To study the aero-optical effect of Laguerre-Gaussian (LG) beams passing through the flow field around a turret, we solve parabolic beam equations of complex amplitude by second-order compact differences and fourth-order Runge-Kutta integration. In the same flow field, light intensity distributions of LG beams with different topological charges, optical path differences (OPD) of the same beam calculated by numerical simulations and integrated along optical path are both compared. Strehl ratio (SR) and imaging displacement are calculated at different Mach numbers, different angles of attack, and different altitudes, and compared among Gaussian beam and LG beams with different topological charges. The simulation results show that in the same flow field, the larger topological charge the LG beam has, the better the shape of amplitude keeps, but the larger the attenuation and imaging displacement are. In the same flow field, the topological charges have nearly no impact on SR of LG beams, and the phase stability of LG beams is always better than Gaussian beam. Changes of altitude and angle of attack have bigger impact on the imaging displacement of LG beams compared with that of Gaussian beams.

Based on the high theoretical accuracy of the Edlen formula method, the value of air refractive index is calculated according to parameters, such as temperature, humidity, and atmospheric pressure, which are measured by the small digital sensor. Aiming at the problem of insufficient accuracy in traditional method, we propose a method based on the second class standard platinum resistance thermometer and the pressure sensor to calibrate and correct the measured values of digital sensors, and use the temperature value to correct the atmospheric pressure, which can improve the accuracy of air refractive index. We use the revised sensor in the measurement, and the experimental results show that the precision of air refractive index reaches to ±5.13×10 -8, which is closed to the theoretical accuracy of 10-8 obtained by Edlen formula. Compared with the results of distance ranging method, the accuracy of measured air refractive index reaches to 10-7. The sensors can be widely used in the air refractive index measurement applications which need miniaturization.

Over the last decade, there have been spectacular development in nonlinear frequency conversion techniques, due to the development of improved nonlinear materials together with the evolution of femtosecond pump lasers. Compared with traditional laser sources, nonlinear conversion techniques represent a simple and effective approach to the direct generation of widely tunable and broadband coherent radiation breaking through the limited bandwidth of gain medium. And thus such techniques are of great interests for different applications. Up to now, our group has built up a variety of high power fiber lasers successfully, which provides a cornerstone for the nonlinear frequency conversion. We review the recent process developments in nonlinear frequency conversion techniques driven by photonics crystal femtosecond fiber lasers, especially in the last five years, including optical parametric oscillators (OPOs), excellent frequency up conversion based on GaAs nanowires, supercontinuum generation and third harmonic generation based on highly nonlinear photonic crystal fibers. In addition, basic principles and some advanced applications are also discussed in this review.

By using the inductively coupled plasma (ICP) deep silicon etching machine and the anodic bonding system, the alkali-metal vapor cell applied to the chip scale atomic clock (CSAC) is fabricated. With the AZ4620 photoresist as a mask, the silicon surface morphology after deep silicon etching is studied and the deep silicon etching rates under different structures are compared. The micro alkali-metal vapor cell with a sandwich structure is obtained by using the anodic bonding, and the saturation absorption line is detected. The experimental results show that a significant saturated absorption phenomenon is observed in the fabricated micro alkali-metal vapor cell when the temperature is 80 ℃.

In this paper, the influences of different structural parameters on the radiation enhancement of metal nanometer surface plasmons are studied to increase the coupling efficiency of the incident electromagnetic wave and the free electron of metal surface. The numerical simulation of Au and Ag nanoparticles is carried out, the local field enhancement of metal nanoparticles with different shapes are compared, the spherical metal nanoparticles have more prominent local field enhancement effect compared to other structures. Therefore, Purcell analysis is carried out by the change of the parameters of spherical metal nanoparticles. The results show that the size of long axis along the polarization direction, the size of short axis perpendicular to polarization direction, refractive index of environment materials as well as the distance of nanoparticles apart from the light source can greatly change the effect of metal nanometer surface plasmons resonance radiation enhancement, and they have great influence on the location of the resonance wavelength. Finally, the metal nanoparticles with ellipsoid shell structure are simulated. It is found that as the change of refractive index of the filling medium and the nuclear shell thickness, the radiation intensities are increased in different degrees.

Aiming at the precision measurement problem of the profile of aero-engine blades, a measurement method based on projected fringe order identification is presented. Firstly, a three-dimensional measurement system with composite structured light is designed and the rotation axis of the system is calibrated by the method of center circle fitting. Then, the aero-engine blades are measured by the digital fringe projection method. In the process of phase unwrapping, the projected fringe order is recognized by projecting two-dimensional code pattern combined with binocular vision, and the front and back surfaces of the blade are reconstructed respectively. In the process of point cloud data stitching, a three-dimensional stitching method combining rotating axis with iterative closest point algorithm is proposed. The experimental results show that the method does not rely on feature extraction and effectively solves the problem of insufficient surface features on aero-engine blades. Which can realize fast and accurate three-dimensional reconstruction of aero-engine blades.

Defocusing amount and spatial distribution of laser energy have a significant effect on the quality of laser processing. It is a commonly used method in laser processing, and the method can adjust the lens distance between beam expanders to meet the different needs of defocusing amounts for the different laser processing materials. We use ZEMAX to model the optical system of laser processing with sequential and non-sequential modes. The beam expander is a Galileo transmission system composed of two lenses. In the simulation environment, the focal position and the spot energy distribution on the working plane are measured at different lens distances and tilt angles. The results show that the defocusing amount is proportional to the variation of lens distance, and the defocusing amount decreases with the decreasing distance. The negative defocusing amount increases with the increasing tilt angle. On the working plane, the peak power of laser spot decreases as the distance between the focal points of two lenses and the tilt angle increase. The effect of lens distance on the laser focusing characteristics is much greater than that of the tilt angle. The displacement of the laser spot is proportional to the tilt angle. The laser spot mode is always base-mode Gauss distribution. Finally, the defocusing amount and the spot energy distribution at different lens distances are measured. The experimental results are in good agreement with the simulation results.

