This PDF file contains the front matter associated with SPIE Proceedings Volume 9276, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and Conference Committee listing.

Phase retrieval methods have useful applications for optical imaging, metrology and 3D reconstruction. One such technique to recover the phase of the object wavefront is digital holography. In this paper we will show applications of digital holographic techniques for the time resolved measurement of deformation of microelectromechanical systems (MEMS) and for determination of residual stresses. Furthermore digital holography can be used for the investigations of microscopic samples and its resolution can be increased by using short wavelength and oblique illumination. We will see as well that dark-field digital holographic microscopy can be used to visualize biological specimens. A phase retrieval methods, which does not use a reference wave is also described in the last part of the paper.

A convenient method based on fringe reflection technique with a single color fringe pattern is presented in this paper for dynamic measurements. A color screen and a color CCD camera are required in the system. The orthogonal color fringe pattern, which is composed with a horizontal fringe pattern in the red channel and a vertical fringe pattern in the blue channel, is displayed by the screen. The CCD camera captures the distorted color fringe pattern via the tested specular surface. The horizontal and vertical fringe patterns will be distinguished directly once the composite color fringe pattern is read by the software like MATLAB. After we get the phase of the horizontal and vertical fringe patterns by Fourier transform profilometry, the two directions’ slope distributions of the tested specular surface can be acquired by the slope-phase relation of fringe reflection technique, and the shape can be reconstructed by intergral of the slope. The whole shape measurement can be completed by a single fringe pattern. The experiment of measuring a plane mirror shows the phase error of the presented method is several times smaller than the existing method, and a vibrating wafer measuring experiment proves the ability of the proposed method to reach dynamic measurement.

This paper presents a novel calibration method to build up pixel correspondence between the IR CCD sensor and the visible CCD sensor of a 2CCD camera by using absolute phase calculation. Vertical and horizontal sinusoidal fringe patterns are projected onto a white plate surface through the visible and infrared (IR) channels of a DLP projector. The visible and IR fringe patterns are captured by the IR sensor and visible sensor respectively. Absolute phase of each pixel at IR and visible channels is calculated by using the optimum three-fringe number selection method. The precise pixel relationship between the two channels can be determined by the obtained absolute phase data. Experimental results show the effectiveness and validity of the proposed 2CCD calibration method. Due to using continuous phase information, this method can accurately give pixel-to-pixel correspondence.

Facing the lunar surface survey of the Lunar Exploring Engineering, the paper summarizes the environment sensing technology based on vision image. For the image matching is the most important step in the process of the lunar exploring images, the accuracy and speed of the matching method is the key problem of the lunar exploring, which play an important role in the rover auto navigating and tele-operating. To conquer difficult problem that there are significant illumination variation of the imaging, lack of image texture, and non-uniform distribution of the image texture, the huge change of the disparity for the prominent target in the scene, in the image process Engineering, the image matching method is proposed which divided the whole image into M×N regions, and each region employs the Forstner algorithm to extract features， by which the semi-uniform distribution features of whole image and avoiding of the features gathering is achieved. According to the semi- uniform distribution features, the Sift and Least Square Matching method are used to realize accurate image matching. Guided by the matched features of the first step, the locale plane is detected to restrict dense image registering. The matching experiments show that the method is effective to deal with the image captured by the lunar exploring rover, that has large variation of illumination and lacking of image texture. The robustness and high accuracy of the method is also proved. The method satisfied the request of the lunar surface exploring.

Measuring high-reflective surfaces using optical method is always a big challenging problem. This paper presents a high-reflective surface measurement method based on conoscopic holography technology using a 4D motion platform equipped with a conoscopic holography optical probe. There are two key problems needed to solve before the automate scan of the complex shape surface: the coordinate calibration and the path planning. To improve the calibration efficiency and accuracy, the coordinate calibration is divided into two parts: the rough calibration and the accurate registration. The path planning consists of two aspects including: the path points generation and the path points verification. In addition, by scanning the objects having high-reflective surfaces, such as the metal blades, coins and other work-pieces, the efficiency of the measurement method has been verified.

In computer assisted quality control the three-dimensional reconstruction of technical surfaces is playing an ever more important role. Due to the demand on high measurement accuracy and data acquisition rates, structured light optical microscopy has become a valuable solution for the three-dimensional measurement of technical surfaces with high vertical and lateral resolution. However, the three-dimensional reconstruction of specular reflecting technical surfaces with very low surface-roughness and local slopes still remains a challenge to optical measurement principles. Furthermore the high data acquisition rates of current optical measurement systems depend on highly complex and expensive scanning-techniques making them impractical for inline quality control. In this paper we present a novel measurement principle based on a multi-pinhole structured light solution without moving parts which enables the threedimensional reconstruction of specular and diffuse reflecting technical surfaces. This measurement principle is based on multiple and parallel processed point-measurements. These point measurements are realized by spatially locating and analyzing the resulting Point Spread Function (PSF) in parallel for each point measurement. Analysis of the PSF is realized by pattern recognition and model-fitting algorithms accelerated by current Graphics-Processing-Unit (GPU) hardware to reach suitable measurement rates. Using the example of optical surfaces with very low surface-roughness we demonstrate the three-dimensional reconstruction of these surfaces by applying our measurement principle. Thereby we show that the resulting high measurement accuracy enables cost-efficient three-dimensional surface reconstruction suitable for inline quality control.

