical system of beam splitting lens and filter were used to established a colorimetric temperature measurement system based on infrared thermal imaging system. Completed the compensation for non-effective pixel, enhancement of contrast, calibration of nonhomogeneity and coherence for infrared thermal imaging system according to the application requirement, then acquired the calibration data with blackbody as radiation source at 200°~500° and fit it. A temperature measurement test performed at last, compared with the result acquired by thermocouple and single waveband thermal imaging system, it was shown that the colorimetric pyrometry system achieve the attractive precision after calibration and applied to measure the temperature of the object with emissivity unknown.
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This paper describe a research theoretically of the conversion result to the surface temperature based on long wave infrared detector, proposed a temperature measurement, then validate it by experiments. First, it introduces the constitution and measurement principle of the medical infrared thermal imager. Then, the conversion drift characteristic of infrared detect is described, the experimental data under variable environment is analyzed, and a temperature measurement and a drift compensation formula is proposed. Finally, some experiment with black body was accomplished. The results show the temperature error is under 0.3°C, confirm the validity of the measurement.
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The fine pointing mechanism of the Acquisition, Pointing and Tracking (APT) system in free space laser communication usually use four-quadrant detector (QD) to point and track the laser beam accurately. The positioning precision of QD is one of the key factors of the pointing accuracy to APT system. A positioning system is designed based on FPGA and DSP in this paper, which can realize the sampling of AD, the positioning algorithm and the control of the fast swing mirror. We analyze the positioning error of facular center calculated by universal algorithm when the facular energy obeys Gauss distribution from the working principle of QD. A database is built by calculation and simulation with MatLab software, in which the facular center calculated by universal algorithm is corresponded with the facular center of Gaussian beam, and the database is stored in two pieces of E2PROM as the external memory of DSP. The facular center of Gaussian beam is inquiry in the database on the basis of the facular center calculated by universal algorithm in DSP. The experiment results show that the positioning accuracy of the high-precision positioning system is much better than the positioning accuracy calculated by universal algorithm.
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Doppler asymmetric spatial heterodyne spectroscopy (DASH) is a new technology for measuring upper atmospheric winds by observing the Doppler shift of atmospheric emission lines from a satellite using a limb viewing geometry. The real-fringe DASH interferometer is a modification of conventional DASH interferometer; it keeps the advantages of the conventional one. Moreover, this interferometer will not need exit optics to image the superposed fringes onto the detector; it will be more compact and lightweight, making it suitable for space-based platforms. We describe the concept of the new interferometer and present the exact expression of spatial frequency and phase of the interferogram. We also describe design and simulation of a real-fringe DASH interferometer for observation of the O [1D] 630nm emission. The simulation results agree with the theory.
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The paper will describe an automated subaperture stitching interferometry for large plano surface based on relevant algorithm, which restruct the whole surface without recording the position of every subaperture. Both correction and data fusion algorithm are used to minimize the stitching error.
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In order to design a online diameter measurement system for Hot-rolled seamless steel tube production line. On one hand, it can play a stimulate part in the domestic pipe measuring technique. On the other hand, it can also make our domestic hot rolled seamless steel tube enterprises gain a strong product competitiveness with low input. Through the analysis of various detection methods and techniques contrast, this paper choose a CCD camera-based online caliper system design. The system mainly includes the hardware measurement portion and the image processing section, combining with software control technology and image processing technology, which can complete online measurement of heat tube diameter. Taking into account the complexity of the actual job site situation, it can choose a relatively simple and reasonable layout. The image processing section mainly to solve the camera calibration and the application of a function in Matlab, to achieve the diameter size display directly through the algorithm to calculate the image. I build a simulation platform in the design last phase, successfully, collect images for processing, to prove the feasibility and rationality of the design and make error in less than 2%. The design successfully using photoelectric detection technology to solve real work problems
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Phase shifting interferometry is commonly used in precision optical surface measurement, but which possesses some limitation because of the sensitivity to environment. Therefore, it is hardly used in optical testing in the workshop environment. Thus, the instantaneous interferometry is a good choice because of the insensitive to vibration. This paper will describe an instantaneous interferometry utilizing spatial carrier and Fourier transform, and discuss the accuracy of the interferometer for optical testing when phase-shifting interferometry is unable to realize the precision measurement. With a lot of experiments, some problems were analyzed, including the relationships between the measurement accuracy and systematic error, vibration, temperature, the test surface cleanliness and so on. The discussed work of error restraint can provide a reference for the instantaneous interferometry applications.
