Lasers demonstrate characteristics of high brightness and good monochromaticity. Moreover, the cost of liquid crystal display (LCD) planes are low as they have been developed extensively. Because of their excellent display performance, laser LCD televisions (TVs), which use lasers as their backlight, demonstrate strong market competitiveness and extensive market potential. The use of a light source array is a common technique for backlight system design. To limit the high power supplied by a single laser diode to an array, this study designed a scanning beam splitting system that divided the high-power laser beam into multiple sub-beams with sufficient power to provide a laser backlight for LCD TVs. The collimated laser beam in this system was initially scanned in two dimensions by a galvanometer scanner and then made to converge into a narrow linear beam by a convex lens and a cylinder lens; finally, it was coupled into an optical multimode fiber array. Thus, beam splitting was achieved. In addition, based on the scanning mirror and multimode fibers, the system also exhibited a speckle reduction effect. The experimental results demonstrated that the coefficient of variation in the average output power of 11 fibers is 16%, with an average value of 674.13 μW, and their average speckle contrast is 0.162.

To improve the accuracy of frequency measurement in a polarization modulation range-finding system, a method based on dual-directional frequency sweep was proposed. First, the principle of the ranging method and the relationship between frequency and ranging stability were analyzed. Then, factors influencing frequency drift, as well as the changing law of drift in the system, were discussed, and it was proved that modulation depth and thermally induced additional phase delay are important factors affecting frequency drift. Accordingly, a compensation method was proposed to compensate for the frequency drift caused by additional thermal phase delay, which can be realized with low modulation depth. Experimental results show that, for the target at 15.23 m, the standard deviation of frequency measurement decreased from 3.822 9×104 Hz to 5.807 5×103 Hz, the ranging error decreased from 7.513 7 mm to 0.866 7 mm, and the validity of the method was verified.

Free-space optical communication has many advantages over traditional communication. Improving the coupling efficiency of free-space optical communication (FSOC) receivers is of great significance for the quality of communication. We used tapered fibers in optical coupling. Based on the simulation results using the BPM algorithm, tapered fibers with low loss transmission were prepared using a fusion taper method. First, the mode field transmission characteristics of the tapered fibers and double tapered fibers were studied. Second, the difference in coupling efficiency and transmission efficiency between multi/single mode fused fibers and tapered fibers was studied using a static spatial light-fiber coupling experiment. The lateral offset tolerances of the coupling efficiency of these two fiber structures were also studied. The results show that the tapered fibers have good filtering characteristics for matching single-mode optoelectronic devices in the back end. They also have higher lateral offset tolerance characteristics than common fibers and a high transmission efficiency of around 70% that demonstrates low-loss transmission characteristics. Therefore, tapered fibers can be widely applied in the optical coupling of FSOC receivers and mode converters.

A frequency-doubling crystal is one of the most important light components in the inertial confinement fusion (ICF) facility. The principal section is closely related to the phase-matching angle and the absorption coefficient of the frequency-doubling crystal. To orient the principal section accurately, an indirect measurement method is presented based on light intensity. A measurement system was established using a laser, power stabilizer, half-plate, crystal, polarizer, and analyzer. The position of extinction, which was the principal section of the crystal, was obtained by rotating the polarizer and analyzer simultaneously. The Jones matrix model for the measurement system was deduced, and an expression formula for the relationship between light intensity, polarizer, and analyzer was derived. Through least squares curve fitting, the orientation of the principal section can be found. The validity of the model was verified using the simulation and experimental results. The test data show that the repeatability of orientation was better than 0.02°. The location accuracy of this method satisfies the requirements of KDP or DKDP frequency-doubling crystals in the ICF.

