Based on the characteristics of laser transmission in atmosphere, the slanting transmission model is used to calibrate the attenuation of laser transmitting in aerosol. According to the laser radar ranging equation, we establish the model of slanting transmission maximum detection range (MDR) of satellite laser ranging (SLR) system. By analyzing the numerical simulation results and the measured values of the MDR of the SLR system in Changchun station, we systematically research the maximum transmission distance of the SLR system. The investigated results indicate the MDR increases along with the elevation of transmitter telescope in a certain range. Compared with other common models, including Kim empirical formula and Mie theory, the MDR calibrated by slanting transmission MDR model is closer to the experimental results, and the relative error is decreased by one order of magnitude, which is only 3.8%. The result suggests the slanting transmission MDR model is much more suitable for calculating the MDR of the SLR system.

In order to evaluate the impact of atmospheric refractive index distribution on timing deviation of time transfer by space laser link at double wavelengths, we propose the model of atmospheric refractive index distribution influenced on timing deviation with the measured meteorological data. The asymmetric delay deviation and the position deviation of the transceiver terminal are simulated respectively in different regions, different months and different zenith angles based on the ground terminal capturing mode and the satellite terminal capturing mode. The results show that the asymmetric delay deviation and the position deviation are smaller when the atmospheric pressure is lower and the atmospheric temperature is higher. The timing deviation of satellite terminal capturing mode is hundreds of picoseconds. The timing deviation of the ground terminal capturing mode reaches to nanoseconds, which can be decreased to about ten picoseconds by further bidirectional precision alignment. In the satellite passing time, the asymmetric delay deviation and position deviation change with the variation of the zenith angle, and there are geographical location differences between the ground terminals. In general, it is necessary to correct the asymmetric delay deviation and the position deviation of transceiver terminals in real time.

The suppression level of internal stray radiation of atmospheric corrector in short-wave is a key indicator for its optical design and performance evaluation, especially for infrared optical systems, in which the internal stray radiation cannot be ignored. In order to measure the output of the stray radiation inside the instrument, a method based on radiation calibration is proposed. First, we obtain the linear relationship between the input and output of the instrument by controlling variables, and the model of the radiation calibration is established. Then, the background signal of the instrument at different ambient temperatures is measured, and a maximum deviation of 4.45% is found compared to theoretical values, which verifies that the calibration model is valid. The proposed method can be used to calculate the internal stray radiation correction of atmospheric corrector at different ambient temperatures and gain values, which simplifies experimental processes and evaluates the stray radiation index of the atmospheric corrector.

Aiming at the insufficient attention to influence of plant chlorophyll fluorescence on the accuracy of CO2 inversion, we investigate the global vegetation fluorescence distribution, and simulate the influence of fluorescence column-averaged CO2 dry-air mixing ratio (XCO2). The simulation shows that when chlorophyll fluorescence is neglected, the inversion maximum error of XCO2 can reach 15×10-6. This bias can be controlled within 0.5×10-6 by synchronous inversion fluorescence in a full-physics based retrieval. We retrieve the summer data of the Greenhouse Gases Observing Satellite (GOSAT) near Park Falls TCCON (The Total Carbon Column Observing Network) site. It is found that the error is corrected from 6×10-6 to less than 2×10-6 based on synchronous inversion fluorescence. This research shows that chlorophyll fluorescence cannot be neglected in high precision CO2 inversion.

We propose a wavefront reconstruction method which improves the wavefront sensing frequency, by compressing the number of the modulation functions. The Walsh functions which are highly correlated with the real part of the incident light field are selected, and their coefficients are calculated relatively. Thus, the real part of the light field is reconstructed. Meanwhile, the imaginary part of the optical field is reconstructed based on the light intensity distribution, which avoids the dependence on the multiplication theorem of the Walsh function and the use of the extra modulation modes. The method sufficiently compresses the number of modulation modes greatly in the wavefront reconstruction and improves the wavefront sampling frequency. The numerical simulation results indicate that the sampling time of wavefront can be decreased to 1/12 based on the proposed method.

In the ultracold atomic system, to observe the Parity-Time (PT) symmetry with the gain balance requires controlled gain/loss of atom population and coherent coupling. We present a proposal to obtain an exponential growth of the atom population by dynamically controlling atom transport in a double-well trap on an atom chip. We numerically investigate the transport dynamics of the atomic ensemble between the sub-wells by using the direct simulation Monte Carlo method. It is found that the initial number and temperature of the atom cloud remarkably affect the transport performance, such as gain rate and transfer efficiency of the atom population in the target trap. Moreover, the effect of the lifting time of the left-well on the growing trend of the atom population in the right-well is analyzed in detail. Our strategy provides an achievable way for realizing a PT symmetric quantum system with gain/loss in ultracold atomic gas.

