Based multi-phase screen numerical simulation, the influences of on-axis scintillation of focus Gaussian beams propagating in the turbulent atmosphere on several typical aberrations are investigated quantitatively. It is found that astigmatism and coma aberrations can restrain and promote the axis-scintillation to some extent, respectively. Stronger coma and astigmatism aberrations can forward and delay the appearance of scintillation saturation, respectively. The distribution of intensity deviates from log-normal distribution when turbulence strength is weaker. It is close to log-normal distribution when the intensity of turbulence rises. The skewness of the intensity distribution is less than zero and its kurtosis is greater than zero basically. Under weak or moderate turbulence intensity, the distribution of intensity fluctuation is always determined by aberrations when the aberration is big enough, however, the effects of turbulence play the main role on the distribution of intensity fluctuation and the aberrations mainly affect the fluctuation distributions of weak intensity areas when the weight of aberration is small. The strong turbulence influences the probability distribution of intensity fluctuation mostly, and the distribution fits to log-normal distribution approximately.

The characteristics of dim point target and background clutter under a complex background are analyzed. A point target detection method based on the omnidirectional multiscale morphology filtering and local characteristic criterion is proposed. The experimental results show that, under the conditions of a complex background and a low signal-to-noise ratio, the detection probability of the proposed method reaches 99.8% with a false alarm probability of 0.1%. The results indicate that, when compared with the methods of Max-median filter, difference of Gaussian scale-space, and Gaussian mixture model, the proposed method possesses a better performance to suppress the complex background, and simultaneously a low complexity and an easy real-time implementation.

The dual energy X-ray grating phase contrast imaging system exhibits a variety of advantages, including high imaging efficiency, low radiation, setups without stepping device, and simple imaging platform. Under different energy levels of X-ray, the relationship between the CsI thickness and the fluorescence transmittance, and the relationship between the Bi thickness and the transmittance of X-ray are studied. Based on the above research, a dual energy analysis grating is designed. The grating structure and the fabrication materials of the gratings are described, and the calculation method of the thickness of the grating bar is analyzed. The simulation of dual energy analysis grating is carried out. The results show that the designed dual energy analysis grating can obtain clear fringe image, and it has good fringe contrast. The designed dual energy analysis grating is applied to dual energy X-ray grating phase contrast imaging system. With simulation, the imaging system can obtain the phase first order derivative image of the measured object, indicating that the designed dual energy analysis grating is valid.

Based on the angular spectrum representation of partially coherent beams and the method of stationary phase, the far-field light intensity and divergence angle properties of nonparaxial partially coherent beams with nonconventional spatial correlation structure are studied. Analyticall expressions of the far-field light intensity and divergence angle of nonparaxial Bessel-Gaussian Schell-model (BGSM) beam diffracted by a circular aperture are derived. The properties of the far-field light intensity and divergence angle of the BGSM beam are illustrated numerically by the expressions. The results show that the far-field light intensity and divergence angle properties of the nonparaxial BGSM beam are obviously different from that of nonparaxial Gaussian Schell-model beam, and are closely related to the spatial correlation structure, beam waist width, coherence length and aperture radius in light source plane of the beams. Modulating the spatial correlation structure of the beam provides a novel way to modulate the propagation properties of nonparaxial partially coherent beam in the far-field.

A type of newcastle disease virus (NDV) immunosensor based on 81° tilted fiber grating (81°-TFG) is proposed. The basic principle and sensing properties of the 81°-TFG are briefly analyzed. Staphylococcus aureus protein A (SPA) is used to modify the surface of 81°-TFG, and then highly purified NDV monoclonal antibodies (MAbs) are immobilized on 81°-TFG surface through SPA molecules. Finally, the NDV immunosensor is successfully developed. The experimental results show that the immunosensor has a lowest limit of detection to NDV of between 0.1 ng/mL and 0.2 ng/mL, gets saturated at about 1.0 ng/mL, and has good linearity with R2 of about 0.982 and sensitivity of about 342 pm/(ng·mL-1) in the concentration range from 0 to 1.0 ng/mL. In addition, this immunosensor shows good reusability and high specificity to NDV, and can also be used in clinical test for NDV. Compared with the traditional biochemical methods such as immunofluorescence technique, enzyme-linked immunoabsorbent assay, this technique proposed in this paper has the advantages of no mark, simple operation, fast detection.

A gas sensor based on the Mach-Zehnder interferometer with copper-deposited tungsten disulfide coated thin-core fiber is proposed. The fiber-core mismatch-type gas sensor is formed by fusion of standard single-mode fiber and thin-core fiber. The relation between the gas concentration and the spectral shift is established by the adsorption of the copper-deposited tungsten disulfide film to the hydrogen sulfide gas. Therefore, the detection of the hydrogen sulfide gas with lower concentration can be achieved. The experimental results show that the detection sensitivity of the hydrogen sulfide gas is 29.3 pm and the sensor has a good linearity and selectivity within the gas volume fraction range of 0~6×10-5. The sensor is especially suitable for online monitoring of hydrogen sulfide gas with low concentration for the advantages of simple structure, high sensitivity and easy to manufacture.