A time-of-flight (TOF) laser range finder based on time-correlated single photon counting (TCSPC) has been developed. By using a Geiger-mode avalanche photodiode (G-APD) with the ability of detecting single-photon events and Time-to-Digital Converter (TDC) with picosecond resolution, a good linearity with 4.5 cm range precision can be achieved in the range of 1-10 m. This paper highlights a significant advance in improving the key parameters of this system, including the range precision and measurement dynamic range. In our experiments, it was found that both of the precision and the measurement dynamic range were limited by the signal to noise rate (SNR) and the inherent jitter of system. The range precision can be improved by enhancing the SNR of system. However, when the SNR is high enough, the main factors affecting the range precision will turn into the inherent jitter, which makes the range precision can not be improved infinitely. Moreover, the inherent jitter generated by pulsed laser and the signal processing module has been measured, and its influence on the system performance has also been discussed. Taking all of these factors into account, some optimized designs have been proposed to improve range precision and dynamic range simultaneously. The final experiment results show that, after all of these optimization designs, the range precision of system is better than 1.2 cm and the measurement dynamic range is enlarged to 54 m when the sampling time is as short as 1 ms, which is sufficient for many applications of 3D object recognition, computer vision, reverse engineering and virtual reality.

This paper intends to thoroughly evaluate the influences of different phase-shifting algorithms, and optimization directions, and initial patterns. For fair comparisons, we used the same number of iterations for optimization and the same size of optimization patches. The variables are optimization domain (i.e., phase and intensity domain), the step number of the phase-shifting algorithm (i.e.. three and four step), the initial pattern (i.e., Bayer dithered and error diffusion dithered pattern), and the optimization direction (i.e., top to bottom, bottom to top, left to right, and right to left). Our ultimate goal is to generate the best possible quality binary pattern after optimization and hopefully provides guidelines on optimization strategies. Our simulation results suggest that an exhaustive optimization is necessary in order to produce the best quality pattern.

This paper presents a high-resolution 3D shape acquisition method for developing hand-held 3D measurement system by projecting structured and unstructured patterns. The structured patterns consist of three-step phase-shifting fringe patterns, and the phase can be computed pixel by pixel to achieve high-resolution 3D measurement, and the phaseshifting method commonly requires many additional images to implement a phase unwrapping procedure for obtaining absolute phase value and removing the correspondence ambiguity, but it would slow down the measurement speed and limits its applications in fast 3D measurement. To address this problem, an unstructured pattern using random speckle is employed to reject wrong correspondence and promises a correct 3D result. Therefore, only four images are required to reconstruct one 3D point cloud, which is suitable for fast 3D measurement in hand-held systems. Moreover, the proposed method can be speed up by parallel computing technology for real-time data processing. The experiments verify the performance of the proposed method.

The efficient particle measurement methods are very important for the assessment of ambient air quality. Compared with other methods, the light scattering method has the advantages of non-destructive and real time detection, and has been used in the detection and analysis of particle composition and concentration. Different from non-polarized light scattering detection, polarized light scattering is suitable for the measurement of fine particles, such as PM₁ and PM_2.5. In this paper, we establish a three-component model to describe three typical particle elements in atmospheric suspended matters, and also set several pollution state changes according to some reported real measured data. By our primary polarization simulation under weak scattering approximation, we analyze Mueller matrix elements fluctuation with the different changes of particle concentration and distribution, and then extract two characteristic elements to follow the status particle composition. The results imply the potential of the backscattered polarization characterization to distinguish and evaluate the parameter variation in an atmospheric particulate model, and also show the possible sensitivity higher than the non-polarization characteristic.

Radiation treatments have been attracted many interests as one of revolutionary cancer therapies. Today, it is possible to treat cancers without any surgical operations. In the fields of the radiation treatments, it is important to regist the 3D position of the cancer inside the body precisely and instantaneously. To achieve 3D position registrations, we aim at developing a compact camera for 3D measurements. In this trial, we have developed a high-speed pattern projector based on the spatiotemporal conversion technique. In experiments, we show some experimental results for the 3D registrations.

3D microscopes based on white light interferometry (WLI) with vertical scanning have been widely used in many areas of surface measurements and characterizations for decades. This technology provides fast, non-contact, and full-field surface 3D measurements with vertical resolution as low as the sub-nanometer range. Its applications include measurements of step height, surface roughness, film thickness, narrow trench and via depths as well as other geometric and texture parameters. In order to assure the highest accuracy of the measurement, scanner linearity needs to be maintained or monitored so that the nonlinearity can be accounted for during the measurement. This paper describes a method that accounts for nonlinearities in real time without the need to store frame data; in addition this method is shown to be less sensitive to vibrations than previous methods described. The method uses an additional interferometer, a distance measuring interferometer to measure the actual scanner position at each scan step.

There is currently a very strong need for building 3D models of the visible surface for a wide variety of objects in shape and size. A hand-held 3D scanner is a useful tool in many situations, in case of the single measurement range size, the sensor-tracking devices or surface markers are need to realize multiple view alignment, thus limiting their functionality. We propose an efficient fast registration methods based on both texture and geometry which can bring in additional information and compensate for ambiguities in the other cues. Together, we can use rotation-invariant geometric or photometric feature descriptors to extract faithful corresponding points for matching without sensor-tracking devices or surface markers. Meanwhile, range data alignment based on photometric properties is performed better using a RANSAC algorithm to rule out mismatching. Experimental results with real objects indicate the effectiveness of the proposed approach. We have applied this method to hand-held structured light 3D scanner. It realizes a single view 3D measurement within 0.12S and Real-time global registration.

Young’s modulus (denoted by E) is an intrinsic and valuable quantity for appropriate estimation of material performance. E can be obtained from the resonant frequency from the vibration of the tested material sample excited by the external forces. In this paper, we present a system design for determining the parameter by using an optical feedback self-mixing interferometry (OFSMI) system. An OFSMI system consists of a laser diode (LD), a micro-lens and an external target. The material sample to be tested is used as the external target. The vibration of the sample causes the variation of the length of the external cavity, and then causes a modulated laser power of the LD. The modulation contains the vibration information of the tested samples. The OFSMI system can achieve high measurement accuracy with an extremely simple and inexpensive set-up, thus can be thought as a good candidate for the evaluation of material properties. The system design in this work includes the mechanical part for holding and exciting the tested samples and the optical part for picking up the vibration information from the samples. In order to accurately determinate E, the exclusive supporting system is used for holding the material sample of specific dimension. The complex waveform of the LD output power is studied and simulated by using our proposed system model. The proposed method is verified by simulation and experiments, and satisfied accuracy of the experiments is achieved.