With a flat chain with the wear failure as the research object, the experiment of laser cladding for the matrix is carried out by using the Fe-based alloy powder. The metallographic structure, micro-hardness and wear resistance under different cladding process parameters are analyzed. The parameters with a laser power of 1600 W, a scanning speed of 600 mm·min-1, a feeding rate of 4.0 rad·min-1 and a cladding layer number of 3 are the optimal process parameter set. Under this parameter set, the cladding layer has a good metallurgical bonding with its matrix , has no pores and other flaws, and has the hardness and wear resistance which are better than those of the matrix.

Fe-based alloys are prepared by the laser rapid forming technique. The influence of scanning speed on the microstructure and crystallization behavior of the formed Fe-based alloys is studied. The results show that, under a certain laser power, the large area of crystallization occurs both in the fusion zone and the heat affected zone with the increase of the scanning speed. The morphology and size of the precipitated phase in the fusion zone do not change obviously, however, the size of the precipitated phase in the heat affected zone decreases gradually. The laser rapid forming process is simulated by the Marc finite-element software, the thermal cycling curves in the fusion zone and the heat affected zone under different scanning speeds are obtained, and the reason why non-crystallization phase occurs for Fe-based alloys is analyzed.

The Fe-based Ni /WC cermet coatings are covered on the surface of 45# steels by the plasma spraying technique, the coatings are remelted under four laser remelting trajectories, and the influences of laser remelting trajectories on the microstructure and properties of the coatings are investigated. The results show that the circular laser remelting trajectory exerts the most obvious improvement on the coating properties. The element transfer occurs between the substrate and the remelted layers under the action of convective mass, and the combination mode between the substrate and the remelted layers changes from mechanical bonding to metallurgical bonding. WC, W2C and other hard phases play the role of dispersion-strengthening in the cladding layer. The micro-hardness and wear loss of the coatings under the circular laser remelting trajectories are 1.4 times and 33.7% of those under dotted laser remelting trajectories, respectively. The porosity of the coating under the circular laser remelting trajectories is the lowest.

The formation of H13 steel powder material is conducted by using the selective laser melting(SLM) technology, and the influence rules of process parameters on the forming defects are obtained via a comparative study by changing the parameters including laser power, scanning speed, scanning pitch and scanning method. The results show that, in a certain range, the increase of laser power or the decrease of scanning speed is beneficial to the formation of parts. A too large or too small scanning pitch has a significant impact on the forming quality and thus the pores or fusion-incomplete defects occur. The quality of forming parts under S-shaped orthogonal scanning is the best if compared with those under Z-shaped orthogonal scanning and single X-direction scanning.

The diffractive optical elements have the advantages of miniaturization, lightweight and so on. Based on the phase function of transitional axicon, the phase functions of three kinds of diffractive optical elements such as diffractive axicon, helical axicon and axicon array are designed. By using the theory of angular spectrum diffraction, a light field analysis model for diffractive optical elements irradiated by parallel light is established. The light field distribution characteristics of three kinds of diffractive optical elements under monochromatic Gaussian beam illumination are numerically analyzed. The simulation results show that, the diffractive axicon has the same beam propagation performance compared with the transitional axicon, which can generate diffraction-free Bessel beam in the focal depth. The order of the Bessel beam generated by helical axicon is the same as the number of topological charges. Axicon array can generates an array of diffraction-free Bessel beam. The proposed diffractive optical elements can be used in the fields of laser processing and imaging.

One-dimensional magneto-optical photonic crystals with a dielectric defect layer, which is composed of dielectric layers and magnetic layers alternately, is designed. Non-reciprocal transmission of electromagnetic wave can be achieved when the external magnetic field in opposite directions are applied to the magnetic layers existing at both sides of the defect layer. The transmission spectra of the structure are analyzed by using the modified transfer matrix method. The results show that when the thickness of the defect layer changes, multiple non-reciprocal channels will appear in the photonic crystal photonic band gap in a certain wavelength range. The larger of the thickness of the defect layer is, the smaller of the spacing between adjacent channels is, and the number of channels that can be accommodated in the forbidden band is greater. Seven non-reciprocal channels in the photonic band gap can be achieved when the thickness of the defect layer is 7500 nm. The proposed structure can be used to fabricate multi-channel optical isolators, and expected to be widely used in areas such as density wavelength division multiplexing optical communication technology and integrated optical circuit system.

For the problem of carrier frequency drift in coherent optical communications, according to the actual coherent optical communication system, we adopt the binary phase shift keying (BPSK) and quadrature phase shift keying (QPSK) modulation modes respectively, and simulate the frequency shift to cause the rotation of the constellation map and the increase of the bit error rate. Based on laser frequency adjustment and control principle, adopting the method of external phase detector, single-chip computer(STM32) and piezo-electricity (PZT) driver amplifier at the signal output end, we design a circuit based on feedback decision control loop, which is used for tracking the frequency of the local oscillator laser to the frequency of the signal laser so as to stabilize the carrier frequency. The experimental results show that the feedback decision circuit can stabilize the frequency drift within the range of ±2 MHz when the intermediate frequency carrier is considered as the reference 100 MHz, which is beneficial to the processing of the demodulated signal, and the frequency drift compensation range can reach GHz magnitude. This scheme is simple and practical, which is suitable for coherent optical communication system.