In order to improve the output performance of all-fiber interleaver, a novel all-fiber Mach-Zehnder interferometer (MZI) interleaver which uses a 2×2 fiber coupler with self-feedback as the output coupler is proposed. An output expression of the system is derived and simulated numerically. The results show that the transmitted waveform of the proposed MZI-Interleaver is close to a square wave, and the rejection in stopband and the rolloff in transition band are improved remarkably. Compared with the traditional MZI-Interleaver based on fiber resonator, the difference between the intensities of two coherent lights dose not exist when the influence of the propagation loss is considered, and the influence of the propagation loss on extinction ratio of all-fiber MZI-Interleaver can be effectively reduced.

Spatial resolution and signal-to-noise ratio are difficult to be improved at the same time due to the small signal and big noise in Rayleigh Brillouin optical time domain analysis (BOTDA) system. A technique of pulse coding is introduced into Rayleigh BOTDA system, and then the signal-to-noise ratio and Brillouin frequency shift measurement accuracy of the system can be improved effectively without decreasing spatial resolution. The principle of the temperature sensing system based on Rayleigh BOTDA is analyzed. The characteristic of Golay complementary sequence is introduced and the expressions of the signal-to-noise ratio between single pulse system and coded pulse system are achieved. Rayleigh BOTDA temperature sensing systems of single pulse and coded pulse are constructed. The temperature sensing characteristic of single pulse system and the spatial resolution and the accuracy of temperature measurement of coded pulse system are measured. The experimental results show that the Brillouin frequency shift obtained by the Rayleigh BOTDA system has a linear relationship with temperature, and the temperature coefficient is (1.109±0.010) MHz·℃-1. The spatial resolution of 1 m and temperature accuracy of 1.39 ℃ are obtained on the heated section of 1.77 km fiber when Golay code is 64 bit and the pulse width is 10 ns.

Based on the principle of compound zoom optical system, a new compound zoom optical system structure is proposed. The structure combines the continuous zoom system with the two-step zoom system to increase the focal length range of the zoom optical system and achieve the larger search range and the longer tracking distance. A mathematical model of optic design of the new compound zoom system is established. Under the guidance of this model, a new compound zoom optical system is designed for long wave infrared uncooled focal plane detector with pixel number of 320×240 and pixel size of 30 μm×30 μm. The working band of the system is 8~12 μm, the focal length range is 10~360 mm, the F number is 2 at 10~60 mm, and the F number is 4 at 60~360 mm. The cam curves and performance of the optical system are analyzed. The results show that the system has such advantages as large zoom ratio, simple structure, good image quality and smooth cam curves, all of which verify the validity of the mathematical model.

Most of the existing single image dehazing algorithms are on the basis of local priors, and there is block effect in dehazing results. The image artifacts are augmented at heavy haze regions, if there is no special treatment. For example, the noise and color overlap which are almost invisible in the original haze image are enhanced after dehazing, and affect the quality of the dehazing images. In order to eliminate these disadvantages, a novel image dehazing algorithm is proposed. Firstly, the non-local prior is adopted to estimate the initial transmission. Then, a regularized method is used to optimize it, the L1/2 norm of gradient difference of original image and dehazing image is used as regularization term to suppress the noise interference. The results show that the proposed algorithm can recover the details and color effectively, and has better robustness than the local prior methods.

The complex sea sky background such as clouds, wave reflection, complex weather, will bring difficulties to the sea sky line detection. To solve this problem of environmental adaptability of sea sky line detection in complex background, a sea sky line detection method is proposed based on the image edge phase encoding. The principle of bilateral filter is used to preserve the image edges and filter out the high frequency noise, and the edge response is enhanced by the Laplace of Gaussian. The edge phase encoding is enhanced and the noise of the system is restrained combined with the Gaussian-Kernel directional filter. Then, the optimized sea sky line is detected by the analysis of cumulative response intensity of scan line in phase component and the difference of pixel intensity distribution mode in sea sky region. The experimental results show that the proposed method can effectively detect the sea sky line in different complex backgrounds, and has low computation complexity and strong environmental adaptability.

Recently, because of its realistic perception, the three-dimensional (3D) imaging technology has attracted more and more attention, and the consequent security issues of 3D image are gradually being taken seriously. Because of the huge data volume of 3D image, the speed of data transmission and processing is very slow. The safety and speed of 3D images transmission has become the primary problem. An optical image hiding technique using fully optical means is proposed, which utilizes the parallelism of optical technology and the theory of compressive sensing to greatly reduce the acquisition time and data volume, it provides the possibility of future 3D image secure transmission. Firstly a secret scene or image is embedded into a host image to perform optical image hiding by using a modified Mach-Zehnder interferometer. Then the hidden image is compressed to a much smaller signal data using single-pixel holographic compression imaging. At the received terminal, the hidden image is reconstructed well via compressive sensing theory and a specified holographic reconstruction algorithm. The preliminary experimental results and numerical simulations show that it is effective and suitable for optical image security transmission in the coming all-optical network for the reason of the completely optical implementation and largely decreased holograms data volume.

A new multi-scale directional guided filter image fusion method based on guided filter and nonsubsampled directional filter bank is proposed. The proposed method possesses the feature of edge preserving and extracting ability of directional information, and can capture the useful information from the source images more effectively. The low-frequency subbands, which are obtained by the multi-scale directional guided filter, include the low-frequency approximation components and strong edge components. These components are separated by Gaussian filter. The low-frequency approximation components and strong edge components are fused based on convolutional sparse representation and adaptive regional energy, respectively. The detail directional subbands are fused via a strategy combined saliency and guided filter to preserve the spatial consistency. Experimental results demonstrate that the proposed method could effectively extract the target feature information and preserve the background information of the source images. The fused results have better subjective visual effect and objective evaluation criteria.