Digital image correlation (DIC) method is a rapid development of photomechanics technology. The basic principle of the method is calculated the correlation between before and after deformation of the specimen surface speckle images, which is used to determine displacement and deformation. DIC measurement system includes hardware and software system. The former is the speckle image acquisition system, the latter are speckle image analysis algorithm and implementation procedures. Because the software analysis algorithm can achieve sub-pixel accuracy or even more, most of scholars have focused on the speckle image analysis algorithms. The system performance caused by the composition of hardware system has been less introduced. The hardware system mainly included the camera, lenses, lighting and other components. If hardware system is not perfect and stable, it will bring hundreds or even thousands of micro strain measurement error. These unfavorable factors make 2D-DIC inaccurate in small deformation tests. To some extent, it limits the application of 2D-DIC in the engineering practice. This paper analyzed that the various components of DIC hardware system impacted on the system performance, It was given that how to reasonably select the various components in the typical cases, as well as involved that the selection of 2D-DIC measurement system is applied to the actual engineering measurements in high temperature environment. These can provide support that 2D-DIC measurement system is better applied to the engineering practice.

If you open a catalog to buy an optic its surface quality will likely be given by a scratch/dig specification. This is useful information and low scratch/dig numbers usually mean a lower rms roughness and lower scatter, but you cannot find the rms roughness or make estimates of scatter levels from scratch/dig. If you measure a surface with a profilometer you can get bandwidth limited values of the rms roughness and the surface power spectral density function, but this information is often limited to spatial frequencies below about 0.1/μm and this is not high enough to even estimate visible scatter beyond about 5 degrees from specular. Scatter can be measured in BRDF or BTDF units, but instrumentation and measurements are expensive and change with incident angle, wavelength and polarization and cannot always be directly related to roughness statistics. This paper reviews what we know about the relationship between these various parameters and offers suggestions on how to approach application specific issues by defining and specifying surface quality.

This paper presents our study on dynamic three-dimensional (3D) shape measuring technique, which is based on the idea of projecting and superposing a carrier fringe pattern onto the changing surface of a tested dynamic object, then recoding a sequence deformed fringe patterns from other view direction and reconstructing its 3D dynamic shape with 2D or 3D Fourier fringe analysis. This paper briefly reviews the basic principles and its typical applications of the combined technology based on grating projection and Fourier fringe analysis that we have developed over past ten years.

This paper presents a thorough comparison between the digital-light-processing (DLP) technology and liquid-crystaldisplay (LCD) projection technology on high-quality 3D shape measurement. Specifically, each individual color channel and the combination of three channels together are studied with the focused sinusoidal pattern (FSP) method and defocused binary pattern (DBP) method. Experimental data indicated that for slow speed measurements, because of its higher contrast, DLP has the advantage for the DBP, or when the precision synchronization is presented for FSP method. Since LCD does not have rigorous timing requirements, it provides more flexibility for system development for FSP method.

Micro system has some restrictions, when optical system have been structured in a multiple style. These affect their applications. In order to solve the problems of multiple structures in the system, new sensors and components are adding in, which is developing the design method and system configuration. Results show that geometrical optics and optical aberration theory as a foundation, the degree of freedom in design is increased without changing the lens weight, size and structure obviously.

Similar to traditional CMM, probing error of industrial CT is used for assessing the 3D measurement error of the machine in a very small measurement volume. A research on the assessment of probing error of industrial CT is conducted here. Lots of assessment tests are carried out on the industrial CT Metrotom1500 in the National institute of metrology, using standard balls with different size and materials. The test results demonstrate that probing error of industrial CT can be affected seriously by the measurement strategy and standard balls. According to some further analysis about the test results, the assessment strategy of industrial CT’s probing error is concluded preliminary, which can ensure the comparability of the assessment results in different industrial CT system.

Single wavelength microscopic interferometry, driven by the Piezoelectric Transducer (PZT), is a common surface topography measurement method. Its measurement accuracy is directly determined by the original phase acquisition precision of every pixels in area array CCD. Traditional phase identification methods adopt 3 points or 4 points algorithm to obtain the phase. However, they require the displacement step, actuated by the PZT, to strictly keep the same to satisfy the 90° phase condition. Therefore, these methods are only suitable for the strict anti-vibration experimental environment or conditions with high precise closed-loop PZT actuator and strict calibration of interferometric wavelength. An auto-acquisition driving step method for the single wavelength microscopic interferometry is presented in this paper. Firstly, interference sequence diagrams, containing the surface topography information, are gathered by the CCD under open-loop PZT actuating. Next, two pixels whose phase difference is approximate 90° are selected as the calculating center to obtain smoothed gray values with regional gray average algorithm, which can reduce the influence of random noise. Finally, an optimal fitting algorithm for the ellipse, formed by the average gray values, is proposed to obtain the amplitudes and offsets of the two gray values array. According these fitting parameters and gray values, the drive step can be calculated by elliptic equations. Experiments have shown that this method can reduce the requirement conditions of measurement conditions and improve the measurement accuracy.

High precision optical non-contact position measurement is a key technology in modern engineering. Laser trackers (LT) accurately determine x-y-z coordinates of passive retroreflectors. Next-generation systems answer the need to measure an object‘s rotational orientation (pitch, yaw, roll). So far, these devices are based either on photogrammetry or on enhanced retroreflectors. Here we present a new method to measure all six degrees of freedom in conjunction with a LT. The basic principle is to analyze the orientation to the LT’s beam path by coupling-out laser radiation. The optical design is inspired by a cat’s eye retroreflector equipped with an integrated beam splitter layer. The optical spherical aberration is compensated, which reduces the divergence angle for the reflected beam by one order of magnitude compared to an uncompensated standard system of the same size. The wave front distortion is reduced to less than 0.1 λ @ 633 nm for beam diameters up to 8 mm. Our active retroreflector is suitable for long-range measurements for a distance > 10 m.