One-dimensional silicon dioxide nanomaterials are one of the hot topics in the research of luminescent materials. As a candidate material for high-efficiency luminescent materials, it is necessary to understand its electronic structure parameters and spectral data. One-dimensional (SiO2)10 molecule with chain structure is selected as the research object, and the molecular ground state is obtained by the density functional B3LYP method. The effect of external electric field intensity on the electronic structure characteristics of the molecule is investigated systematically. Meanwhile, the excitation characteristics of the molecule at different electric field intensities are explored using the time-dependent density functional theory TD-B3LYP. The results show that the obtained molecular electronic structure parameters agree well with the existing literature values. The increase or decrease of the Si-O bond length in each unit ring is entirely determined by the direction of applied electric field. For the excitation characteristics, the absorption peak appearing around 240 nm, which is consistent with the existing experimental results, and the obtained 180 nm absorption peak with relatively high intensity is rarely mentioned in the literature. With the increase of the external electric field intensity, the excitation energy of the excited states decreases, and the wavelength of the absorption spectra has a red shift. At the same time, it has been found that certain external electric fields can make some forbidden excited states into transitional excited states, which means that a specific external electric field regulation can be used for the molecule to absorb the spectrum at some certain wavelengths.

The theory about the further factorization of the dispersion equation of the grating mode under the incidence of Bragg angle and transverse electric and transverse magnetic polarizations is proposed, and the equivalent relationship between the factorized equation and the symmetry of the grating mode is confirmed. The symmetry of grating modes is beneficial to illustrate the physical picture of the diffraction process within gratings. By the analysis of the distribution property of the root of the grating mode equation, a method to improve the computation efficiency of the effective refractive index is proposed.

A novel ghost diffraction scheme for the quantitative phase retrieval of objects is proposed, in which a special transmission screen is inserted in the reference light path of the ghost imaging setup. The corresponding theoretical analysis and the experimental simulation are shown. The simulation results are basically consistent with the theoretical ones, which confirms the correctness and the feasibility of this proposed experimental scheme.

According to the dynamic population grating formation mechanism, a fiber-optic system with linear double-wave mixing structure is designed. In the system, light from a semiconductor distributed feedback (DFB) continuous wave(cw) laser operating at 1490 nm, as the incident light, is launched to a 3-m Er-doped optical fiber through a fiber optic circulator. The incident light is reflected from the vibrating mirror mounted on a piezoelectric actuator as reflected light. The dynamic population gratings are recorded along the longitudinal direction of the Er-doped optical fiber by spatial hole burning in standing-wave cavity formed by the two counter-propagating mutually coherent recording waves. The two-wave mixing (TWM) signal is observed as an intensity modulation wave in the output of the circulator when the reflected wave from vibrating mirror is phase modulated. Mechanical vibration induced by piezoelectric vibrating mirror can be detected through the designed two-wave mixing system. The results demonstrate that the two-wave mixing detection system displays a good dynamic response, with a frequency range of 50 Hz~10 kHz, and the frequencies of acquired vibration signals exactly agree with the driving signals from piezoelectric actuator.

A nonlinear equalization algorithm is proposed based on the general regression neural network (GRNN) in the coherent optical orthogonal frequency division multiplexing (CO-OFDM) system with high-order quadrature amplitude modulation and large laser linewidth. After phase recovery at the receiver, the training data is chosen to carry out the training and studying in the GRNN. In the process, the smoothing factor, the only parameter, can be decided in the GRNN. Then, for the detecting data at the receiver, the nonlinear equalization is performed by the GRNN. The numerical simulations have been completed by the proposed GRNN nonlinear equalization algorithm in the CO-OFDM system with a transmission rate of 50 Gb/s and a transmission distance of 100 km. Compared with the back propagation neural network nonlinear equalization (BPNN-NLE) algorithm, under lager laser linewidth and high-order quadrature amplitude modulation (QAM), the proposed method has a better nonlinear equalization performance and a shorter time of training running, which will greatly promote the application of CO-OFDM system in the fiber transmission with long and medium distance.

The phenomenon of dual resonance coupling exists in few-mode long period grating coupled between core modes LP01 and LP11. The two resonant dips drift to opposite bands as temperature or strain increases. We research the mechanism of dual resonance from theory and experiment, and design a dual-parameter sensor of temperature and strain. Compared with the long period gratings coupled between core fundamental mode and cladding mode, this sensor has the advantages of refractive index insensitivity, spectrum stability, and high sensitivity.

A dual-polarization paralleled carrier phase recovery algorithm with better linewidth tolerance and lower computational complexity is presented for polarization division multiplexing and 16-order quadrature amplitude modulation (PDM-16QAM) system based on linear Kalman filter (LKF). The symbols in first and third rings of two polarizations are used to perform phase noise estimation. The simulation results for PDM-16QAM system with the transmission rate of 224 Gb/s demonstrate that the linewidth tolerance of dual-polarization LKF is about seven times of that of single-polarization LKF. The linewidth tolerance is improved to 2800 kHz from 400 kHz. The dual-polarization LKF processes about four times symbols in one block than single-polarization LKF, which reduces the algorithm computational complexity and enhances the real-time performance. Finally, the proposed algorithm is verified in the transmission experiment of PDM-16QAM system with the transmission rate of 224 Gb/s.

