Laser shock processing is a new type of surface modification technology that can improve the fatigue life of materials by using laser-induced plasma shock waves. It has the advantages of significant strengthening effect, strong controllability and good adaptability. Laser shock processing plays an important role in improving the structural reliability, the fatigue strength of parts and the service life of materials. In recent years, the technology has received widespread attention and developed rapidly. This paper briefly introduces the basic principle, characteristics and application fields of laser shock processing, and summarizes the development and research results of laser shock processing. In view of the current situation of laser shock processing at home and abroad, some problems of the technology that need to be solved now are put forward. Finally, the application prospect of laser shock processing is forecasted.

In the complex background, the traditional saliency detection methods often encounter the problems of unstable detection results and low accuracy. To address this problem, a saliency detection method fused depth information based on Bayesian framework is proposed. Firstly, the color saliency map is obtained by using a variety of contrast methods which includes global contrast, local contrast and foreground-background contrast, and the depth saliency map is obtained by using the depth contrast method based on the anisotropic center-surround difference. Secondly, using the Bayesian model to fuse the color-based saliency map and the depth-based saliency map. The experimental results show that the proposed method can effectively detect the salient targets under complex background and achieve higher detection accuracy on the published NLPR-RGBD dataset and NJU-DS400 dataset.

Terahertz time-domain spectroscopy (THz-TDS) is a spectral detection method. The information of the material is measured through the broadband terahertz pulse carrying the medium information (such as amplitude and phase). The ceramic matrix composites and silica gel materials were tested with the detection method of transmission. The optical parametric models of the material were established, and the values of the refractive index and the absorption coefficient were extracted. The curves of the refractive index and the absorption coefficient with frequency were plotted. The refractive index of the ceramic matrix composites with different density are respectively convergent to a constant of 1.11, 1.14 and 1.16, and the refractive index of silica gel with different thickness is 2.1, which is not dependent to frequency. While the frequency dependence of the absorption coefficient is evident, and the absorption of samples with different material properties is significantly different. Based on the Gaussian error theory, the errors of the optical parameters are simulated and modeled. The experimental results show that there are several error sources in the optical parameters of the ceramic matrix composites with density of 2.8 g/cm3. The standard deviation of the refractive index and the absorption coefficient are obviously related to the frequency, and the standard deviation is in the order of 0.001, which is of great significance to the precise extraction of the physical parameters such as the refractive index and the absorption coefficient.

Aiming at the combined effects of the Exponentiated Weibull atmosphere turbulence, aero-optical effects and pointing errors on space optical links, the bit error rate (BER) performance of the orthogonal frequency division multiplexing (OFDM) optical communication link is investigated. OFDM links adopted PSK modulation. The closed-form expression for average bit error rate is derived based on a Meijer’s G function. The relationship between the BER performance and the transmitted optical power under different parameters such as the atmosphere turbulence, the normalized jitter standard deviation and the normalized beam-width is analyzed by simulation. The results show that the BER performance is similarly improved in different intensity turbulence by increasing the transmitted optical power. The BER performance is obviously improved by increasing the transmitted optical power when the normalized jitter standard deviation is less than 0.7 and the modulation order is less than 4.

In order to meet the unmet commerce needs of high pixel mobile phone, more and more designs come into being. According to the theory of ray optics, a 13 mega-pixel mobile phone lens was designed based on code V, an optical design software. It consists of five aspherical lenses and a filter. The F-number of the lens is 2.2, the half field of view is 35 degrees, the effective focal length is 3.6, and the total length of the lens is 3.6 mm. The MTF(modulation transfer function) of central field of view is greater than 0.6, the high frequency is greater than 0.2 and in the 0.8 field of view the middle frequency is greater than 0.4. In a word, the lens can meet the requirement of the high imaging quality camera.