To improve the surface quality of polyimide (PI) optics, a polishing method for polyimide membranes based on Reactive Ion Etching (RIE) was proposed. The working principle and experimental research for the proposed method were discussed in this study. Owing to the low surface tension and mobility of the PR fluid, surface defects on the PI surface were required to be filled by a PR coating. In addition, owing to the highly anisotropic and identical RIE rates for PR and PI, the smooth PR surface could be precisely transferred onto the PI surface. The polishing of PI membranes then was realized. Experimental results indicate that for a surface roughness with PV of 1.347 μm and RMS of 340 nm, the respective values can be reduced to 75 nm and 13 nm after double polishing. Furthermore, for a surface roughness with PV of 61 nm and RMS of 8 nm, the values can be reduced to 9 nm and 1 nm, respectively. Hence, the proposed polishing method based on RIE can efficiently improve the surface finish of PI membranes, which in turn can provide novel schemes for precision manufacturing of PI-based flexible polymer devices.

To detect and locate the corona discharge of insulators quickly in unmanned aerial vehicle (UAV) power line inspection, a corona detection and location method for power lines in a UAVs track was investigated. First, the corona discharge power detection model was analyzed and established, and a formula for ultraviolet radiation power from a discharge source was obtained. Then, a corona detection device with high sensitivity was designed, and a positioning method for finding insulator defects in a UAVs track was developed. This method was used to detect the power line tower from two different angles. By comparing the two detection results, the position of the defective insulator could be determined. Finally, a method for electro spark and ultraviolet (UV) light-emitting diode (LED) detection based on location was designed. The results show that the detector can accurately detect the ultraviolet power produced by a spark. Influenced by the loss of UV light in the air, the measured value decreases with the increase of distance, and the relative error is within 11.5% at different distances. In the UV LED detection experiment, the measured values are more accurate when the detection angles are selected as 0° and 15°. In general, the method is accurate and effective in the detection of weak corona discharge, and it can meet the positioning requirements for defective power line insulators in a UAVs track.

To improve the high-temperature oxidation resistance of titanium alloys. Two kinds of Ti∶Al∶Si=41∶41∶18 (at.%) and Ti∶Al∶Si=35∶35∶30 (at.%) composite coatings were fabricated by laser cladding in-situ synthesis on TC4 titanium alloy. The microstructure and phase composition of the composite coatings were characterized by X-ray Diffraction (XRD), Optical Microscopy (OM) and Scanning Electron Microscope (SEM). The oxidation resistance of the coatings and the substrate sample under 800 ℃×24 h×5 times cycle oxidation condition was tested by tube resistance furnace. The mechanism of high-temperature oxidation resistance was analyzed by oxidation kinetics curves and oxidation mass gain. The results show that the cladding coatings are mainly composed of Ti5Si3, Ti7Al5Si12, Ti3Al, TiAl and TiAl3 phases, and there are no epitaxial columnar crystal structures as considered by a general laser cladding coating, all of which are fine equiaxed crystals. Under the condition of 800 ℃×24 h×5 times cycle oxidation, the weight gain per unit area of TC4 substrate is about 35.1 mg·cm-2, and the laser cladding composite coatings are about 2.8 mg·cm-2 and 3.3 mg·cm-2. The high-temperature oxidation resistance of the two kinds of coatings is 12.5 and 10.6 times higher than that of the titanium alloy substrate. The oxidation resistance of laser cladding in-situ synthesis Ti-Al-Si composite coatings has been significantly improved. On the one hand, the continuous dense TiO2, Al2O3 and SiO2 oxide layers have been obtained on the surface, which hinders the diffusion of oxygen and improves the oxidation behaviors. On the other hand, the adhesion of the oxide layer is improved so that the oxide layer is not easily peeled off from the coating surface and the non-oxidized portion of the coating is well protected.

