Both the mathematical principle of the maximum probability (MP) method and the process of iterative equations are introduced. Then we use the real satellite data as an example to demonstrate the calculation of MP method and obtain the volume scattering ratio profiles and scattering coefficient profiles of polar mesospheric clouds (PMCs). We compare the inversion results of the MP method with those of the traditional onion peeling (OP) method, and find that the former hardly have any distortion, while the latter show serious distortion. The fundamental reason for this difference is that the OP method assumes that the volume scattering intensity has a uniform distribution in the same atmospheric layer, while the MP method assumes that the volume scattering intensity can exhibit a non-uniform distribution within a certain varied range of the layer. This assumption of MP method is more suitable for the natural characteristics of PMCs, because the spatial distribution of PMCs often changes greatly in a short time.

The distributed feedback (DFB) laser, featured in its stability and single-mode emission, is widely used in various domains such as pumping lasers and optical communications. As a key component in the DFB laser, the grating plays an important role in laser performance. The design and fabrication of the grating for the 976 nm DFB semiconductor laser are presented. The experiment starts with the optimization of the grating structure parameters based on the coupled mode theory. The gratings are fabricated through laser interference lithography and inductively coupled plasma (ICP) etching technique. The pattern quality of the fabricated grating is improved by the introduction of surface coating SiO2, and the fidelity of grating pattern transfer from photoresist to substrate is improved as well. Influence of exposure time and ICP etching time on grating surface morphology is investigated. The experiments show that the fabricated grating has uniformly distributed fringes and better surface morphology, and the expected design is realized.

A kind of novel photonic crystal fiber with easy fabrication, high birefringence and double zero-dispersion is proposed. The cladding is made of two circular air holes of different sizes in the form of quasi-rectangular and triangular lattices. The optical characteristics are analyzed by the full vector finite element method. The results show that birefringence of 2.59×10-2 is obtained at wavelength of 1.55 μm when d1 =0.80 μm, d2=1.10 μm, Λ=1.00 μm, and nonlinear coefficients in X and Y polarization directions are 46 km-1·W-1 and 36 km-1·W-1, respectively. In addition, two zero-dispersion points are located in the visible and near-infrared bands and distance between two dispersion points is 0.68 μm. Through reasonable parameter setting, positions of double zero-dispersion points, dispersion points spacing and flatness of dispersion curve are adjustable. The optical fiber with the structure is easy to fabricate in existing drawing process, which will be conducive to large-scale applications of the fiber in the supercontinuum generation, polarization system control and optical fiber sensing.

In order to improve the reliability of asynchronous clock sampling signal recovery data in deep space optical communication, an asynchronous clock delay sampling data recovery scheme based on optical pulse position modulation is proposed. The scheme divides output signals of the photon detector arrays into two groups. The output signals of odd arrays are sampled into a certain slot frequency, and the output signals of even arrays are sampled after half slot sampling. Finally, the two groups of sampling signals are merged and interpolated separately to complete the process of data recovery. The simulation results show that the sampling performance of delay sampling data recovery scheme is better than that of traditional sampling scheme. When the sampling frequency is with one times slot frequency, the proposed scheme can effectively reduce the signal loss caused by the traditional sample mode, and suppress the pulse shift error caused by the delay jitter. The system performance can be improved obviously.

In order to meet the needs of bridge structure health monitoring, the home-made long-gauge fiber Bragg grating (FBG) macro strain sensor is used to measure average shear strain and identify occurrence of oblique cracks. The FBG is used as a measuring element and five couples of crossed topologies are designed. We use the cross topological theory to measure different parts of concrete T-beam, and analyze relationship between the average shear strain of the structure and load in crossed topological coverage. The experimental results show that the measuring method of the long-gauge FBG crossed topology is effective to identify occurrence and development of oblique cracks, and this method has good application value in engineering practice.

The actual laser Doppler velocity signal is always mixed with noise, which leads to great difficulty to find required Doppler frequency shift. In view of this problem, a wavelet threshold de-noising method is presented. According to the characteristics of the Doppler signal, the optimal effect of wavelet threshold de-noising is obtained when we choose proper wavelet decomposition layer number, wavelet basis function, threshold function and threshold estimation method. Results of Matlab simulations and experiments show that the wavelet threshold de-noising method can eliminate the noise in Doppler signals quickly and effectively, so that the signal to noise ratio is improved and the useful signal is obtained. In addition, the method is helpful to find required Doppler frequency shift more accurately, and the hierarchical threshold de-noising effect in wavelet threshold de-noising method is better than the global threshold de-noising effect.

We propose a new method for threshold selection to improve the filtering effect. Based on theoretical analyze of spectral coefficients of phase fields, considering the scaling effect of fringe amplitude on spectral amplitude, we obtain fringe amplitude by using maximal spectral coefficients. Then, a new threshold about windowed Fourier transform filter method for speckle pattern interferometry is calculated. Through the verification of simulated speckle fringe pattern and real fringe pattern, the new threshold selection method can effectively filter out high-frequency noise, which performs better in filtering.

A multiple watermarking method combining a double random phase encryption system, frequency division multiplexing technology and quick response (QR) code is proposed. In order to enlarge the watermark capacity, an effective coding region of QR code is combined into a new image, and then the two composite images are used as real and imaginary parts respectively to form double QR code complex signals. The complex signal is encoded with random phase masks in the space domain and the spatial frequency domain into an encrypted watermark signal in form of complex noise. The double QR code encryption watermark signals are preprocessed and frequency division multiplexing is used to generate multiple watermark. The watermark signal is embedded redundantly in the medium-high frequency region of the residual components of the host image after Laplace decomposition. The watermark signals can be recovered without original host image, and the blind extraction can be achieved. Simulation results show that the proposed method is robust in scaling, filtering and rotation, and has a certain robustness for JPEG compression, cropping and Gaussian noise. The multiplexing capacity and the influence of random phase mask as a key on the quality of reconstructed watermark are also analyzed.