There is a problem of non-uniformity response between multiple channels for a time-delayed integration (TDI) charge-coupled device (CCD) imaging system. Due to this problem, a correction method research based on radiometric calibration is conducted. A theoretical model for correction is deduced according to the flow of signal processing. A correction method is proposed based on weighted least square, which needs to acquire three sets of image data in 1/4, 1/2 and 3/4 saturation. Three sets of correction parameters are fitted by weighted least square using Gaussian weighting function to achieve the optimized parameters. The experimental verification is carried out using a TDI CCD imaging system. The results show that the photo response non-uniformity reduces from 4.09% to 0.85%, which is better than 1.93% obtained by two-point correction method. And it has a good performance in wide response range with advantages of high precision and good practicability. This method can be applied in many kinds of airborne or spaceborne camera payloads and lay the technical foundation to achieve high-quality remote sensing image data.

The metalnano wire grating is the core component of pixelated polarizing camera,and the micro-polarizer array engraved on the wire grating is one to one correspondence with the photodetector. This micro-polarizer array has high non-uniformity and large influence on image quality. Aiming at this problem, we improve the mathematic model of pixel-level vector transfer matrix measurement algorithm based on the structure of the nano wire grating and the polarization transfer theory. Combined with the matrix least squares algorithm, a number of measurements are established to fit the optimal transfer matrix algorithm, and then the core calibration parameters are provided for pixel-level non-uniform calibration of the polarization camera. Considering the structure of the nano wire grating, a calibration algorithm with high spatial resolution is proposed. The non-uniformity of polarization camera decreases from 2.00% to 0.26% after calibration. On the outfield experiment, the information entropy of the target polarization image rises from 5.34 to 15.15. The results show that the proposed algorithm can effectively correct the non-uniformity of the nano wire grating and improve the quality of polarization image.

The downward-looking three-dimensional synthetic aperture radar (DL 3D SAR) imaging method based on compressed sensing could complete the high-resolution imaging by using the sampling data below the Nyquist sampling rate. However, the existing DL 3D SAR imaging methods which used for cross-track profile reconstruction are based on the single measurement vectors (SMV) model and has defects of time-consuming and noise-affected. Based on the multiple measurement vectors (MMV) model, the order of cross-track and along-track in the DL 3D SAR imaging process are exchanged. By using the same sparse structure in cross-track domain for different along-track measurements, the DL 3D SAR imaging method based on MMV model is proposed. The proposed method is superior to the SMV-based method both on time-consuming, reconstruction accuracy and anti-noise performance, and the effectiveness is verified by the simulation experiments.

This work aims at covering the shortage of the complex measurement procedure of nonlinear two-line atomic fluorescence (NTLAF), and a new calibration method based on tunable diode laser absorption spectroscopy (TDLAS) is proposed. First, three calibration constants are combined into one. The new constant is calculated by an iteration of the fluorescence intensity and TDLAS real-time path integral temperature. Finally, the temperature profile is deduced. Numerical simulations for the calibration of NTLAF temperature by TDLAS are performed. The influence of temperature profiles and initial values is analyzed. The precision of the simulation results is almost equivalent to that obtained by conventional point-wise temperature calibration methods, and the uncertainty is within 5%. Different temperature profiles have little influence on this calibration method. A proper initial value will always result in the same final value.

Based on the theory of aperture diffraction, a set of co-phase error optical detection system with segmented mirrors is designed, and the dual-wavelength narrow band co-phase algorithm is used to realize the co-phase detection of synthetic aperture segmented mirrors. In the scheme, circular aperture mask plate, phase difference plate and prism array have been designed for the system. By numerical simulation, a set of template pictures about the circular aperture diffraction with a series of different optical path differences have been obtained. Then, the correlation of the test image and template pictures will be figured out to calculate the optical path difference of the two adjacent sub-mirrors. Before applying the scheme to the segmented mirror detection, a known amount of phase difference in the optical path is introduced by phase plates to carry out the simulation, so that the diffraction patterns are sampled and matched. Results of the experiment verify the feasibility of the scheme, and high accuracy co-phase detection of the synthetic aperture segmented surface can be realized.

The directional polarization camera is an ultra-wide-angle polarization imaging sensor, and stray light is one of the important factors that affect the radiation and polarization measurement precision. In order to avoid the influence of stray light on the inversion of high-precision quantitative parameters, special analysis, measurement and correction should be carried out in the laboratory. According to the characteristics of the optical system of the directional polarization camera, the stray light which affects the instrument is divided into local stray light and global stray light. The causes and performance characteristics of these two kinds of stray light are analyzed emphatically. On this basis, the stray light model of the instrument is constructed, and the method of obtaining the stray light coefficient matrix by partition of the illumination for correction the image is proposed. In the cases of unsaturation and supersaturation, by dividing the rectangular area and the two-dimensional rotation scanning imaging of the field of view, the relationship between the amount of radiation in the target area and the amount of scattered light in other non-target areas is established. Finally, the 11×11 regions of the stray light coefficient matrixes are obtained. The image is corrected according to the measured stray light coefficient matrixes. The results show that this correction method can eliminate at least 90% of stray light.

