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Issue 1 ， 2018
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Calibration method of silicon 〈111〉 orientation and its application in fabrication of silicon grating by anisotropic wet etching
Abstract：Gratings with many types of groove profiles such as rectangles and triangles can be fabricated by wet etching silicon, during which a key step is to accurately align the grating line of the mask with the 〈111〉 orientation of silicon. Sidewall roughness can be visibly reduced by high-precision alignment, which is necessary for the fabrication of large grating structures. A fanned alignment pattern was designed and fabricated, which was then etched to accurately determine the 〈111〉 orientation of silicon. Aft Keywords：wet etching;silicon grating;calibration of crystal direction;anisotropy- 96
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Published：2020-08-13 -
A compact underwater Raman spectroscopy system with high sensitivity
Abstract：In order to reduce the volume and weight of the underwater Raman system, and to improve its portability and detection sensitivity, a compact underwater Raman spectroscopy system with high sensitivity was developed and assessed. Through elaborate selection of components, a compact structural design was realized with both the weight and the volume well controlled. The size of the main body was kept at 795 mm in length and 260 mm in diameter, with a weight of 548 N, one third of the weight of reported DORISS ( Keywords：Raman spectroscopy;underwater in-situ detection;compact;high sensitivity- 119
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Published：2020-08-13 -
Comparison of diffuse attenuation coefficient of downwelling irradiance products derived from MODIS-Aqua in the South China Sea
Abstract：The diffuse attenuation coefficient of downwelling irradiance Kd(490) is of great value for evaluating the coastal water quality and estimating the optical depth accurately. In this paper, the performance of MODIS-Aqua Kd(490) products derived using the algorithms of Muller, Werdell, Morel, Lee, and KD2M with MODIS-Aqua remote sensing reflectance Rrs(λ) and Chl-a products were compared in the South China Sea (SCS) based on the relaxed match-ups between MODIS-Aqua products and in situ data collected from 200 Keywords：optical remote sensing;MODIS-Aqua;diffuse attenuation coefficient of downwelling irradiance Kd(490);the South China Sea (SCS);accuracy assessment- 126
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Published：2020-08-13 -
Tunable mode-locked fiber laser pumped supercontinuum source
Abstract：In order to realize supercontinuum (SC) generation with broadband spectral range covering more visible wavelength, a pump wavelength tunable all-fiber SC fiber laser was experimentally investigated. A tunable nonlinear polarization rotation mode-locked fiber laser was proposed, which could output picosecond dissipative solitons pulse with nine different central wavelengths from 1 041 to 1 076 nm. After two-stage power amplifier, the tunable laser with relatively high power was coupled into 10 m long photoni Keywords：mode-locked fiber laser;supercontinuum;tunable;nonlinear polarization rotation- 93
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Published：2020-08-13 -
Sensing demodulation system using US-FBG spectral linear region
Abstract：To study a fiber grating sensing and demodulation system applied to satellites, ultra-short fiber Bragg gratings with grating length of less than 0.5 mm, reflectivity of over 40%, 3 dB bandwidth of over 5 nm, and the edge linear region of the reflection spectrum of over 2 nm were fabricated by the hydrogen enrichment of high germanium fiber and optimization of UV exposure power. A novel method was proposed to transmit the ultra-short FBG as a sensor and demodulate it by using its spectral linear region in t Keywords：fiber optics;optical fiber sensing;fiber Bragg grating;spectral linear region- 100
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Published：2020-08-13 -
Zoom lens design using mixed lens modules
Abstract：To facilitate zoom lens design, a systematic zoom lens design approach, based on mixed lens modules, is proposed in this paper, which consists of paraxial lens design, lens type determination, and aberration design. During paraxial lens design, Gaussian brackets and matrix optics are adopted, with which the relationship between component interval distances and component focal lengths can be easily determined. A lens module classification model is trained, with which the lens type can be determined from its Keywords：optical design;thin lens module;thick lens module;aberration design;zoom lens;telecentric lens- 108
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Published：2020-08-13 -
Design of mobile vehicle-based adaptive optical wave-front processor
Abstract：In order to meet the demands of a mobile vehicle-based adaptive optical system, the traditional wave-front processor hardware architecture was redesigned. In this study, we combined a wave-front processing board, wave-front processing daughter board and DA conversion board, using optical fiber for board communication. In this way, the reliability of the system was improved while the functional requirements were satisfied. Meanwhile, the wave-front processor is the computing center of the closed-loop control Keywords：adaptive optics;wavefront sensor;wave-front processing;Field Programmable Gate Array (FPGA)- 63