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A model experiment was designed, and Faraday instabilities were generated in a plexiglass cylinder excited by a pneumatic shaker. A contacting distance meter and a single-point fiber-optic vibrometer were applied to measure the displacement/velocity of the shaker, both of the results are in good agreement with each other. Besides, the fibre-optic laser vibrometer was exploited to measure the velocity of the interface between potassium hydroxide aqueous solution and Galinstan. It shows that the fibre-optic vibrometer can be applied to measure the interface movements without Faraday instabilities, whereas there are strong scatter and the interface displacement can only be obtained qualitatively. In this case, a scanning vibrometer or a high-speed CCD camera should be used to record the interface movements.
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Four different shapes of probe tips are employed to perform scanning experiments on highly ordered pyrolytic graphite samples. I-Z curves and I-V curves for the tunnel current on the surface are obtained and, in the meantime, the influences of tip shape on the height scanning image are analyzed. The results show that tip shape differences have remarkable influences on the sharpness of probe tip, the resolution of the height scanning images increases with the sharpness of probe tip. The requirement for ladder scan level is much lower than that for the atom scan level. Different shapes of probe tips have little effects on the I-V curves for ladder scan. Accordingly, probe tips with only two cuts, which are suitable for ladder scan, can be obtained easily and accurately
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Single photon detectors nowadays are widely used in numerous applications such as quantum cryptography, laser ranging, single molecule spectroscopy and so on. And the calibration of the detection efficiency is quite important for some of the applications. In recent years, researchers find that correlated photon pairs can be employed to calibrate the detection efficiency of single-photon detectors with quite high precision. Firstly, we calibrated the InGaAs single photon detector quantum efficiency at 1550nm by correlated photon pairs. Consistency between the measurement result using correlated photon pairs and the reference value is better than 0.8%. Secondly, the detectors are calibrated with an attenuated laser source. Thirdly, the two methods for measuring the quantum efficiency of single photon detectors, correlated photon pairs and laser attenuation, respectively, are discussed and analyzed in detail. Finally, results derived from the two methods have been compared with each other.
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The aerosol transmittance on the transmission route can not be ignored in atmosphere transmittance calculation. The classical mathematic models at present just calculate the vertical transmittance. MODTRAN is a good choice, but it is difficult called in users own project. In this paper, we build a model of the vertical transmittance for aerosol patterns by exponential regression analysis, and calculate aerosol transmittance on slant route by the simple mathematical relationship of vertical transmittance and horizontal transmittance. In this way, the aerosol transmittance on common route can be calculated just by the altitude of detector and slant angle of the route. We suggest the method in this paper can be easily used for the calculation in users project of real-time infrared simulation of missile-borne or airborne detector. According to the experiments, the average residuals of transmittance on slant route is less than 0.0005, while that on horizontal route is less than 0.0003.
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Laser Rayleigh-Brillouin scattering is an effective non-intrusive method for measurement of density, temperature and pressure in gas flows. In theory, the power of Rayleigh-Brillouin scattered laser light is proportional to the gas density, the full width at half maximum (FWHM) and the Brillouin shift of the Rayleigh-Brillouin scattering spectrum is related to the gas temperature and pressure, respectively. In this paper, a measurement device based on Fabry-Perot interferometer (FPI) is designed to measure the Rayleigh-Brillouin spectrum of nitrogen gas. The experimental data is obtained at different pressures under room temperature conditions. The L3 model is used to fit the experimental data to obtain the FWHMs and Brillouin shifts of the Rayleigh-Brillouin profiles. The composite Rayleigh-Brillouin profiles which consist of Rayleigh peak, stokes peak and anti-stokes peak are represented by three distinct peaks of Lorentz functions. Fitting results show that the error of FWHMs and Brillouin shifts obtained by L3 model is less than 10% compare with the Tenti S6 model. Some factors that affect the measurement accuracy of the Rayleigh-Brillouin parameters are also analyzed and discussed.