Compared to common fiber Bragg grating (FBG) strain sensor, the FBG strain sensor with low temperature sensitivity has low sensitivity to temperature and high sensitivity to strain. We apply the FBG strain sensors with low temperature sensitivity to static pressure PHC pipe pile penetration test, and monitor the variations of force of pile shaft, toe resistance of pile, and side resistance of pile during the static pressure penetration of the PHC pipe pile. The experimental results indicate that application of FBG sensor with low temperature sensitivity on monitoring static pressure PHC pipe pile during penetration process is suitable, which provides a new testing device for monitoring and analyzing on static pressure PHC pipe pile during penetration process.

We propose a calculation method of the bit error rate of space coherent optical communication link, to solve the influence of laser linewidth on the performance of space coherent optical communication system. The influence of the laser linewidth on the transmission error rate of the link in the turbulent atmosphere is studied, and the error rate model of the spatial coherent optical communication link in the atmospheric turbulence is established. The influence of different parameters on the bit error rate is analyzed, and the result of numerical settlement is given. It is found that, the linewidth increases by 1 times and the bit error rate increases by about 2.7 times; the linewidth increases by an order of magnitude and the corresponding bit error rate increases by nearly one order of magnitude.

We propose a distributed optical fiber vibration sensing scheme based on space difference interference of Rayleigh backscattering, to detect the swing of the optical fiber composite overhead ground wire (OPGW) over large areas. In this scheme, Rayleigh backscattered light with phase changes induced by the swing of the OPGW is split and fed into an imbalanced Michelson interferometer. We use the arm length difference of the interferometer to realize the Rayleigh backscattered light interference of adjacent space segments along the sensing fiber. The phase information is demodulated via 3×3 coupler demodulation technology, and the accurate measurement of the vibration signal is realized. We achieve the swing at 0.9 Hz and non-swing at 2.3 Hz in the transmission line swing laboratory.

In the traditional parallel micro-ring structure, we can achieve the slow light effect tuning by adjusting the coherence distance, but cannot achieve dynamic tuning. Improved micro-ring array, embedding the heater in the cladding, uses thermo-optical tunability to adjust the adjacent ring between the phase shifter, in order to achieve continuous adjustment of any channel slow light effect. We use the transfer matrix method to establish the function model of dense wavelength division multiplexing (DWDM) and simulate the slow light effect of 1×4 DWDM by Matlab. The simulation results show that the DWDM with tunable optical delay channel is obtained by changing the additional phase shift between the corresponding microcircuits, the full width at half maximum (FWHM) of spectral intensity for out channel is about 0.05 nm, and the channel spacing is 100 GHz. The method can switch and dynamically adjust optical delay channel, and enhance the flexibility of the optical device.

In order to achieve accurate optical measurement method in micro-displacement and improve the accuracy of micro-displacement, we propose a novel micro-displacement optical fiber sensor based on surface plasmon resonance. In order to achieve precise measurement of micro-displacement, we use the characteristics that the propagation angle of the beam in the graded-index multimode fiber changes with the position of the incident light, and the resonant wavelength of the surface plasmon resonance sensor has the high sensitivity to the resonance angle variation. In order to achieve the resonance conditions, we polish the graded-index multimode fiber into a wedge with a suitable angle and precisely control the length of the graded-index multimode fiber. In addition, the fiber probe should be immersed into liquid such as water. A white light source is coupled from the end face of the graded-index multimode fiber to the fiber probe via a 630 nm single mode fiber, and an optical spectrum analyzer is employed to collect light beam and process the sensing signal. The fiber probe and single mode fiber are placed in a high precision displacement platform to control the radial relative position of the fibers. The experimental results show that when the fiber polishing angle is 12° and the liquid refractive index is 1.350, the micro-displacement optical-fiber sensor has a maximum sensitivity of 10.32 nm·μm-1 and a minimum resolution of 1.9 nm.

We use phase optical time domain reflectometer (Φ-OTDR) distributed optical fiber measurement system for safety early warning and leak location for city water pipeline. By analyzing the different characteristics of time domain signal, the signal power spectrum, information entropy, space frequency energy distribution, and high-pass filter, we conduct safety early warning and location of pipeline leak. Based on the deep analysis and comparison of the various signal parameters, the space frequency energy distribution is considered as an effective and reliable parameter used for the safety early warning and location of pipeline leak. The experimental results show that positioning error is less than 10 m within 2000 m measurement range based on the method.

Owing to the complex morphology of the blood vessel boundary, the stenosis detection with pixel level cannot reflect the details effectively. We propose a sub-pixel automatic detection method of the blood vessel stenosis based on the digital subtraction angiography (DSA), which can identify the location and the degree of the stenosis more accurately and can obtain accurate quantitative results of the stenosis through sub-pixel analysis. Firstly, we extract the central axis of the blood vessel based on the adaptive multi-scale filtering and morphological operations. Secondly, we perform sub-pixel level detection of the blood vessel by the rotation invariance of Zernike moments. Finally, we quantize the diameter using the diameter measurement algorithm based on dynamical ball. Thus, the sub-pixel automatic detection of blood vessel stenosis based on DSA is realized.