The telescope system based on Fresnel incoherent correlation optical path can obtain the digital hologram of the object at a long distance. Based on Fresnel diffraction theory, the imaging process of the point spread function (PSF) is calculated. The imaging principle, the lateral magnification and the reconstruction distance of the system are deduced. A digital holographic telescope system based on the Fresnel incoherent correlation on-axis light path is constructed, and the CCD is used to receive the holograms under the white light. The conjugate image and the zero-order image are eliminated by phase-shifting, and then the clear reconstruction image is obtained by the angular spectrum reconstruction algorithm. By introducing aperture diaphragm, we solve the problem, and improve the imaging quality. The resolution, depth of field and three-dimensional (3D) imaging characteristics of the system are verified experimentally. The experiment shows that the resolution is 16.00 lp/mm when the angle magnification is 2.0 and the distance is 900 mm.

Based on the existing standard adaptive median filtering algorithm and gradient inverse weight smoothing algorithm, we propose an image filtering algorithm based on adaptive median and gradient inverse weight, aiming at the difficulty of mixed noise filtering by either single liner filter or non-linear filter. In order to filter the mixed noise, this algorithm adaptively adjust the window size to detect the salt & pepper noise and does median filtering, meanwhile, the gradient inverse weight smoothing is performed for the Gaussian noise by setting threshold. Experimental results show that this algorithm filters well for Gaussian noise, salt & pepper noise and the mixed noise, compared with the standard adaptive median filtering algorithm and the gradient inverse weight smoothing algorithm. And it has obvious filtering advantages for the high intensity image noise.

In order to improve the registration efficiency of three-dimensional point cloud, a two-step point cloud registration algorithm is proposed based on the key point initial matching using the normal vector distribution feature and the accurate registration using the iterative closest point (ICP). Firstly, the definition of the adjacency region and the normal vector distribution feature model of point cloud are presented, and a key point selection algorithm is proposed based on the model. Secondly, the fast point feature histograms of key points are calculated using the local coordinate system, and the false matches are eliminated by the sampling conformance registration algorithm. According to the corresponding relation, the rotation and translation matrices are calculated and the initial registration is completed. Finally, the final registration result is obtained using ICP algorithm. The experimental results show that the proposed algorithm can effectively improve the registration efficiency while ensuring the accuracy of the registration in the data of unordered point cloud and the self-acquired depth point cloud.

Depth estimation of monocular infrared image is a key to scene understanding of night driverless vehicle. Aiming at the depth estimation of night driverless vehicle scene, a depth estimation method based on the deep convolution-deconvolution neural network is proposed. Infrared images and radar depth data are fed to the deep convolution-deconvolution neural network. The depth estimation problem is transformed to a pixel-wise classification task in the training of the depth estimation model. The radar depth values are quantized into discrete bins corresponding to the pixels of infrared image and the bins are labeled according to their depth range. The deep convolution-deconvolution neural network based depth estimation model is trained by classifying each pixel to the corresponding depth. The experimental results show that the depth estimation time is 0.04 s/frame, which use the depth estimation model to estimate the scene depth information of infrared image captured by the night driverless vehicle, and the real-time requirement in practical applications is reached.

Two sub-pixel rendering algorithms based on the three primary colours are proposed, which add much more green sub-pixel to the traditional RGB structure. They transfer the RGB data of original image into new RGBG data, and then rendering the converted RGBG data. The proposed algorithms ensure that the image has same resolution as the traditional RGB arrangement, and also increases the pixel per inch (PPI). Simulation results show that, the proposed two algorithms can keep the clarity and saturation of original image, and increases the PPI by 50%, with more exquisite and smooth display effect.

In order to increase the recognition rate of plant leaf images, the improved neural network algorithm is proposed. The model is established by radial basis function neural network. The multi loop quantum algorithm is used to determine the selection probability of each quantum individual, and the quantum rotation gate is dynamically adjusted in a certain range, and the node information of different rings shares the probability of nonlinear dynamic changes. The plant leaf image recognition includes shape features and texture features. The multi loop quantum algorithm is used to realize the radial basis function neural network parameter optimization. The experimental results show that the proposed algorithm has a higher average recognition rate of plant leaf image than other algorithms, with the geometric features 91%, texture features 89% and comprehensive features 93%, and the training and recognition time are 3.5 s and 2.5 s respectively.

For the synthetic aperture digital holography, the effects of speckle noise on image registration accuracy based on the feature point matching are investigated. An experimental setup for the digital off-axis holography is established, and the scale-invariant feature transform (SIFT) algorithm and the speeded-up robust feature (SURF) algorithm are used to extract the feature points of the image to be matched and the reference image. The feature point matching is performed by the nearest neighbor search method based on Euclidean distance and the parameters of the image transformation model are estimated using the maximum likelihood estimation sample consensus algorithm. The experimental results show that the SIFT algorithm is more robust to speckle noise. For the SIFT algorithm, when the signal-to-noise ratio is greater than 1.4, the relative error of registration is less than 0.02, and for the SURF algorithm, when the signal-to-noise ratio is greater than 1.7, the relative error of registration is less than 0.05.

Based on the measurement principle of refractive index of triangular prism, the relative uncertainty is theoretically analyzed by using minimum deviation angle method, glancing incidence method and vertical bottom edge incidence method respectively. The results show that the relative uncertainty of the refractive index decreases with the increasing of the vertex angle of the triangular prism. The effect of the beams with different wavelengths on the relative uncertainty of the refractive index is small. And the relative uncertainty of the refractive index increases with the increasing of the uncertainty of the angulation. Moreover, when minimum deviation angle method is used, the effect of the deviation angle near the minimum deviation angle position on the incident angle is not obvious. But the unapparent variation range of the deviation angle decreases with the increasing of the vertex angle of the triangular prism. Finally, the optimal scheme is provided for obtaining the minimum relative uncertainty of refractive index, which provides a theoretical basis for the accurate measurement of the refractive index of the triangular prism.