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Due to environmental interference and atmospheric disturbance and other factors, the interference fringes are always drifting. So, the traditional hardware phase shift could not meet the high accuracy demodulation of interference. In this paper, virtual phase shift based on moiré fringes are introduced to realize the phase demodulation of interference fringe. The virtual digital phase shifting interference fringes are generated by computer, and superposed with tested interference fringe to generate phase shifting moire fringe, which are processed through applying phase shift demodulation techniques and the Fourior transform then to obtain the phase information tested. To verify the technique here, a specific experiment for a diameter of 50mm flat optics is executed, and the experimental result is compared with ZYGO-verifire PE interferometer. Our method eliminates the nonlinear error of the hardware phase shifter while improving the processing accuracy, and especially suitable for high-precision testing for optical component with complex environment or for large-aperture optical component, or even the system greatly simplifies the structure of interferometer.
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Temporally and Spatially Modulated Fourier Transform Imaging Spectrometer (TSMFTIS) is a new imaging spectrometer without moving mirrors and slits. As applied in remote sensing, TSMFTIS needs to rely on push-broom of the flying platform to obtain the interferogram of the target detected, and if the moving state of the flying platform changed during the imaging process, the target interferogram picked up from the remote sensing image sequence will deviate from the ideal interferogram, then the target spectrum recovered shall not reflect the real characteristic of the ground target object. Therefore, in order to achieve a high precision spectrum recovery of the target detected, the geometry position of the target point on the TSMFTIS image surface can be calculated in accordance with the sub-pixel image registration method, and the real point interferogram of the target can be obtained with image interpolation method. The core idea of the interpolation methods (nearest, bilinear and cubic etc) are to obtain the grey value of the point to be interpolated by weighting the grey value of the pixel around and with the kernel function constructed by the distance between the pixel around and the point to be interpolated. This paper adopts the gauss-based kernel regression mode, present a kernel function that consists of the grey information making use of the relative deviation and the distance information, then the kernel function is controlled by the deviation degree between the grey value of the pixel around and the means value so as to adjust weights self adaptively. The simulation adopts the partial spectrum data obtained by the pushbroom hyperspectral imager (PHI) as the spectrum of the target, obtains the successively push broomed motion error image in combination with the related parameter of the actual aviation platform; then obtains the interferogram of the target point with the above interpolation method; finally, recovers spectrogram with the nonuniform fast Fourier transform algorithm. Compared with the accurate spectrogram, the spectrogram recovered with the relative deviation-based kernel regression interpolation method has remarkable improvement over the previous methods.
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Large-aperture optical elements are widely employed in high-power laser system, astronomy, and outer-space technology. Sub-aperture stitching is an effective way to extend the lateral and vertical dynamic range of a conventional interferometer. Most of the commercial available sub-aperture stitching interferometers measure the surface with a standard lens that produces a reference wavefront, and the precision of the interferometer is generally limited by the standard lens. The test accuracy can be achieved by removing the error of reference surface by the absolute testing method. In our paper we use the different sub-apertures as the different flats to get the profile of the reference lens. Only two lens in the testing process which is fewer than the traditional 3-flat method. In the testing equipment, we add a reflective lens and a lens which can transparent and reflect to get the non rationally symmetric errors of the testing flat. The arithmetic is present in this paper which uses the absolute testing method to improve the testing accuracy of the sub-aperture stitching interferometers by removing the errors caused by reference surface.
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The ultrafast laser polishing technology is a new surface processing technology in recent years. Because this technology has the characteristics of the polishing quality and less heat effect, it is very suitable for high precision polishing for hard brittle materials. This paper from the ultrafast laser polishing system structures, experimental design, and data analysis, etc., studies the ultrafast laser polishing principle and processing technology of single crystal silicon. In the experiment, the system with femtosecond laser (λ=515nm, f=4kHz) and picosecond laser (λ=532nm, f=200kHz) polishing materials, after processing, system using digital microscope and surface profiler tests the surface roughness and surface morphology of the region. This paper analyzes the laser energy density, the spot overlap and scanning mode for ultrafast laser polishing quality. The orthogonal experiment design can be clearly analyzes the importance of factors are in polishing effect. And the single factor experiment design can be clearly analyzes the parameter level changes on the polishing effect. Combining with two methods of experiment, parameters can be optimized scientifically and comprehensively.