Previously, ozone products could not be generated due to the abnormal solar irradiance for a total ozone unit (TOU) on FY-3C, because the instrumental degradation coefficient could not be measured. After investigating the irradiation measurement data and degradation trends of FY-3B/TOU and combining this with FY-3C/TOU radiance and irradiance data, methods for calculating instrumental degradation coefficients were explored based on clear ocean pixel data. An area in the atmosphere above the Pacific Ocean was chosen as a representative “clean” atmospheric sample, which is an area without pollution, to calculate the radiation from the earth and the model radiation with a vector radiative transfer mode. By selecting clear pixels and comparing measured and modeled values, the FY-3C/TOU instrument degradation with time was evaluated. On comparing the new total ozone results with WMO/WOUDC data, it is found that the change in the satellite monitoring data over time and the site results agreed well. Further, the mean square error of the two results is within 5%. Thus, the clear-sky pixels method for FY-3C/TOU works well and has the potential to solve problems regarding in-orbit radiation calibrations.

To improve the state control safety of a fuze and enhance its ability to resist electromagnetic interference, this paper proposes a silicon-based Micro-Opto-Electro-Mechanical Systems (MOEMS) arming device used in the miniature safety and arming system of a fuze. The device adopts two optical fibers as the carriers of energy transmission, and their misalignment and alignment are controlled through an electrostatic driving mechanism, which determines the safety and arming state of the fuze. The overall structure and coupled optical path of the MOEMS arming device are designed, and subsequently, it is manufactured through a silicon-on-insulator deep reactive-ion etching process. Through experiments evaluating the performances of the electrostatic driving mechanism and optical path, it is concluded that the displacement output of the electrostatic driving mechanism can reach 130 μm, the arming time and restore safety time are 13 ms and 5 ms, respectively, and the light energy transfer efficiency is 46.1%. The MOEMS arming device can satisfy the functional requirements of a fuze and it can have natural resistance to electromagnetic interference, which improves the intrinsic safety of the fuze.

High-speed magnetically suspended Turbo Molecular Pumps (TMPs) have been widely used in industrial applications for their high energy density, micro-vibration, and no lubrication requirements. However, the Active Magnetic Bearing (AMB) system will lose magnetic force once the main power fails, which may cause severe damage to the rotor and stator systems. In this study, an improved Power Failure Compensation Control (PFCC) method based on Average Power Balance Control (APBC) was proposed. First, a motor energy feedback circuit was designed. Then, a nonlinear controller consisting of double control loops was proposed, of which the fast inner current loop used Sliding Mode Control (SMC) and the outer voltage loop used APBC. The Lyapunov function was structured and analyzed to ensure system stability. Finally, a platform based on the high-speed magnetically suspended TMP was built. Several experimental results verify that the proposed PFCC method has fast response and robustness; meanwhile, the touchdown speed of the rotor is reduced to 3 900 r/min from the rated speed of 21 000 r/min with a higher energy conversion efficiency of up to 96.6%, which greatly improves the safety of the AMB system.

To build a ground simulation experiment system for an in-orbit assembly, based on cold gas propulsion, we design a three-degrees-of-freedom free-flying robot simulator, and analyze the structural design, gas path system, dynamic modeling, and control system of the simulator. First, we adopt a modular design to partition the main structure of the simulator for different functions. Second, according to the working principle, we analyze and verify the bearing capacity of the simulator through an experiment. Subsequently, we arrange the nozzle in a partially decoupled way with the entire air path system, which is further designed. Then, we analyze the factors that influence the thrust size of the nozzle theoretically and verify them experimentally. Finally, we use the Newton-Euler method to establish the dynamic equation of the simulator. Simultaneously, combined with Simulink and Adams, we build a control simulation model and perform a motion simulation. The experimental results show that the simulator can carry a weight of more than 800 kg, with a force of 8 N on a single side and an overall running time of 30 min. Through simulation, we observe that the simulator has a good tracking effect on the reference input. The designed simulator can provide a mobile carrier for ground experiments of a super-redundant modular manipulator.