With the introduction of the effective elastic constants including the residual stress in the ideal theoretical model, the half-infinite residual-stress theoretical calculation model of SiO2 is established. The influence of residual stress on the Young modulus detection of SiO2 bulk materials by the laser-induced surface ultrasonic wave technique is studied, and the error judgment basis is proposed. The results show that, when the residual compressive stress of SiO2 bulk materials is less than 900 MPa, the relative error is less than 5% and the influence of residual stress can be ignored. While when the residual compressive stress is more than 900 MPa, the error is more than 5%, and the influence of residual stress should be taken into account.

Laser scanning system is widely used in high precision systems, such as laser machining and imaging. The optical quality is the final index of manufacture process. In mass production, the tolerance analysis of the optical system is needed to meet the demand of use and reduce processing cost. For example, the laser scanning system is simulated by the unified field optical analysis. The position tolerance and rotation tolerance of each workpiece of the system is analyzed based on the optical properties of the laser scanning systems. The overall system meets the design and uses requirements through tolerance constraints for each workpiece. The measurement platform is built, and the measurement result is consistent with the analysis of unified field tracing.

Based on the thermal-optical analysis, the glass thickness of the corrector mirror used as an optical window is optimized under the complex environment. The intensity and the thermal environment of the corrector mirror is analyzed. By mapping the temperature field to structural model, the deformation and surface data of the corrector mirror under the thermal-force coupling condition are calculated by the finite element method. The surface data of corrector mirror is fitted and calculated. Finally, the processed surface data of corrector mirror is brought into the optical design scheme, and the effect of the thickness of corrector mirror on the performance of spectrometer is analyzed. The results show that the thickness of the corrector mirror should be no less than 10 mm. If the thickness of the corrector mirror is 15 mm, the effect of thermodynamics on corrector mirror can be ignored. It is conclused that the corrector mirror acting as optical window can not only meet the strength and reliability requirements, but also meet the optic index of the spectrometer. These results provide the guidance for the optical window design.

A optical time domain reflectometry (OTDR) system based on LabVIEW is designed. A 1625 nm wavelength pulsed laser module is used as the light source. The high-sensitivity avalanche diode photodetector and high-speed data acquisition card are used to collect, process and storage the optical signal under the control of the LabVIEW integrated virtual instrument development environment, in order to realize on-line real-time monitoring of fiber. An algorithm combining digital average method and weighted sliding-average is adopted to reduce the noise of the returned backscatter signal, and the effect of the digital average time, smooth width and smooth type on the result of signal processing of the OTDR system is quantitively analyzed. Then the best smooth model is given. The first derivative method is used and the double thresholds of derivative and amplitude are set to locate the point of the reflection event. The experimental results of practical optical cable line with the proposed system show that the optimal smoothing filter proposed in this paper improves the dynamic range by 1.1 dB and the signal-to-noise ratio by 1.25 times compared with the traditional smoothing filter at the same smooth width. The proposed positioning algorithm can be used to locate the point of the reflection event accurately, which indicates that the proposed algorithm has certain practical value.

A new rapid human body measurement method based on depth sensor skeleton tracking is proposed. The method obtains the skeletal joint information and human depth data through depth sensor, so as to complete the measurement of part length and circumference in human body feature size. Experimental results show that this method can obtain more accurate results in a short time and realize the acquisition of some human body feature sizes in low space with low cost equipment.

At dynamic situation, acquiring the dynamic pose error of machine tools in real time is one of the key factors to improve the accuracy of machine tool. For multi-axis machine tool, two path lasers are used to track the space motion trajectory of two measuring points on the main-spindle measuring rod in real time. Two measuring points of 3D data are obtained and two space circles are fitted out. Then the line connecting the centre of two circles is used to identify the direction and position error of the tool. As the real-time ram errors moving along Z-axis changes with the change of the thermal error and dynamic motion error caused by the change of parameters, and the ram errors affect the final position of the tool direction. The ram errors should be predicted, measured, and corrected with the adaptive Kalman filter algorithm. The original error parameters in the error compensation model are replaced by the calculated optimal estimation value to correct the pose error of the tool. Finally, the error correction compensation and the uncompensated process are applied for the frustum specimen and the S-type workpiece. The comparison of the accuracy of the measured workpiece shows that the real-time measuring method of the tool position error and the adaptive correction compensation can effectively increase the processing accuracy of five-axis machine.

With a high-power and short-pulse Nd∶YAG laser, TC17 titanium alloys are processed by laser peening (LP), the isothermal oxidation weight gain experiment at the temperature of 400 ℃ is carried out, and the effect of LP on the isothermal oxidation performance of titanium alloys is analyzed. The study results show that, as for the TC17 titanium alloys after LP, if compared with those before LP, the isothermal oxidation weight gain at 400 ℃ decreases by 64.9%, and the oxide film on the material surface becomes more dense, which can resist the oxygen diffusion more effectively. The surface energy spectral analysis results show that the Cr on the surface of the oxidized sample after LP is more than that before LP. A large amount of Cr can improve the adhesive force between the oxide layer and the substrate, and thus LP can improve the isothermal oxidation resistance property of titanium alloys.

The laser welding experiment of 304 stainless steels with powder filling is carried out, the effects of different laser welding process parameters on the cross-sectional morphology, tensile strength and fracture morphology of welding seam are studied, and the optimal process parameters are obtained. The results show that, in the experimental range, there is a positive correlation between the width of welding seam and the laser energy density. When the defocusing distance changes from zero to positive or negative value, the top welding seam width increases while the bottom welding seam width decreases. The low laser power and the zero defocusing distance can weaken the tensile strength of welding specimen. With the increase of welding speed, the tensile strength of specimens increases first and then decreases. With the increase of tensile strength, the fracture appearance is, in turn, manifested as a side-shaped cleavage fracture, a quasi river-like cleavage fracture, and an alveolate-dimpled plastic fracture. The optimal process parameters obtained from the orthogonal test are a laser power of 2.7 kW, a welding speed of 160 mm·min-1, and a defocusing ditance of +5 mm.