In order to improve the coupling image quality between optical molecular image and computed tomography (CT) image, the free-form surface optical channels of tumor lesion tissue in optical molecular image and CT image are established based on free-form surface optical technology, and dual-mode image fusion display is realized. The design method of microscopic, multi-spatial and multi-focal free-form surface optical lens and imaging surface of tumor lesion tissue is used. The differential equation of fused lens and imaging surface of dual-mode image is established. The light focal change curve of optical surface of the free-form surface in lesion tissue is solved. The optical channel surfaces of lesion tissue free-form surface are discreted and reconstructed by optical reconstruction technique of free-form surface in reverse engineering, which improves the dual-mode image fusion quality of the optical molecular image and CT image. It is reasonable and feasible to use free surface optical channel technology to fuse dual-mode image of the optical molecular image and CT image, which improves the sharpness and signal-to-noise ratio of fusion image signal.

Focusing on the issue that the traditional tracking method is difficult to adapt to the target scale variation in real time accurately, an adaptive scale target tracking algorithm based on kernel correlation filtering tracking framework, which adapts a scale estimation method, is proposed. Firstly, the regularized least squares classifier is used to obtain the filter template, and the position of the target is estimated by detecting the candidate samples. Then, the scale of current frame is determined based on the target size of the previous frame, and the scale samples are obtained by the maximum response value through the scale estimation method. Finally, the target and scale model parameters are updated online according to the occlusion detection mechanism. The experimental results show that the proposed algorithm improves the distance precision by 17.12% and the success rate by 10.77% as compared with the best of the other tracking algorithms. In complex scenes, such as background clutters, severe occlusion, and illumination, posture and scale variation, the proposed algorithm still has a good tracking performance.

The non-damage, high speed, and ultra-high resolution characteristics of optical coherence tomography (OCT) technology in in vivo imaging application make it a broad space for development in the biomedical imaging field. Generally, a large amount of OCT data are acquired , and fast Fourier transform (FFT) in the image reconstruction process requires much calculation time. Therefore, the traditional central processing unit (CPU) serial data processing mode is difficult to meet the requirements of real-time imaging. To this end, the compute unified device architecture (CUDA) parallel programming technique is applied to the data processing of skin tissue imaging in the spectral-domain optical coherence tomography (SD-OCT) system, and it is implemented in the graphics processing unit (GPU). We detail the parallelization of the system algorithm and the parallel processing of the data collected by the system to improve the imaging speed. In the experiment, we use the SD-OCT system to image the skin of the finger and collect the data. The data collected by the laboratory's existing data processing platform MATLAB and GPU are processed respectively, and the imaging speed and image quality of different data processing platforms are compared. The experimental results show that the GPU and CPU hybrid programming model has a processing speed up to 10 times faster than the CPU-based MATLAB method while the image quality remains the same, which meets the clinical requirement of real-time imaging in the clinic.

The influence of the sea foam channel on the polarization scattering of photons in the quantum communication can lead to the increase of the polarization bit error rate. A polarization compensation scheme based on wavelength division multiplexing (WDM) is used to compensate the state of polarization. Based on the feasibility of the WDM polarization compensation scheme, to solve the problem of the polarization errors caused by the wavelength interval in the sea foam channel, we propose a single-reference-pulse error calibration polarization compensation scheme and a double-reference-pulse error calibration polarization compensation scheme. We simulate the deviation angle distribution of the compensated signal pulse under different wavelength intervals. The results show that the two schemes both can effectively eliminate the polarization bit error rate caused by wavelength interval. The performance of double-reference-pulse polarization compensation scheme is more excellent and the compensation effect is more obvious. However, the multi-reference-pulse scheme has more requirements for laboratory equipment. It is also found that the smaller the wavelength interval is, the smaller the deviation angle of the signal pulse is, and the lower the corresponding polarization error rate is.

The stability of two-dimensional (2D) graphene-like GaAs is theoretically verified by the first-principles method based on the density functional theory (DFT) and the molecular dynamics (MD). The energy band structure, density of states (DOS), and parameters for describing optical properties of 2D GaAs are calculated. The results show that, two-dimensional GaAs is different from three-dimensional GaAs, and it shows a metallic property because the two highest bands are overlapping. The dimension reduction results in the enhancement of the interaction among electrons in s and d states of As. More DOS peaks occur with peak position shifts towards a low energy direction. The lower energy bands are composed of Ga-d, As-s and As-p states, and the higher energy bands are composed of As-s and As-p states. The 2D GaAs has a static permittivity of 3.67, and has a strong absorption for ultraviolet light. It shows a metallic reflection characteristic in the photon energy ranges of 3.90-4.71 eV and 5.69-6.90 eV.

A broadband reflection polarization converter in the terahertz frequency regime is proposed based on the L-shaped microstructured cell arrays. The characteristics of this polarization converter composed of L-shaped microstructured cell array, dielectric layer, and metal plates are numerically analyzed. The results demonstrate that the proposed polarization converter can not only convert a linearly polarized (LP) wave into a cross-polarized wave, but also convert LP waves into circularly polarized (CP) waves at two specific frequencies. In the frequency range of 0.64-1.19 THz, the polarization conversion ratio (PCR) is more than 80%, and the maximum PCR is more than 95%. In addition, the proposed converter can maintain a good polarization conversion performance under certain oblique incidence conditions.

A novel left-handed structure is designed by periodically arranging metal wires and square diagonal-opening resonators on a single side of a substrate material. Based on the theoretical analysis and software simulation, the effective electromagnetic parameters of this designed left-handed material are extracted. The results show that, in the frequency band of 11.7-20.5 GHz, this structure possesses a good negative refraction effect and double negative characteristics and its absolute bandwidth is 8.8 GHz, which coverages the whole Ku band (8-12 GHz), and the loss of unit cell is less than 0.4 dB. Its real object is fabricated and tested, and its left-hand characteristic is confirmed. Compared with the conventional left-handed materials, the designed left-handed material realizes a low loss and a wide bandwidth.