The random error introduced by CCD camera and the nonlinear error caused by the nonlinear response function of illuminant and CCD camera are two main errors in phase measuring deflectometry. Based on the analysis of the factors affecting the phase error, we establish the analysis model of fringe pattern quality and the factors such as phase error, F value of camera lens, the period of coded fringe pattern, and modulation. The reliability and correctness of the proposed model are verified by computer simulation and experiment. The results of theoretical analysis, simulation, and experimental results show that the contrast ratio of the obtained fringe pattern is proportional to F value of the camera lens and the period and the modulation of the fringe pattern. The sinuousness of fringe is inversely proportional to F value of the camera lens and the period and the modulation of the generated fringe pattern. According to the proposed fringe quality analysis model, high quality fringe pattern can be obtained by optimizing the system parameters. The proposed model can apply to other techniques, such as surface-structured light three-dimensional measurement.

A solar directly pumped Nd∶YAG solid-state laser with low threshold power is designed, in which Fresnel lens with the surface of 1.03 m2 and focal length of 1.2 m is used as the primary solar radiation concentrator, and gold-plated conical cavity with a liquid light-guide lens is used as the secondary concentrator. The continuous and stable 1064 nm laser is obtained by end-side pumping Nd∶YAG grooved rod with diameter of 5 mm and length of 75 mm, under combined action of liquid light guide lens and the gilded taper cavity. Theoretical model is established by optical design software ZEMAX and laser resonator simulation software LASCAD, experimental results are verified, and system design is optimized by numerical simulation. The experimental results show that output power of the laser pumped Nd∶YAG solid-state laser is highest 31.5 W, laser collection efficiency is 30.58 W/m2 , laser threshold power of is 102 W and slope efficiency is 4.25%. The energy conversion efficiency from solar radiation to laser is 3.2%.

A semiconductor laser temperature control system with board-level multi-channel is developed to control the temperature of multiple semiconductor lasers simultaneously in the detection of mixed gas. The system consists of multi-channel temperature acquisition module, digital signal processor module, thermoelectric cooler (TEC) and TEC control modules. The round-robin scheduling algorithm and integration-separated digital proportional integral differential algorithm are used to precisely control the temperature of multiple semiconductor lasers in real time. Temperatures of both the wavelength-tunable distributed feedback lasers centered at 1.65 μm and 1.56 μm are controlled when we use the proposed system. The temperature control experiment is carried out, and the luminescent spectra of the two lasers are detected. Results show that the system can control the temperatures of the two lasers simultaneously. The accuracy of this system can reach -0.011-0.015 ℃ and the response time is less than 3 s. The stability of the temperature controller is tested. The temperatures of the two lasers can stay stable after operation for 6 h, and the emitting peak wavelengths are stable in spectrum test for 10 h. For its tiny size, low cost, capability to be integrated, great stability as well as reliability, the temperature control system has great application prospect in mixed gas detection.

In order to improve the robustness and accuracy of the visual odometry in the dynamic scene, a stereo visual odometry based on moving object detection is proposed. Firstly, a scene flow calculation model considering the camera pose is established to represent the motion vector of the objects. Secondly, the method of constructing virtual map points is proposed. On the one hand, the motion object detection can be complied according to the virtual map points and the scene flow, on the other hand, the virtual map points ensure that there are still enough matched point pairs to estimate the pose when the proportion of the moving objects in the image is too large. Finally, the feature points in the current frame will be matched with the local map points and the virtual map points, and according to the matching results, the nonlinear optimization model considering the virtual points is constructed to estimate the camera pose. It can not only ensure that the static map points do not match with the feature points of the motion object, but also avoid the failure of the visual odometry when the effective point pairs are too few. The results of the dataset experiment and the online experiment in the actual scene show that the proposed method improves the robustness and accuracy of the visual odometry in the dynamic scene.

Making use of information in infrared images to build an effective observation model is the basis for realizing robust infrared target tracking. Besides the regular factors that have adverse influence on visual target tracking, infrared target tracking is faced with other difficulties as well, such as lack of edge and texture information, low signal-to-noise ratio and background clutter. An infrared target tracking algorithm based on histograms of sparse coding (HSC) and the distractor-aware model (DAM) is proposed, which exploits K singular value decomposition algorithm to obtain an overcomplete dictionary. With the dictionary, sparse code of every pixel is computed to compose HSC as a descriptor, and DAM is utilized to strengthen resistance against background clutter. The proposed algorithm does not only use structural information of tracked object but also eliminates the influence of background clutter. Compared with other tracking algorithms, the proposed algorithm achieves 3.8% and 4.4% enhancement on VOT-TIR2015 dataset with respect to precision and success rate, respectively, possessing high research and practical value.