We propose a dynamic beam waist adjustment scheme based on Marcum Q-function to solve the problem that the inter-satellite optical communication is deeply affected by pointing error. In the absence of any approximation, a closed-form expression for calculating the state of the instantaneous channel is given by Marcum Q-function. The optimization model is set up and a simple algebraic solution for the optimal dynamic beam waist radius is derived by the model, when the instantaneous direction error angle is known. A new dynamic waist adjustment scheme is given, which can effectively reduce the effect of the pointing error. Numerical results show that the system performance with dynamic beam waist is obviously better than that with fixed beam waist, and the proposed scheme here can improve the performance of bit error rate and outage probability to a certain extent.

We propose a phase-noise compensation algorithm by using radio frequency pilot (RF-Pilot) method in combination with extend Kalman filter (EKF) in time domain for the coherent optical orthogonal frequency division multiplexing (CO-OFDM) system with large linewidths and high-order circular quadrature amplitude modulation (C-QAM). We realize the coarse phase-noise compensation in time domain by setting a RF-Pilot at the receiver, and then complete the channel evaluation and channel balance. After accomplishing the initial pre-decision in the frequency domain, we use EKF to realize the final phase noise compensation, according to the judged temporal signal and the channel equalization temporal signal. We numerically verify the algorithm by transforming in a 50 Gb·s-1 CO-OFDM system with 100 km transmission distance under C-16QAM and C-32QAM. The results show that compared with original RF-Pilot phase-noise compensation algorithms, the proposed method has better performance on the phase noise compensation while has no obvious decrease of frequency utilization, and the complexity is not increased significantly. For CO-OFDM systems with C-32QAM and a laser linewidth of 2.1 MHz, the bit error rate achieves the upper limit of forward error correction. It theoretically confirms that the proposed algorithm can improve the tolerance of laser linewidth on the CO-OFDM system. We can use the inexpensive distributed feedback lasers with relatively large linewidth as the source of the object and the oscillator of the receiver. The proposed phase-noise compensation algorithm is beneficial to the application of CO-OFDM system in long distance access network and metropolitan area network.

The unconstrained face images collected in the real environments are influenced by many complicated and changeable interference factors, and sparsity preserving projection cannot well characterize the low-dimensional discriminant structure embedded in the high-dimensional unconstrained face images, which is important for the subsequent recognition task. To solve this problem, we propose an effective dimensionality reduction method named as supervised sparsity preserving projections based on global constraint (SSPP-GC) which firstly enhances the reconstruction relationship of the same class of samples by adopting supervised over-complete dictionary and coefficient compactness constraints, and then appends the global constraint penalty in the step of the low-dimensional projection to further weaken the influence of other classes of samples. The experimental results on AR, Extended Yale B, LFW and PubFig databases demonstrate the effectiveness of the proposed approach.

Performance of sparse coding based on image super resolution reconstruction model is influenced by dictionary selection. A dictionary learning algorithm based on collaborative sparse representation is proposed. In training stage, training image patches are grouped into different clusters by applying K-means clustering algorithm. A series of high- and low- resolution dictionaries are trained over every clusters by collaborative sparse dictionary learning model which is based on constraint of simultaneously sparse. The complex mapping relationship between low-and high-resolution image patches is transformed into a simple linear mapping by using an L2-norm based sparse coding model, and a series of mapping matrices corresponding to each different clusters are obtained. In reconstruction stage, each input image patch is mapped to a high-resolution patch by a mapping matrix which is selected by searching out the cluster with largest similarity to input patch. Experimental results show that the proposed method achieves better reconstruction quality by improving the dictionary learning process.

Aiming at the process of the registration of hyperspectral images and high spatial resolution images, it is difficult to choose the high-precision registration band because of the large difference between the bands of hyperspectral images. An algorithm for selecting high precision matching band of hyperspectral image based on Cram'er-Rao lower limit (CRLB) theory is proposed. Several bands with large amount of information and a small correlation in the hyperspectral image are selected by the band selection method. These bands are registered with the high spatial resolution image, respectively. The CRLB for each band's registration result is calculated. The high accuracy registration band is selected according to CRLB. The CRLB's registration quality evaluation performance is verified to be better by comparing CRLB and root mean square errors after each registration. And compared with the selected band registration results of CRLB and other methods, it is proved that the accuracy of the band registration selected by the proposed algorithm is high. The above band provides better data for the registration of hyperspectral images and high spatial resolution images.

In order to meet the demands of space imaging with high resolution and large dynamic range at low light level (LLL), digital domain time delay and integration (TDI) technology based on scientific complementary metal-oxide-semiconductor (sCMOS) image sensor with global shutter is proposed, and image data processing algorithm is deduced. Corresponding signal-to-noise ratio (SNR) model is established, dynamic range extension imaging method based on digital domain TDI is proposed, and modulation transfer function degradation due to velocity errors is analyzed. Experimental results show that the proposed method can significantly improve LLL image quality. System's SNR increases from 5.04 dB to 19.78 dB with 30 TDI stages, and dynamic range increases by 29.54 dB compared to traditional digital domain TDI method, which highlights the potential of the proposed method for space LLL imaging with high resolution and large dynamic range.

