A dual-layered sub-wavelength grating consisting of two kinds of materials, aluminum and ZnSe, is developed to improve the performance of polarimetric elements in long-wavelength infrared (LWIR) polarization imaging system. Parameters of the designed grating’s morphological structure are optimized on the basis of analyzing the effects on the polarization performance through the rigorous coupled wave theory, which helpfully calculates the diffraction efficiency. With a rectangular profile, the grating designed for applications in LWIR band has periods of 1 μm and 50%-fill-factor. The depths of aluminum and ZnSe in the grating region are 0.6 μm and 0.4 μm respectively. A TM transmission greater than 87.54% with an extinction ratio exceeding 47 dB is achieved in the 7~15 μm band when the angle of incidence is from zero to sixty degree. The grating maintains an extinction ratio better than 50 dB and TM transmission over 90.80% above 10.6 μm incident wavelength, which is superior to single-layered aluminum gratings with the same depth in the transmission performance in comparison. The simulation results show that this grating has excellent polarization performance in the broad LWIR band. Key

A broadband multi-focus lens based on metasurface holography in the far-infrared region is designed. By designing 8 C-shaped resonant rings, when linearly polarized light waves are incident normally to this set of resonators, cross-polarized component of transmitted light will form the phase shift from 0 to 2π, meanwhile the amplitude transmittance remains constant. Full-wave simulation was utilized to verify anomalous refraction properties when linearly polarized light waves irradiated this set of resonators vertically. The phase distribution of multi-focus lens was obtained by adopting the computer-generated hologram (CGH) method. According to ar-ranged resonant rings based on the calculated phase distribution, a squared multi-focus lens based on metasur-face was obtained. Simulation for the designed lens was conducted. Results show a good multi-focusing per-formance at the central frequency 28 THz in the focal length of 108 μm. Key

In order to solve the problem that existing blind sidewalk recognition algorithms have bad real-time performance, a highly real-time blind sidewalk recognition algorithm based on boundary tracking is proposed, mainly including accurate recognition and tracking recognition. First, accurate recognition step mainly calculates gray level co-occurrence matrix of the initial frame, and uses clustering and Hough transform to find the bounda-ry lines of blind sidewalk in image. Then tracking recognition step takes over next frame. The location of blind sidewalk’s boundary in previous frame is used to predict the small-scale region of interest (ROI) of the boundary in current frame, and boundary lines in that region are extracted based on gray gradient feature. After that, the algorithm checks up the validity of tracking by estimating the consistency of color distribution on both sides of the boundary in previous and current frames: tracking is considered to be valid if the consistency is high, and tracking recognition step continues, otherwise accurate recognition step restarts. In many experiments, the time of accu-rate recognition and tracking recognition in each image frame under normal illumination are about 0.8 s and 0.1 s, respectively, and the average time of recognition per frame decreases significantly while the recognition rate of blind sidewalk is more than 90%. Meanwhile, the adaptability is good in shadow environment. Experimental re-sults indicate that the algorithm can significantly enhance the real-time performance of blind sidewalk recogni-tion in the premise of ensuring the recognition rate. Key

For autofocus system of the microscope, this paper presents a hybrid search algorithm combining the mountain-climb search strategy with the approximation function strategy. In this algorithm, the mountain-climb search strategy adopts the two-stage algorithm of rough and fine focusing stage. In the rough focusing stage, the gray variance function is used to approach the focusing position quickly. In the fine focusing stage, the Laplacian function is used to locate the focusing position accurately. The algorithm narrows the focus interval by comparing three pictures and the approximation function strategy is used to fit the best focus in this range. This method greatly reduces the number of images required for autofocus and greatly improves the search accuracy. The experimental results indicate that this algorithm can make the search accuracy better than 1 μm.

The optical microcavity has high Q factors and high sensitivity, and has a good application prospect in high-precision biosensing. In order to deal with the problem that the Lorentz fitting algorithm cannot fit the asymmetric waveform and the splitting mode waveform of the optical microcavity, the implicit function model al-gorithm is proposed. Firstly, according to the method, the template waveform was established and operated by panning and zooming.Then the parameter values were optimized by the Levenberg-Marquardt (LM) algorithm. Finally, data fitting of symmetrical waveform, asymmetric waveform and splitting mode waveform could be achieved. Through constructing the data acquisition system of optical microcavity, the Gauss, the Lorentz and the implicit function model algorithm were used to fit the experimental data of different refractive index of solutions. The results show that MSE of the implicit function model algorithm is one order of magnitude lower than other two algorithms, and has a coefficient of determination (R2) of 0.99. The resonant frequency error of implicit func-tion model algorithm is the smallest, the resonant frequency of implicit function model algorithm is the largest, and the sensitivity of implicit function model algorithm is the highest. Therefore, the fitting effect of the implicit function model algorithm is better and it can efficiently improve the sensitivity of the optical microcavity.

