Chinese Version Light学术出版中心
Latest Issue
Issue 6 ， 2021
-
Damage effect of TEA CO2 long wave infrared laser on detector assembly of infrared staring imaging system
Abstract：To explore the mechanism of damage caused to a HgCdTe infrared detector by a long-wave infrared laser， the damage caused by a 9.3 μm laser to an HgCdTe infrared detector was experimentally analyzed. A finite element simulation model of the HgCdTe infrared detector irradiated by the laser was established in ANSYS. The temperature rise distribution of the detector model under CO2 laser irradiation with a 9.3 μm pulse was obtained. The theoretical damage threshold of the detector was determined based on whether the melting temperature had been reached. Subsequently， the damage threshold of an HgCdTe infrared detector in an actual working environment was determined through field experiments. The results show that the damage threshold is 0.54-1.1 J/cm2. The simulation results， which predict a damage threshold of 0.69-1.23 J/cm2， and the experimental results are in agreement with the Bartoli theory and are thus considered to be valid.Keywords：infrared detector;finite element method;HgCdTe;TEA CO2 laser- 268
- |
- 61
- |
- 1
Published：2021-07-03 -
Crosstalk effects of IT-CCD irradiated by laser
Abstract：Crosstalk effect is one of the most important jamming phenomena that occurs when a CCD imaging sensor is irradiated by a laser beam. An interline transfer CCD was experimentally irradiated by a 532 nm laser beam. A series of crosstalk phenomena were observed， and the saturation threshold of CCD was calculated to be 0.32 mW/cm2. According to the working principle and driving pulse time sequence of an interline transfer CCD， we divided the crosstalk phenomenon into two overflowing processes： overflowing during the integral period and overflowing at the readout transfer moment. Crosstalk images were simulated based on this theory. First， laser intensity distributions on the detector surface were simulated based on the transmission transformation law of Gaussian beam. Then， photo-induced charge distribution was simulated by photoelectric conversion. It was followed by crosstalk charge distribution simulation based on the two overflowing processes. Finally， crosstalk images were obtained by simulating voltage detection and gray quantitative processes. The relative error of simulation was less than 40%， which shows that the simulation results are in good agreement with experimental results.Keywords：laser irradiation effect;crosstalk effect;charge coupled device;imaging sensor;image simulation- 135
- |
- 25
- |
- 1
Published：2021-07-03 -
Single quantity estimation method for single photon lidar dehazing imaging
Abstract：Conventional lidar cannot be used to extract a target signal from the strong backscatter noise in fog-penetration imaging because of the inherent detection and reception sensitivity limitations of lidar. Therefore， achieving the fog penetration effect is difficult. To address this problem， a novel single-quantile estimation method was proposed for the fog-penetration imaging algorithm based on Geiger-mode avalanche-photodiode lidar. According to the Geiger-mode trigger detection model， the backscattering distribution was obtained through the maximum likelihood estimation of the echo photon. Fog-penetration imaging was then achieved through subsequent extraction of the target echo position and backscattering noise suppression. The experimental platform of laser fog-penetration imaging was developed， and fog-penetration imaging under various fog conditions were performed. The results revealed that the single-estimation method outperformed the peak and double-estimation methods. When the attenuation coefficient was 0.11 m-1， the distance information recovery of the peak method increased by 8.26% and the target recovery degree decreased by 16.22%. When the attenuation coefficient was 0.86 m-1， the distance information recovery of the peak method increased by 86.86%， and the target recovery degree increased by 20.51%. When the attenuation coefficient was 2.37 m-1， the distance information recovery of the peak method increased by 253.19%， and the target recovery degree increased by 53.44%. A high degree of target restoration was achieved in signal-level dehazing by using the single-quantity estimation method.Keywords：lidar;Backscatter;Geiger-mode avalanche-photodiode （GM-APD）;Gamma distribution;Single quantile estimation- 203
- |
- 49
- |
- 1
Published：2021-07-03 -
Development of monitoring device for laser direction with small volume and long focus
Abstract：To accurately combine and launch several visible laser beam with different wavelengths， a compact optical monitoring device for beam direction was designed. First， main performances of the monitoring device were measured based on the application requirement of combining and launching laser systems. Subsequently， photo detect， optical system， and mechanism structure of the monitoring device were selected or designed using the application space of device. The length of the monitoring device was compressed considerably using the six times folding beams and upper and lower layered optical path. Finally， the monitoring device was tested for focal， modulation transfer function （MTF）， and monitoring accuracy by conducting experiments after carefully manufacturing， assembling， and adjusting. The results show that the designed monitoring device with low volume （200 mm×180 mm×140 mm）， long focus （approximately 1 002 mm）， and high monitoring accuracy （more than 10.0 μrad） can satisfy the application requirements of combining and launching laser systems.Keywords：optical system design;small volume;long focus;monitoring laser direction;modulation transfer function;monitoring accuracy- 113