A novel high-precision phase retrieval imaging method based on beam splitting amplitude modulation is proposed. The incident beam to be measured is split into many diffracted replicas by a two dimensional grating, and these diffracted beams are illuminated on a modulation plate with known structure. When the modulation plate is weakly scattered, the diffraction patterns formed on the detector are clearly separated with each other. Both the amplitude and phase of incident beam can be reconstructed iteratively by using the recorded diffraction patterns and the known structure of the modulation plate. This method has the high imaging speed of Gergberg-Saxton algorithm and the high precision of ptychographical iterative engine and potentially can be applied for X-ray imaging and online detection of high power laser.

The lighting mode has great influence on the resolution of optical imaging system. Based on the coherence theory of light field, the main factor which influence the imaging resolution of first-order autocorrelation imaging and the second-order autocorrelation imaging of intensity fluctuation via multi-frame speckle illumination are studied. The theory and numerical simulation results show that the transverse coherence length of speckle on the object plane and the resolution of first-order autocorrelation imaging and the second-order autocorrelation imaging of intensity fluctuation are not monotonic relationship. In addition, compared with the traditional incoherent imaging, the first-order autocorrelation imaging and the second-order autocorrelation imaging of intensity fluctuation can only slightly improve the imaging resolution. The result of second-order autocorrelation imaging of intensity fluctuation is just the sharpening of the result of first-order autocorrelation imaging, which can't further improve the imaging resolution.

Due to the limited updating rate of spatial light modulator (SLM), the reported methods based on SLM can't satisfy the requirements of biological tissues endoscopic imaging in vivo. Considering the updating rate of digital micro-mirror device (DMD) is two orders of magnitude higher than the fastest SLM, a method is proposed for focusing and scanning light through a multimode fiber (MMF) based on binary amplitude modulation DMD technique. Theoretical analysis shows that there exists a quadratic function between the total light intensity within the focused region at the distal end of the MMF and the amplitude modulation coefficient of the sub-region on DMD. Thus, it can be realized that focusing and scanning light through a MMF by modifying the incident wavefront with the binary amplitude modulation DMD technique. What’s more, for a given number of modulation sub-regions, the number of iterations for this method is 1/256 of that for the phase iterative optimization methods or 1/3 of that for the optimal phase computation optimization methods with three-step phase shift. We demonstrate that focusing and scanning light in three-dimensional space through a 5 m length and 105 μm core diameter MMF with this method. The results show that the proposed method has the advantages of fast modulation speed, high algorithm reliability and good uniformity of focused spots.

To improve the registration of point clouds scanned by 3D laser in terms of accuracy and efficiency, and solve the registration problems when data points are missing and out of order, based on the invariant characteristics of global and local structure features of point clouds, an initial registration algorithm using global structure features and a fast and accurate registration algorithm using local structure features are proposed. First, the global structure feature and the initial registration method are defined. The validity of the initial registration is strictly proved when the data point is lost. Then, we propose a way to partition the spatial region and find out the corresponding points of the two point clouds in the spatial region. Finally, the two clouds achieve precise registration through the corresponding points found. In the processes of simulation and experiment, the proposed algorithm can effectively perform accurate and rapid registration of missing and scattered point clouds. It has obvious advantages in efficiency and accuracy than other algorithms.

The measurement of surface topography is a prerequisite for studying the processing technology, processing quality and sealing performance of the sealing plane. In order to apply the digital holographic measurement technology to the on-line measurement of the sealing plane surface topography and to meet the requirements of visual display and three-dimensional (3D) model output of the measurement results in the industrial field, we propose a method of measuring surface morphology of sealing plane. The method combines digital holography with virtual manufacturing technology. Firstly, the surface topography of the sealing plane is measured based on digital holographic measurement technology and the measurement results are transformed into point cloud. Then, the 3D model is generated based on the point cloud. Finally, the accuracy of the measurement and model reconstruction is evaluated by the method of coordinating flatness with distance distribution between models. In addition, the proposed method can also indirectly measure the mating relationship between the topography of the sealing plane after assembly. The effectiveness of the proposed method is validated by the examples of a flange surface and the cylinder head surface of an engine block cylinder. The results show that the proposed method can quickly measure the topography of the sealing surface and output the results as a 3D model, which meets the needs of the industrial field for surface topography measurement.

As large-scale integrated circuit chips manufacturing steps into the era of tens of nanometers technology node, the focus control of the lithography machine becomes more and more difficult with the precision of several tens of nanometers. In this paper, a statistical analysis method of immersion lithography focusing control is studied based on the architecture and lithography focusing principle of actual lithography machine focusing control system. A series of error sources are obtained based on the system structure, and their contribution way and relationship to the total defocus error are investigated. The results show that due to the non-normal distribution error contribution term in lithography focusing error, the 3σ principle used in the normal statistical distribution can not meet the 99.7% focusing success rate requirement. In the manufacturing process of 28,14,7 nm technology node integrated circuit chips, the difference of the total focusing success rates of immersion lithography can be as high as 28.4%, 55.1% and 62.9%, when 3σ and 4σ principles are used respectively. In order to reach 99.7% focusing success rate, the 4σ principle should be used in the focus control of immersion lithography.