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Published：2020-08-13 -
Passively
Q -switched laser with a Yb: YAG/Cr4+: YAG/YAG composite crystalAbstract：In order to research the applied advantages of composite crystals to the passively Q-switched lasers, a compact diode-end-pumped passively Q-switched laser was built up with a Yb:YAG/Cr4+:YAG/YAG composite crystal for generating efficient 1 030 nm and 515 nm pulsed lasers. The effects of pump power and initial transmissionT0 on the laser properties were studied. As a result, a 1 030 nm laser with an average power of 1.97 W is obtained at T0 of 95% with slope efficiency of 33%, and the pulse peak power reach Keywords：laser diode;all solid state lasers;composite crystal;diode-end-pumped;passively Q-switched;frequency doubling- 131
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Published：2020-08-13 -
Optical path design of LED and GRIN lens projection system
Abstract：The existing Digital Light Projection (DLP) systems, in which the components such as color wheel and relay lens are used, resulting in a complex projection system. Aiming at this defection, a new DLP projection system was designed, where the three-color LED were used as the illumination light source and refractive index lens were used to produce the parallel light. Compared with the conventional projection system, components such as the color wheel, the relay lens, the mirror could be saved. Besides, the structure of the optical system was simplified. The simulation results and ray tracing by the Tracepro software show that the light spot uniformity reaches 96.9%. The results indicate that optical path of the projection system is simplified, and uniformity of the spot is also improved. The design only need to select the appropriate projection lens, that it can eliminate the influence of extended LED on the projection spot.Keywords：optical design;projector;gradient refractive index lens;Light-emitting Diode (LED)- 73
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Published：2020-08-13
Modern Applied Optics
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Comparison of diffuse attenuation coefficient of downwelling irradiance products derived from MODIS-Aqua in the South China Sea
Abstract：The diffuse attenuation coefficient of downwelling irradiance Kd(490) is of great value for evaluating the coastal water quality and estimating the optical depth accurately. In this paper, the performance of MODIS-Aqua Kd(490) products derived using the algorithms of Muller, Werdell, Morel, Lee, and KD2M with MODIS-Aqua remote sensing reflectance Rrs(λ) and Chl-a products were compared in the South China Sea (SCS) based on the relaxed match-ups between MODIS-Aqua products and in situ data collected from 2004 to 2012. Further, taking into account the unique optical properties of the SCS waters, the performance of Kd(490) products derived using the above algorithms with field reflectance Rrs(λ) and Chl-a data were evaluated in order to analyze the causes of the uncertainties of Kd(490) products and the necessity of regional algorithm optimization. The results show that MODIS-Aqua Kd(490) products derived using the algorithms of Muller, Werdell, and Morel with MODIS-Aqua Rrs(λ) and Chl-a products underestimated the in situ data, while the algorithms of Lee and KD2M overestimated the data, with average relative errors (APD) of 20.12%, 29.22%, 17.98%, 22.61%, and 21.61%, respectively. The algorithm of Morel performed the best, with a coefficient of determination R2 of 0.5. There are significant improvements in the accuracy of the above algorithms by using field Rrs(λ) and Chl-a data, especially for the algorithms of Werdell and Lee, with an APD of 5%-11% improvement. The algorithm of Morel performed the best, with an APD of 15.44%. It is necessary to choose the proper algorithm and conduct algorithm regionalization correction for the accuracy estimation of Kd(490) products in the SCS.Keywords：optical remote sensing;MODIS-Aqua;diffuse attenuation coefficient of downwelling irradiance Kd(490);the South China Sea (SCS);accuracy assessment- 49
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Published：2020-08-13 -
Passively Q-switched laser with a Yb: YAG/Cr4+: YAG/YAG composite crystal
Abstract：In order to research the applied advantages of composite crystals to the passively Q-switched lasers, a compact diode-end-pumped passively Q-switched laser was built up with a Yb:YAG/Cr4+:YAG/YAG composite crystal for generating efficient 1 030 nm and 515 nm pulsed lasers. The effects of pump power and initial transmission T0 on the laser properties were studied. As a result, a 1 030 nm laser with an average power of 1.97 W is obtained at T0 of 95% with slope efficiency of 33%, and the pulse peak power reaches to 87 kW at T0 of 85% with pulse width of 3.14 ns. In addition, in the frequency-doubled experiment with LBO, a green laser with higher output power of 634 mW is obtained at T0 of 90% with slope efficiency of 11.2% and pulse width of 15 ns. Finally, the red shift of spectrum and the leakage of output mirror were studied, as well as the method for increasing output power of green laser.Keywords：laser diode;all solid state lasers;composite crystal;diode-end-pumped;passively Q-switched;frequency doubling- 56