Thermal-vacuum environment adaptability is one of the key performances of space optical instru-ments, especially for hyper-spectral instrument, and spatial heterodyne spectrometer (SHS) should provide high spectral stability for the detection of atmosphere CO2. Based on the research of the spatial heterodyne interfer-ence principle, simulation test in thermal-vacuum environment and quantitative analyses are carried out. The re-lationship among environment changes and the divergence half-angle of collimating lens, Littrow wavelength of field widened interferometer, different defocusing amount and pantograph ratio of imaging lens are analyzed. In order to verify the theoretical analysis, thermal-vacuum experiment is performed. The results show that the spec-tral deviation and profile are matched with theoretical analysis, and spectral stability is less than ±0.01 nm under the temperature from 19 ℃ to 21.2 ℃ by the substrates made of fused Silica (Corning 7980 0F). Quantitative analyses provide theoretical basis for the thermal control requirement and Littrow wavelength selection in normal atmospheric pressure.

Dim and small infrared target easily flooded in complicated background. In order to improve the ability of target detection, the background is often suppressed to enhance the target signal. Referring to the lack of ro-bust adaptability of the gradient inverse weighted filtering for background edges , an improved gradient inverse weighting filtering algorithm is proposed through the establishment of background local correlation function. The use of background local statistical characteristics of adaptive filter parameters, can better adapt to the drastic change in the background, and improve the ability to suppress background suppression algorithm. Experimental results show that the improved gradient inverse weighted filtering could effectively suppress the background of images, presenting a superior overall performance to other background suppression methods.

The high altitude calibration of solar cells is of great significance to study solar cells for space applica-tion. This paper presents a measurement scheme to measure the I-V curves of solar cells at a high altitude. The paper studies the hardware testing system based on FPGA, the method of acquiring the current and voltage data in parallel and the automatic measurement method of software in this system. An algorithm for fitting the cur-rent-voltage curve of solar cells based on chaos algorithm and genetic algorithm is proposed. According to the experimental data of ground testing, the curve fitting algorithm is carried out by using solar cell single diode mathematical model. The results show that the fitness value of the chaos genetic algorithm is 4.0289×10-4, which means that the curve fitting is better than particle swarm algorithm and genetic algorithm.

In view of the issue that the present domestic industrialization of laser shock peening equipment is not high, a laser shock peening equipment has been developed by using fixed optical system structure and modular design method. The design scheme of laser shock peening equipment, the characteristics of laser optical path arrangement and the system control method are analyzed, and the technical specifications of laser shock peen-ing equipment are tested. When the room temperature stables at (22 ± 2) ℃ and 20 minutes after the device is switched on, the technical parameters such as the maximum output single pulse energy up to 25 J, energy insta-bility < 3%, pulse width which can be continuously adjusted between 16 ns and 20 ns, pulse width instability < (-1 ns~1 ns), beam divergence < 2.5 mrad, beam points instability <50 μrad, the repetition rate of 0.5 Hz~5 Hz are achieved, the transmission efficiency of the optical system is about 92%, the thickness of the constraint layer is uniform and the flow rate is continuously controlled. The test results show that the performance of the laser shock peening equipment is good enough for industrial applications.

Laser shock peening is a new type of metal surface modification technology. Compared to the traditional strength-ening method, its enhancement effect and applicability are better. The applications of laser shock peening tech-nology are closely related to the equipment development technology. At present, foreign countries have developed a series of laser shock enhancement equipments, but there is a big gap between domestic and foreign countries because of the late start and foreign related technology blockade, mainly for the performance of equipment insta-bility, poor environmental adaptability and low degree of automation control. It is difficult to achieve industrial production applications. In view of the above problems, a fixed optical system structure and modular design method are used to develop a laser shock peening equipment. It can complete the processing of aero engine blade with once clamping, and has a high degree of automation and high precision characteristics. Laser shock peening equipment is mainly composed of the control system, high-energy pulse laser, optical shaping system, trajectory robot, water supply robot, monitoring system and other modules. Under the coordination of the control system, the laser outputs short pulse high energy, and laser beam forms a different mode of laser through the optical path shaping system. Meanwhile, the track robot and waterjet robot in accordance with the pre-programmed program movement, and equipment equipped with monitoring system can monitor the operation of each sub-module sys-tem and read the running data and fault alarm in real time, and the formation of closed-loop control system feed-back control each sub-module system. When the room temperature stable at (22 ± 2) ℃ and 20 minutes after the device is switched on, the technical parameters such as the maximum output single pulse energy up to 25 J, energy instability < 3%, pulse width which can be continuously adjusted between 16 ns and 20 ns, pulse width instability within -1 ns~1 ns, beam divergence < 2.5 mrad, beam points instability <50 μrad, the repetition frequency of 0.5 Hz~5 Hz are achieved, the transmission efficiency of the optical system is about 92% , the thickness of the con-straint layer is uniform and the flow rate is continuously controlled. The test results show that the performance of the laser shock peening equipment is good.