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A high precision radius automatic measurement method using laser differential confocal technology is proposed. Based on the property of an axial intensity curve that the null point precisely corresponds to the focus of the objective and the bipolar property, the method uses the composite PID (proportional-integral-derivative) control to ensure the steady movement of the motor for process of quick-trigger scanning, and uses least-squares linear fitting to obtain the position of the cat-eye and confocal positions, then calculates the radius of curvature of lens. By setting the number of measure times, precision auto-repeat measurement of the radius of curvature is achieved. The experiment indicates that the method has the measurement accuracy of better than 2 ppm, and the measuring repeatability is better than 0.05 μm. In comparison with the existing manual-single measurement, this method has a high measurement precision, a strong environment anti-interference capability, a better measuring repeatability which is only tenth of former’s.
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An equipment for measuring transmission index of optic material in high temperature is introduced in the paper. A kyptol was used as infrared light source and narrow band filter was used to generate the monochrome light. Two parallel flat reflectors separated the light source into two ways, one was sample beam and the other was reference beam. A chopper was used to modulate the light and a lock-in amplifier was used to detect the infrared light. High precision temperature heater was used to control the temperature of sample material. The equipment has the ability to measure the transmission index of optic material from 1μm to 14μm and the temperature scope from room temperature to 700℃. Measurement principle and makeup of the equipment are introduced in the paper. Transmissions of Al2O3 and germanium in high temperature were reported in the end.
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In order to measure high-precision and large scale sensing signal and solve two-values question in signal detecting of strain sensor, we design a new kind of FBG matching demodulation system based on fiber Bragg grating matching demodulation principle. Through paralleling connection two groups of grating-matching whose center wavelength equal to sensing grating’s, and then analyzing reflectance spectrum, we could get the relationship of strain and optical power detected by photoelectric detector. Then we can set up the theoretical model and complete system simulation. The simulation results show that the scheme is feasible. The scheme not only can solve the problem of double values and can simultaneously detect the positive and negative strain. The sensor measurement range can be up to952ue.
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In this paper, an optical fiber multiplexing interferometric system including a Fizeau interferometer and a Michelson interferometer is designed for remote and high precision step height measurement. The Fizeau interferometer which is inserted in the remote sensing field is used for sensing the measurand, while the Michelson interferometer which is stabilized by a feedback loop works in both modes of low coherence interferometry and high coherence interferometry to demodulate the measurand. The range of the step height is determined by the low coherence interferometry and the value of it is measured precisely by the high coherence interferometry. High precision has been obtained by using the symmetrical peak-searching method to address the peak of the low coherence interferogram precisely and stabilizing the Michelson interferometer with a feedback loop. The maximum step height that could be measured is 6 mm while the measurement resolution is less than 1 nm. The standard deviation of 10 times measurement results of a step height of 1 mm configurated with two gauge blocks is 0.5 nm.
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This paper introduces the research and design of laser triangulation measurement system based on linear array CCD, and the correctness of the theoretical analysis and the feasibility of the design will be verified by the experiments. The principle of optical system of direct-incident laser triangulation measurement is analyzed theoretically from laser triangulation measurement principle and practical measurement requirement. A measurement system, which consists of a semiconductor laser source, an imaging Plano-convex lens, and a high-speed linear CCD, is designed. In these experiments, the high-speed linear array CCD optoelectronic data are obtained by acquisition and transmission system of USB interface. Through the corresponding relation between displacement variation of measured object and the pixel position of laser spot imaging on linear CCD, the measurement system uses the different fitting equations to be calibrated. Comparing displacement variation of the calibration results calculating with the actual one, the results shows that the measurement precision of using the four fitting can reach 0.47mm, the range of measuring is 200mm. The results show that the measurement system is correct and valid for medium displacement measurement.
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This paper proposes a novel geometric statistical measurement of long sequence moving objects, which can accurately measure the geometry of the moving objects in non-contact measurement environment. The proposed algorithm adopts detecting-learning method for tracking moving objects in a long-term, gets the moving sequence data, extracts the geometric contour and computes the geometric and motion parameters of the objects. Then we analyze the long sequence to train the parameters. Experimental data showed that the adoption of geometric measurement of moving objects based on detecting-learning mechanism performs favorably. The method can provide high-accuracy geometric and motion parameters of the objects.