Aiming at depth test of pipeline inwall defects, we propose a method of measuring the depth of pipeline defects, which based on the active thermal excitation by eddy current and infrared thermography. The theory of infrared imaging pipeline defects measuring is described. According to the special requirements of buried pipeline detection, a test device of eddy current thermal excitation with adjustable parameters is designed. Some specimens are fabricated according to the shape of the pipeline. With the active thermal excitation experiment based on eddy current, the influences of three important parameters, such as resonant frequency, lift-off distance and input electrical power on thermal excitation efficiency are analyzed, and the optimized values are obtained. Based on the above work, the infrared images of specimens with pre-designed defects which have different depths are acquired. The thermal image data analysis shows that the difference of grayscale between the defects and the non-defective areas varies with the defect depth, and the two factors show a single value correspondence, which has a good linearity under certain conditions. The defect depth detection model of groove-like and circular defects are established by the law. The experimental results show that the established model has certain detection accuracy. The research results show that the depth of defect can be calculated by infrared thermal image under the optimized active eddy current excitation condition. The proposed method based on active eddy current excitation of infrared thermal imaging pipeline is feasible.

A measurement technique of one-dimensional (1D) sub-aperture splicing based on an interferometer with the aperture of 600 nm is proposed. With the analysis of pixel offset error simulation results, a 1D large air-float precision scanning splicing platform is designed and developed, the splicing detection of full aperture optical homogeneity of a large aperture laser glass with a diagonal close to 1 m is realized, and the accuracy and the repeatability of this technique are tested. The results show that the splicing results are smooth, the relative error between the homogeneous splicing and direct measurement results is superior to 2×10-7, the repeatability of full aperture homogeneity is superior to 4×10-8, and the largest difference between the measurement homogeneity results of single-aperture and the same region after splicing is 2×10-7.

The simultaneous imaging polarimeter is a type of polarimetric remote sensors with high spatial resolution based on a large aperture off-axis three-mirror system, and the system adopts simultaneous polarimetric measurement based on the prism to divided amplitude. As the instrument has many polarizers and their characteristics are complex, the measurement matrix of instrument deviates from the ideal value. In order to ensure the polarization measurement accuracy of the instrument, we need an effective polarization calibration method. In this paper, a calibration method using the standard liner polarization light source and circular polarization light source is proposed for amplitude-divided simultaneous imaging polarimeter. The linear polarization calibration source calibrates the first three columns of the instrument measurement matrix. The calibration coefficients are obtained by the least-squares fitting Fourier coefficient. The circular polarization calibration source calibrates the fourth column of the instrument measurement matrix. To eliminate non-ideality of the circular polarization state of the light source, two measurements with light source rotated 90°are averaged. Finally, the polarization measurement accuracy of the simultaneous imaging polarimeter is verified by the test. The results show that the polarization measurement accuracy after calibration is better than 1%(P≤0.3).

To precisely estimate the micro-motion parameters and realize target identification under high order motion, we propose a separation and estimation method based on phase information. The main motion and micro-motion are separated by removing the polynomial phase signal part through the derivation of unwrapped echo phase. For the sinusoidal frequency modulation items with multi-dimensional micro-motion parameters after separation, an improved particle filter (PF) static parameter estimation method is proposed, and the efficiency of the algorithm is improved by designing the adaptive variance method and changing the number of particles. By designing cumulative residuals as a function of observed probability density, the simultaneous estimation of multi-dimensional parameters is realized in the nonlinear model. Simulation and experimental analysis verify the effectiveness and necessity of the proposed algorithm. The nonlinearity and the amount of calculation are reduced by processing the phase, which improves the anti-noise performance. The PF based parameter estimation method avoids the error transfer and improves the estimation accuracy effectively.

A one-dimensional (1D) edge-emitting photonic crystal laser is designed based on the ridge waveguide of organic conjugated polymer poly[2-methoxy-5-(2-ethylhexyloxy) phenylenevinylene-1,4-diyl] (MEH-PPV) and the special optical modulation characteristics of photonic crystals. The band gap structure and the band edge effect of photonic crystal are employed to construct the resonator formed by photonic crystal total mirror and partial transmission mirror. 1D photonic crystal defect component is introduced on the ridged waveguide in the resonator and suppresses effectively the mode competition based on the property of photonic crystal defect-mode. The boundary-mode effect caused by composite structure is analyzed, and empirical formula for the cavity length of this kind of non-metallic microcavity laser is obtained. The simulating result shows that a single longitudinal mode laser output with the central wavelength of 588 nm and the full width at half maximum of 0.131 nm is achieved in 1D edge-emitting organic photonic crystal laser.