Laser shock peening is a new type of metal surface modification technology. Compared to the traditional strength-ening method, its enhancement effect and applicability are better. The applications of laser shock peening tech-nology are closely related to the equipment development technology. At present, foreign countries have developed a series of laser shock enhancement equipments, but there is a big gap between domestic and foreign countries because of the late start and foreign related technology blockade, mainly for the performance of equipment insta-bility, poor environmental adaptability and low degree of automation control. It is difficult to achieve industrial production applications. In view of the above problems, a fixed optical system structure and modular design method are used to develop a laser shock peening equipment. It can complete the processing of aero engine blade with once clamping, and has a high degree of automation and high precision characteristics. Laser shock peening equipment is mainly composed of the control system, high-energy pulse laser, optical shaping system, trajectory robot, water supply robot, monitoring system and other modules. Under the coordination of the control system, the laser outputs short pulse high energy, and laser beam forms a different mode of laser through the optical path shaping system. Meanwhile, the track robot and waterjet robot in accordance with the pre-programmed program movement, and equipment equipped with monitoring system can monitor the operation of each sub-module sys-tem and read the running data and fault alarm in real time, and the formation of closed-loop control system feed-back control each sub-module system. When the room temperature stable at (22 ± 2) ℃ and 20 minutes after the device is switched on, the technical parameters such as the maximum output single pulse energy up to 25 J, energy instability < 3%, pulse width which can be continuously adjusted between 16 ns and 20 ns, pulse width instability within -1 ns~1 ns, beam divergence < 2.5 mrad, beam points instability <50 μrad, the repetition frequency of 0.5 Hz~5 Hz are achieved, the transmission efficiency of the optical system is about 92% , the thickness of the con-straint layer is uniform and the flow rate is continuously controlled. The test results show that the performance of the laser shock peening equipment is good.

Solar cell is an important part of the energy of spacecraft, and the accurate calibration of solar cell can provide data reference for the assembly of solar panels. The ground solar simulator may bring in error, and can’t accurate-ly reflect the performance of solar cell under conditions of high altitude, which may have a bad impact on the ap-plications of solar cell in space. So it has a very important significance to research calibration technology of the solar cell under conditions of high altitude. Originated in the United States, high altitude solar cell calibration technology is mainly applied to study the performance of solar cells in high-altitude environment. Initially, char-acteristics of the short-circuit current of the solar cell were studied in the high altitude, and then with the devel-opment of science and technology, the I-V characteristic curve of the solar cell was measured. China is still in the primary stage of high altitude solar cell calibration technology, and only two kinds of exploratory solar cells short-circuit current tests were carried out.Taking the imperfection of high altitude solar cell testing technology, and insufficiency of theoretical research into consideration, we focused on the key technologies of high altitude solar cell testing and calibration methods. Research for the power generation mechanism and electrical characteristics of the solar cell was carried out. Ac-cording to the test environment, the key technologies and methods of I-V characteristics of solar cells in high-altitude environment were introduced. An I-V characteristic test system based on programmable electronic load for solar cells was designed, which could execute tests on solar cell automatically.According to the measurement error of experimental data, the curve fitting algorithm was developed to get more accurate I-V curve data. On the basis of the analysis of equivalent mathematical model of solar cells, a method based on chaotic genetic algorithm was proposed to fit the I-V curve of solar cells. In view of the solar cell’s I-V characteristics data, the algorithm, which provided the value of the parameters of the equivalent mathematical model, was executed to achieve curve fitting. The fitness value of the chaos genetic algorithm is 4.0289e-4. The comparison results show that curve fitting with chaotic genetic algorithm is better than particle swarm algorithm and genetic algorithm. Based on the equivalent mathematical model of solar cell, the characteristic parameters of solar cells corresponding to experimental conditions can be calculated.

Solar cell is an important part of the energy of spacecraft, and the accurate calibration of solar cell can provide data reference for the assembly of solar panels. The ground solar simulator may bring in error, and can’t accurate-ly reflect the performance of solar cell under conditions of high altitude, which may have a bad impact on the ap-plications of solar cell in space. So it has a very important significance to research calibration technology of the solar cell under conditions of high altitude. Originated in the United States, high altitude solar cell calibration technology is mainly applied to study the performance of solar cells in high-altitude environment. Initially, char-acteristics of the short-circuit current of the solar cell were studied in the high altitude, and then with the devel-opment of science and technology, the I-V characteristic curve of the solar cell was measured. China is still in the primary stage of high altitude solar cell calibration technology, and only two kinds of exploratory solar cells short-circuit current tests were carried out.Taking the imperfection of high altitude solar cell testing technology, and insufficiency of theoretical research into consideration, we focused on the key technologies of high altitude solar cell testing and calibration methods. Research for the power generation mechanism and electrical characteristics of the solar cell was carried out. Ac-cording to the test environment, the key technologies and methods of I-V characteristics of solar cells in high-altitude environment were introduced. An I-V characteristic test system based on programmable electronic load for solar cells was designed, which could execute tests on solar cell automatically.According to the measurement error of experimental data, the curve fitting algorithm was developed to get more accurate I-V curve data. On the basis of the analysis of equivalent mathematical model of solar cells, a method based on chaotic genetic algorithm was proposed to fit the I-V curve of solar cells. In view of the solar cell’s I-V characteristics data, the algorithm, which provided the value of the parameters of the equivalent mathematical model, was executed to achieve curve fitting. The fitness value of the chaos genetic algorithm is 4.0289e-4. The comparison results show that curve fitting with chaotic genetic algorithm is better than particle swarm algorithm and genetic algorithm. Based on the equivalent mathematical model of solar cell, the characteristic parameters of solar cells corresponding to experimental conditions can be calculated.