According to the management mode of the heat capacity laser, the crystal thermal model of the pump stage and the cooling stage are established respectively by analyzing actual working characteristics of microchip laser crystal. Then the equation of the heat transfer coefficient is introduced and the expressions of the temperature field of heat capacity laser are obtained with the status of side-end-pumping and cooling of laser diode (LD). The factors of spot radius and pump time that influencing the crystal temperature field are analyzed respectively. The results show that when the thermal conductivity of Nd∶YAG crystal is constant and variable, the maximum temperature rises of pump end face are 459.24 ℃ and 535.78 ℃,respectively. The mass ratio of neodymium ion in the crystal is 1.0%. The size of microchip is Φ20 mm×1 mm. The pump power is 60 W. The absorption coefficient of Nd∶YAG crystal is 910 m-1 . The super-Gaussian beam order is 3 and the pump light spot radius is 800 mm. The analysis results are helpful to the design of LD end-pumped solid-state heat capacity lasers resonator.

1.70 μm band laser sources have larger applications in many fields, such as biomedical medicine, infrared light generation and so on; the gain spectrum in 1.70 μm band is an international hotspot. A home-made multimode fiber laser is applied as the Raman pump in order to avoid stimulated Brillouin scattering. The pumped signal is injected into the high nonlinear fiber (HNLF) and dispersion shifted fiber (DSF) through 1550 nm/1650 nm wavelength division multiplex (WDM). Firstly, the principle of generating gain spectrum using the multimode laser is analyzed. Then, the forward and backward spectra are analyzed, these spectra are produced by HNLF and DSF with different lengths under the condition of different powers. The results show that, 1 km long HNLF and 6 km long DSF can be used to obtain the best backward gain spectrum with maximum power and peak wavelength of near 1700 nm. The experimental results provide technical reference for 1.70 μm band continuous wave lasers and ultrafast lasers.

By using Nd∶YAG solid-state lasers, the scanning test of 50CrNiMoVA spring steels is performed, and the butt welding with W2Mo9Cr4VCo8 high-speed steels is also done. The influences of laser process parameters on weld formation are analyzed, the microstructures of welding joints are observed, the welding joint performance tests are carried out, and the effect of heat treatment on the microstructures and properties of welding joints are discussed. The test results show that, when the laser power is 1000-1100 W, the welding speed is 3 m·min-1, and the flow rate of protecting gas Ar is 15 L·min-1, the smooth welding seams without obvious defects and also with a high aspect ratio, a good surface forming, a high strength, and a firm joining between tooth and back materials can be obtained. After welding, the heat treatment makes the bending and tensile properties of joints improve obviously, and the bending angle is larger than 90°. The welding seam does not crack along the longitudinal and transverse directions. The sawing life test result shows that the joints can meet the requirements of saw belt production.

With the Nd∶YAG transparent ceramics as the gain media, a laser property evaluation system is built. The effect of the Nd∶YAG transparent ceramic size on the laser property is studied. The experimental results show that, when the Nd∶YAG transparent ceramic size is relatively small, the laser output power increases with the increase of the size under the same pump power, but the increase amplitude declines. When the Nd∶YAG transparent ceramic size is 3 mm×3 mm×9 mm, the continuous laser output with a power of 4.94 W and a corresponding slope efficiency of 37.7% is obtained. When the pump power is 17 W, the numerical simulation results on the variation of the laser output power with the Nd∶YAG transparent ceramic size is consistent with the experimental results. Compared with the Nd∶YAG monocrystal, the Nd∶YAG transparent ceramics can be used to improve laser properties if its doping concentration is enhanced.

The experiment of micro-groove processing on super-hard cutting tool surfaces by using fiber lasers is carried out, and the effects of laser process parameters on micro-groove surface morphologies are studied. The study results show that the micro-groove arrays with a uniform size and a good morphology can be obtained after the optimization of laser process parameters, and the effective control to the micro-groove surface morphologies of super-hard cutting tools can be realized.

The brightness perception characteristics of the night vision vehicle head up display (HUD) information which read by the driver in the dark environment at night are studied to build the brightness adjustment model of the night vision vehicle HUD in different illumination conditions. The specific experimental system is set up to simulate different illumination conditions in which 100 drivers are chosen to evaluate the values of the minimum brightness, optimum brightness and the maximum brightness of the HUD information. The experimental data is statistically analyzed, the brightness adjustment curve and the driver brightness perception model are both presented, and the brightness law of the driver′s reading the night vision vehicle HUD under the dark environment is subsequently summarized. The experimental results show that the proposed model can be used as the quantitative reference for the engineering design optimization of the night vision vehicle HUD and improve the efficiency and user experience of human-computer interaction.

Aiming at the high false detection rate due to the image translation and rotation, the low efficiency and low reliability of manual inspection, and the impact of image registration precision on the detection accuracy, a method based on Fourier-Mellin transform for liquid crystal display (LCD) defect detection is proposed. The basic fundamental of the method is as follows. The rough matching based on the Fourier-Mellin transform is performed between the detected image and the standard image firstly, and then the fine matching based on the speed-up robust features/scale-invariant feature transform (SURF/SIFT) algorithm is performed. The weighted average fusion is used for the standard image and the image after registration to obtain the final image. The LCD defects are inspected by local adaptive threshold segmentation and subtraction method, with the defect location and information marked. The experimental results show that the proposed method is robust to image translation and rotation, and can effectively detect the LCD defects with an accuracy rate up to 98.667%.

Aiming at the difficulty of scene segmentation in the process of robotic random bin picking, a point cloud segmentation method based on the improved Euclidean clustering is proposed. The pass-through filter and the iterative radius filtering are used for the pretreatment to obtain the point cloud of scattered workpieces after removing the interference points. The edge points in the point cloud are removed by the edge detection based on normal angle, and the inter-collision workpieces are separated in space. The improved radius adaptive Euclidean clustering is adopted for the point cloud segmentation to obtain the point cloud subsets of many workpieces. The removed edge points will be put into the point cloud subsets based on the distance constraint, and thus the point cloud segmentation is completed. In addition, the offline template point cloud provides reference for the selection of segmentation parameters, which ensures the accuracy of segmentation results and improves the segmentation speed. The experimental results show that the proposed method can accurately segment the interested workpieces, and the segmentation time is about 696 ms. It is satisfied with the real-time requirement of industrial robot picking.