In order to improve accuracy of large-scale scene model in three-dimensional (3D) reconstruction, we extract two kinds of partial stable invariant features, under the premise of ensuring the efficiency of the algorithm, and use a multi-feature fusion method to match image features. Considering both problems of the joint modeling based on aerial and urban street images, we propose a matching method based on the two kinds of partial stable features. The method comprises the following steps. Firstly, we extract ASIFT (Affine Scale Invariant Feature Transform) feature points and MSER feature areas, and improve the MSER (Maximally Stable Extremal Regions) algorithm to get the two stable features described by SIFT (Scale Invariant Feature Transform) feature descriptor; secondly, we use the homography matrix to match features by the feature matching algorithm; finally, we parallelly optimize feature matching by using graphics processing unit(GPU). A large number of experiments and comparison results show that more than twice correct matching pairs can be obtained by the proposed algorithm than other two algorithms.

The Census transform is sensitive to noise, so it is difficult to obtain high matching accuracy with stereo matching algorithm. An anti-noise stereo matching algorithm based on the improved Census transform and outlier elimination is proposed. Firstly, at the initial match cost stage, the median of the window neighborhood is taken as the reference value and the outliers are controlled by the mapping function, which improves the reliability of the single pixel matching cost. At the cost aggregation stage, the outliers are eliminated from the initial cost value of dynamic aggregation window. Finally, the final disparity maps are obtained by disparity calculation and disparity optimization. The Middlebury benchmark images are used to test the stages of the initial matching cost, cost aggregation, and final disparity map on the VS2013 software platform. Experimental results show that the proposed algorithm has better noise-robust performance than the existing Census transform algorithms, and the error matching rate is 5.71%.

For the problems about robust tracking and precision scale estimation of the visual objects in the complex tracking conditions, a target scale adaptive robust tracking algorithm based on the fusion of multilayer convolutional features is proposed. First, the multilayer convolutional features are extracted from the target candidate area using VGG-Net-19 deep convolutional network architecture. By constructing the two-dimensional location filters by correlation filtering algorithm and fusing the multilayer convolutional features, the center location of the target is determined. Then, through the multi-scale sampling of target, the histogram of oriented gradient features are extracted to construct the one-dimensional scale filter to achieve the optimal scale estimation. The experimental results show that the proposed algorithm gains the best success rate and precision compared with the six state-of-the-art methods. Meanwhile, this algorithm achieves an adaptive tracking to the fast scale changing of target effectively, and possesses a fast tracking speed.

The current approach for binocular camera calibration is to obtain the rotation and translation relationship between cameras through matrix transformation, and the final parameters are obtained by optimization. The nonlinear optimization procedure is tedious, and the internal and external parameters of the camera are coupled with the lens distortion. We present a calibration method for the binocular camera with the combination of a distortion correction and a plane homography matrix. Firstly, based on the principle that three-dimensional linear projection to the image plane is still a straight line for the image without distortion, while any two points on the right line of vectors has the same direction, the direction of the vector angle should be zero. The distortion coefficient can be solved based on this characteristics. Then the measurement matrix is constructed by plane homography matrix, and the initial values of inside and outside parameters of the camera are obtained through matrix decomposition. Finally, all parameters of binocular camera are calculated by the nonlinear optimization. Simulations and experimental results show that this method is highly stable, and has equal accuracy compared to the traditional calibration methods. It spends less time and has better efficiency than the traditional calibration methods.

The conventional feature preserving point cloud simplification method needs to calculate the differential information of all point clouds, but there is a certain deviation in the results by direct calculation with the high density or noise-containing point cloud, resulting in poor effect of point cloud simplification. We present a point cloud simplification method based on grid dynamic partitioning. Firstly, the model is divided into space grids in which the interference points are eliminated with the random sample consensus method. Secondly, the flatness value of grid is calculated by using the least squares method in remaining points, judging whether the grid needs to be subdivided according to the flatness value. Thirdly, the flat areas are achieved and pressed into large spacing grid, and the features-rich areas are divided into small grids as well. For the points in small grids, Gaussian function is introduced to reduce the weight of distant points for recognition features, and the feature points are identified by integration of the surface variation and neighborhood normal vector angle information and then retained. Points in the large grid are sampled at different sampling rates according to the grid spacing. Comparative experiments are carried out with the random sampling method, grid method, curvature method and the proposed method. It is shown that this method can maintain the fine features of model and avoid the appearance of holes, and the maximum deviation of the simplified model is 1.502 mm, much smaller than those of the other three methods. Moreover, as the noise intensity increases, the simplification error of this method is small and gentle. Under the noise condition of 35 dB, the average deviation is only 40% of those of random sampling method and grid method, as well as 50% of that of the curvature method.

To improve the acquisition speed of polarized fluorescence images, a fluorescence microscopy system with high speed polarization is proposed based on the polarization direction control of exciting light with an electro optical modulator, and polarized fluorescence images are recorded with a camera. The polarization distortion induced by the excitation optical path is measured and precisely compensated to ensure the precision of polarization direction control on sample plane. The experimental system is tested with giant unilamellar vesicles. The results show that the proposed system can effectively map the orientation information of biomolecular at a video frame rate and can be used to monitor orientation information of dynamic sample molecules.