Because the distance between the infrared imaging system and the target is usually far away, the background in the infrared image often contains clouds, clutter, and infrared correction caused by uneven undulation or stripes as well as all kinds of noise. At the same time, the small target of image in the pixel is less, and the lack of shape and texture information, the signal-to-noise ratio (SNR) is low, easily submerged in the complex background, which makes the detection and tracking of infrared dim and small target difficult. In order to improve the abilities of de-tection and tracking of infrared dim and small targets, it is necessary to effectively suppress the complex back-ground in infrared images. The background prediction is a valid complex background suppression method. By dividing the original image from the predicted background, a differential image is obtained, and the difference image can sufficiently suppress the complex background and the target is effectively preserved.At present, the commonly used background prediction algorithms include low-pass filtering, median filtering, morphological filtering, two-dimensional least mean square error filtering (TDLMS), mixed of Gaussian, back-ground prediction based on pixel estimation method, and so on. The above background prediction methods are effective for the background of stable or slowly changing, but they are ineffective for the large span background. In view of the shortcomings of the above methods, considering the ability of gradient inverse weighting filter has the advantages of good detail preserving and strong clutter resistance, it is introduced into the paper for background suppression. However, because its key parameters cannot be adjusted in real time according to local clutter, in order to enhance its adaptability, this paper proposes an improved gradient inverse weighting filtering algorithm through the establishment of clutter local correlation function. The use of background of the local statistical char-acteristics of adaptive filter parameters, can better adapt to the drastic change in the clutter, and improve the ability to suppress clutter suppression algorithm.For evaluation of background prediction result, three performance indices are used in this study, mean squared error (MSE), structural similarity (SSIM) and local signal-to-noise ratio gain (GSNR), to evaluate the effect of image background prediction. By comparing and analyzing these three indexes, MSE, SSIM and GSNR, it could be seen that the improved gradient inverse weighted filtering could effectively suppress the complex background of images, presenting a superior overall performance to other background suppression methods.

Spatial heterodyne Spectroscopy is an interferometric technique to achieve many hyper-spectral detections that have been developed for several decades by J. M. Harlander, F. L. Roesler et al. In particular, passive hyper-spectral spatial heterodyne spectrometer (SHS) is significant instrument for space applications to measure colume densi-ties of trace gases (CO2, CH4, CO), mesospheric OH density, global chlorophy II fluorescence and so on from recent information and progress report. Hence, the recovered spectrum of SHS also depends on its thermal-vacuum en-vironment. Thermal-vacuum environment adaptability is one of the key performances for hyper-spectral instru-ment, and SHS should provide high spectral stability especially for space detection of atmospheric trace gases. In this case, the spectral band spans 757 nm~771 nm with a spectral resolution of ~ 0.03 nm, even though an ex-tended source (extent of ~73 mrad, entrance diameter of 21 mm) is used. This channel for Oxygen (O2) measure-ments is intended to investigate influence on Carbon Dioxide (CO2) column abundance including atmospheric pa-rameters and surface height. Based on the research of the spatial heterodyne interference principle, simulation test in thermal-vacuum environment and quantitative analyses are carried out. The relationship between environmen-tal changes and the divergence half-angle of collimating lens, Littrow wavelength of field widened interferometer, different defocusing amounts and pantograph ratio of imaging lens are analyzed. With low thermal expansion co-efficient of 5.7×10-7/K and high thermal refraction index of 9.2×10-6/K, Fused Silica is well suited for grating sub-strates with high groove density, but it is not necessarily the best choice for beamsplliter and field widened wedge. In order to verify the theoretical analyses and determine if SHS performance would achieve its science goals, thermal-vacuum experiment by CS-800 and integrating sphere light source is performed at Key Laboratory of Op-tical Calibration and Characterization (KLOCC) of Chinese Academy of Sciences (CAS). The results, especially for relationship between recovered spectral profiles and different out-of-focus amounts due to optical degradation of interferogram modulation in the harsh space environment, show that the relative spectral intensity deviation and spectral profile are matched with theoretical analysis, and spectral stability is less than ±0.01 nm under the tem-perature from 19 ℃ to 21.2 ℃ by the substrates made of Fused Silica (Corning 7980 0F). Quantitative analysis provides theoretical basis for the thermal control requirement and Littrow wavelength selection in normal at-mospheric pressure. SHS is well suited for low light and high spectral resolution detection, but active thermal controller, calibration and correction under on-orbit conditions are necessary for space applicaitions.