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Laser ranging technology is an industrial non contact measuring technology. With the rapidly development of electronics and optical technology, the measuring precision has been improved continuously. In this paper, a simple structure measuring system which based on laser triangulation measuring theory, was built. The system consist of single point laser and CMOS receiver, its measuring range is from 90mm to 110mm. In order to get a higher position accuracy of light spot, gauss cumulative method was used in this paper. For realize the precision system calibration, a linear calibration method was introduced. The experiment shows that the system get a measuring precision of 10um.
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Lateral shearing interference detection is a economically efficient method which is used to the online testing process of aspheric surface. Whereas, when shear plate is used in lateral shearing interference to detect large aperture aspherical surface, the real moving shear plate can produce shearing error, which brings error into the two-dimensional wavefront reconstruction of aspheric surface. So, for shearing error, Zernike polynomial fitting method is used to study shearing displacement error on the influence of two-dimensional wavefront information reconstruction by computer simulation. For the same measured non-spherical surface, different shearing displacement error influences on the precision of wavefront reconstruction are compared by computer simulation,and finally build the corresponding relations between wave information integrity and shearing displacement error
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Fast, precise 3-D measurement of step-structures fabricated on microelectronic products is essential for quality assurance of semiconductor, flat panel display and photovoltaic products. Optical interferometers have long been used, but not that wide-spread for step-structures due to their phase ambiguity or low spatial coherence. Femtosecond pulse lasers can provide novel possibilities to optical profilometry both in the time and the frequency domain. In the time domain, step-surfaces can be measured over wide area by exploiting low temporal but high spatial coherence of femtosecond pulses; in the frequency domain, multi-wavelength interferometry permits the absolute measurement over the discontinued surface profiles while maintaining the sub-wavelength measurement precision.
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We demonstrate a novel method which is simple, real-time, and non-destructive to measure the core diameter of a coaxial cylinder. An optical fiber is an example of coaxial cylinder. The diameter measurement method is based on side-light-incidence scattering principle. For a cladding diameter 126μm coaxial fiber, our method could be used to measure core diameter ranging from 8 to 40μm. We could measure the core diameter of a coaxial cylinder for cladding diameter varying from 50 μm to 125 μm from our database. The accuracy of core diameter measurement could reach over 95%.
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In dental restoration, its important to achieve a high-accuracy digital impression. Most of the existing intraoral measurement systems can only measure the tooth from a single view. Therfore,if we are wilng to acquire the whole data of a tooth, the scans of the tooth from multi-direction ad the data stitching based on the features of the surface are needed, which increases the measurement duration and influence the measurement accuracy. In this paper, we introduce a fringe-projection based on multi-view intraoral measurement system. It can acquire 3D data of the occlusal surface, the buccal surface and the lingual surface of a tooth synchronously, by using a senor with three mirrors, which aim at the three surfaces respectively and thus expand the measuring area. The constant relationship of the three mirrors is calibrated before measurement and can help stitch the data clouds acquired through different mirrors accurately. Therefore the system can obtain the 3D data of a tooth without the need to measure it from different directions for many times. Experiments proved the availability and reliability of this miniaturized measurement system.
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In this work it is shown the benefit of using waveform integration of the avalanche pulses of MPPC for enhancing the photon number resolving capability of Multi-Pixel Photon Counter (MPPC). Up to 47 photon equivalent peaks can be distinguished in the Photon-Number-Resolving (PNR) spectrum with a repetition frequency of 80 MHz, which is the largest reported number obtained at room temperature as far as we know.
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Imaging systems with high temporal resolution are needed to study rapid physical phenomena ranging from shock waves, including extracorporeal shock waves used for surgery, to diagnostics of laser fusion and fuel injection in internal combustion engines. However, conventional streak cameras use a vacuum tube making thus fragile, cumbersome and expensive. Here we report an CMOS streak camera project consists in reproducing completely this streak camera functionality with a single CMOS chip. By changing the mode of charge transfer of CMOS image sensor, fast photoelectric diagnostics of single point with linear CMOS and high-speed line scanning with array CMOS sensor can be achieved respectively. A fast photoelectric diagnostics system has been designed and fabricated to investigate the feasibility of this method. Finally, the dynamic operation of the sensors is exposed. Measurements show a sample time of 500 ps and a time resolution better than 2 ns.
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Laser-induced plasma spectroscopy (LIPS) made a great progress as a potential technology for nuclear analysis and detection. In this article, the instrumentation of LIPS for In-situ and stand-off application was introduced. The application of LIPS in nuclear industry was reviewed, such as international nuclear safeguard, nuclear materials analysis, hazard material detection and monitoring process, etc.