Seven-dimensional spatial information of a target scene can be obtained with utilization of the polarization imaging spectroscopy. The polarization imaging spectroscopy is applied more and more widely due to its ability of getting rich data information. We design an optical system of multi-slit polarization imaging spectrometer based on the double Amici prism. As a light splitting element, the double Amici prism can provide parallel beam dispersion of wide field to meet the needs of the multi-slit. We optimize the optical structure of the multi-slit based on the conventional slit imaging spectrometer. The pupil of wide field in the multi-slit spectrometer structure must match with the pupil of the front telescope. The imaging system and polarization spectrometer system adopt telecentric structure to match the pupil. The total length of the system is 279 mm. The system has coaxial optical path, and its structure is very compact. We evaluate the image quality of the optical system by using modulation transfer function (MTF) and spot diagrams. The results show that the MTF at typical wavelengths in each typical field is close to the diffraction limit, and the MIF is over 0.75 at 39 lp/mm. The spot diagram at each typical wavelength is in the Airy spot, which means that the imaging is almost perfect. Three slits correspond to three different polarization states. Polarizations information, spatial information, and spectral information of the target scene can be obtained by pushing-brooming.

In this paper, the algorithm of the optimal trade-off synthetic discrimination function (OTSDF) filter based on wavelet transform(W_OTSDF) is proposed. And the optimization design is carried out. The advantages of multi-scale analysis and the band-pass filtering features of wavelet transform are taken to improve the correlation output peak intensity and signal-to-noise ratio (SNR) in planar integrated 2f optical correlator. Using Matlab to build the simulation model of the system and get the optimization algorithm of W_OTSDF filter. The simulation results show that in planar integrated 2f system, when the distortion target with rotation, scaling or both of them are recognized, the performance indexes of peak to correlation energy (PCE), peak side-lobe ratio (PSR), and SNR of optimized W_OTSDF filter are all improved greatly, which is compared with OTSDF filter. The theoretical analysis and simulation results all demonstrate that the W_OTSDF filter has better recognition effect than OTSDF filter.

The dispersion and transmission characteristics of antisymmetric bound and symmetric bound modes in metal-insulator-metal (MIM) waveguide Bragg grating (WBG) structure are analyzed. The cut-off property and dispersion relations of the two modes with different dielectric materials are discussed, when the metal is set as silver and the insulator thickness is 700 nm. On the basis of this, the band structure of the antisymmetric and symmetric modes of the MIM WBG structure is proposed by using the Bloch mode analysis method. The transmission spectrum is calculated by transfer matrix method, and mode filtering properties of the structure in communication waveband are found. Furthermore, the dependent relationship between the cutoff frequency of the symmetrical mode, the mode transmission characteristic, the material and structural parameters is discussed. Through the selection and optimization of material parameters and geometrical dimensions, mode filter function can be achieved in a particular band, which can be broad or narrow. The structure has potential applications in the field of optical communications and integrated optics.

A refractive index sensor with a composite structure based on dielectric grating with metal films is designed. The surface plasmas in the composite structure are excited by the transverse magnetic polarized light with a wavelength of 632.8 nm from a He-Ne laser and the refractive index sensor with a high sensitivity is obtained. With the finite element method, the reflection spectra for the analyte with different refractive indexes, grating thicknesses, and periods are numerically simulated. A grating thickness of 100 nm and a grating period of 500 nm are selected as the optimal parameters after the parameter optimization for the composite structure with a duty cycle of 0.5 and a metal film thickness of 45 nm. The variation of the resonance angle of the interface between the metal film and the analyte with different refractive indexes is calculated under the optimal parameters, and an angular sensitivity of 500 (°)/RIU is obtained. This refractive index sensor possesses the advantages of simple operation, low cost, and high angular sensitivity, which has considerable application prospects.

The influence of the cladding and substrate materials on graphene transverse electric (TE) mode surface plasmonic properties have been theoretically investigated based on the optical dispersion equation in the two-layer/three-layer dielectric system. It is found that the TE mode is highly sensitive to the dielectric contrast between the cladding and the substrate materials on both sides of graphene in the near-infrared regime. When the dielectric contrast between the cladding and the substrate is tiny, the TE mode surface plasmons can be transmitted. As the dielectric contrast increases, the TE mode dispersion curve behaves differently. The effective refractive index of the TE mode increases obviously and the propagation loss decreases continuously. For the three-layer parallel-plated waveguide structure with graphene embedded between two dielectric medium layers, the numerical results show that the control for the TE mode is significant especially when the dielectric constants for the propagation layer and the substrate layer is close to each other. It originates from the coupling between the electromagnetic wave and graphene leading to the surface plasmons between them. The results provide a theoretical support for the design of graphene surface plasmons based optoelectronic waveguides, such as modulators, detectors, and filters.

We propose a new kind of partially coherent beams whose non-conventional correlation function, also called spectral degree of coherence (SDOC), contains two nonconventional components, i.e., a cosine and a Lorentz functions. Such beam meets the sufficient condition established by Gori, and thus it is physically realizable. Analytical expressions of the cross-spectral density function of the proposed beam passing through a paraxial ABCD optical system are derived based on the generalized Huygens-Fresnel diffraction Collins formula. The light intensity distribution properties of beams focused by a thin lens are further analytically investigated. Results show that the proposed beam exhibits extraordinary propagation properties such as self-splitting and self-shaping, and these transmission properties are closely related to the properties of the correlation function. The cosine-function factor of the total SDOC is responsible for the self-splitting behavior and the Lorentz-function factor determines the self-shaping phenomenon. It is clearly shown that modulating the non-conventional SDOC of a partially coherent beam can alter the coherence length and the degree of nonuniformity, and thus provides an effective way to manipulate its focusing properties. Therefore, the results provide an alternative method for realizing four square beam spots, and have important application prospect in the engineering field.