A method for simulating the intrinsic stress of thin films is proposed, and the thermal stress and the intrinsic stress of the multilayer films during the deposition process are numerically analyzed. By introducing the intrinsic stress coefficients and using the existing thermal stress finite element analysis program, the intrinsic stress of the films is simulated, and the correctness of this method is verified from a theoretical perspective. The growth of materials is simulated by using the model reconstruction and stress initialization method. The stress analysis model of multilayer films is established. The analysis results from the engineering examples indicate that the intrinsic stress and thermal stress of the multilayer films at each deposition stage can be conveniently simulated by using this method and procedure.

Ni-Cr-Mo alloy coatings are prepared on Q235 steel surface by using a continuous diode laser. The assisted thermal treatments of these coatings are made under pulsed currents with different processing time, which improves the quality and property of coatings. The microstructure, phase composition as well as the mechanical and anticorrosion properties of coatings are investigated. The results show that the pulsed current processing is beneficial to promoting the precipitation of eutectic structures on the grain boundaries of laser cladded coatings. The precipitation amount of eutectic structures increases with the increase of processing time, and the hardness within the depth around 0.1 mm away from the coating surface increases as well, however, the anticorrosion property of coatings increases first and then decreases.

The spectrum shaping approach of chirped laser pulse is studied based on the non-colinear optical parametric chirped pulse amplification (OPCPA) with angular spectral dispersion (ASD). The effect of angular dispersion ratio on the phase mismatching of each signal frequency component, the conversion efficiency and the spectral distribution after amplification is discussed in detail. The coupled wave equations are simulated numerically when signal pulse is pumped by 532 nm with the central wavelength of 800 nm and the bandwidth of 20 nm. The results show that the bimodal spectrum with 28 nm bandwidth is obtained by use of the non-colinear OPCPA with ASD, under the optimal angular dispersion ratio. The results also indicate that the angular dispersion ratio has a considerable effect on the overall conversion efficiency and the shaped spectrum of the signal pulse after the amplification. Furthermore, the frequency-shift of signal spectrum after amplification could be modulated by adjustment of the time-delay variation between the pump and the signal pulse properly. The shaped spectrum is available to compensate the gain narrowing and spectroscopic redshift effect to some extent.

Under the conditions of different amplitudes, truncation coefficients, and nonlocal degrees, we numerically study the evolution of shedding soltions generated by two kinds of symmetric Airy pulses with space-reversed shapes in a strongly nonlocal nonlinear medium by split-step Fourier method. The results indicate that as the amplitude increases, truncation coefficient and nonlocal coefficient decrease, a tail-leading Airy beam not only generates a shedding soliton at the main lobe, but also generates the shedding solitons at the side-lobes. Thus the number of shedding soliton further increases. However, no matter how the amplitude, truncation coefficient, and nonlocal coefficient change, only one shedding soliton is generated at the main lobe of a tail-trailing Airy beam, while the shedding soliton cannot be generated at the side-lobes. Therefore, we can control the generation and number of shedding soliton by manipulating the amplitude and the truncation coefficient of an Airy beam, and controlling the nonlocal coefficient of a medium.

Parallel light exposure machine with large area is an important manufacturing equipment for electronic products such as printed circuit board (PCB), display panel, touch screen, and so on. Due to the use of non-axisymmetric Kohler illumination light path with fly-eye lens and a mirror, the uniformity of the exposure machine is only about 0.85, which cannot meet the needs of high-precision machining. Aiming at this problem, a fly-eye lens with free-form surface is proposed to replace traditional spherical fly-eye lens, and a free-form surface design method of high-uniformity fly-eye unit is established. The experimental results of ray tracing simulation analysis show that the exposure uniformity is improved to more than 0.91 by using the proposed method, which can meet the needs of high-precision machining. The designed fly-eye lens with free-form surface, which has continuous surface and can be machined by diamond turning, is expected to be widely used in the illumination path of parallel light exposure machine with large area.

According to the requirements of real-time and accuracy of people detection, we propose the support vector machine based on optimized kernel function in people detection, which uses histogram of oriented gradients algorithm to extract the features of people and the support vector machine algorithm as the classifier. On the basis of the traditional algorithm, we propose the combined kernel function as the kernel function of the classifier. After setting the slack variable and introducing the penalty factor, we combine genetic algorithm and K-fold cross validation optimization to select and optimize the combination coefficients and parameters, and build the final classifier for people detection based on the optimize parameters. Results show that the proposed algorithm achieves better result, and can satisfy the requirement of real-time and accuracy in people detection.

In order to overcome the limitations of traditional total variation (TV) regularization in image restoration only considering the first-order gradient characteristic of the image with the deficient ability of detail recovery and sensitivity to the noise, the total generalized variation (TGV) is applied into image deblurring. An adaptive weighted TGV image deblurring model is proposed, which can adaptively adjust the weights according to the local image structure, avoiding the staircase effect while preserving the edges of the image and suppressing the noise. In order to solve the proposed model, the adaptive weighted TGV is proposed based on primal-dual algorithm. The experimental results show that our method can obtain high quality recovery images and the solving algorithm has low time complexity and fast solving speed.