Spatial heterodyne Spectroscopy is an interferometric technique to achieve many hyper-spectral detections that have been developed for several decades by J. M. Harlander, F. L. Roesler et al. In particular, passive hyper-spectral spatial heterodyne spectrometer (SHS) is significant instrument for space applications to measure colume densi-ties of trace gases (CO2, CH4, CO), mesospheric OH density, global chlorophy II fluorescence and so on from recent information and progress report. Hence, the recovered spectrum of SHS also depends on its thermal-vacuum en-vironment. Thermal-vacuum environment adaptability is one of the key performances for hyper-spectral instru-ment, and SHS should provide high spectral stability especially for space detection of atmospheric trace gases. In this case, the spectral band spans 757 nm~771 nm with a spectral resolution of ~ 0.03 nm, even though an ex-tended source (extent of ~73 mrad, entrance diameter of 21 mm) is used. This channel for Oxygen (O2) measure-ments is intended to investigate influence on Carbon Dioxide (CO2) column abundance including atmospheric pa-rameters and surface height. Based on the research of the spatial heterodyne interference principle, simulation test in thermal-vacuum environment and quantitative analyses are carried out. The relationship between environmen-tal changes and the divergence half-angle of collimating lens, Littrow wavelength of field widened interferometer, different defocusing amounts and pantograph ratio of imaging lens are analyzed. With low thermal expansion co-efficient of 5.7×10-7/K and high thermal refraction index of 9.2×10-6/K, Fused Silica is well suited for grating sub-strates with high groove density, but it is not necessarily the best choice for beamsplliter and field widened wedge. In order to verify the theoretical analyses and determine if SHS performance would achieve its science goals, thermal-vacuum experiment by CS-800 and integrating sphere light source is performed at Key Laboratory of Op-tical Calibration and Characterization (KLOCC) of Chinese Academy of Sciences (CAS). The results, especially for relationship between recovered spectral profiles and different out-of-focus amounts due to optical degradation of interferogram modulation in the harsh space environment, show that the relative spectral intensity deviation and spectral profile are matched with theoretical analysis, and spectral stability is less than ±0.01 nm under the tem-perature from 19 ℃ to 21.2 ℃ by the substrates made of Fused Silica (Corning 7980 0F). Quantitative analysis provides theoretical basis for the thermal control requirement and Littrow wavelength selection in normal at-mospheric pressure. SHS is well suited for low light and high spectral resolution detection, but active thermal controller, calibration and correction under on-orbit conditions are necessary for space applicaitions.

Due to its high quality factor and high sensitivity, the optical microcavity has well promising applications in opti-cal sensing, biomedical, nonlinear optics, environmental monitoring and quantum physics. The principle is that when analyses enter the optical microcavity, the effective refractive index of the solution will change, and the res-onant wavelength will be shifted. Therefore, it is very important to find out the variation of resonant wavelength to improve the sensing accuracy of the optical microcavity. A traditional method to do this is using the Lorentz algo-rithm to fit the transmission spectrum of the optical microcavity. However, the Lorentz fitting algorithm cannot well fit the spectrum when it is an asymmetric waveform or there is a splitting mode waveform within the optical microcavity. In order to deal with the problem, the implicit function model algorithm is proposed in this study. The process of our method can be described as follows. The template waveform was selected and established first, followed by the panning and zooming operations. Then, a traditional method was used to set the initial value of the parameter of objective function, and the parameter values were optimized by the Levenberg-Marquardt (LM) algorithm, which could achieve data fitting results of symmetrical waveform, asymmetric waveform and splitting mode waveform. Note that there was no definite mathematical expression according to the implicit function model algorithm, so different methods were used to obtain the partial derivative of the factor in the Jacobian matrix by means of the template data. In this study, experimental platform, including the optical microcavity, tunable laser source and controller, data acquisition and control system, was established. Different concentrations of solutions of dimethyl sulfoxide, glucose and glycerol were tested as the analyte, and the Gauss, the Lorentz and the implicit function model algorithm were used to fit the experimental data of different transmission spectrums. The results show that MSE of the implicit function model algorithm is one order of magnitude lower than other two algorithms, and the coefficient of determination (R2) is 0.99. The resonant frequency error of implicit function model algo-rithm is the smallest, the resonant frequency of implicit function model algorithm is the largest, and the sensitivi-ty of implicit function model algorithm is the highest. Therefore, the fitting effect of the implicit function model algorithm is better and it can efficiently improve the sensitivity of the optical microcavity and has a reliable basis on the follow-up to find the spectral resonance center to detect the biological components. The digital implicit function model algorithm will have a wide application prospect in any shape waveform data fitting.