Haze monitoring is one of the key technologies for environmental governance. At present, the cost of the ground haze monitoring is very high and the accuracy of the multispectral remote sensing haze monitoring is low. The hyperspectral sensing data haze monitoring is studied by deep learning. A hyperspectral haze monitoring algorithm based on deep residual network is presented. The features of haze hyperspectral curves are obtained with the deep network. The difficulty of the network training is decreased with the residual leaning method, and a haze monitoring model is achieved. The experimental results of the Suzhou Hyperion hyperspectral data sets show that, compared with other methods of remote haze monitoring, the proposed method has higher recognition accuracy in haze monitoring.

The salt ion in halophytes is an important index to evaluate the nutritional status of plants, which reflects the adaptive strategies of vegetation to salt stress. In this study, the halophytes of the Ebinur Lake Wetland Nature Reserve are taken as the target area. The salt ion content data and the leaf spectral reflectivity date of seven types of halophytes in October 2016 are used to analyze the correlativity between salt ion Ca2+, K+, Mg2+, Na+ and ratio vegetation index (RVI), difference vegetation index (DVI) and normalized difference vegetation index (NDSI). The best band combination is selected. The estimation models of 12 salt ions of leaf and spectral reflectivity are built. The best fitting model is selected from accuracy test. The results show that the correlativity between the salt ion content of leaf and the original spectral reflectivity is low. And the significant negative correlation with reflectivity of each band is mainly Na+ content. The correlation between Na+ content and the vegetation indices of RVI, NDSI and DVI is the best. The correlation is above 0.5, and the band is mainly locating in the region of near infrared and middle infrared. The best estimation models for Na+, Ca2+, Mg2+ and K+ are VDVI(R1750,R1480), VDVI(R478,R440), VNDSI(R450,R375) and VRVI(R405,R375), which use the independent variables to build the cubic polynomials, respectively. The maximum correction index of the mode is the biggest (R=0.806), and the mode usesVRVI(R1100,R1125) as independent variable to build the cubic polynomial. It shows that the model has high fitting degree and good prediction effect. It can be used to monitor the salt status of halophytic vegetation leaf in real-time and provide a technical approach for the accurate diagnosis of salt content of halophytic vegetation leaf.

A star sensor calibration method based on the attitude correlated frame (ACF) is proposed, which can realize the calibration by the astronomical observation outdoors. First, the correlated superposition among the multi-frame star maps is achieved by utilizing the high accuracy angle information provided by the gyro unit which is installed in a strapdown manner with the star sensor. Then, the imaging mapping model between the star and the image point among the multi-frame star maps is established. Finally, the global optimization of the intrinsic parameters for the star sensor is realized by using the least square algorithm. The simulation results show that the proposed method is more precise and robust than the calibration method based on the interstar angles. Moreover, the installation matrix between the star sensor and the gyro unit can be calibrated simultaneously by this method, and thus it is suitable for the parameter calibration of the shipboard, airborne inertial/celestial integrated navigation systems.

To achieve laser remote sensing classification of helicopter, propeller and turbojet aircraft, a texture feature extraction algorithm of aircraft target based on time-frequency image is studied. Three types of aircraft rotating parts echo signal are simulated according to the rotor micro-Doppler model, and the grayscale image is generated by the time-frequency distribution obtained by smoothed pseudo Wigner-Ville transform. OTSU method combined with grayscale stretching is used to perform threshold de-noising on the image, and the gray-level co-occurrence matrix (GLCM) feature and the Tamura feature are extracted. Feature optimization is carried out for the time-frequency difference, and finally the support vector machine (SVM) is used to classify the aircraft targets. Simulation data classification results show that the GLCM feature is sensitive to noise performance. When the time-frequency image is denoised by the proposed method and the signal-to-noise ratio (SNR) RSN=0 dB, the classification correct rate reaches to 96.4%. The Tamura feature has a higher classification accuracy under high SNR conditions, but decreases significantly when RSN<5 dB. Therefore, good classification performance can be obtained with the extraction of the texture feature of time-frequency image, and accurate classification of targets can be achieved by the improved GLCM feature under low SNR conditions.

When the bidirectional reflectance distribution function (BRDF) empirical model and semi-empirical model describe the scattering characteristics of the material, the limitation of these models for the description of different scattering characteristics results in large errors between the fitting result and the measured data. To solve the problem, a BRDF model suitable for commonly used materials on space targets with different characteristics is constructed based on deep neural network (DNN). The DNN model, which contains four hidden layers, is based on TensorFlow implementation. It is optimized by AdaDelta gradient descent method, and combined with Dropout method for regularity. Part of the material measurement data is randomly selected as the training sample, and finally the mapping relationships between the BRDF and the angles of the incident zenith, the reflection zenith and the observation azimuth are obtained. A large number of experimental results show that the DNN model has good ability to describe the scattering characteristics of materials, and the fitting error of the DNN model is less than that of the empirical model for the same material.