Three-dimensional block-matching (BM3D) algorithm can effectively suppress the noise in stationary signal. However, it is not feasible for the speckle noise in synthetic aperture radar (SAR) image with random characteristics due to the single 3D transform threshold and the local neighborhood for searching similar blocks. We propose a BM3D algorithm based on K-Mean clustering for SAR image denoising. First, we calculate the feature vector according to the mean, variance, and poor value, and estimate noise variance of each image block. The adaptive 3D transform threshold will be determined through the estimated noise variance. Second, we can find similar image blocks of reference image block in the corresponding class of image blocks, and can find global similar image blocks quickly. The experiments demonstrate that the proposed algorithm achieves better visual effect and and higher peak signal to noise ratio than the BM3D algorithm and non-local mean algorithm.

Aiming at the defects of fragmentation, low matching precision, and slow speed for Terracotta blocks matching, we propose a fracture surface matching method based on intrinsic shape signature (ISS) feature points. Firstly, the outer surfaces of blocks are segmented, and the fracture surfaces are extracted. Secondly, the ISS feature points of fracture surfaces are extracted, the feature sequences of feature points are calculated, and the fracture surfaces are matched based on feature sequences. Finally, an improved iterative closest point algorithm based on simulated annealing is used to match the feature point sets again. Thus, the fine matching of fracture surfaces is completed, and the blocks are matched accurately. We match four groups of Terracotta blocks, and the results show that the proposed method is more accurate and faster than other methods and effective for Terracotta blocks matching.

In order to meet the needs of building shadow detection in high resolution remote sensing images, we study the shadow detection method based on shadow probability constraint by principal component transformation and spectral feature extraction in hue, saturation, and intensity (HSI) space. Based on the results of principal component transformation and the difference of the spectral characteristics of ground objects in HSI space, we eliminate the influence of dark objects and detect the shadow of buildings in the water using shadow probability. Compared with traditional methods, the proposed method avoids the false detection and missed detection caused by the similar spectral characteristics of water bodies and buildings. Experimental results based on Jilin No.1 images show that the false detection rate and missed detection rate of the proposed method are less than 6%, the overall classification accuracy and Kappa coefficient are higher than 0.9, the impact of water on shadow detection results is reduced, and the overall effect of image shadow detection is improved.

Four-dimensional block matching cooperative filtering (BM4D) has a good performance when it is used for seismic signal denoising. But it has to predict noise standard deviation. To overcome this issue , we present a three-dimensional seismic signal denoising algorithm based on BM4D combined with principal component analysis (PCA). We first use PCA to estimate the noise standard deviation of the seismic signal, and then use the result of estimation for BM4D denoising. The experimental results of synthetic and actual 3D seismic signal denoising show that the proposed algorithm is feasible and can not only achieve the good denoising effect, but also avoid the sensitive limitations of noise level estimation. Compared with other five noise estimation algorithms, the experimental results show that the proposed algorithm has advantages in both noise estimation time and accuracy.

To solve the problem of poor recognition effect of difference local directional pattern (DLDP), a face recognition method based on orthogonal gradient difference local directional pattern (OGDLDP) is presented. The pixel gray values in the fields of 3 pixel×3 pixel and 5 pixel×5 pixel are convolved with two different sets of 8 Kirsch operators, respectively. We differentiate the two sets of edge response values according to the corresponding numbers and take the absolute value in accordance with the corresponding number to obtain 8 edge response differences in horizontal and vertical directions. If the edge response values near the edge obtained in the 3 pixel×3 pixel field are made the differences before and after the counterclockwise direction and the absolute values are taken, the 8 edge response differences in horizontal and vertical directions will also be obtained. The OGDLDP code is produced by taking the maximum edge response difference values from the two orthogonal groups corresponding to the direction of the subscript, which are encoded into a double-digit octal number. The experimental results on Yale and AR face databases show that the proposed algorithm improves the recognition rate, and has robustness to the changes of illumination, expression, and shelter.

Spatial texture information extraction of hyperspectral image by filter often falls into local texture extraction. According to the problem, an algorithm of hyperspectral image classification based on adaptive manifold filtering (AMF-SVM) is proposed. This method uses adaptive optimization. The first manifold is calculated. Then, hyperspectral image with manifold is recursively splatted, blurred, and sliced according to the height of the manifold tree. Combined with the handling results, hyperspectral image is applicated to the linear filtering, the results are classified by support vector machine (SVM), and then the optimal classification is obtained. Experimental results show that the AMF-SVM algorithm is better than original SVM classification methods using the spectrum information, dimensionality reduction, and the spatial-spectral information, and the methods of edge-preserving filtering and recursive filtering. Performance of the classification for hyperspectral image with AMF-SVM is greatly improved, and effectiveness of this method is fully verified.

The flame pattern is artificially designed by most of the traditional flame detection methods based on physical signal of the flame, and is identified according to the pattern recognition method. These methods are easy to be interfered by the external environment. Because the generalization of artificially designed flame feature is not strong, the recognition accuracy will reduce when the flame shape or scene changes violently. To solve this problem, a method of deep learning for detecting the flame based on the regional full convolution network (R-FCN) with the residual network (ResNet) is proposed. The feature is extracted automatically by the feature extraction network, and the flame position is determined by R-FCN, and it is secondary classified by ResNet for further reducing the false alarm rate. The proposed method, which eliminates the feature extraction process of the traditional flame, realizes end-to-end automatic acquisition of flame characteristics and performs corresponding detection processes. An average recognition accuracy reaches to 98.25% in the flame video data set of Bilkent University.