In order to solve the problem that the traditional methods of object shape classification spend too much training time and the shape is represented inaccurately, an image classification method is proposed based on the improved Bayesian program learning. Firstly, the preprocessed object contours are segmented into fixed-length fragments and the feature information is represented with the shape descriptors. Then, the contour fragments in the same object class are trained into a contour fragment library using the Gaussian mixture model. Finally, the Bayesian classifier is used to calculate the similarity between the ten fragments of the test object and each contour fragment library, and the classification result is the category with the highest similarity value. The experimental results on standard Animal database show that the proposed method has a good classification accuracy, meanwhile, it greatly shortens the training time.

In order to solve the cooperative pose of small-scale space robots by means of visual measurement, a cooperative pose measurement system based on monocular vision is designed. Firstly, a cooperative target with wide range of functions, high precision and strong robustness is designed for complex space working conditions. Secondly, one-pixel-width edge extraction algorithm is designed by image gradient method, and target identification is done with center matching and other constraints. Thirdly, the relationships between distance of feature points and precision of pose measurement are derived, and the extraction strategy of feature points based on partition processing is designed to realize the extraction and number of feature points in complex conditions, expand the working distance and improve the precision of pose measurement. The experimental results show that the processing speed is about 84.3 ms/frame in Matlab for the image of 640 pixel×480 pixel. Pose measurement errors are less than 5 mm and 1° within the range of 2.2 m. This system meets the cooperative task need of small-scale space robots.

Focusing on the travel problem of blind people, an audio-visual fusion blind guiding robot system is designed, which can realize the detection of environmental obstacles, the identification of road traffic signs, the planning of path and the real-time interaction of information. In terms of hardware, the real-time visual information are collected through various types of optical sensors, and the information interaction with the users are carried out in the voice form. In terms of software, the neural network algorithm is used to carry out the data fusion from multi-sensors so as to realize the environmental information recognition, and the double pole coefficient method and the image segmentation based on the color histogram are used to realize the recognition of the zebra crossing and the blind road, respectively. The path planning is implemented based on the artificial potential field method. To verify the effectiveness of the proposed scheme, we build a prototype system and test it in a real environment. The test results show that the blind guiding robot has the advantages of high recognition accuracy and robust performance to complex environment, and it is satisfying the travel needs of blind people.

A novel anti-counterfeiting encoding method based on the nanoparticle upconversion luminescence is proposed. This method combines the image processing algorithms based on MATLAB, support vector machine (SVM) classification and radial basis function neural network classification. With the analysis of the upconversion luminescence spectral characteristics of the green and red lights emitted from the nano-materials which are pumped by the 980 nm laser, and the spatial distribution characteristics of these nano-materials on the anti-counterfeiting substrate, the anti-counterfeiting method with a high-security and an automatic capability of database building and pattern recognizing is realized. The experiment confirms that it is difficult to replicate the prepared anti-counterfeiting markings whose characteristic patterns have a high stability, and the identification accuracy is up to 95.4%.

Based on metamaterials, a new type of absorber is designed. After the optimization of structural parameters, the absorptivity of this absorber can approach 100%, and the absorption bandwidth is over 18.5 GHz when the absorptivity is larger than 90%. The simulation results show that the electromagnetic energy loss comes mainly from the lumped resistance in the electromagnetic metamaterials. With the decrease of the reflection of the incident wave, and the increase of the absorptivity of the absorber, the broadband absorption can be achieved.

Using SiH4 and H2 as sources, we use hot-wire chemical vapor deposition to prepare intrinsic amorphous silicon (a-Si∶H) on c-Si wafers surface. Quasi-steady state photo conduction method and I-V method are used to analyze the influence of process parameters on the passivation effect. C-V method and deep level transient spectroscopy (DLTS) method are employed to test the defect state of the passivated silicon wafer surface. The experimental results show that, under the condition of 200 kHz, the surface defect density of the c-Si wafer with surface recombination velocity of 54 cm/s is 1.02×1011 eV-1·cm-2 and the fixed charge density is 6.12×1011 cm-2. The passivation effect of a-Si∶H on the surface of the silicon wafer is determined by the dangling bond on the surface of the thin film silicon saturated by hydrogen bond and the surface fixed charges forming the field passivation effect. The a-Si∶H passivated deep-level defect on the surface of the wafer is characterized as electron trap. The active energy, capture cross section and defect concentration is 0.235 eV, 1.8×10-18 cm2, and 4.07×1013 cm-3, respectively.

By using the first principles based on the density functional theory and the general gradient approximation method, the electronic structures and optical properties of N, Co single-doped and N-Co co-doped anatase TiO2 are studied, and the effects of two kinds of different substitutions where the O site replaced by N are explored. The study results show that the impurity energy levels of both N and Co single-doped anatase TiO2 appear within the band gaps, and as for N-Co co-doped anatase TiO2,the more complicated impurity energy levels appear within the band gaps. The band gaps of the doped anatase TiO2 become narrower. Compared with that of the N, Co single-doped anatase TiO2, the stability of the co-doped anatase TiO2 is better, the optical absorption efficiency in the visible light region improves obviously and the absorption spectral redshift is more obvious. Compared with the type 1, the type 2 of co-doped anatase TiO2 has a higher absorptivity in the visible light region and a wider absorption spectral redshift range.