The interference of space beam in gain medium generates space burning hole phenomenon, and forms the gain grating. The gain grating formed by the four-wave mixing function has adaptive, self-tuning Q and spatial filtering capability, and can obtain holographic conjugate output. But all of them start from the spontaneous emission in the cavity. Spontaneous emission is easily influenced by the pump, and its bandwidth is wide, which will cause a certain fluctuation in the output frequency. In this paper, a single-frequency Q-switched pulse output locked in the seed spectrum range is obtained by an external single-frequency narrow linewidth source injection in a self-starting single-frequency laser based on a gain grating. Comparative experiment shows that in the same observation time, the spectral stability of the injected output is much higher than the self-starting output. This phenomenon also proves that the steady frequency output can be obtained by the adaptability of the gain grating formed by external seed injection.

By using injection-locking technique, we develop a diode-pumped Er∶YAG ceramic single frequency pulsed laser seeded by an Er∶YAG nonplanar ring oscillator (NPRO) laser. The 1645 nm single frequency laser with output energy of 11.45 mJ, pulse width of 174 ns and pulse repetition rate of 200 Hz, is obtained. The corresponding M2-factors are 1.45 and 1.42 in x and y directions, respectively. The full width at half-maximum (FWHM) of the frequency spectrum of the heterodyne beating signal between the pulse and the seed is 2.67 MHz. The result indicates that Er∶YAG ceramics have good performance in generating 1.6 μm lasers. This single-frequency pulsed laser can be employed as the seed of coherent wind lidars and remote sensing lidars in the field of laser lidar.

Overhead ground wire detection under complex field environment is one of the key technologies of automatic obstacle surmounting for a high voltage transmission line inspection robot. The varying illumination and wire surface condition are the key factors affecting the detection accuracy. To address the problem, a field wire detection algorithm based on off-line learning is proposed. In the training phase, the adaptive homomorphic filter is applied to the input samples to compensate illumination, followed by local binary pattern histogram feature extraction and support vector machine training to get a binary classifier. In the on-line detection phase, each sample is divided into patches, followed by classification through the trained classifier to get the wire patch candidates. Then, the random sample consensus algorithm is adopted to remove mistakenly identified patches, and the remaining candidates are fitted into a line to get the wire parameters in the image coordinate system. The results of a number of experiments with field surroundings and different wires show that the proposed method has good adaptability to varying illumination and can detect both old and new wire accurately. Furthermore, this work has laid a solid foundation for the subsequent three dimensional positioning and grasping control of the ground wire.

Aiming at the occlusion phenomenon in the visual object, we propose a novel occlusion boundary detection approach for deep images based on the spectral clustering. Firstly, a new occlusion-related feature, effective standard deviation feature, is defined. Secondly, some pixels are extracted by using mean chi-square set distance, and the similarity matrix is constructed based on the occlusion-related feature. Thirdly, the Laplacian matrix of all the pixels and approximation eigenvectors are approximated by Nystrom approximation method based on the similarity matrix. Then, the obtained approximation eigenvectors are clustered to divide all the pixels in the depth image into two categories, namely the occlusion boundary points and non-occlusion boundary points. Finally, the occlusion boundary of the depth image is obtained by visualizing occlusion boundary points. Experimental results show that the proposed method which does not need any labeled samples has good effectiveness and generality for occlusion boundary detection of the object in the depth image.

A new image stitching algorithm is proposed based on depth images series, to overcome the limit of field-of-view of depth reconstruction from three-dimensional light field. At pre-processing stage, bilateral filter and interpolation is utilized to de-noise. A corner detection algorithm based on edge local-maximum curvature value, and a matching algorithm based on minimum curvature variance control are proposed. Improved weighted average method is adopted to complete image fusion, both retain image's details and expand field-of-view. Experimental results show that the proposed system can easily obtain a complete depth image, which is helpful for three-dimensional reconstruction of whole scene.

In order to recover depth information from two-dimensional color image, a visual-dictionary-based depth map generation algorithm is proposed. A data-driven method is used to find depth information of various spatial structures from depth map library, so as to obtain initial visual words which consist of image patches with similar structure. Hard example mining method is used to find hard negative examples of visual word, and visual word classifier is updated to get best classification result. Visual dictionary composed of visual word classifiers and visual words is used to detect target image at multiple scales to get corresponding depth map, to which edge-preserving smoothing filter will be applied. Experimental results show that depth maps generated by the proposed algorithm match depth change of target images, and has a good improvement in both subjective visual effects and objective evaluation indexes.

The region proposal search is one of the most active research topics of machine vision. The low efficiency of object detection using the traditional exhaustive search can be improved by optimizing the accuracy of search algorithm. The Girvan-Newman (GN) splitting for community discovery in complex networks is introduced as well as the features of small object regions. A novel method to generate small object regions is proposed by using the network structure of image. The algorithm constructs the relationship between the images and the graphs based on the similarity of color histograms between regions. It can obtain possible regions through the generation of connected subgraphs. This algorithm can meet the higher recall rate in the case of generating fewer candidate regions and further optimize the time consumption of small object detection.