Assembly correctness identification of internal part of complex component is one of the essential processes for industrial product testing. However, there is still lack of a detection method with high systematic robustness to improve the whole testing process. To solve this problem, based on the convolution neural network classification and computed tomography (CT) technology, we propose a detection method to identify automatically the area of interested image, which is different from the detection methods characterized by the connected area in the past. Thus, the judgment criteria of the qualified products is changed from the regional characteristics to individual characteristics. The sequence of projection data collected by CT system is input to the convolutional neural network model to precisely locate and classify the internal parts of the workpiece. The result of the internal components classification is taken as the criterion of the detection for the missing parts. The projection of standard workpiece is matched to the projection of the test-workpiece, which can detect the displacement of the parts. The experimental results show that the method can identify missing and misaligned internal parts of the workpiece in the simulation and the experiment. The overall system is robust for the situation such as overlapping among the internal parts of the workpiece.

We propose an expression recognition algorithm based on asymmetric region Weber local descriptor (AR-WLD) and block similarity weighting, which can reduce the interference of occlusion area to facial expression recognition and the impacts of the final discriminants in unconstrained environment. In the feature description, compared with the traditional WLD, the AR-WLD extends the original square neighborhood into an asymmetric neighborhood, and enhances the feature analysis in a multiscale. In order to distinguish the contribution of different facial regions to expression recognition, the non-overlapping expression regions are classified in classification discrimination. Information entropy is introduced to measure the uncertain information contained in different sub-blocks, and the weight of similarity distance is defined according to the information amount. The facial expression discrimination is achieved by the block similarity weighted summation. The experimental results on the databases of JAFFE and CK show that the AR-WLD can effectively improve the classification performance and robustness of the WLD when the expression image is partially occluded, and the classification algorithm based on block similarity weighting can further reduce the interference of the occlusion area to facial expression recognition.

High dynamic range (HDR) images are the images with HDR of lightness that can be recognized by human eyes, which can show more details about scenes. Aimed at one-exposure low dynamic range (LDR) images, we propose an HDR image generation method by fusing multi-level gamma-transformed images. The LDR image is firstly divided into four regions according to its histogram distribution. The Gamma parameter is calculated in each region based on the lightness level. Then, four images with richer details of different regions are generated by multi-level Gamma transform. Finally, they are fused into one HDR image with higher dynamic range and richer details. The tone-mapped HDR images generated by proposed method are compared with those by fusing multiple pseudo-exposure images. The results show that the proposed method has higher entropy and shorter running time.

In order to realize the blind recovery of motion blurred image, we present a blind recovery method based on combining l1/l2 norm with the high order and low order total variation. We adopt the ratio of l1/l2 norm regularization prior item which has high sparse expression ability, and add the high order and low order total variation regularization item. High order total variation regularization model can suppress the ladder effect and ringing effect that may occur in the region of non-edges. Low order total variation regularization model can protect the sparse feature of natural image edges. The solution of high-quality image and the solution of blurred kernel are given respectively, both of which employing Bregman iterative algorithms to split the objective function into multiple sub-problems. The experimental results show that the proposed method can restrain ringing effect and protect the image edge details. The robustness of proposed algorithm is better in the visual quality and objective quality evaluation comparing with other methods for blind recovery of motion blurred images.

By using rigorous coupled-wave analysis method, the process tolerance of broadband polarization independent reflector with multi-subpart profile resonant grating is investigated. The theoretical analysis shows that, in the wavelength range of 1.62-1.76 μm, the change of 20 nm of critical structural parameters such as period and thickness, modulation profile, middle layer thickness, buffer thickness of micro-nano resonant grating has a negligible effect on the reflectance spectrum of the device. The results show that the proposed reflector has good processing tolerance in the existing processing error range, which is conducive to the processing and fabrication of the device.

The TE oscillating guided modes and their propagation properties in a taper slab waveguide with anisotropic metamaterials are investigated. From Maxwell equations, based on continuous boundary conditions for tangential electromagnetic fields, we obtain a dispersive equation and a power flow equation of TE oscillating guided modes with a variable separation method. Based on the above equations, using a curve fitting technique, we plot some corresponding curves. It is found that the electric field intensity considers the influence of x and z directions, and the power flow changes periodically with the increase of the waveguide length; as the slope of the taper slab waveguide k=0.1, the waveguide length of the guided mode transmission is less than 2.5 mm; as lower frequencies (f=5.0 GHz) and k=0.01,for different mode orders, the variation of waveguide thickness has little effect on power flow transmission. The properties will help us to minimize the waveguide and decrease the accuracy requirement of the waveguide processing in the future.

As the basic structure of all-optical computing basic logic unit, the research progress of all-optical switch affects the development of all-optical computing and even the development of integrated optical field. An ultrafast all-optical switch with silicon-based silica structure is designed. The extinction ratio and the switch response time of the optically controlled optical switch are measured through two-color pump-probe experiment. The design of ultrafast all-optical switch with the switch intensity ratio of 7:1 and the switching time of 500 fs is realized.

For the weak target detection, the existing methods still have the problem of large detection error. In order to improve the accuracy of the centroid detection of the Shack-Hartmann wavefront sensor, an improved distance-power index centroid detection algorithm is proposed. The proposed algorithm is compared with several existing centroid algorithms under different conditions, the simulation results show that the centroid detection error of proposed algorithm is lower and more stable than that of other algorithms under the factors of different signal-to-noise ratios, different spot diameters and different pixels in sub-area.