Based on the Mie scattering theory, the scattering effect of related parameters of sea foam on photon polarization scattering is analyzed with the hollow layered particle model. The equations of quantum bit error rate and photon-polarization fidelity are deduced. The whole process of photons passing through a foam layer is simulated with the Monte Carlo method. The relationships among the quantum bit error rate, foam scattering coefficient, foam absorption coefficient, thickness of foam layer and scale parameter of foam particles are discussed. The simulation results show that the increasing of the foam scattering coefficient and the thickness of foam layer may result in the increasing of the scattering times, which strengthens the depolarization degree of photons and reduces the photon-polarization fidelity. When scattering coefficient of foam is over 0.5 cm-1 and the thickness of the foam layer is over 6 cm, the quantum bit error rate caused by the foam reaches to 6.5%. The foam absorption increases the transmission loss and decreases the quantum key generation rate. Within the classical value range of the foam scale parameter, the quantum bit error rate decreases with the increase of the scale parameter.

In order to provide references for purchase and usage of displays from the point of view of blue light hazard and circadian effect, the spectral distributions of four kinds of displays including cold cathode fluorescent lamp (CCFL) backlight liquid crystal display (LCD), light emitting diode (LED) backlight LCD, organic light-emitting diode (OLED), and crystal ray tube (CRT) are measured at different color temperatures (1200-6500 K). Blue light hazard factor, circadian factor, 400-500 nm blue light ratio and 446-477 nm blue light ratio of four kinds of displays at different color temperatures are calculated according to the fitting results of response functions of human eyes to visible light. Results show that blue light hazard factor and circadian factor increase with the increase of color temperature; blue light hazard factor of OLED is the smallest in four kinds of displays when the range of color temperature is from 1200 K to 6500 K; 400-500 nm blue light ratio instead of blue light hazard factor can be used to characterize the strength of blue light hazard; when the color temperature is 6500 K, considering blue light hazard and circadian effect at the same time, the quality order of four displays from good to bad is as follows: LED backlight LCD, OLED, CCFL backlight LCD, and CRT.

The effect of pulse energy on the formation of femtosecond laser plasma filament is studied by the fluorescence spectrum method and the photographic imaging method, and the influence of pulse energy on the length and the starting position of femtosecond laser plasma filament is obtained. The experimental results show that the long plasma filament forms after focusing of lens when the femtosecond laser transmits in the air. As the laser energy is increasing, the starting position of plasma filament moves toward the position of the focusing lens and the plasma filament length increases. The position of the peak intensity of the N2 337 nm fluorescence spectrum is close to the focusing lens, and the whole fluorescence spectrum intensity increases. Compared with the photographic imaging method, the fluorescence spectrum method has high reliability in the plasma filament length measurement. Finally, the influence of pulse energy on the starting position and the length of plasma filament is explained theoretically.

The helmet-mounted display demands light weight, suitable size, and compact structure. Aiming at the demands, we use the off-axis catadioptric principle to design a helmet-mounted display system, and the monolithic freeform surface prism is utilized to solve the problem of small exit pupil diameter. The designed system parameters are as follows: the diameter of the exit pupil is 8 mm, the angle of field of view is 20°(H)×15°(V), distance of exit pupil is 20 mm, a 0.47 in OLED-XLTM display is selected, the display area is 9.6 mm×7.2 mm, the pixel number is 640 pixel×480 pixel, and the pixel size of 15 μm×15 μm. A single element is adopted to design the system, whose volume is less than 13 mm×25 mm×17 mm. K26R is selected. The modulation transfer function at 30 lp/mm in the full field of view is higher than 0.25. The system is designed with a single element, and realizes small volume and light weight with imaging quality taken into consideration.

The collimation system of reducing smoke alarm system collects wide angle near infrared rays to generate the parallel beam, which ensures that the rays travel long distances without divergence. Reducing smoke alarm collimation system is optimized by point by point calculation. The initial discrete data points of smoke alarm system for ideal point light source are calculated based on the principle of equal optical path and refraction law. The discrete data points are fitted into freeform curves. Using optical simulation software to build the model and optimize the initial structure of the collimation system, and better LED freeform collimation system is got. The thickness of freeform surface collimation system is 20 mm, the diameter is 28 mm, the collimation angle is ±1.5° and the energy efficiency is 89.82%.

A polarization beam splitter (PBS) based on silica on silicon is designed by using asymmetric Mach-Zehnder interferometer (MZI). Within the wavelength range of 1535-1565 nm, the polarization extinction ratio is larger than 20 dB, and the insertion loss is larger than -0.5 dB. In addition, the finite difference-beam propagation method is adopted, the effect of errors of width/length of multimode waveguide and asymmetric arms on the performance of PBS is calculated, respectively. The simulation results indicate that, when the length errors of multimode waveguide and asymmetric arms are less than ±2 μm and ±4 μm, respectively, the extinction ratio and the insertion loss are still well. To keep the polarization extinction ratio more than 20 dB, width error of multimode waveguide should be less than ±500 nm, and width error of asymmetric arms should be less than ±4 nm (wide arm) and ±2.5 nm (narrow arm). The widths of asymmetric arms ask for high requirement in fabrication process. The thermo-optic effect should be used to regulate refractive index of the waveguide, thus compensating the phase error caused by waveguide dimensional change, so it can be used to fabricate high-performance silica on silicon PBS in the next step.

In order to rapidly evaluate and screen G4 lamp with light-emitting diodes (LED) light source (LED G4), the photoelectric performance of LED G4 lamp is studied. Using the integrating sphere, variations of the performance parameters such as luminous flux, luminous efficiency, color temperature with input voltages of drive circuit changing from 10 V to 34.5 V are tested and analyzed in both initial and steady states. The results show that luminous flux and color temperature of tested lamp increase with the raise of input voltage of drive circuit in both initial and steady states, but luminous efficiency tends to decrease. In initial state and steady state, the luminous flux increases as much as 91.40% and 39.34%, and luminous efficiency decreases by 24.3% and 28.1%, respectively. Furthermore, the highest temperature of the center over the tested lamp is tested by thermal imager. The temperature increases with the increase of input voltage of drive circuit. The difference between its start value and end value reaches 40 ℃. Experimental results show that excessive input voltage of drive circuit is not suitable for high performance of LED G4 lamp and temperature rise has a negative impact on its performance. Therefore, we should choose appropriate operating voltage and improve the performance of heat dissipation in practice.