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Published：2020-08-13 -
Accurate and rapid contour extraction of visual measurement for rail wear
Abstract：In order to ensure the high precision of dynamic visual measurement of rail abrasion, image acquisition and image processing technology were used to get clear light-stripe image and extract the sub-pixel coordinates of the light-stripe accurately. First, according to the high contrast between the light-stripe and the background brightness, a method of automatic exposure of the camera based on the brightness of the light-stripe was proposed, which could ensure a clear image of the light-stripe. Then the dyna Keywords：visual measurement;automatic exposure;image processing;sub-pixel light-stripe center- 97
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Published：2020-08-13
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Measurement of residual stresses in pulsed laser deposited thin films
Abstract：To measure the residual stresses in thin films with limited area prepared by pulsed laser deposition, as well as to solve the problem of the relatively large error introduced by the Stoney equation under certain circumstances, a measurement method for residual stresses in thin films based on cantilever structures and numerical calculation was proposed in this article. In this method, atomic force microscopy probes with zero initial curvature were used as substrate cantilevers, and thin films were deposited Keywords：pulsed laser deposition;residual stress;vanadium dioxide;thin film;cantilever;numerical calculation- 85
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- 17
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Published：2020-08-13 -
Feed-forward compensation control of nonlinear friction for high acceleration motion system
Abstract：Modeling compensation of nonlinear friction is vital to improve the trajectory tracking performance of high acceleration motion systems. To overcome the problem of inaccurate estimation of the start-stop stage nonlinear friction (including friction overshoot) associated with the traditional parametric model for high acceleration motion systems, this paper describes a novel extended parametric model combining the traditional model structure with the extended Stribeck model. The training data for identifying Keywords：high acceleration motion;nonlinear friction model;feed-forward compensation;trajectory tracking control- 93
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Published：2020-08-13 -
Double-foot piezoelectric linear motor with secondary lever and flexure hinge composite structure
Abstract：In order to improve the rapid positioning of precision mechanical devices and the amplification ability of displacement amplification structures for the output displacement of piezoelectric stacks in piezoelectric linear motors, a new kind of double-foot driving piezoelectric linear motor with secondary lever and flexible hinge was proposed. First, the operating principle of the motor was analyzed and the trajectory equation of the driving feet was formulated. Next, the parameters of the straight circular f Keywords：double-foot piezoelectric linear motor;piezoelectric stack;secondary lever;flexure hinge;orthogonal test- 101
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Published：2020-08-13 -
Inverse dynamic modeling and control of spatial rigid-flexible parallel manipulator
Abstract：To improve the trajectory tracking performance of a spatial rigid-flexible 3-RRRU parallel manipulator, a nonlinear control strategy based on a multibody inverse dynamic solution by means of a transient kinematic correction method was proposed. First, the nonlinear inverse dynamics of a spatial 3-RRRU parallel robot with flexible links was developed according to both the Natural Coordinate Formulation (NCF) and the Absolute Nodal Coordinate Formulation (ANCF). The derived models consider the shear deformati Keywords：spatial manipulator;parallel manipulator;dynamics;multibody system;control strategy- 92
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Published：2020-08-13 -
Lens shutter for aerial photography
Abstract：In this study, a novel type of lens shutter with compact structure, reasonable layout and high reliability was designed for use in digital aerial photography mapping cameras. The double-blade shutter achieved the same shutter efficiency as a five-blade shutter. A coaxial gear train with different transmission ratios drives the double-blade rotation by miniaturized design, thereby controlling exposure. The speed of the blade is varied continuously by controlling motor speed, which helps attain the appropriate exposure. Simulation and experimental analysis of the shutter indicates that the range of shutter exposure time reaches 1/100 s-1/1000 s, and the shutter efficiency can increase to 85%. The shutter with wide exposure time and high shutter efficiency is found to have small effects on optical distortion, and sufficient stiffness to meet the camera requirements.Keywords：lens shutter;shutter efficiency;exposure time;distortion;shutter-blade- 131
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Published：2020-08-13 -
Deformation of glass sheet supported by gas bearing under optical testing