Aiming at the problem that the existing light detection and ranging (LiDAR) point cloud filtering method cannot effectively exclude the data hole interference in the digital surface model (DSM), a skewness balance point cloud filtering method based on multispectral data guidance is proposed. This method introduces the multispectral data into the point cloud filter as the guiding image to realize the fast denoising with the spectral similarity of the noise points. The experimental results show that this method can effectively eliminate the interference caused by the data hole to the point cloud filtering, and the obtained filtering error is reduced by 0.4%-0.8% compared with the original skewness point cloud filtering method. Compared with the popular filter algorithm based on support vector machines (SVM), the error of this method is reduced by 0.1%-0.4%.

In order to solve the dual-Kinect external parameters calibration problem in scanning large object with dual-Kinect, we use an improved random sample consensus (RANSAC) method to extract the key parameters of sphere and plane model of the point cloud. The relationship between sphere center coordinate and normal vector of plane in different Kinect coordinate systems is analyzed. A new calibration method of dual-Kinect spatial position based on sphere and plane model is proposed. The calibration of the rotation translation matrix with large change in view and position movement is realized. Compared with the traditional iterative closest point (ICP) algorithm and improved ICP algorithm to calibrate dual-Kinect external parameters, the proposed method is faster and more accurate. Finally, the feasibility of this calibration method is verified by the actual model registration results. The proposed method provides a quick and accurate calibration scheme for dual-Kinect external parameters calibration with large change in view and position movement.

Airborne LiDAR systems are widely used in urban objects extraction and recognition because of the advantages in obtaining 3D information conveniently and rapidly. However, it considers geometrical features regardless of buildings and vegetation spectral features and error rate is high in the dense canopy. Aiming at this problem, an algorithm of building extraction by fusing spectral features in aerial images and geometrical features in LiDAR data is proposed. Firstly, the spectrum information can be obtained by registering with LiDAR data. Then, the new feature which fuses spectral and geometrical information is formed by improved tensor voting. Finally, building extraction is achieved by random forests algorithm. Simulation test datasets are provided by ISPRS. Through the comparison of results before and after fusing spectral features, the accuracy of the proposed algorithm is obviously high and the extraction quality of proposed algorithm reaches to 94.26%. The simulation results prove the importance of fusing spectral features in building extraction.

The fast recognition of counterfeit liquor is significant in the field of food safety, while the existing liquor detection technologies cannot quickly identify various kinds of counterfeit liquors in the market. We propose a quick method of liquor-authenticity identifying. Firstly, we use laser induced fluorescence technique to collect fluorescence spectra of the liquor under test. Then we adjust the size of fluorescence spectra to input into the deep learning algorithm, Finally, we can identify the authenticity based on the algorithm. We select four samples, which are three liquor brands with two liquor degrees, and collect 100 fluorescence spectra for each liquor sample. Then we select 80 spectra from the 100 spectra randomly for model training deep learning algorithm. Finally, we detect the rest 20 spectra for the trained model. The experimental results show that there are significant differences of fluorescence spectra in different liquor brands and different liquor degrees. In model test, the recognition rate of fluorescence spectra in four samples is 98.44%. The results indicate that the laser induced fluorescence technology and deep learning can identify the brand and degree of liquor precisely.

For the case of broad spectrum and high resolution spectral measurement under limited number of pixels and the pixel size of the photodiode array, we propose a recording oblique interferogram scheme based on the two-dimensional (2D) shear interference, which is used to stitch those pixels on different rows of the focal plane array to improve the resolution in the long-wave and avoid the cut-off in the short-wave caused by increase in unit shear. We use the Wollaston prism polarization interferometer to verify the 2D-directional shear interference by rotating the image plane, and calculate the carrier frequency relation of the lateral shear volume in the coordinates of CCD. The complete interferogram is composed of several columns by connecting the margin pixels of equal-phase. Using the FRED software to simulate the polarization interference process, we calculate 1064 nm, 1550 nm, and 1970 nm laser lines from quasi-monochromatic when using calcite crystal and C-RED ONE detector. The results show that when the slope of the rotation angle is 1/3, the position precision of retrieved spectral lines by 2D-shear interference is less than 1 nm, and the amplitude ratio is 0.9958∶0.9759∶1. The spectral resolution at 1970 nm increases to 13 nm, which is 2.38 times of the original value. The near-infrared reflectance spectra of the wax are compared with two kinds of recovery. The spectra inversion of the extended optical path difference including 768 pixels shows more absorption characteristics, showing a higher spectral resolvability compared to the inversion by optical path difference of 320 pixels, though some high-frequency disturbance is introduced in the short-wave direction. The relationship between the angle error tolerance and the rotating angle, the observed wavelength, the shear angle and the segmented optical path difference is given when imaging magnification is constant. Based on the 2D shear interference spectrometer by rotating the photodiode array, the contradiction between the high spectral resolution and the high-frequency cut-off caused by simply increasing the amount of shear is avoided, which expands the solution range of system parameters and related error tolerance, providing a choice for wide range and high-spectral measurement.

Famotidine is a histamine H2 receptor antagonist, which has a significant inhibitory effect on gastric acid secretion. The quenching effect between famotidine and bovine serum albumin (BSA) is studied with the analysis of fluorescence spectrum and ultraviolet visible absorption spectrum, and the interaction mechanism between them is elucidated. The results show that famotidine has strong quenching effect on the endogenous fluorescence of BSA, and the quenching mechanism is static quenching. The apparent binding constant KA of famotidine and BSA at 306 K and 314 K is determined to be 9.861×10 4 L/mol and 3.891×104 L/mol. The calculated thermodynamic parameters show that the interaction between famotidine and BSA is mainly hydrogen bond and van der Waals force. According to the F rster nonradiative energy transfer theory, the interaction distance of famotidine and BSA is calculated to be 1.25 nm, and nonradiative energy transfer occurs.