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This paper proposes that surface roughness of optical element is detected using total integrated scattering method, Meanwhile, establishing the relational model between surface roughness and subsurface damage to get the depth of subsurface damage rapidly and accurately after we measured surface roughness so as to achieve the goal of detection of optical element’s surface microstructure.
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In this paper, we used FDTD Solutions software to simulate the reflectance of two-dimensional photonic crystal by changing duty ratio from 40% to 70%. The different models, which are referred by Stavenga, Southwell and Grann et al, were used for obtaining the equivalent refractive index. And then the simulations of double layer dielectric structure designed in FDTD Solutions was used for getting the reflectance curves by importing the data of the equivalent refractive index. After comparing these curves we could obtain that the accuracy of different models are related to the ratio of the period(P) and wavelength(λ). Thus the equivalent refractive theory has its most applicable models of micro structure in different period scales. The imprecise quantitative explaining of micro structures’ antireflection by using equivalent refractive theory models was solved in this paper, which has important significance in many areas.
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One important approach to characterize full three-dimensional information is to simulate the etching process of a sample with subsurface damage reversely. The simulation starts from the morphology of the sample at a certain time when the subsurface damage can be opened totally. In the etching experiment, it is possible for us to get the surface morphology at any time. The paper presents a finite difference algorithm to simulate the morphology evolution in an etching process and by the finite difference algorithm the morphology of the sample at a specific time can be given. Comparison of the simulated morphology and measured one provides us the clue of improving the finite difference algorithm. In this paper, the accuracy can be calculated through comparing the simulation with experimental result, and the maximum error of subsurface damage will be calculated.
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Recently, more focuses have been put on organic semiconductors because of its advantages, such as its flexibility, ease of fabrication and potential low cost, etc. The reasons we pay highlight on small molecular photovoltaic material are its ease of purification, easy to adjust and determine structure, easy to assemble range units and get high carrier mobility, etc. Simulation study on organic small molecular solar cells before the experiment can help the researchers find relationship between the efficiency and structure parameters, properties of material, estimate the performance of the device, bring the optimization of guidance. Also, the applicability of the model used in simulation can be discussed by comparison with experimental data. This paper summaries principle, structure, progress of numerical simulation on organic small molecular solar cells.
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This paper reports a flexible fabrication method for 3D solenoid microcoils in silica glass. The method consists of femtosecond laser wet etching (FLWE) and microsolidics process. The 3D microchannel with high aspect ratio is fabricated by an improved FLWE method. In the microsolidics process, an alloy was chosen as the conductive metal. The microwires are achieved by injecting liquid alloy into the microchannel, and allowing the alloy to cool and solidify. The alloy microwires with high melting point can overcome the limitation of working temperature and improve the electrical property. The geometry, the height and diameter of microcoils were flexibly fabricated by the pre-designed laser writing path, the laser power and etching time. The 3D microcoils can provide uniform magnetic field and be widely integrated in many magnetic microsystems.
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Miniaturization is a development trend of electronics, machinery and information systems, while micro structure brought a large amount of new development for industrial and research applications, whereas, slow measuring speed and two-dimensional results of traditional micro measurement could not meet our needs, it’s urgent to find a matching testing techniques with more sensitivity, more effectiveness and better to have a real-time three-dimensional display. Digital holography applied to the measurement of micro structure, it made up for the lacking of traditional micro structure measure systems of too much time consuming, poor immunity, easily damaging samples with its simple structure, high accuracy, non contact features and three-dimensional reproduction. This paper analyzed the key factors of digital holographic recording and reproducing process.In order to solve the low quality of holograms captured by traditional recording system, holograms and pre-processing algorithm was combined for real-time, by observing the holograms and delicate adjusting the system, to ensure that the collected holograms with full use of CCD width while convenient for subsequent processing. In the processing of reproduction,the influence of spectrum choice, reconstruction wavelength and algorithms and unwrapping algorithm was been studied, and finally obtained an accurate three-dimensional topography of the object. The improved rerecording system and reconstruction algorithm mentioned above solved the low holography quality, much noise and not clear shortcomings of the reconstructed image. Experiment on a raster, compared with traditional system and algorithm results, results showed that the recording system and determine algorithms can reproduce the three-dimensional topography of the object with high precision and has a broader applicability.