Abstract：There are strict requirements for the deformation of glass plate in the vertical direction in the process of on-line detection of LCD glass substrate. In order to determine the nozzle requirements in index spacing, the theoretical analysis of the LCD glass plate supported by gas suspension was carried out based on the small deflection bending theory of elastic sheet, and the LCD glass sheet maximum deflection formula under the action of the blowing and suction nozzles was derived. The analysis shows that th Keywords：glass substrate detection;continuous load;deflection;Fluent simulation;gas suspension- 110
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Published：2020-08-13 -
A novel inchworm linear micro actuator
Abstract：In consideration of the issues of small output force and low speed of inchworm linear actuator, a novel inchworm linear micro actuator based on compliant mechanism was presented. The micro actuator was composed of two clamping mechanisms, a driving mechanism and an output shaft. The movement was characterized by the drive mechanism, which drives the clamping mechanism to create reciprocating linear motion, and the clamping mechanism, which was driven by linear motion from the output shaft. The flexible leve Keywords：inchworm actuator;compliant mechanism;lever mechanism;pseudo rigid body method- 99
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Published：2020-08-13 -
Robotic grinding process planning for complex blade surfaces
Abstract：In order to realize intelligent grinding and machining of workpieces with complex surfaces, robotic grinding process planning for complex blade surfaces was performed.The position planning algorithm of the grind point and the posture planning algorithm based on the maximum contact principle were studied. First, the grind path was obtained through the secant transverse line cutting method and described by NURBS curve, and then the curve feature parameters were extracted and grinding position planning was per Keywords：Non-uniform Rational B-Spline (NURBS) surface;robotic grinding;position planning;posture planning- 93
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Published：2020-08-13 -
A frequency-selective surface structure arbitrarily switched between band-pass and band-stop responses at low frequency
Abstract：To obtain a frequency-selective surface (FSS) structure with band-pass and band-stop spatial filtering functions at low frequency in different time domains, a design method for switching between band-pass and band-stop responses of the FSS was proposed. It was consisted of mounting PIN diodes on the miniaturized FSS, which was designed based on a convolution technique, and utilizing EM/Circuit Co-Simulation for calculations and analysis. It was noteworthy that the convoluted pattern was not only the filteri Keywords：frequency selective surface;EM/Circuit Co-Simulation;PIN diode;bridge network- 73
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Published：2020-08-13
Micro/Nano Technology and Fine Mechanics
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Optimize-by-priority on-orbit task real-time planning for agile imaging satellite
Abstract：In order to realize quick response and effective detection in emergencies such as flight missing and natural disaster, an optimize-by-priority on-orbit task real-time planning algorithm based on priorities of targets was proposed. First, ground targets were divided into several priorities in order of importance, and the task planning was transformed to an optimization problem with objective of maximizing the imaging gain by analyzing constraints between target locations and satellite performance. Then, the Keywords：agile imaging satellite;on-orbit task real-time planning;optimize by priority;target selection- 70
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Published：2020-08-13 -
Full-waveform LiDAR data decomposition based on skew-normal distribution with unknown number of components
Abstract：To decompose asymmetric full-waveform LiDAR data with unknown number of components, a full-waveform LiDAR decomposition method was proposed based on skew-normal distribution and reversible-jump Markov Chain Monte Carlo (RJMCMC) algorithm, which can automatically determine the numbers of components. First, the energy function was used to describe the differences between the actual waveform and the ideal waveform that obeyed the skew-normal distribution, and the likelihood function was defined by Gibbs distri Keywords：full-waveform LiDAR;waveform decomposition;skew-normal distribution;RJMCMC algorithm- 111
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Published：2020-08-13 -
Planar feature extraction from unorganized point clouds using octree voxel-based region growing
Abstract：An efficient method for extraction of planar features from point clouds was proposed based on the concepts of self-adaptive octree voxel generation and voxel-based region growing. The proposed method involved the selection of correlated thresholds through statistics of voxel information. A voxel-based region growing approach was employed for planar feature extraction, instead of a point-based one. A point cloud was voxelized in initial voxel width and the geometrical features for each voxel were calculated, Keywords：point cloud;planar feature;octree;voxel;region growing- 94
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Published：2020-08-13 -
Face reconstruction fused with generic morphable model