Fringe projection profilometry (FPP) has been widely used for three dimensional (3D) imaging and measurement. The fringe acquisition of FPP mainly depends on the diffuse light from the surface of objects, thus the characteristics of object surface have significant influence on phase calculation. One of the essential factors related to phase precision is modulation index, which has a direct relationship with the surface reflectivity. This paper presents a comparative study which focuses on the modulation index of different materials. The distribution of modulation index for different samples is statistical analyzed, which leads to the conclusion that the modulation index is determined by the diffuse reflectivity rather than the type of materials. This work is helpful to the development of effective de-noising algorithms to improve the measurement accuracy.

Optical flat is commonly used in optical testing instruments, flatness is the most important parameter of forming errors. As measurement criteria, optical flat flatness (OFF) index needs to have good precision. Current measurement in China is heavily dependent on the artificial visual interpretation, through discrete points to characterize the flatness. The efficiency and accuracy of this method can not meet the demand of industrial development. In order to improve the testing efficiency and accuracy of measurement, it is necessary to develop an optical flat verification system, which can obtain all surface information rapidly and efficiently, at the same time, in accordance with current national metrological verification procedures. This paper reviews current optical flat verification method and solves the problems existing in previous test, by using new method and its supporting software. Final results show that the new system can improve verification efficiency and accuracy, by comparing with JJG 28-2000 metrological verification procedures method.

Laser is a usual light source in many measurement applications, because it has good coherence. To measure the light transmission of a large-core fiber, we designed and setup a testing system using a He-Ne laser. The light from the laser could be focused to an ideal point to incident the fiber. On the other hand, the output spot from the fiber suffers serious coherent noise, which is called as speckle. Even using multi-image average or removing mask filter, we can’t reduce the influence of the speckle remarkably. So we made a mode-disturbing device to vibrate the fiber at a certain frequency and amplitude. To check the effectiveness of the fiber vibrating method and to find the best parameters for our fiber mode-disturbing device, we set different working frequencies from 0 to 80 Hz. And we set the CCD exposure time at 100ms, 200ms, 500ms and 800ms. According to the experimental results, the speckle is much more sensitive to the working frequency of vibrating the fiber than the exposure time. After comparing different frequencies, 70Hz is chosen as the optimized frequency to effectively suppress the speckle, decrease the speckle contrast. The output of the large-core fiber could fit to a 2-D Gaussian function. So we can measure the diameter of the spot based on the fitting result. Using this mode-disturbing system, we measured the focal ratio degradation of a large-core fiber and studied on the bend effect of the fiber.

Base on the principles of the LED package structure and the LED optical model, we use Tracepro to do the simulation of LED devices. By changing the parameters of LED model, such as the package structure, the size of reflective cup, the height of chip and the angle of the reflective bowl, etc. We simulate the light intensity distribution curve of LED in different structures and find different results. That is a bigger height, a lager angle and a smaller curvature will make a better condenser effect. Compare with measurement data which shows that intensity distribution abide by some laws. Those conclusions can be used in guiding the package structure design of LEDs.

Phase space distributions such as the Wigner Distribution Function are very powerful tools to characterize the behavior of optical beams propagating in various optical systems. For instance, it is well known that when a beam passes through an ideal thin lens, the associated Wigner distribution function experiences a shear along the frequency axes. However, practical optical systems are not ideal. One must take the lens aberrations into account when analyzing and designing an optical system, in particular for imaging and metrology applications. In this paper, we present a theoretical and numerical study of how the Wigner Distribution Function evolves when a beam passes through a thin lens with aberrations characterized by the Zernike polynomials. The result shows that a deformation effect occurs in the Wigner distribution function when aberrations present. Thus the design of optical imaging and metrology systems is to reduce or eliminate the deformation from phase space optics point of view.

A comparison of different transfer standard optical fiber power detectors is present. Traceable to cryogenic radiometer, these planar, focus-planar and trap detectors have different characteristics during the optical fiber power values transfer because of the different input angles or fiber connectors. For different types of fibers and fiber connectors, a new trap detector is capable for the optical fiber power measurement, which has very little sensitivity for a variety of input conditions. Comparison of fiber power measurement using a planar and a trap detector is present by employing a three-lens method. A good agreement between the two types of detectors shows the feasibility of fiber power transfer using planar detectors.

Nonflatness of stage mirror surface affects the position accuracy of the wafer stage in lithography tool. Precise surface flatness measurement is needed for the computer controlled polishing of stage mirror. A subaperture stitching system using a commercial 4-inch Fizeau interferometer was presented in this paper. Absolute test was used to calibrate the surface figure of the reference mirror with the accuracy better than λ/100 PV (λ = 632.8nm）. Subaperture stitching was used to extend the measurement aperture larger than 450×50mm. Stitching measurements were carried out for stage mirrors during surface polishing. Comparison tests were also made with a 24-inch interferometer. The results show that the stitching system has the advantages of larger dynamic range, higher spatial resolution, and better measurement accuracy in local area.

Currently most domestic factories still manually detect machine arbors to decide if they meet industry standards. This method is costly, low efficient, and easy to misjudge the qualified arbors or miss the unqualified ones, thus seriously affects factories’ efficiency and credibility. In this paper, we design a specific high-speed camera system with auto adjustable ROI for machine arbor’s outline dimension measurement. The entire system includes an illumination part, a camera part, a mechanic structure part and a signal processing part based on FPGA. The system will help factories to realize automatic arbor measurement, and improve their efficiency and reduce their cost.