To reduce the high costs of mirror polishing and opto-mechanical assembly, and to correct low-order aberrations caused by thermal and gravity deformation, the so called “warping harness” has been used to apply moment to the pivot of whiffletrees to achieve real-time correction of the mirror surface. Indeed, warping harnesses have been adopted in some large astronomical telescopes. This study aimed to optimize the layout of actuators that may be applied to large optical telescopes in China in the near future. Firstly, the correction ability of the warping harness was determined according to engineering experience and the wider literature. Secondly, integrated modeling of the segment support assembly was carried out using 3D drawing software. Finally, the layout of actuators was optimized using finite element simulation and the least-squares method. The results show that an optimized design of 18 actuators can correct aberration of focus, astigmatism, coma, and trefoil. The design of 18 actuators not only meets the requirements of optical design, but also has a lower cost and higher efficiency.

Traditional path planning methods of a free-floating space robot cause severe disturbance to the base satellite. To solve this problem, a path planning method based on the parameterization of control variables is proposed. This method transforms the path planning problem into an optimal control problem using minimum base posture disturbance as an objective function along with a series of constraints. The control variable parameterization method is used to discretize the problem, and the optimal control problem is transformed into a nonlinear programming problem. In addition, a complete theoretical convergence proof is provided. Thus, the optimal path of the end effector of the free-floating space robot can be accurately estimated. The simulation results indicate that the attitude disturbance of the base satellite caused by the motion path of the proposed method is 0.104 rad, which is 17.53% lower than that of the traditional method of decomposition acceleration, which verifies the effectiveness and optimality of the proposed path planning method.

In this study, a new high-efficiency and high-precision Z-pin pre-insertion based on a combination cam was developed to solve the problems, such as low efficiency, easy breaking, and slipping of Z-pin insertion. One of the aims is also to promote the application of the Z-pin composite technology in both military and civil fields. First, the functional requirements of the pre-insertion machine were analyzed according to the pre-insertion technology requirements of laminated composite members of the rectangle-type aviation. Second, the mechanism motion scheme of the “shear after implant” combined cam-type program was proposed for the pre-insertion machine. The cam mechanism of the pre-insertion machine was designed using the analytical method, and the theoretical profile curve of the cam mechanism was deduced. Third, the elastic dynamics model, including the clearance cam mechanism, was constructed. Next, the rotational speed of the combined cam was optimized, and its virtual prototype motion simulation was performed. Subsequently, the experimental prototype was designed and manufactured, and the correctness and rationality of the combined cam design were verified by conducting the implant experiment. The implant motion scheme was optimized according to the problems found in the experiment. The experimental results showed that the scheme could greatly improve the efficiency of the Z-pin implantation. Its efficiency reached 5 080 mm2/min, the implantation success rate was controlled above 99%, and the implant parameters such as the implant spacing, implantation depth, and fiber length were controlled within ±0.01 mm. Hence, the pre-implanting machine is easy to operate, human-machine interface-friendly, stable in long-term operation, and there are no problems such as Z-pin breaking, which can meet the current requirements of implant efficiency and implantation accuracy of Z-pin implanted devices.

To improve the servo bandwidth of fast steering mirrors with large stroke, a fast steering mirror with linear driving mode was proposed. Voice coil actuators were used to drive the fast steering mirror, and ball splines were used to constrain the direction of the drive, which transforms the traditional arc drive into a linear drive. First, the structure of a fast steering mirror driven by linearity was designed. Subsequently, the composition and characteristics of linear driving were analyzed. Subsequently, after the influence of the factors of the driving forms on the servo bandwidth was analyzed considering the constraint condition, the dynamic equations of the fast steering mirror with large stroke in the two driving modes were obtained. Finally, the mechanical resonance frequencies of the fast steering mirror were obtained through finite element analysis, and its servo bandwidths were verified through experimental tests. The experimental results indicate that, under the same experimental conditions, compared with the traditional arc drive, the resonant frequency of the fast steering mirror increases from 121.8 Hz to 229.9 Hz, and the servo bandwidth increases from 40.3 Hz to 75.1 Hz, indicating an increase of 88.8% and 86.4%, respectively. These results satisfy the design requirement of high servo bandwidth for fast steering mirrors in large stroke state.