Abstract：Stereo reconstruction from image pairs is a genetic method for 3D acquisition of human faces. Depending on available imagery and reconstruction algorithm, the resulting 3D reconstructions may have deficits. We improve generic morphable model and fused with stereo reconstruction to remedy such deficits. Firstly, we obtain the face bounding box by Max-Margin Object Detection, and recognition the face feature points directly from a sparse subset of pixel intensities by the Ensemble of Regression Treesmethod. S Keywords：3D-reconstruction;face morphable model;feature exaction;information fusion- 93
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Published：2020-08-13 -
Detection of small target in sea clutter based on spatio-temporal chaos analysis
Abstract：To improve the performance of the clutter suppression and small target detection, a detection algorithm for a small target in sea clutter was proposed, based on the spatio-temporal chaos analysis. First, the sea clutter phase space was reconstructed as a chaotic dynamical system, and the chaotic parameters of the sea clutter sequence image were extracted to verify that the sea clutter owns chaotic properties in the spatial and temporal domains. Furthermore, the spatial chaotic reconstruction function, the t Keywords：target detection;dim targets;sea clutter suppression;spatio-temporal chaos analysis;space-time coupling effect- 94
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Published：2020-08-13 -
Optical remote sensing image retrieval based on convolutional neural networks
Abstract：A method for remote sensing image retrieval based on convolutional neural networks was proposed. First, the convolution and pooling of remote sensing images were conducted by multi-layer convolutional neural networks. The feature maps of each image were obtained, and the high-level features were extracted to build the image feature database. In this process, the training of networks' parameters and the Softmax classifier were completed using feature maps. Then, in the image retrieval stage, classification w Keywords：remote sensing image retrieval;deep learning;image classification;convolutional neural networks;softmax classifier- 140
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Published：2020-08-13 -
Scanning control of spaceborne infrared imaging with super-swath and low distortion
Abstract：The relation between ground distortion and instantaneous field of view of the imaging system was analyzed; variable-speed scanning imaging was proposed and angular scanning speed formula was derived with infrared zoom scanning imaging system of super-swath low distortion in space as research object in this paper. Meanwhile, a kind of rapid fly-back method of sine acceleration was designed to solve the shortcomings such as low scanning efficiency of uniform 360° rotation, scanning line appliance needed to be Keywords：wide swath;low distortion;variable-speed scanning;sine acceleration;high scanning efficiency- 83
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Published：2020-08-13 -
Combined application of lightning detection data from satellite and ground-based observations
Abstract：Research on the lightning activities by taking advantage of the lighting detection data from satellite and ground-based observations is of great importance for lightning monitoring and early warning for thunderstorm. A satellite-based lightning imager can detect lightning signals over both ocean and land areas, and provide total lightning data including intracloud and cloud-to-ground lightning. However, a ground-based lighting location system usually gets the cloud-to-ground lightning. The two ways detect o Keywords：lightning detection;lightning imager;geostationary satellite;lightning density- 126
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Published：2020-08-13 -
Action recognition via restricted dense trajectories and spatio-temporal co-occurrence feature
Abstract：To overcome the limitation of improved dense trajectories for using in real environment, a novel human action recognition algorithm using restricted dense trajectories and spatio-temporal co-occurrence descriptors was proposed. Firstly, a human detector was applied to get the rectangular and the traditional dense interest points in the videos were refined via expanded rectangular box, which greatly reduces the number of trajectories while preserves the discriminative power. Then, the restricted dense trajec Keywords：action recognition;restricted dense trajectories;spatio-temporal co-occurrence feature;bag of visual words- 68
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Published：2020-08-13 -
Visual passive ranging system based on target feature size
Abstract：In order to overcome the shortage of traditional optical passive ranging system such as low stability, difficult to guarantee insufficient ranging accuracy in long-distance condition and difficult to reduce the system volume and weight, a method for visualization of optical passive ranging system based on target feature size was presented in this paper. Passive ranging model was established and ranging principle was analyzed. Theoretical analysis was carried out to obtain the distance inversion formula and Keywords：feature size;passive ranging;visualization- 65
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Published：2020-08-13
Information Sciences
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