Measuring the 3D structure of vegetation canopy is of great significance for the validation of remote sensing data and vegetation radiation transfer modeling. When using laser triangulation, because of the limitat ion of the field of view of measuring system, multi-view measurement followed by a registration of the measured point cloud is needed. Most of the existing registration methods cannot be directly applied to our registration task. This paper presents a registration method based on leaf profile matching. Firstly, segment the point cloud into subsets that are correspond to the single leaves. Then the profile of every single leaf is extracted and fitted with splines. Finally, by calculating and matching the parameters of the splines' parameters, the profile of the same leaf in different views are registered, thus the registration of multi-view point cloud is achieved. The experiments on measurement data are presented to show the feasibility of the proposed method.

Correction of refraction index is important for length measurement. The two-color method has been widely used for correction. The wavelengths of lasers have been used as a ruler of that. Based on the analogy between the wavelength and the adjacent pulse repetition interval length (APRIL), in this paper we investigate the possibility of two-color method based on adjacent pulse repetition interval lengths. Since the wavelength-based two-color method can eliminate the inhomogeneous disturbance of effects caused by the phase refractive index, therefore the APRIL-based two-color method can eliminate the air turbulence of errors induced by the group refractive index. Our analysis will contribute to high-precision length measurement.

Fast and precise 3D inspection system is in great demand in modern manufacturing processes. At present, the available sensors have their own pros and cons, and hardly exist an omnipotent sensor to handle the complex inspection task in an accurate and effective way. The prevailing solution is integrating multiple sensors and taking advantages of their strengths. For obtaining a holistic 3D profile, the data from different sensors should be registrated into a coherent coordinate system. However, some complex shape objects own thin wall feather such as blades, the ICP registration method would become unstable. Therefore, it is very important to calibrate the extrinsic parameters of each sensor in the integrated measurement system. This paper proposed an accurate and automatic extrinsic parameter calibration method for blade measurement system integrated by different optical sensors. In this system, fringe projection sensor (FPS) and conoscopic holography sensor (CHS) is integrated into a multi-axis motion platform, and the sensors can be optimally move to any desired position at the object’s surface. In order to simple the calibration process, a special calibration artifact is designed according to the characteristics of the two sensors. An automatic registration procedure based on correlation and segmentation is used to realize the artifact datasets obtaining by FPS and CHS rough alignment without any manual operation and data pro-processing, and then the Generalized Gauss-Markoff model is used to estimate the optimization transformation parameters. The experiments show the measurement result of a blade, where several sampled patches are merged into one point cloud, and it verifies the performance of the proposed method.

Nowadays, more attentions may be paied to irradiance and temperature during the electrical performance tests of solar cell and module. But the light spectrum will also largely determine test results. During the electrical performance test, irradiance is generally traced by standard solar cell. Considering that the short circuit current (Isc) is generally used in the testing process as a basis for the irradiance calibration, and the Isc of reference cell consists of spectral distribution of light source and the spectral response of the cell together. So spectral mismatch should be analyzed from this two aspects. Natural light spectrum will be affected by atmospheric conditions and seasons, and artificial solar simulator’s spectrum is differ in thousands ways. Also because of the response wave band of the spectrum range is different, when use standard solar cell or pyranometer as the basis of the irradiance calibration, there should be respectively different results. Beyond that, two cells made of polycrystalline silicon with different spectral response may also leads to different results. We analyzed the deviation based on above factors, and discussed how to reduce the spectral mismatch deviation, then increase the accuracy of the solar cell electrical performance test methods.

A new technique for coded targets recognition in optical 3D-measurement application is proposed in this paper. Traditionally, point cloud registration is based on homologous features, such as the curvature, which is time-consuming and not reliable. For this, we paste some coded targets onto the surface of the object to be measured to improve the optimum target location and accurate correspondence among multi-source images. Circular coded targets are used, and an algorithm to automatically detecting them is proposed. This algorithm extracts targets with intensive bimodal histogram features from complex background, and filters noise according to their size, shape and intensity. In addition, the coded targets’ identification is conducted out by their ring codes. We affine them around the circle inversely, set foreground and background respectively as 1 and 0 to constitute a binary number, and finally shift one bit every time to calculate a decimal one of the binary number to determine a minimum decimal number as its code. In this 3Dmeasurement application, we build a mutual relationship between different viewpoints containing three or more coded targets with different codes. Experiments show that it is of efficiency to obtain global surface data of an object to be measured and is robust to the projection angles and noise.

In order to avoid the defects of contact measurement, such as limited range, complex constructing and disability of 3-D parameter acquisition, we built a binocular videogrammetric system for measuring 3-D geometry parameters of wind tunnel test models, for instance, displacement, rotation angle and vibration, in low-speed wind tunnel. The system is based on the principles of close-range digital photogrammetry. As a non-contact system, it acquires parameters without interference in the experiments, and it has adjustable range and simple structure. It is worth mentioning that this is a Realtime measurement system, so that it can greatly compress the experiment period, furthermore, it is also able to provide some specific experiments with parameters for online adjustment. In this system, images are acquired through two industrial digital cameras and a PCI-E image acquisition card, and they are processed in a PC. The two cameras are triggered by signals come from a function signal generator, so that images of different cameras will have good temporal synchronization to ensure the accuracy of 3-D reconstruction. A two-step stereo calibration technique using planar pattern developed by Zhengyou Zhang is used to calibrate these cameras. Results of wind tunnel test indicate that the system can provide displacement accuracy better than 0.1% and rotation angle accuracy better than 0.1 degree, besides, the vibration frequency accuracy is superior to 0.1Hz in the low-frequency range.