Using compressive sensing technology in atmospheric turbulent wavefront detected data compression can greatly reduce the amount of measured data, can effectively reduce the pressure of data transmission and storage, which is good for real-time measurement of turbulent wavefront. However, the wavefront signal is required to be sparse or can be sparsely represented in one transform domain. In this paper, a preliminary study of the sparsity of the atmospheric turbulent wavefront gradient signal is carried out. Based on the statistical characteristics of atmospheric turbulence, the golden section (GS) is used to make the turbulent power spectrum in the frequency domain, and the sparse basis is established to meet the physical characteristics of the turbulent gradient, then the sparsity of the gradient of the turbulent wavefront is clarified. The sparse decomposition of the wavefront gradient is simulated by using the GS sparse base, and the sparse decomposition effect of different sparsity bases on the wavefront gradient is compared. On this basis, using the GS basis as the initialization training dictionary, K singular value decomposition (KSVD) dictionary training is carried out to get the training base (KSVD-GS), and then the sparse representation performance of this training base to the wavefront gradient signal is analyzed. This paper verifies that the wavefront gradient can be sparsely decomposed and build a better sparse basis, and provides the precondition for the application of compressive sensing.

The horizontal propagation steady-state thermal blooming effects of laser beams with different intensity distributions, such as Gaussian beam, flat-top beam, and flat-top beam with center obscuration, have been investigated by numerical simulation. The impacts of the output power, the propagation distance, the beam diameter, and the wind velocity vertical to the propagation direction on the steady-state thermal blooming have been discussed for the above mentioned three kinds of beams. Furthermore, the steady-state thermal blooming induced Strehl ratio degradation and peak intensity offset versus the generalized thermal distortion parameter N after long-path horizontal propagation of laser beams with above mentioned three types of intensity distributions have been derived. The simulation results show that, for certain other parameters, the greater output power or longer propagation dis- tance will induce the stronger thermal blooming, and the increment of the launch diameter or the convection wind velocity vertical to the propagation direction will weaken the thermal blooming oppositely. Furthermore, for laser beams with different intensity distributions, the impacts of the thermal blooming on the propagation are so different. Under the same generalized thermal distortion parameter N, the thermal blooming effect on the Gaussian beam is the most serious, followed by the flat-top beam, and flat-top beam with center obscuration is the smallest.

In order to solve the problem of weak signal, messy waveform at zero-point and difficult demodulation, when the optical Doppler vibrometer in the long-distance non-contact measurement, in this paper, a new type of optical fiber collimation system is proposed. The system mainly uses an augmented beam shaping system at the end of a small C-lens optical fiber collimator and the Gaussian beam is collimated and optimized by ZEMAX software. Through the coupling test of finished product of optical fiber collimation system, and compared with the signal coupling efficiency of C-lens collimator. The experimental results show that the improved collimation system can meet the working distance of 2 meters, and the coupling efficiency of space return optical up to 6.3%, which greatly enhances the Doppler signal contrast and improves the long-distance optical fiber Doppler vibration measurement accuracy.

To overcome the problem of a single image source, complex processing and inaccurate positioning, a visual identification and location algorithm based on multi-modal information is proposed, and the fusion processing is performed by extracting the multimodal information of the two-dimensional image and the point cloud image to realize object recognition and positioning. Firstly the target 2D image information is obtained by RGB camera. The contour is recognized through the contour detection and matching process. Then the image SIFT feature is extracted for location tracking and the position of the object is obtained. Meanwhile obtaining a point cloud image by RGB-D camera and the best model can be sorted through pre-processing, Euclidean cluster segmentation, computing VFH feature and KD-tree searching, identifying the point cloud image. Then the orientation is obtained by registering the point clouds. Finally, the two-dimensional images and point cloud image are used to process object information, complete the identification and positioning of the target. The effect of the method is verified by the robotic gripping experiment. The result shows that the multi-modal information of two-dimensional image and point cloud image can be used to identify and locate different target objects. Compared with the processing method using only two-dimensional or point cloud single-mode image information, the positioning error can be reduced to 50%, the robustness and accuracy are better.

Localized surface plasmon resonance (LSPR) provides an effective approach to further improve the performance of photodetectors. In this work, we introduce the Al nanoparticles (Al-NPs) on the surface of β-Ga2O3 thin film by rapid thermal annealing in order to improve the performance of β-Ga2O3 solar-blind ultraviolet photodetectors Al nanoparticles arrays, which can not only decrease the dark current but also enhance the responsivity and specific detectivity. As a result, the responsivity of β-Ga2O3-based metal-semiconductor-metal (MSM) solar-blind ultraviolet photodetectors with Al-NPs can reach 2.7 A/W, and the specific detectivity can reach 1.35′1014 cm×Hz1/2×W-1 under the 254 nm radiation and 10 V bias. Both parameters are more than 1.5 times and 2 times higher than those without Al nanoparticles, respectively.