To address the problem that the stiffness of the probe support mechanism cannot be changed during the measurement process using a traditional micro-nano measuring device, a micro-nano probe with variable stiffness was designed based on the constraint support of the suspension wire. A piezoelectric device was employed to drive the compliant guide mechanism, which produces a displacement. Thus, the axial tension of the suspension wire changed. Based on the principle of stress stiffening, the transverse stiffness of the suspension wire was changed, and the overall stiffness of the probe support mechanism was varied to obtain a novel micro-nano probe with variable stiffness performance. Depending on the stiffness variation of the probe support mechanism during the measurement process, the theoretical model of the Z-direction and the transverse stiffness of the micro-nano probe were established in the rigid and flexible modes, respectively. Based on the finite element simulation and the established theoretical stiffness model, the curve of the stiffness change of the probe versus the terminal force applied on the suspension wire was obtained. Comparing the simulated and theoretical values of the probe stiffness, the average relative errors of the Z-direction and transverse stiffness of the probe were observed to be 2.41% and 4.72%, respectively. This indicates that the theoretical model had high accuracy. The research results laid a preliminary theoretical foundation for variable stiffness control of this type of probe.

The terminal flight of the gliding missile involves high complexity, strong uncertainty, and many constraints. It is difficult to model and solve the corresponding trajectory planning and guidance problems. To increase the maneuvering range of the gliding missile and reduce the difficulty of trajectory planning, a multi-constrained trajectory intelligent planning method was proposed. This method included waypoint design and maneuverability prediction using the Continuous Deep Belief Network (CDBN). The CDBN was used to predict the maneuvering ability online, and the feasibility of the waypoints state was determined rapidly. With the intelligent design of the waypoints, optimized allocation of energy was realized, which increases the flight envelope. To realize oscillatory maneuvering, the Line of Sight (LOS) relative to the target was designed as a trigonometric function, which was tracked by designing the optimal maneuvering guidance law. Finally, the desired velocity constraint was satisfied by adjusting the frequency of the LOS angle. The simulation results show that the CDBN has higher maneuverability prediction accuracy than the BP network. The proposed method can realize oscillatory maneuvering and achieve a large increase in the flight envelope while satisfying the terminal velocity constraint. Online trajectory planning based on the CDBN can be completed in half a second, which satisfies the rapidity requirements for engineering applications.

Hyperspectral Image (HSI) always suffers from various noises such as Gaussian noise, impulse, stripe noise, etc. To ensure the performance of subsequent applications, a new method for HSI restoration was proposed based on weighted Schatten norm Low-Rank Representation (LRR). The proposed method introduced the LRR model into the HSI restoration. It can accurately approximate rank using the weighted Schatten norm instead of the nuclear norm. Furthermore, the initial noiseless image was utilized as the dictionary for LRR to improve the restoration ability. Then, the Laplacian regularizer was used to describe the intrinsic geometric information of the data and to protect details of the HSI. Experimental results on synthetic and real HSI data demonstrated that the proposed method achieves better visual quality and quantitative indices than several existing related methods. Compared with the classical restoration method based on low-rank priori, the mean peak signal-to-noise ratio and structural similarity indices of this algorithm increased by 2.74 dB and 0.03 respectively, and the mean spectral angle was reduced by 1.40. The new method not only takes advantage of the low-rank prior information in the spatial domain, but also keeps the intrinsic geometric structures in data, which helps restore quality clean images.

To meet the requirements of timeliness and reliability of the lunar rover system for obstacle detection, a semi-global stereo-matching algorithm based on the plane constraint and adaptive penalty coefficient was proposed. First, the Scale Invariant Feature Transform (SIFT) feature extraction and matching algorithm was used with two images of epipolar rectification from which edges are extracted. Second, the matched SIFT feature points were used to fit the plane, and the disparity search ranges of all pixels were estimated in the left and right images. Finally, based on the traditional semi-global matching algorithm, the adaptive penalty parameter strategy was applied to the stereo matching of the left and right images. Experimental results show that the algorithm can effectively reduce computational complexity to 19.9% that of the traditional methods. In addition, this method can obtain accurate matching results for the disparity discontinuous and occlusion regions. Compared with the traditional semi-global matching method, the processing speed and matching accuracy are clearly improved. This method can provide a foundation for further application.