Using high-accuracy extend blackbody as the standard radiation source, we set up the radiometric calibration system and perform a radiometric calibration experiment for long wave infrared camera. Based on the practical response data, the relationship of response characteristics with incident radiation and integration time is analyzed, and a mathematical model of radiometric calibration is establish. Thereout, the fast radiation calibration method, which is choose of three pictures under two temperatures at two typical integral time, is proposed. The unknown parameters in the calibration model can be obtained by data processing. Finally, using 398 sets of available data from 420 sets of measured data, we verify the reliability of the simplified radiation calibration model. The results show that the relative error between the calculated and measured values is less than 1%, and the fitting degree is greater than 0.999. Experiments show that the calibration method can ensure the accuracy of rapid radiation calibration under different integral time.

The preparation of high-fidelity quantum state is a basic requirement for precise control of quantum system. In this paper, by using superadiabatic technology and introducing an auxiliary field strength parameter, we investigate the problem of high-fidelity superadiabatic quantum driving in the Demkov-Kunike model, and discuss the influence of the auxiliary field strength parameters, chirp parameters, coupling strength and static detuning parameters on the adiabatic process of the Demkov-Kunike model. The results show that the fidelity of the system is closely related to the auxiliary field strength parameters. When the appropriate auxiliary field parameters are selected, the system has good parametric robustness, no matter the system is at no static detuning case or static detuning case. The oscillation of transition probability can be suppressed in all parameter ranges. The system can achieve high-fidelity, fast, and superadiabatic quantum driving.

The PBC00 protocol with excellent security features is studied. For the purpose of preparing polarization states and realizing protocol, the polarization states of the PBC00 protocol are changed to the |1〉, |0〉 and |+〉. For the purpose of analyzing the secutity of protocol, it is assumed that the eavesdropper uses the intercept-resend strategy to eavesdrop during the quantum key distribution (QKD) process. The measurement basic vectors that the eavesdropper may use are analyzed and the key error rates caused by the eavesdropper are calculated. The modified three-state QKD protocol based on the BKM07 protocol is introduced and its security is analyzed. The study results show that the modified PBC00 protocol has a stronger ability to detect eavesdroppers, is easy to implement, and has a practical application potential.

A modified scheme of measurement-device-independent quantum key distribution (MDI-QKD) protocols based on the heralded pair coherent state (HPCS) is proposed, which decreases the error rate caused by the dark count in the long distance quantum key distribution. The simulation results show that, compared with a weak coherent source, the HPCS can reduce the quantitative proportion of vacuum and thus increase the transmission distance. Compared with a heralded single photon source, the HPCS can enhance the quantitative proportion of single-photon pulse and thus increase the secure key generation rate. The impact of the finite key length on the MDI-QKD of the three decoy state based on the HPCS is analyzed.

According to the entanglement features of GHZ (Greenberger-Horne-Zeilinger) states, a quantum secret sharing protocol based on the five-particle GHZ state is designed. In the protocol, the quantum sequence of the five-particle GHZ state is prepared by the initiator, and the total number of the secret sharing parties is 4. Only when all the four people are involved in decryption can the secret information be solved. The correctness and security of the protocol are analyzed, and the results show that the protocol can be used to resist the interception retransmission attack, the man-in-the-middle attack and the entanglement attack. When the temptation particles exist, the probabilities of being found for the eavesdroppers under different noise environments are obtained by using the modeling tool Prism.

Time-of-flight laser ranging technique of single transmitted pulse has very important application prospect in fast response applications, such as moving target tracking measurement, vehicle anticollision, robot motion control and so on. The research status of time-of-flight laser ranging technique of single transmitted pulse is introduced. The principle, method and error compensation of single transmitted pulse ranging based on leading edge timing and resonance timing are analyzed. The technical indices, such as the range of single transmitted pulse ranging and the accuracy of single transmitted pulse ranging are given.

Current point cloud intensity correction is confined to single scan station. In order to solve this problem, we propose a histogram equalization method for multi-scan intensity based on Gaussian mixture model. Firstly, the range-intensity and incidence angle-intensity correction models are used to correct the intensity for a single scan station. Then Gaussian mixture model is used to fit the histogram of intensity distribution after correction and segment the histogram. Finally, normalization of multi-scan intensity is achieved through sub-histogram matching. The experiment results indicate that the proposed method can not only correct the intensity of a single scan station efficiently, but also improve the inconsistence among different scan stations.

In order to improve classification accuracy of hyperspectral image based on the joint sparse representation, we propose a classification algorithm based on neighborhood similarity. Compared with conventional joint sparse representation algorithm, the weight of different feature categories pixels to pixel P to be test in neighborhood is different. Similarity threshold can be set based on the similarity of all pixels in neighborhood and pixel P. Category of pixel P can be obtained by joint sparse representation pixels which have high similarity with pixel P. And then the spatial information is used to modify classification algorithm, which associates with the categories of the neighboring pixels and gets smooth classification results. Experiment results demonstrate that the proposed algorithm has higher classification accuracy and more stable results.

Either in the solid state or in the fiber amplifier, femtosecond pulse energy is limited by the thermal and nonlinear effects. Chirped pulse amplification (CPA) solely cannot break the barrier of high peak power and average power. Coherent pulse combination, such as the spatially or temporally divided pulse amplification, has the potential to produce higher pulse energies at high repetition rate. Furthermore, coherent pulse stacking from high repetition rate, high power fiber amplifier may even surpass the chirped pulse amplification and produce many order higher pulse energy with high repetition frequency.