It is one of the technical difficulties for the inspection robot of high voltage transmission line to identify obstacles effectively under the changes of outdoor lighting conditions. According to the robustness problem of obstacle identification under the low-light conditions, an intelligent method of obstacle recognition based on robot vision is put forward, so that the inspection robot can deal with various degrees of low-light changes. The obstacle images are processed by self-adaptive homomorphic filtering to reduce the influence of illumination partially. A obstacle image is divided into uniform sub-regions. The improved local direction pattern is used to extract the feature histogram vector of each sub-region image, and the sub-block feature histograms are concatenated one by one into the total histogram. The Chi distance is used to perform statistical identification. The experimental results show that this method can make the inspection robots effectively recognize the counterweight, suspension clamp and insulator string on the transmission line. Compared with other algorithms, the improved local directional pattern has a better anti-light interference effect and higher accurate recognition rate, and improves the robustness, adaptability and accuracy of image recognition during robot inspection. It greatly promotes the sustainability of inspection robots in the power industry.

This study is carried out on the basis on the fourth-order integrable equation(LPD equation) of the Schr dinger hierarchy, which contains both fourth-order dispersion terms and fourth-order nonlinear terms. Firstly, using the Darboux transformation method, we drive a one-breather solution of LPD equation, and the dynamic characteristics of the breather are researched. The conversion relations from breather to W-shaped soliton, oscillation W-shaped soliton and periodic wave are obtained. Secondly, with the aid of the recurrence of the Darboux transformation, the two-breather solutions of the LPD equation are obtained, and the collision characteristics between the breather and the soliton, the breather and the periodic wave are studied by using the transition from the breather to the soliton. Finally, the collision characteristics of two-breather are studied in more details, and the conclusion that the dynamic characteristics of two-breather such as cross-collision, parallel superposition and degenerate state of two-breather are obtained.

In this paper, a high reflector based on one-dimensional photonic crystal of hetero-structure in infrared region(3-5 μm) is investigated. The reflection characteristics of light wave in one-dimensional periodic photonic crystals are systematically analyzed. The reflectivity and the optimal forbidden band width of the λ/4 dielectric film system are verified by transfer matrix theory calculation and simulation. On this basis, Si and Y2O3 are selected to construct the one-dimensional photonic crystal of double hetero-structure with 24 layers. The simulation result shows that the reflectivity in infrared region (3-5 μm) is between 97.418% and 99.999%. In order to reduce the number of the film layers, using metal silver as an substrate, we design the dielectric layer structure of Si and Y2O3 with 9 layers of one-dimensional metal enhanced photonic crystal. The simulation result shows that the reflectivity is between 98.943% and 99.979% in the infrared band of 3-5 μm.

It is a problem that the conventional stereoscopic display imaging does not satisfy with the regular imaging rules of human eyes. Besides, the miniaturization of wearable device needs to be considered. In order to solve these problems, Zemax is used to design a multifocal planes projection optical system combined with the digital micro-mirror device(DMD) and piezoelectric deformable mirrors(PDM), based on calculating analysis of optical system parameters. This optical system uses double-telecentric optical path which is composed of seven lenses with a total length of 200 mm and a field of view of 40°. According to the overall analysis, changing the curvature radius of PDM can realize the multifocal planes imaging. At a particular position, human eyes can observe the overall three-dimensional effect which is overlapped by two dimensional images at the location of each focal plane (range from 0 to 3 m-1). Finally, the imaging quality of the system is analyzed. The result shows that the modulation transfer function (MTF) value of the system is higher than 0.4 at the limit resolution of 37 lp/mm in all field of view. The performance is well and it meets the design requirement.

In order to improve the energy utilization of red LED array devices, we study the photoelectric characteristics of flip-chip AlGaInP-based light emitting diode (LED) array device. Firstly, the light output power characteristics of AlGaInP-based LED with vertical type and flip-chip type structures are tested and compared with each other. The results show that the light output power of flip-chip LED is higher than that of the vertical LED. Then, a model to calculate the output power of flip-chip LED array is proposed, which is used to calculate the relationship between light output power, ambient temperature and base thermal resistance. The results reveal that with the increase of the base thermal resistance and ambient temperature, the output power of the LED array device decreases, the injection current at saturation shifts forward, and the photoelectric performance of LED array decreases. The 6×6 flip-chip AlGaInP-based LED array device is prepared using the transfer method. The testing results are consistent with the theoretical predictions. Finally, the numerical relationships between the thermal resistance of Cu and polydimethylsiloxane (PDMS) with different basement structures and ambient conditions are analyzed by finite element method. The results show that the heat dissipation capacity of Cu is relatively uniform and its thermal resistance is not sensitive to the structure and the air convection rate. However, for PDMS materials, the thermal resistance is relatively large and can be effectively reduced by optimizing its structure and increasing the air convection rate, thereby improve the photoelectric performance of the micro LED array device.

Based on the phase modulation of axicons and the amplitude modulation of films, an exactly and high-efficiency generation scheme of non-diffractive Mathieu beams is proposed. With the stationary-phase technique, the theoretical mechanism of the generation of Mathieu beam by this scheme is verified. The amplitude modulation film with an angular Mathieu function is prepared by the usage of the film recorders, and a family of Mathieu beams is experimentally generated. The theoretical and experimental results show that the proposed method for generating Mathieu beams based on axicons and the amplitude modulation is simple, flexible and highly efficient.