In rail transportation, rail plays an important role in supporting and guiding the vehicle running. However, in the process of vehicle running, the friction and the pressure on the rail easily lead to wear and deformation. When rail wear and deformation reach a certain degree, it will bring potential dangers to the vehicle running. The measure-ment of rail shape and surface defects has become a focus in the railway industry. In recent years, 3D measure-ment techniques based on fringe projection have been introduced into online measurement of rail profile and sur-face defects. Phase measurement profilometry (PMP) is a widely-used method, which is suitable for 3D online measurement of rail with high precision and easy to measure online. In online PMP, when the velocity of the object is quite high, the collected reformed fringes often appear to be motion-blurred, which increases the measurement error, or even leads to the 3D reconstruction failure. In the 3D measurement of rail shape and surface flaw with online PMP, in order to clarify the blurred reformed fringes of the rail, several restoration methods, such as Wiener Filtering, Point Spread Function algorithm, Blind Deconvolution algorithm, and Richardson-Lucy algorithm were compared and analyzed. And the peak signal to noise ratio (PSNR) is used for evaluating the restoration effect. The PSNR is higher, the image quality is better. Meanwhile, the relationship between the vehicle speed and the restora-tion effect was studied, the error was analyzed and the 3D rail shape was reconstructed based on online PMP. The-oretical and experimental results show that in the online 3D measurement of rail shape and surface flaw, the Rich-ardson-Lucy algorithm is best for image restoration of motion blur, and the relationship between the effect of im-age restoration and the vehicle speed is a polynomial. When online PMP method is used for reconstructing 3D motion blurred image, the 3D shape quality of the rail will be poor, and the 3D restoration of the reconstructed fringe images can get good 3D shape of the rail. In actual measurement, the obtained motion blurred fringe images are processed with Richardson-Lucy algorithm, and online PMP is used to reconstruct the 3D shape of the rail. In comparison with the 3D shape of the standard rail, the abrasion of the rail is obtained. If the rail surface is defec-tive, the accurate position and size of the defect can be determined by the reconstruction of the 3D shape of the rail.

In rail transportation, rail plays an important role in supporting and guiding the vehicle running. However, in the process of vehicle running, the friction and the pressure on the rail easily lead to wear and deformation. When rail wear and deformation reach a certain degree, it will bring potential dangers to the vehicle running. The measure-ment of rail shape and surface defects has become a focus in the railway industry. In recent years, 3D measure-ment techniques based on fringe projection have been introduced into online measurement of rail profile and sur-face defects. Phase measurement profilometry (PMP) is a widely-used method, which is suitable for 3D online measurement of rail with high precision and easy to measure online. In online PMP, when the velocity of the object is quite high, the collected reformed fringes often appear to be motion-blurred, which increases the measurement error, or even leads to the 3D reconstruction failure. In the 3D measurement of rail shape and surface flaw with online PMP, in order to clarify the blurred reformed fringes of the rail, several restoration methods, such as Wiener Filtering, Point Spread Function algorithm, Blind Deconvolution algorithm, and Richardson-Lucy algorithm were compared and analyzed. And the peak signal to noise ratio (PSNR) is used for evaluating the restoration effect. The PSNR is higher, the image quality is better. Meanwhile, the relationship between the vehicle speed and the restora-tion effect was studied, the error was analyzed and the 3D rail shape was reconstructed based on online PMP. The-oretical and experimental results show that in the online 3D measurement of rail shape and surface flaw, the Rich-ardson-Lucy algorithm is best for image restoration of motion blur, and the relationship between the effect of im-age restoration and the vehicle speed is a polynomial. When online PMP method is used for reconstructing 3D motion blurred image, the 3D shape quality of the rail will be poor, and the 3D restoration of the reconstructed fringe images can get good 3D shape of the rail. In actual measurement, the obtained motion blurred fringe images are processed with Richardson-Lucy algorithm, and online PMP is used to reconstruct the 3D shape of the rail. In comparison with the 3D shape of the standard rail, the abrasion of the rail is obtained. If the rail surface is defec-tive, the accurate position and size of the defect can be determined by the reconstruction of the 3D shape of the rail.

Auto-focusing is one of the key technologies in the area of robot vision, digital imaging systems and precision op-tical instrument. With the continuous development of science and technology and improved application demands, it is more and more urgent to develop an auto-focusing with high precision, fast speed and good stability. While the existing auto-focusing techniques can’t meet the above requirements, a further study on auto-focusing makes a very important practical significance. The depth from defocus method and the depth from focus method are two typical passive auto-focusing methods of autofocus method based on digital image processing. The depth from defocus method is popularly used in depth estimation and scene reconstruction, which can measure the position of samples by just a few images. Therefore, the efficiency of the method is high. However, the accuracy of the depth from defocus method is relatively low because the small number of images is collected by the method. The depth from focus methods are based on the fact that the image formed by an optical system is focused at a partic-ular distance whereas objects at other distances are blurred or defocused. Very high accuracy can be achieved by depth from focus methods. In order to achieve efficient autofocusing, several commonly used search algorithms are studied, and a new low-computational search algorithm is presented, which combines the mountain-climb search strategy with the approximation function strategy to realize the hybrid search algorithm accurate and effi-cient autofocus. In this algorithm, the mountain-climb search strategy adopts the two-stage algorithm of rough and fine focusing stage. In the rough focusing stage, the large step distance takes into account the fastness of the algo-rithm, and the gray variance function is used to approach the focusing position quickly. In the fine focusing stage, the small step distance takes into account the sensitivity of the algorithm and the Laplacian function is used to locate the focusing position accurately. The algorithm narrows the focus interval by comparing three pictures and in the range uses the approximation function strategy to fit the best focus position. This method makes greatly improve the search accuracy. The experimental results indicate that this the algorithm can make the search accu-racy better than 1 μm. And the method only needs to capture 17 pictures, reducing the number of image acquisi-tion and evaluation. As a result, the time of the autofocus system is shortened and the search efficiency of the al-gorithm is improved.