Planar targets with circular marked points are widely used in camera calibration and visual measurement. To obtain the real circular center in the image of a planar target and improve calibration precision, a circular center extraction method based on dual conic geometric characteristics was proposed. The key to this method was that the dual conic matrix C*A of the marked point A in the image has a generalized eigenvector associated with the dual conic matrix C*B of the marked point B in the image, and this generalized eigenvector passed through the two center projections of both points A and B. As a result, after obtaining the subpixel edge points and fitting the ellipse conic function, a vector linking the two center projections could be computed by using the dual conic matrices of the two marked points, and the standardized interpoint of the eigenvectors would be the center projection. To test the extraction accuracy of center projection with the proposed method, the center projection of a huge marked point with a diameter of 90 mm is extracted when the relative angle between the charge-coupled device and the target plane is 40°, and the errors are found to be within 0.1 to 1 pixel. The camera parameters of a handheld scanner are calibrated with these center projections. A three-dimensional workpiece and a planar target with known marked points are scanned with the handheld scanner, and distance errors are within 0.2 mm. The extraction accuracy of this proposed method is higher than that of the elliptical center method and is superior to the precision of camera calibration.

The auto-focusing method has been widely incorporated in various optical instruments. To address the issue of auto-focusing for push-broom hyperspectral cameras, a method was proposed for estimating the optimal focus of a camera by employing a spectral quality evaluation function based on quaternion wavelet transform. A single line spectral data of the push sweep line was transformed into a two-dimensional matrix, and the matrix was subsequently decomposed into four low frequency and high frequency sub-bands. The spectral quality evaluation function was developed by incorporating the low frequency and high frequency amplitude and phase information for realizing the auto-focus feature. During the focusing process, the spectral quality metrics were calculated for different foci by rotating the lens at a certain stride length through an auto-focus mechanism. A Gaussian distribution function was fit between the spectral quality metrics and the extent of lens expansion and contraction, and the optimal focus was thereby estimated. Obtained results indicate that the proposed spectral quality evaluation function has superior sensitivity and accuracy. Furthermore, the proposed auto-focus method has superior accuracy owing to the usage of a single line of spectral data for focusing.

To examine the annealing effect of Single Event Upsets (SEU), a single device from a Low Earth Orbit (LEO) satellite running in sun-synchronous orbit for more than nine years was selected as a sample. The working temperature from satellite telemetry data was investigated, and details of the SEU nadir and time were discussed in relation to the geomagnetic field, F10.7, neutrons monitoring data, etc. By averaging the SEU time intervals, a model was developed to estimate the annealing characteristics, and this model was analyzed using telemetry data. The results of this analysis indicate that the SEU nadir occurred above the South Atlantic Abnormal area more than 67% of the time, more than 16% over the polar area, and less than 17% over the remaining areas. Moreover, the SEUs have the highest probability of occurrence (more than 38%) in August, September, October, and December. However, the probabilities are equal when one group of months spans April to September and the other group contains the remaining months. Furthermore, the SEU frequency is influenced by cosmic rays in the long-term when the sun is relatively quiet and by the sun in the short-term when the sun is relatively active. The annealing estimation shows that the mean time interval between SEUs is about 4.57 d, the annealing zero value is close to 1.56×10-13 d with an annealing factor of 7.94×10-15 d-1, and the degradation zero value is nearly 24.34 d with a factor of 0.12 d-1. The estimation results indicate that the annealing effect is approximately negligible.