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The etching process of the high aspect ratio of Si deep trench is the key technology in MEMS field. Having used Oxford Plasmalabsystem100 ICP-180 etcher with SF6 and C4F8 as the etching gas, the influence on the deep Si etching process of Bosch under different ICP power, bias voltage, temperature, pressure and other parameters has been studied. The experimental result shows that under appropriate parameters, the high-aspect ratio of silicon deep trench is greater than 26:1, the sidewalls’ vertical degree is 89.9°, and the etching rate is greater than 2μm/min; the high aspect ratio of SOI deep trench is greater than 28:1, the sidewalls’ vertical degree is 89.7°, and the etching rate is greater than 2μm/min.
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The four kinds of atoms, such as carbon (C), oxygen (O), copper (Cu) and sodium (Na), are adsorbed on the Si (001) surface, the curves of the band structure and density of states with different elements were plotted. From the curves, the pseudogap, forbidden bandwidth, energy curve of the ups and downs, the trend of Fermi level in the graphics and density of states at the Fermi level were analyzed and compared for different elements absorption. Through comparative analysis, the conclusions were come to. Research Conclusions: the property of absorption element decides the localization properties of electronic, the pseudogap, forbidden bandwidth, Energy curve of the ups and downs, the trend of Fermi level in the graphics, density of states at the Fermi level and etc.
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Microchannel plates(MCPs)are the key component of the image intensifier. Compared with the traditional MCPs, the Si MCPs which are fabricated by micro-nanofabrication technologies have a high gain, low noise and high resolution etc. In this paper, the lithography process is studied in the process of fabricating periodic micropore array with 10 um pores and 5 um pitch on Si. The effects of exposure time, reversal bake temperature and development time on the lithography quality are focused. By doing a series of experiments the better result is got: the photoresist film is obtained at a low speed 500/15(rpm/s) and a high speed 4500/50(rpm/s); the soft bake time is 10min at 100℃; the exposure time is 10s; the reversal bake time is 80s at 115℃; the development time is 55s. By microscope observation and measurement, the pattern is complete and the size of the pattern is accure, it meets the requirement of lithography process for fabricating Si-MCP.
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In this study, a three-dimensional (3D) micromixer with cross-linked double helical microchannels is studied to achieve rapid mixing of fluids at low Reynolds numbers (Re). The 3D micromixer takes full advantages of the chaotic advection model with helical microchannels; meanwhile, the proposed crossing structure of double helical microchannels enables two flow patterns of repelling flow and straight flow in the fluids to promote the agitation effect. The complex 3D micromixer is realized by an improved femtosecond laser wet etching (FLWE) technology embedded in fused silica. The mixing results show that cross-linked double helical microchannels can achieve excellent mixing within 3 cycles (300 μm) over a wide range of low Re (1.5×10-3~600), which compare well with the conventional passive micromixers. This highly-effective micromixer is hoped to contribute to the integration of microfluidic systems.
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SiGe-OI (Silicon Germanium on insulator) material is a new type of semiconductor material, and the refractive index of waveguide region can be effectively improved in electro-optic modulator with SiGe-OI materials. More importantly, used SiGe-OI material, the injection efficiency of electro-optic modulator can be improved. Based on the early research of SiGe-OI optical waveguide, PIN structure is selected as electrical modulation structure of electro-optic modulator, and the electrical modulation mechanism of PIN structure is studied. PIN structure is built by ISE-TCAD soft, and the carriers injection efficiency are analyzed. The doping concentration of active region, the width of active region, the width between active region and waveguide, Ge content and the other parameters are analyzed and optimized. Finally, compared with SOI electro-optic modulator, the carriers injection efficiency of SiGe-OI electro-optic modulator are increased 87.5%, in other words,modulation voltage of SiGe-OI electro-optic modulator can be reduced, so as to effectively reduce modulation power.