Computer visual travel aids (VTA) are effective means to assist the blind, while blind sidewalk recognition is an important function of VTA. The so-called blind sidewalk recognition is a method that segments blind sidewalk and detects boundary lines via image processing technology. After blind sidewalk recognition, VTA locate the bounda-ry based on stereo vision and then guide the blind to sidewalk by control signal. In order to solve the problem that existing blind sidewalk recognition algorithms have bad real-time performance, a highly real-time blind sidewalk recognition algorithm based on boundary tracking is proposed, mainly including accurate recognition and tracking recognition. First, the preprocessing of shadow removal is performed for each frame image before recognition, which calculates a residual model based on the Retinex theory to detect shadow and uses regional color compen-sation to remove shadow. Next, accurate recognition step mainly calculates gray level co-occurrence matrix of the initial frame, and uses clustering and Hough transform to find the boundary lines of blind sidewalk in image. Then tracking recognition step takes over next frame. The location of blind sidewalk’s boundary in previous frame is used to predict the small-scale region of interest (ROI) of the boundary in current frame, and boundary lines in that region are extracted based on gray gradient feature. After that, the algorithm checks up the validity of tracking by estimating the consistency of color distribution on both sides of the boundary in previous and current frames: tracking is considered to be valid if the consistency is high, and tracking recognition step continues, otherwise accurate recognition step restarts. We apply our algorithm on binocular VTA and the blind wear the VTA to walk along blind sidewalk for the algorithm performance test. In many experiments, the time of accurate recognition and tracking recognition in each image frame under normal illumination are about 0.8 s and 0.1 s, respectively, and the average time of recognition per frame decreases significantly while the recognition rate of blind sidewalk is more than 90%. Meanwhile, the adaptability is good in shadow environment and is acceptable in other envi-ronment, including strong and weak light, damage of blink sidewalk, and blurring. Experimental results indicate that the algorithm can significantly enhance the real-time performance of blind sidewalk recognition in the prem-ise of ensuring the recognition rate. Therefore, our algorithm is more suitable for real-time visual navigation than traditional ones.

Multi-focus lens is applied widely as an important optical element, but it has stringent requirements for manufac-turing and assembling micro-lens array which is used for multi-focusing in traditional methods. So tiny error is inevitable, which may affect the usage performance. Therefore, it is necessary to design a new type of multi-focus optical device. Metasurface is a kind of artificial surface which consists of many subwavelength antenna units different from traditional optical element. Metasurface utilizes the anomalous refraction properties that subwave-length antenna units response to the electromagnetic wave to modulate wave front. Subwavelength scale antennas with different structural parameters are arranged according to certain rules, so it can realize flexible modulation to amplitude and phase of electromagnetic wave. Metasurface has been widely used in the designing of various new optical components in recent years. Compared to the conventional multi-focus lens, metasurface is used to design multi-focus lens with its unique advantages. In finished works, when designing the multi-focus lens based on metasurface, the phase retrieval algorithm is used to obtain the phase distribution of lens commonly, and multiple iterations are performed between metasurface and the focusing surface. However, this method for phase calcula-tion is of great computation load, and sometimes it is easy to fall into local optima. Meanwhile, metasurface-based flat-lens array also be proposed. It consists a number of regularly arranged lenslets to achieve multi-focusing function, but the array structure is not favorable to be integrated. Computer-generate holography (CHG) method to design multi-focus lens based on metasurface has been proposed in far-infrared region. This method is simple, straightforward, accurate, and easily implemented and realized. Firstly, 8 C-shaped resonant rings aimed at central frequency 28 THz(wavelength 10.71 μm) were designed, which was able to modulate the phase of transmitted cross-polarized wave from 0 to 2π and amplitude transmittance remains constant, that can be used in the design of multi-focus lens. Secondly, the anomalous refraction functions of this set of resonators were verified by full-wave simulation when linearly polarized light waves were irradiated normally. It can be seen that the wavefronts of the deflected waves with cross-polarization are well deflected, further demonstrating the broadband property of the resonators. Finally, the four spot light source in focusing plane were set as certain distance away from the plane where metasurface located. The phase distribution of multi-focus lens at metasurface was calculated by the method of complex amplitude superposition. Then, according to arranged C-shaped resonators based on obtained phase distribution, a square metasurface-based lens was got, and the structure was simulated as a integer by CST Microwave Stdio. Simulation results show a good multi-focus performance at 28 THz while the focal length is 108 μm, as certain broadband response characteristics in 27.6 TH~28.5 THz.