Quantum adiabatic process is one of general ways to prepare and manipulate the quantum states, which usually needs long operation time and makes the manipulation fidelity drop fast in a dephasing system. Theoretically, the technology of quantum shortcut to adiabaticity is proposed to eliminate the non-adiabatic effects during its evolution, which can speed up the quantum adiabatic process. When the technology of quantum shortcut to adiabaticity is applied in the stimulated Raman adiabatic transfer, it can realize the fast and robust quantum control. The basic concept of the technology of quantum shortcut to adiabaticity and its experimental progress are summarized, and its application in the stimulated Raman adiabatic transfer is emphatically introduced.

Because of the selective recognition ability, molecular imprinted polymers (MIPs) have great advantages as sensitive materials for sensors. Optical fiber sensors based on MIPs (OFS-MIPs) have a good prospect for applications and have been widely used in various fields, such as environment, chemistry, medicine, food safety and so on. The research progress of OFS-MIPs is reviewed. The coupling methods between the optical fiber sensing and the molecular imprinting, the application fields and open problems of OFS-MIPs are investigated, and the prospects are prospected.

The feasibility for the quantum signals transmission in the atmospheric channels has been demonstrated in many experiments. The quantum communication terminals are added to mobile platforms, which is considered as one of the most significant practicable applications and can satisfy the requirements of the construction of global quantum secure networks, the strict security of military communications, and so on. The crucial technologies involved in the quantum key distributions between the ground and the mobile platforms are reviewed. The current status and challenges in the development of mobile quantum key distribution technique are introduced and the development direction for the practicable applications is also discussed.

The effects of the composition and the fusion behavior of welding wires and welding-wire-related parameters on the laser welding process are summarized. With appropriate process parameters and under the condition that the continuous and smooth transition of the filler wire is ensured, a stable welding process can be realized, welding defects can be avoided, and a substantial increase of laser welding quality and weld performance can be obtained. In order to keep the laser welding with filler wire to be of intelligence, high efficiency and high quality, it is necessary to do further research on the multi-objective optimization of the interconnected process parameters, the precise control of the composition of the filler wire, the precise control and optimization of the wire-heating energy and the welding-wire temperature.

Vortex lasers are the optical beams possessing intensity center of zero and orbital angular momentum. In recent years, generation of the vortex lasers and chirality-control techniques get more and more attention due to their unique applications in particle manipulation, information communication and super-resolution imaging, etc. The techniques of the vortex lasers directly generated from solid-state cavities are summarized, and the corresponding merits and drawbacks are respectively analyzed. Then, the optical field distributions of opposite-handedness vortex lasers in the standing wave cavity are derived through theoretical simulation. Finally, based on the field distribution characteristics of vortex lasers with different handednesses, the handedness-control techniques for vortex lasers directly generated are reviewed, and their principles and technical proposals are further compared and analyzed.

Laser tweezers Raman spectroscopy (LTRS) is used to study the effects of various environmental factors on staphyloxanthin biosythesis. Staphylococcus aureus cells are cultivated at the temperature ranging from 22 ℃ to 37 ℃, pH from 4.5 to 8.5, glucose mass concentration from 0 g/L to 10.0 g/L, and flavone mass concentration from 0 mg/L to 175 mg/L. The intensity of Raman band at 1523 cm-1 is used to characterize the relative content of staphyloxanthin in bacterial cells. The experimental results show that the temperature ranging from 22 ℃ to 37 ℃ has no significant effect on staphyloxanthin biosynthesis, the neutral pH is most favorable for staphyloxanthin biosynthesis, and glucose in a certain mass concentration range (0.2-5.0 g/L) promotes staphyloxanthin synthesis in a dose-dependent manner whereas flavone inhibits staphyloxanthin synthesis in a dose-dependent manner. The LTRS technology can serve as a rapid and reliable method for quantitative determination of staphyloxanthin content as well as an effective approach to screening and evaluating inhibitors of staphyloxanthin biosynthesis.

The selection of spectral characteristic band is one of the important basis of plant hyperspectral classification. On the basis of measured hyperspectral data of five typical vegetation in Poyang Lake and data preprocessing and analysis, a method of spectral characteristic band selection based on the average and range threshold method is proposed, and the Mahalanobis distance-spectral angle method is used to identify the species of different vegetation. The results show that the proposed method effectively extracts the spectral characteristic band of the vegetation, the band is 1111-1132 nm, 1466-1522 nm, and 1577-1750 nm, respectively, and all of them are located in the infrared region. In the spectral characteristic band, the Mahalanobis distance-spectral angle method can effectively identify different vegetation types, the spectral classification accuracy of Triarrhena is the highest, the accuracy of Cynodon is 84%, and the overall classification accuracy is 91%, which shows that the classification effect is good.

The solvent concentration distribution in the curing process of the acetone/polymethyl methacrylate (PMMA) coating solution is measured by the laser confocal Raman spectroscopy method. The Raman spectra of acetone, PMMA, and acetone/PMMA coating solutions with different mass concentrations are respectively measured, and the relationship between the peak intensity ratio and the mass concentration ratio of PMMA to acetone is established with the least squares method. The experimental results show that the linear correlation coefficient of the calibration curve is above 99.9%. The peak intensity ratio of PMMA to acetone can be obtained from the spectra by real-time measurement and subsequently the solvent concentration at this moment is obtained.

With the development of femtosecond laser technology and wide applications of polymethyl methacrylate (PMMA), the research on optical properties of PMMA has become a hot spot. Filamentation phenomenon appears in the process of transparent materials by femtosecond laser. Generation principles of self-focusing and filamentous are analyzed. One of the most important characteristics of laser beam is polarization state. Linearly polarized light, circularly polarized light, radially polarized light and angularly polarized light can be controlled by the combination of spatial light modulator, 1/2 wave plate and 1/4 wave plate. Generated polarized light with energy of 1 μJ is used in the line processing on PMMA, and then the comparative analysis is conduct on the length and initial position of filamentation under different polarized light. Experimental results show that linearly polarized light and circularly polarized light result in filamentation with short length, and filamentation position of linearly polarized light is close to the incident plane. Radially polarized light and azimuthally polarized light result in long length, and the distance of filamentation position to the incident plane is long.