Sparse bundle adjustment is widely applied in computer vision and photogrammetry. However, existing implementation is based on the model of n 3D points projecting onto m different camera imaging planes at m positions, which can't be applied to commonly monocular, binocular or trinocular imaging systems. A novel design and implementation of bundle adjustment algorithm is proposed in this paper, which is based on n 3D points projecting onto the same camera imaging plane at m positions .To improve the performance of the algorithm, a novel sparse block matrix partition method is proposed. Experiments show that the improved bundle adjustment is effective, robust and has a better tolerance to pixel coordinates error.

A method for high-speed three-dimensional measurement with low-speed camera is proposed. The spatial frequency encoded fringes are projected with high frame rate and deformed fringes are captured with low frame rate. Several fringes are integrated in one captured image. The directions and/or frequencies of these fringes are different. The spatial frequency spectrum of these fringes is separate in spatial frequency domain. So, the phases of different fringes can be obtained by filtering the image with different filters. Then several 3D shapes of different time are obtained from one captured image. The experiments are carried out to verify proposed method and measurement results are demonstrated. The method improves the speed of 3D shape measurement and reduces the cost of measurement system as well.

In the high-power laser system, the stray light which is generated by the surface’s residual reflection of optical elements and the multi-pass transmission in the system will lead to temperature increase in part of the system, the optical elements deformation and damage, distortion of wave-front and change of the beam’s divergence angle, which seriously influence the beam’s quality and propagation properties and damage the components in the system. So, it is very important to use the relevant software to analyze the stray light rigorously because the reliability and precision of the software is the guarantee of reliable results. Through two types of software we performed the simulation of the stray light in the system, including ghost’s distribution in the case of different states of rotating defocusing, beam’s pointing. Simultaneously, the impact of processing and assembling errors is analyzed in details. We built a specialized experiment to verify the reliability of results of the software and the related parameters of system are conveniently measured with the device.

We proposed a cost-effective and full-field method for measuring vibration of loudspeaker using general industrial camera and fringe projection. The loudspeaker is excited by a sinusoidal signal. The fringe pattern is projected on the measured loudspeaker membrane that is dynamically deformed. Then the deformed fringes are captured by a camera. A trigger generation circuit is designed to control the camera. The Fourier Transform Profilometry (FTP) is adopted for 3D shape reconstruction. The validity of this method is approved by experiments. The cost of proposed measurement system is dramatically lower than that using high-speed camera.

In the field of optical information security, the research of double random phase encoding is becoming deeper with each passing day, however the encryption system is linear, and the dependencies between plaintext and ciphertext is not complicated, with leaving a great hidden danger to the security of the encryption system. In this paper, we encrypted the higher dimensional Wigner distribution function of low dimensional plaintext by using the bilinear property of Wigner distribution function. Computer simulation results show that this method can not only enlarge the key space, but also break through the linear characteristic of the traditional optical encryption technology. So it can significantly improve the safety of the encryption system.

Pentaprism scanning system has been widely used in the measurement of large flat and wavefront, based on its property that the deviated beam will have no motion in the pitch direction. But the manufacturing and position errors of pentaprisms will bring error to the measurement and so a good error analysis method is indispensable. In this paper, we propose a new method of building mathematic models of pentaprism and through which the size and angle errors of a pentaprism can be put into the model as parameters. 4 size parameters are selected to determine the size and 11 angle parameters are selected to determine the angles of a pentaprism. Yaw, Roll and Pitch are used to describe the position error of a pentaprism and an autocollimator. A pentaprism scanning system of wavefront test is simulated by ray tracing using matlab. We design a method of separating the constant from the measurement results which will improve the measurement accuracy and analyze the system error by Monte Carlo method. This method is simple, rapid, accurate and convenient for computer programming.

To meet the need of long distance transmission in low turbidity measurement system for low-loss, a new optical structure with wavelength 1310nm and 1550nm as the incident light is employed. In this research, experiments have been done for different optical length of the two wavelength light sources. The results show that: first, the transmitted light intensity has big difference under the circumstance of same concentration and optical length, though the loss has no remarkable difference transmitted in optical fiber between 1310nm and 1550nm. Second, the optimized optical length for better absorbance has been determined for 1310nm and 1550nm and it is irrelevant to the incident intensity. Third, the intensity of the two transmitted light decreases exponentially with the increase of optical length. For example, when the range of the optical length of 1310nm is 0.5mm-2mm, the transmitted intensity is about 60%-79% and the absorbance is 0.12-0.42. The transmitted intensity is about 5%-44%. When the range of the optical length of 1550nm is 0.5mm-2mm and the absorbance is still 0.12-0.42. Our experimental data provides the basis both for the optical length selection of these two light sources in water and the near-infrared spectral wavelength selection.

In order to eliminate the noise in images acquired by the sparse aperture system, the modeling and filtering of electrical and optical noise are analyzed by the case of three-mirror aperture optical system. The study shows that the median filter can be applied to remove Gauss and salt & pepper noise, meanwhile high-pass filter with Gauss function can eliminate the influence of non-uniform illuminating on imaging. The Lucy-Richardson algorithm is used to restore the image, by which the resolution is heightened.

A new type vertical calculable capacitor has been built at National Institute of Metrology (NIM) cooperated with National Measurement Institute of Australia (NMIA). The calculable capacitor is the highest accuracy equipment apparatus except the quantum voltage and the quantum resistance in the electromagnetic metrological field. In order to measure the capacitance precisely, the accurate displacement measurement among the two guard electrodes in the calculable capacitor is a pivotal part. This paper describes a method of measuring the displacement of a Fabry-Perot interferometer, and this interferometer is component of two mirrors in two guard electrodes of the calculable capacitor at NIM. One concave reflective mirror, with 5 m radius and 70% reflectivity, is on the top of the bottom fixed guards electrodes. The other planar mirror is placed at the end of the moveable guard electrodes. This Fabry-Perot interferometer employs a home-made lamb-dip stabilization He-Ne laser at 633 nm to measure the displacement of the movable guard electrode. The internal modulation, which is used for laser stabilization, is also employed for locking the Fabry-Perot interferometer. The displacement of the movable guard electrode could be measured, when the Fabry-Perot interferometer is locked to the stabilization laser at two positions respectively. An iodine stabilization He-Ne laser at 633 nm is employed to simultaneously calibrate the wavelength of lamb-dip working laser. A reproducibility of 1.43×10^-8(k=3) for the range of 205 mm can be obtained at present, and that is estimated from the experimental results of calculable capacitor.