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A three-dimensional model of the field in the vicinity of a spherical inclusion in fused silica illuminated by a laser beam is established based on Mie scattering theory, and intensity distributions of the scattered field modulated by the inclusion are studied. The effects of refractive index and the radius of inclusion on light intensity enhancement factor (LIEF) and the position of the maximum intensity are analyzed. The results show that modulation effect of inclusion can be considered ineffective when inclusion radius is below 40 nm. When the radius is above 40 nm, inclusions (voids, Al, Fe, ZrO2) act as positive or negative lenses for the incident laser. Maximum light intensity is two orders of magnitude larger than the incident wave intensity in some parts distance away from inclusion. For a non-dissipative inclusion, maximum LIEF increases with the increasing difference between refractive index of inclusion and fused silicon. With the increasing of refractive index, the point of the maximum intensity moves from the backward to the forward of the inclusion. For a dissipative inclusion, with the increasing of the imaginary part of the refractive index, real part of the refractive index has less effect on LIEF. LIEF increases with increasing radius, and the points of maximum intensity move from the forward to the backward of the inclusion.
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In recent years, deep reactive ion etching (DRIE) has become a key process in the fabrication of microelectromechanical systems (MEMS). By combining the etching power of reactive ion etching and sidewall passivation, it provides a precise anisotropic etch that can be used to create very deep etches as well as very narrow structures in silicon. The standard Bosch process for DRIE alternates between two steps: etching and passivation. This combination provides the ability to etch very deep, vertical structures.
In this article, silicon was etched with the Bosch process and cryogenic processes for patterning high-aspect-ratio features. The two leading techniques were compared. The influences of process parameters on the aspect ratio, etching rate and sidewall roughness of silicon were studied. Strong dependence of etch rate on loading was observed. The result showed that the etching rate rely on the process parameters. The aspect ratio of 23 was obtained and is able to be further improved.
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Distributed optical fiber sensing technologies and corresponding instruments have been greatly developed in the recent 30 years. Many instruments such as optical time domain reflectometry (OTDR), Brillouin optical time domain reflctometry (BOTDR), Brillouin optical time domain analyzer (BOTDA), Raman optical time domain reflectometry (ROTDR), coherent optical time domain reflectometry (COTDR), optical frequency domain reflectometry (OFDR) and so on, have been playing important roles in structure health monitoring and other fields needing distributed status parameter sensing. However, these distributed optical fiber sensing instruments produced by different companies or institutes do not follow the same standards and their structure has huge difference. To build a universal structure standard for the distributed optical fiber sensing instruments (OFSI), a concept which adopts functionally divided modules to define OFSI is proposed and its feasibility is discussed. Generally, OFSI can be divided into five functional modules: controller module, pulse generator module, photo-electric module, signal gathering and processing modules and standard processing chassis module. Then the characteristics of OFSI are embodied mostly by the photo-electric modules. The novel method makes full use of the common functional parts and enhances the flexibility of OFSI, which can reduce the cost of OFSI. Additionally, to produce an instrument by functionally divided modules is a technical trend, and it will promote the standardization of OFSI.
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In scalar coherence theory, the van Cittert-Zernike theorem plays an importance role for studying the propagation processes of partially coherent fields. In the past few years, a lot of work has been done to describe an extension of the van Cittert-Zernike theorem in terms of the 2×2 matrix to examine coherence and polarization properties of the field generated by a partially polarized incoherent electromagnetic beam. In this paper, we would like to experimentally demonstrate the unified theory of coherence and polarization of random electromagnetic beams by a modified radial shearing interferometer, which may be regarded as a tensor version of van Cittert-Zernike theorem. The experimental results show that the mutual intensity matrix of the electromagnetic field produced by a polarized incoherent source increases on propagation whereas the degree of the polarization remains unchanged.
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In this paper, we proposed a novel optical geometry for direct visualization of spatial coherence function. The full-field distribution of the coherence function from an incoherent circular aperture source is experimentally investigated. Meanwhile, the experiments of non-diffracting coherence function from an incoherent circular slit source have also been done. The experimental results show that the coherence function generated by an incoherent circular aperture source is in the form of Fresnel diffraction integral which diffracting during the propagation and the coherence function generated by an incoherent circular slit source is unaltered by propagating in free space.
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Coherence Holography is an unconventional holography technique, where a computer generated hologram is illuminated by spatially incoherent light and the recorded object is reconstructed by the 3D distribution of a spatial coherence function. Because of its unique capability of controlling and synthesizing spatial coherence of quasi-monochromatic optical fields in 3D space, coherence holography has been applied for spatial coherence tomography, profilometry, and the generation of coherence vortices. In this paper, we experimentally demonstrate three particular spatial coherence functions by using coherence holography, and study the propagation characteristic of the coherence functions.
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