To realize the super sensitive detection of the toxic heavy metal element lead and to ensure safety of drinking water, we study the combined technique of laser-induced breakdown spectroscopy (LIBS) with laser-induced fluorescence (LIF) technique. A wood slice is used to absorb water to convert liquid samples analysis into solid samples analysis, which eliminates the influence of water on atomic emission as well as an optical collecting system in direct analysis of liquid samples with LIBS. Meanwhile, a beam of tunable dye laser is used to excite lead atoms in laser-induced plasma resonantly, and LIF of lead is detected to improve its spectral analysis sensitivity significantly. A calibration curve of lead in water is obtained under optimized experimental conditions. The detection limit of lead in water is determined to be 3.2×10-9 under current experimental conditions. It is demonstrated that the LIBS-LIF technique combined with the method of selecting a wood slice as a water absorber can be applied to realize direct, fast, and super sensitive detection of trace lead in water, thus the water pollution due to toxic heavy metals can be monitored.

The interaction between mitiglinide calcium and bovine serum albumin (BSA) is studied by fluorescence emission spectroscopy, UV-visible absorption spectroscopy and synchronous fluorescence spectroscopy. Experimental results show that mitiglinide calcium leads to the fluorescence quenching of BSA, and the quenching mechanism is a dynamic quenching procedure according to the Stern-Volmer equation. The binding distance between mitiglinide calcium and BSA is calculated to be about 5.461 nm based on F rster theory. The effect of mitiglinide calcium on the conformation of BSA is studied by synchronous fluorescence spectroscopy. The results show that a slight blue shift is observed when the difference between excitation wavelength and emission wavelength is 60 nm. The blue shift indicates that the peripheral microenvironment near tryptophan residue of BSA is affected by the mitiglinine calcium molecule, which makes the polarity of the microenvironment decrease and the hydrophobicity of BSA increase.

The content of total volatile basic nitrogen (TVB-N) is an important index for evaluation of pork freshness. To achieve rapid and nondestructive detection of pork freshness, we use a light-emitting diode (LED) light source containing optimal characteristic wavelengths to set up a multispectral detection system by selecting optimal characteristic wavelengths related to the content of TVB-N in pork, and the content of TVB-N in pork is detected by the detection system. Firstly, a visible near infrared (VIS-NIR) hyperspectral system is applied to detect pork to acquire hyperspectral reflectance data, and then different preprocessing algorithms including the first derivative (FD), standard normal variable transformation (SNV), and other methods are utilized to build partial least squares regression (PLSR) model of the TVB-N content in pork. Secondly, some variable selection methods including the step wise algorithm (SWA), successive projections algorithm (SPA), and genetic algorithm (GA) are used to screen the characteristic wavelengths related to TVB-N content. PLSR model and multiple linear regression (MLR) model are established by these characteristic wavelengths. The model results are compared to choose optimal characteristic wavelengths. Lastly, the LED light source containing characteristic wavelengths is used in the multispectral detection system to establish PLSR and MLR models, so that the detection of TVB-N content in pork is completed. The results indicate that the screening characteristic wavelengths by using the SWA, SPA, and GA can reflect full spectral information well. The effect of the established model is good, and the number of variable decreases greatly. The LED light source containing characteristic wavelengths can detect the TVB-N content in pork well in the multispectral detection system. The results of the established MLR model are better than those of the PLSR model. The correlation coefficient and square error of calibration (SEC) set of the MLR model are 0.9050 and 3.63×10-5, respectively, and the correlation coefficient and square error of prediction (SEP) set are 0.9040 and 3.81×10-5, respectively.

A distributed Bragg reflector (DBR) for space GaInP/(In)GaAs/Ge triple-junction solar cell is designed by the optical film design software (TFCalc). The experimental results show that the reflectivity of 15-pair Al0.2Ga0.8As/Al0.9Ga0.1As DBR is 96% at the center wavelength of 850 nm. The light in the spectral range of 800-900 nm is reflected and then absorbed twice, which enhances the anti-radiation ability of the middle subcell. According to the detailed balance principle and p-n junction formation mechanism, the thicknesses of the original cell structure and the new cell structure containing the DBR are optimized. By comparing the external quantum efficiency (EQE) of the original cell structure with middle subcell thickness of 2.93 μm and the new cell structure with middle subcell thickness of 1.2, 1.6 and 2.0 μm, we conclude that the influence of the battery current attenuation by thinning base can be almost made up by the new structure. By analyzing the electrical properties of the two types of solar cell structures before and after irradiation, we find that the DBR structure significantly improves the decay of the current after irradiation. The efficiency of the new structure with the middle subcell thickness of 1.6 μm is up to 24.87%, which is increased by nearly 2% than that of the original structure,close to that of the new structure with the middle subcell thickness of 2.0 μm, and significantly higher than that of the new cell structure with middle subcell thickness of 1.2 μm.

A terahertz beam-splitter structure with polyester films as the support based on ultrathin metallic films is proposed, and the splitting model based on the transmission matrix theory is built. The influences of the metallic Cr films and the polyester films with different thicknesses on the reflectivity, transmissivity and splitting ratio of this ultrawide-band terahertz beam-splitter are also analyzed. The theoretical results show that the splitting performance of the proposed terahertz beam-splitter is relatively sensitive to the thickness of metallic Cr films but insensitive to the thickness of polymer films. On this basis, the terahertz beam-splitters with different thicknesses of metallic Cr films are fabricated and tested experimentally. The experimental results are consistent with those from theory analysis. The structural parameters of this device with a splitting ratio of 1∶1 are determined.