The phase diversity wavefront sensing (PDWFS) technique is an a posteriori image-based wavefront sensing technique which has been successfully implemented to the Hubble Space Telescope. The analytical form for the phase diversity Cramér-Rao lower bound(CRLB) of Golay3 aperture is firstly derived. Monte Carlo analysis of the PDWFS CRLB is used due to the dependence of CRLB on the true values of aberration parameters being estimated. Then the ensemble average of mean-squared errors(MSE) quantities of CRLB is used to evaluate the performance of imaging schemes with different photon distributions and different amounts of defocus. The numerical simulation shows that for a point source target, if a third image implies the inclusion of extra photons, the MSE would be reduced to a degree in accordance with the amount of the extra photons, the MSE remains nearly unchanged if the totoal photons is finite, no matter for a two-channel or a three-channel system. We also find that varying the defocus of one image becomes meaningless if the defocus of the other image is at a high level.

Traditional laser angular interferometers based on a Michelson Interferometer or its modifications have the same principle: changing the angle displacement to an optical path difference. However, measuring the angular error of stage travels is a dynamic process. The main trouble is lack of displacement information and need to be solved urgently. A obvious method is using two dual-frequency interferometers to get the displacement and angular. In this paper, a new kind of displacement and angle interferometer (DIAI) is introduced. In this DIAI, displacement and angular are measured simultaneously by special optical path. The DIAI consists of a stabilized orthogonal polarization dualfrequency laser, a monolithic prism and additional optical and electronic components. The dual-frequency laser is divided into reference light and measurement light by a beam-splitting prism. The measurement light spatially separated into horizontal polarized light and vertical polarized light by the polarization splitting prism. Changing by a fixed 45°- tilted reflector, the vertical polarized light is parallel to the horizontal polarized light. These parallel lights reflected by two corner cube retroreflectors at a moving target. Compared with the reference light, the displacement and angular are measured. Different from the traditional method, there is only one reference corner cube retroreflector in this system. Thus, the angular measurement accuracy is better. The accuracy of the DIAI is better than ±0.25 arcsec in comparison with an autocollimator.

A 2-dimensional thickness measurement ellipsometer based on the liquid crystal variable retarder (LCVR) is proposed and setup in order to provide precise, real-time measurement in a manufacturing environment. Images are collected sequentially by CCD camera with respect to pre-determined polarization state of incident light derived by the LCVR attached with compensator. A phase-shifting algorithm and a Fourier series approach algorithm are used to obtain full-field distributions of the ellipsometric parameters, and then a polarization model (ambient-film-substract) is used to calculate the thickness of a thin film in two dimensions precisely and quickly. Theoretically, the speed and precision of this method benefit from applying voltage on the LCVR to produce polarization modulation that is able to avoid mechanical vibrations that could affect the accuracy of the measurements. The experimental results verify the ability and performance of the 2-dimensional thickness measurement ellipsometer.

A method using a pair of femtosecond frequency combs can realize ranging at a high precision of 1μm by Fourier Processing. In simulation of this system based on Matlab/Simulink, it is found that the choosing of repeating frequencies has great impact on frequency of the sampled signals, which influences the ranging precision a lot. The sampled signals are analyzed and classified into three types, which can be judgment criteria in system setting. Filter at Nyquist frequency is advised to decrease the edge effect of FFT, and a supplement means of cutting in data processing is proposed to improve precision.

Binocular Vision Technique is widely used in three-dimensional（3-D）measurement. Matching of pictures captured from two cameras is the most critical and difficult step in 3-D shape reconstruction. The method combines codedstructured light and spatial phase is usually adopted. However, being time consuming in matching, this method could not meet the requirements of real-time 3-D vision. In order to satisfy the high speed characteristic of real-time measurement, a novel method using gray level vector modulation is introduced. Combining binary code with gray coding principle, new coding patterns using gray level vector method is designed and projected onto the object surface. Each pixel corresponds to the designed sequence of gray values as a feature vector. The unique gray level vector is then dimensionally reduced to a resulting value which could be used as characteristic information for binocular matching. Experimental results further demonstrated the correctness and feasibility of the proposed method with fewer component patterns and less computational time.

This paper addresses the range image registration problem for views having overlapping area and which may include substantial noise. The current state of the art in range image registration is best represented by the well-known iterative closest point (ICP) algorithm and numerous variations on it. Although this method is effective in many domains, it nevertheless suffers from two key limitations: It requires prealignment of the range surfaces to a reasonable starting point and it is not robust to outliers arising either from noise or low surface overlap. This paper proposes a new approach that avoids these problems for precision range image registration, by using a new, robust method based on ASIFT followed by ICP. Up to now, this approach has been evaluated by experiment. We define the fitness function to calculate the time for the convergence stage of ICP, because the time required is very important. ASIFT are capable of image matching even when there is fully affine variant. The novel ICP search algorithm we present following ASIFT offers much faster convergence than prior ICP methods, and ensures more precise alignments, even in the presence of significant noise, than mean squared error or other well-known robust cost functions.

A new geometrical model and mathematical method for three-dimensional surface reconstruction with phase- shifting structured light technique is proposed. First, with the proposed method, there will be no restriction to camera and projector's relative alignment on parallelism and perpendicularity. Furthermore, the depth map can be directly derived from the phase map by a simple function. The x and y coordinates are inferred from the depth z coordinate. Second, no special calibration hardware is needed; a simple two-step plane-based calibration procedure is adopted to acquire the system intrinsic and extrinsic parameters. Third, a look-up-table compensation method is presented to avoid the accumulation of errors introduced in the structured light system. The experimental results demonstrate the e®ectiveness and accuracy of the proposed methods.