The spontaneous emission properties of the two-level atoms placed near a topological insulator (TI) slab with a finite thickness or inside its cavity are investigated. The spontaneous emission rates of the dipole parallel or perpendicular to the material boundary are expressed via the dyadic Green function. The reflection matrix of this slab is calculated based on the multiple reflection theory, and the various factors which influence the spontaneous emission rate are numerically calculated and analyzed. The research results show that, when the dissipation is ignored, the spontaneous emission rate of the parallel dipole is suppressed, however, that of the perpendicular dipole is enhanced. When the dissipation of the slab or its cavity is included, the TI can effectively suppress the spontaneous emission rate of the atoms and make all of the decays of atoms near it along any diploe directions suppressed.

The propagation model of a continuous variable quantum communication system on an airborne platform is established in the case that the atmospheric turbulence and aero-optical effects are considered. The influence of channel characteristic on the security key rate of this system is numerically analyzed. The results show that, the smaller the refractive index structure constant of the atmospheric turbulence is, the more obvious the influence of the change of the refractive index structure constant on the security key rate of this system is. The influence of the atmospheric turbulence and the aero-optical effect on the security key rate of the system cannot be ignored. According to the atmospheric channel characteristics, the corresponding compensation module for this system is designed to adaptively adjust the relevant parameters of the quantum communication system so as to enhance the robustness of the system.

A set of measuring device for the transmittance of the solar attenuation screen is introduced. Two set of data are required: light signals transmitted through the test fixture with and without the solar attenuation screen. Then the solar attenuation screen transmittance is the ratio of the screen-on data to the screen-off data under the same geometric condition. The method of polynomial fitting interpolation is proposed, which is used to solve the problem of dense on-orbit angle. The error of the method is less than 0.04%. The results show that the average transmittance of the solar attenuation screen is 13.3%, and the uncertainty of the device is better than 0.54% (covering factor k=2). The results indicate that the device can provide data support for the use of the solar attenuation screen on orbit.

In order to make full use of the Doppler shift information in the phase-modulated signal, we combine the frequency-discriminating parameters in the direct current with beat components of the phase-modulated signal in sequence to construct a new frequency-discriminating parameter. It is proved theoretically and experimentally that the new frequency-discriminating parameter inherits the characteristics and advantages of amplitude-Doppler shift measurement of phase-modulated beating frequency signal. In comparison, the dynamic range is increased by about one times and the measuring accuracy is improved approximately by six times. In order to make use of the idle optical power of the echo signal, we propose a new dual-edge phase Doppler shift measurement method based on the new frequency-discriminating parameter. It is proved theoretically that the proposed method can double the measurement sensitivity.

Calibration-free trace detection of acetylene gas is achieved by near infrared tunable diode laser absorption spectroscopy combined with a self-designed cylindrical mirror multi-pass absorption cell. A distributed feedback diode laser emission at 1.53 μm and the cylindrical mirrors multi-pass absorption cell with an effective optical path length of 10.5 m is used. The calibration-free wavelength modulation absorption spectroscopy is used to detect the acetylene, and the Allan variance is used to analyze the system performance. This technology is compared with the traditional wavelength modulation spectroscopy. The results show that compared with traditional wavelength modulation absorption spectroscopy, calibration-free wavelength modulation absorption spectroscopy has advantages of simple structure, high sensitivity, and calibration-free of concentration and optical power, which improve detection sensitivity and measurement accuracy of the system. The measurement error of the technology is less than 5%, and it is 3.5 times that of traditional wavelength modulation technology. The detection sensitivity of the system is 0.127×10 -6 with average time of 1 s, and the detection sensitivity is 0.031×10-6 with average time of 118 s.

A dynamic model based on the momentum distribution of the final state in the striped photoelectron energy spectra is constructed. An equal-value line reconstruction (ELR) algorithm is proposed, which includes the real momentum-time distribution of the electron wave-packet corresponding to the radiation pulse and is essentially different from the traditional attosecond streak measurement method of FROG-CRAB with a central momentum approximation. The research results show that, compared with those obtained by the FROG-CRAB method, the parameters of the pulse width and the chirp obtained by the method of ELR have a higher accuracy.

In order to study the focusing and imaging performance of Angel lobster eye X-ray micro pore optic lens, the numerical model of the X-ray in the square channel is established based on X-ray reflection principle and rotating coordinate system. By solving the intersection, the transmission path of all the rays is obtained. In order to verify the accuracy of the model, the focal length and transmission efficiency of the lens are both simulated and tested. At the focal length of 365 mm, the reflected X-rays are focused into cross line, and the center focal spot intensity is the largest, which is consistent with the simulation results. As for the transmission efficiency of the lens before and after coating Ir, the simulation results are 1.23% and 9.18%, respectively, at the energy of 4.5 keV. Accordingly, the experimental results are 1.44% and 10.14%, respectively, which is consistent with the above data. The results show that the numerical model is reasonable and provides the theoretical and simulation basis for the fabrication of the lens.