In order to improve the efficiency and quality of aerospace software testing, an approach to cross-company aerospace software defect prediction was proposed, especially for the scarcity of within-company software and the long cycle of development. Considering the complexity, large scale, and independent functions of aerospace software, the idea of building a defect prediction model based on static classification was proposed. In this paper, the transfer learning method was introduced. Using the nearest neighbor classifier and data gravity model, the distribution characteristics of training data were corrected to improve the similarity between training data and target data. In order to improve the generalization ability of the model to adapt to the diversity of target data, a small amount of target data was added to the training data for model training. The approach was applied to the test for aerospace software testing. The results of application show that, compared with existing software defect prediction methods, the proposed method can effectively improve the recall rate (close to 0.6) with a low false alarm rate (not higher than 0.3). The overall credibility is effectively enhanced (G-measure is over 0.6), and the method has high stability and strong generalization ability. This method can control the test scale in practical projects and improve testing efficiency.

Based on the error relation of a group of typical characteristic points, the most favorable function relation between indirect measurement and direct measurement was established, and the error influence of other characteristic points was synthesized according to the error propagation theory. Finally, a new method of error step-by-step analysis of the PNP problem with complete azimuth, pitch, and tilt angle error analysis model was proposed. Taking the P4P problem as an example, the analytical formulas of the error functions of the related parameters and variables in monocular vision measurement were derived, and the error rules affecting the attitude measurement were revealed. The correctness of the error mathematical model and the validity of the step-by-step error analysis method based on error propagation theory were verified by the simulation of P4P attitude calculation. Under the determined measurement parameters of monocular vision condition, the error analysis model shows that the azimuth angle measurement error is independent of the azimuth angle value, and the error is proportional to the ratio of camera height to cooperative mark size. The pitch/tilt angle has little effect on the measurement error in a larger range. The pitch/tilt angle measurement error is related to pitch/tilt angle value, and the error is proportional to the square of the ratio of camera height to cooperative mark size. The measurement error of the azimuth angle is less than that of the pitch/tilt angle. The analysis method and error function analytical formulas can provide guidance for the design of a monocular vision measurement system.

Target detection for Hyperspectral Images (HSIs) is gaining importance owing to its important military and civilian applications. This study proposed a novel target detection algorithm for HSIs based on tensor representation. The algorithm employed tensor analysis including CP and tensor block decompositions to implement blind source separation on hyperspectral data. First, effective spatial and spectral features of the blocks of local images were extracted. Then, a detection model based on sparse and collaborative representations was established. Experiments were conducted to evaluate the performance of our approach under multiple scenes with complex backgrounds. From the visual representation of the results, it can be concluded that the proposed approach effectively extracts the spatial-spectral features from scenes with strong noise and complex backgrounds. The approach has good ability to suppress the background and the target is salient. In addition, the performance of the approach is evaluated using quantitative metrics such as Receiver Operating Curve (ROC) and area under the ROC curve (AUC). Considering the popular HSI image of San Diego as an example, the approach achieves 90% detection rate with a false alarm rate of 10%, and the AUC is greater than 0.95. Hence, our approach outperforms other popular approaches.

It is significant to realize effective single underwater image restoration for acquiring clear image in underwater exploration and underwater environment monitoring field. Most existing algorithms use dark channel priors to restore images, which lead to inaccurate estimates of the background light and transmission map. Hence, a novel method with adaptive background light estimation and nonlocal prior was proposed. Firstly, the candidate water light regions could be obtained by a threshold segmentation algorithm owing to the fact that water light regions have the properties of flat and high brightness. Then, the water light value could be decided from the candidate regions by the dominant tone of the input image. Secondly, the nonlocal prior was built to estimate the transmission map by taking into account the wavelength dependence of the attenuation. Finally, in order to remove the additive noise from the medium and microorganisms, a minimal optimization problem with the solution strategy of guided filter was proposed for obtaining the de-noising result. The experimental results verify that the proposed algorithm not only ensures operation efficiency, but can also estimate the correct transmission map. In general, the restoration precision has improved by 18% compared with the existing algorithm. It can be used in the engineering practice of restoring a single underwater image.