Multi-focus lens is applied widely as an important optical element, but it has stringent requirements for manufac-turing and assembling micro-lens array which is used for multi-focusing in traditional methods. So tiny error is inevitable, which may affect the usage performance. Therefore, it is necessary to design a new type of multi-focus optical device. Metasurface is a kind of artificial surface which consists of many subwavelength antenna units different from traditional optical element. Metasurface utilizes the anomalous refraction properties that subwave-length antenna units response to the electromagnetic wave to modulate wave front. Subwavelength scale antennas with different structural parameters are arranged according to certain rules, so it can realize flexible modulation to amplitude and phase of electromagnetic wave. Metasurface has been widely used in the designing of various new optical components in recent years. Compared to the conventional multi-focus lens, metasurface is used to design multi-focus lens with its unique advantages. In finished works, when designing the multi-focus lens based on metasurface, the phase retrieval algorithm is used to obtain the phase distribution of lens commonly, and multiple iterations are performed between metasurface and the focusing surface. However, this method for phase calcula-tion is of great computation load, and sometimes it is easy to fall into local optima. Meanwhile, metasurface-based flat-lens array also be proposed. It consists a number of regularly arranged lenslets to achieve multi-focusing function, but the array structure is not favorable to be integrated. Computer-generate holography (CHG) method to design multi-focus lens based on metasurface has been proposed in far-infrared region. This method is simple, straightforward, accurate, and easily implemented and realized. Firstly, 8 C-shaped resonant rings aimed at central frequency 28 THz(wavelength 10.71 μm) were designed, which was able to modulate the phase of transmitted cross-polarized wave from 0 to 2π and amplitude transmittance remains constant, that can be used in the design of multi-focus lens. Secondly, the anomalous refraction functions of this set of resonators were verified by full-wave simulation when linearly polarized light waves were irradiated normally. It can be seen that the wavefronts of the deflected waves with cross-polarization are well deflected, further demonstrating the broadband property of the resonators. Finally, the four spot light source in focusing plane were set as certain distance away from the plane where metasurface located. The phase distribution of multi-focus lens at metasurface was calculated by the method of complex amplitude superposition. Then, according to arranged C-shaped resonators based on obtained phase distribution, a square metasurface-based lens was got, and the structure was simulated as a integer by CST Microwave Stdio. Simulation results show a good multi-focus performance at 28 THz while the focal length is 108 μm, as certain broadband response characteristics in 27.6 TH~28.5 THz.

Polarization measurement is able to effectively solve the problems that are beyond the reach of conventional photometry. When it comes to long-wavelength infrared (LWIR) polarization imaging system, polarization device plays a vital role in measuring the targets’ radiation and reflection and distinguishing them from busy background, which compensates for the lack of traditional thermal imaging if the difference in temperature is unobservable. Sub-wavelength wire-grid polarizer (WGP) is characterized by small volume and compact structure with the mi-cro- or nano-manufacturing technology. It is a grating structure whose period is smaller than the incident wave-length and when that is smaller than the critical one, the grating will only have zero-ordered diffraction, which helps improve the utilization ratio of polarization information. A dual-layered sub-wavelength grating consisting of two kinds of materials, aluminum and ZnSe, is developed to improve the performance of polarimetric elements in LWIR polarization imaging system. Parameters of the designed grating’s morphological structure are optimized on the basis of analyzing the effects on the polarization performances through the rigorous coupled wave theory, which helps describe the diffraction of electromagnetic waves by periodic grating structures and calculate diffrac-tive efficiencies of different orders. With a rectangular profile, the grating designed for applications in LWIR band has a structure of 1μm-period and 50%-fill-factor. The depths of aluminum and ZnSe in the grating region are 0.6 μm and 0.4 μm respectively. A TM transmission greater than 87.54% with an extinction ratio exceeding 47 dB is achieved in the 7 μm ~15 μm band when the angle of incidence is from zero to sixty degree. The grating maintains an extinction ratio better than 50 dB and TM transmission over 90.80% above 10.6 μm incident wavelength, which is superior to single-layered aluminum gratings with the same depth in the transmission performance in compar-ison. The structure is featured for the excessive etching on substrate, resulting in a series of air grooves. Therefore, the dielectric grating layer beneath the metal wire grid is formed. This method for improving polarization perfor-mances is easier to implement than coating anti-reflective films. It is investigated that the TM transmission in-creases with the depths of both metal and dielectric layers when the extinction ratio is dominated by the depth of metal layer, while the single-layered ZnSe grating shows little potential in extinction ability for the lack of metal component. Compared with the existed designs of WGP, the simulation results show that the TM transmission and extinction ratio are effectively improved in broad LWIR band with the proposed structure. Besides, the an-gle-tolerance indicates that the design has great capability in applications with wide field angle.

Volumetric imaging enables quantitative and global measurements of a three-dimensional (3D) complex system. It allowed quantitation of molecules in the whole volume of a specimen, and has proven to be in-valuable in the studies of cell metabolism, brain func-tion, and developmental biology. Light-sheet fluores-cence microscopy and optical projection tomography have been reported to image 3D volumes with high resolutions and at high speeds. Such methods, however, usually rely on fluorescent labels for chemical targeting, which could perturb the biological functionality in liv-ing systems.

Holographic display technology can greatly improve the display of top three-dimensional (3D) TV, and gra-dation representation method in color comput-er-generated hologram (CGH) is essential for the color-ful display of the 3D reconstruction image. At present, the gray level of a 3D reconstruction image can be achieved by controlling the intensity or display time of the reference light.

Long-distance entanglement distribution is essential for both foundational tests of quantum physics and scala-ble quantum networks. Owing to channel loss, however, the previously achieved distance was limited to ~100 km.