For the sake of the increasing demands of oil and gas essential, scientists and engineers have exerted great efforts in obtaining natural resources deposited in the deep water. Risers, as the channel between platform and wellhead, play a key role in oil and gas transportation. Subjected to coarse environmental conditions and uncertain loading patterns, risers would display complex dynamic behaviors which could result in severe fatigue damages. Recently, riser response is commonly measured using passive and durable Fiber Bragg Grating (FBG) strain sensors for industry safety, especially for Integrity Management (IM). However, for technique difficulties as well as economical consideration, it is impossible to execute distributed fatigue monitoring on the whole riser, which makes it essential to find out an optimized method utilizing the least number of sensors and reconstruct the global response of risers. This paper propose a method which combines H₂ norms and Kalman filter to give optimal state estimation of risers based on limited FBG-based dynamic strain information. The H₂ norms are used to give guideline for optimized sensor placement. Meanwhile, Kalman filter realize the global response reconstruction of risers as well as minimize the environmental disturbance. The accuracy and efficiency of the method has been verified by a numerical case. This study provides an FBG-based early warning technique for industry application of deepwater risers in future.

Presently, unscrupulous traders in the market use the industrial wax to wax the rice. The industrial wax is a particularly hazardous substance. Visible-near infrared hyperspectral images (400-1,000 nm) can be used for the detection of the waxed rice and the non-waxed rice. This study was carried out to find effective testing methods based on the visible-near infrared imaging spectrometry to detect whether the rice was waxed or not. An imaging spectroscopy system was assembled to acquire hyperspectral images from 80 grains of waxed rice and 80 grains of non-waxed rice over visible and near infrared spectral region. Spectra of 100 grains of rice were analyzed by principal component analysis (PCA) to extract the information of hyperspectral images. PCA provides an effective compressed representation of the spectral signal of each pixel in the spectral domain. We used PCA to acquire the effective wavelengths from the spectra. Based on the effective wavelengths, the predict models were set up by using partial least squares (PLS) analysis and linear discriminant analysis (LDA). Also, compared with the PLS of 80% for the waxed rice and 86.7% for the non-waxed rice detection rate, LDA gives 93.3% and 96.7% detection rate. The results demonstrated that the LDA could detect the waxed rice better, while illustrating the hyperspectral imaging technique with the visible–near infrared region could be a reliable method for the waxed rice detection.

For apples, soluble solids content (SSC) and firmness are two very important internal quality attributes, which play key roles in postharvest quality classification. Visible-near infrared hyper spectral imaging techniques have potentials for nondestructive inspection of apples’ internal qualities, which will be used for the SSC and firmness non-destructive inspection and varieties discrimination of apples. Spectrums of 396 apples from four varieties were extracted. There were 264 apples used for calibration and the remaining 132 apples for prediction. After collecting hyper spectral images of calibration apples, the sugar meter and firmness tester was used to measure SSC and firmness’s reference values of each calibration apples. Then the principal component analysis (PCA) was used to extract effective wavelengths of calibration apples. The reference values and effective wavelengths’ reflectance of apples can be used to set linear regression models based on partial least squares (PLS). Once the prediction model was established, in order to get the SSC and firmness’s predicted values of apples, it only need achieve the effective wavelengths’ reflectance of apples combing with the program of MATLAB. Finally, the SSC and firmness values of prediction set were used as independent variables of the Linear Discriminant Analysis (LDA) to realize varieties discrimination. The correlation coefficients were 0.9127 for SSC and 0.9608 for firmness values of prediction models. The accuracy of varieties discrimination was 96.97%. The results indicated that the methods to SSC and firmness non-destructive inspection and varieties discrimination of apples based on Vis–NIR hyper spectral imaging was reliable and feasible.

In this paper, we propose a Driver’s Awareness Catching System to sense the driver’s awareness. The system consists of a fisheye camera and a Kinect. The Kinect mounted inside vehicle is used to recognize and locate the 3D face of the driver. The fisheye camera mounted outside vehicle is used to monitor the road. The relative pose between two cameras is calibrated via a state-of-the-art method for calibrating cameras with non-overlapping field of view. The camera system works in this way: First, the SDK of Kinect released by Microsoft is used to tracking driver’s face and capture eye’s location together with sight direction. Secondly, the eye’s location and the sight direction are transformed to the coordinate system of fisheye camera. Thirdly, corresponding view field is extracted from fisheye image. As there is a small displacement between driver’s eyes and the optical center of fisheye camera, it will lead to a view angle deviation. Finally, we did a systematic analysis of the error distribution by numerical simulation and proved the feasibility of our camera system. On the other hand, we realized this camera system and achieved desired effect in realworld experiment.

The rapid development of micro-electronics and micro-nano material engineering make it an urgent task to characterize the mechanical properties of micro-device and micro-nano material accurately. Due to the advantages of high precision, high sensitivity and full field measurement, moiré method has been applied in the micro-deformation measurement widely. Since the grating is the indispensable deformation sensor of moiré method, how to fabricate high frequency grating with high quality is the key problem to solve for moiré method. In this paper, some fabrication techniques developed recently with their applications will be summarized, including holographic photolithography, electron beam lithography (EBL), focused ion beam (FIB) and nano-imprint lithography(NIL), aiming to popularize the applications of moiré method in the micro-deformation measurement and provide some valuable guidelines on how to choose a proper fabrication technique.

Ambiguity in plane angle definition is considered. Autocollimator performance is regarded from geometric ray optics and wave diffraction optics points of view. Few typical aberrations and their influence on image formation in autocollimator are presented. Modeling estimates of aberration influence on angle measurements are outlined.