- |
- 36
- |
- 1
Published：2021-07-03 -
Common aperture optical system of single photon laser and medium wave infrared
Abstract：A medium-wave-infrared （MWIR） and single-photon-laser common-aperture optical system was developed to realize target detection， tracking， and ranging of long-distance civilian aviation aircraft. In this study， the working principle of the laser/infrared common-aperture system was presented， and the target radiation characteristics， system operating range， and size of the aperture were analyzed. An R-C optical system with a dichroic lens as a secondary mirror was used to realize the dichroic design of the common-aperture system. A small aperture was set in the path of the single-photon laser， and the stray light suppression of the aperture was verified by modeling and simulation. High-precision assembly and line-of-sight calibration revealed that the laser/MWIR common-aperture optical system exhibited high-quality imaging. The modulation transfer function of the laser/MWIR optical system was measured to be 0.28（@20lp/mm. The prototype was used to detect and track a civilian aviation aircraft， and the results of the experiment revealed that the range of the common-aperture system exceeded 225 km. The proposed device can satisfy the application requirements for early warning and ranging of long-distance targets in aviation， aerospace， and ground detection.Keywords：optical system design;single photon laser;midium-wave infrared;common aperture;small aperture;long-distance detection- 250
- |
- 59
- |
- 0
Published：2021-07-03 -
Research progress of sub-nanosecond lasers for 3D imaging lidar
Abstract：Due to the advantages of high resolution and accuracy， compactness and high data rate， lidar has been widely used in the 3D information acquisition and atmospheric detection. The micropulse lidar could achieve the quasi continuous detection of the target， and improve the compactness and efficiency of the lidar system， which promotes its aerospace applications. A comprehensive overview for the development and the latest achievements of micropulse lidar and the employed laser sources is given in this article. The characteristics of high repetition rate， sub-nanosecond laser produced with different techniques are compared and the development of sub-nanosecond laser in micropulse lidar is predicted.Keywords：lidar;single-photon detection;Q-switched;laser amplifier- 200
- |
- 67
- |
- 3
Published：2021-07-03 -
Influence of laser communication Risley prism system error on pointing accuracy
Abstract：The error source of the Risley prism system is analyzed and used to establish the beam-pointing model by using the light vector propagation method. The beam pointing model is used to calculate the partial derivative of the pointing deviation of the output beam from the Risley prism system to each error in the system. In the pointing area， the influence of errors on pointing accuracy is analyzed according to the accuracy of each error. The simulation calculation results show that the maximum theoretical pointing deviation is 0.362 0°， and the theoretical root mean square deviation is 0.047 0°. The desktop experimental results show that in 99.54% of the pointing area， the maximum experimental deviation is 0.356 3°， and the experimental deviation root mean square of 0.023 3° is less than the calculated simulation value. This result shows that the error analysis of the Risley prism system is accurate and could be used as a reference for the design and compensation of the Risley prism platform.Keywords：laser communication;Risley prism;pointing model;error analysis- 184
- |
- 37
- |
- 1
Published：2021-07-03 -
Integrated guidance and control design considering angle of view constraint of strap-down optical seeker and input constraint
Abstract：This paper proposes a new type of guidance control for optically guided vehicles that considers the seeker’s field of view constraint and the actuator input constraint simultaneously. Specifically， to allow for a strapdown optically guided vehicle to strike a moving target against a background， we integrate the strapdown decoupling principle with the state constraint control method. This integrated design method follows three key steps： firstly， full strapdown guidance and control with strict feedback is modelled； secondly， an adaptive law for estimating the unknown upper bound square is designed for model uncertainty； thirdly， based on an integral obstacle Lyapunov function combined with dynamic surface control， the seeker’s field of view angle constraint problem is solved. Moreover， the actuator input constraint problem is solved using a smooth approximation to the saturation function in combination with the Nussbaum gain function. Finally， application of the Lyapunov theory proves that the design of the integrated guidance and control method is uniformly bound and stable. Numerical simulation results of typical scenarios show that this method can simultaneously meet the 8°， 8.5°， and 9° field of view constraints of strapdown optical seekers and the 10° input constraints of rudder actuators.Keywords：strap-down optical seeker;integrated design of guidance and control;line-of-sight constraint;input constraint- 113
- |
- 21
- |
- 0
Published：2021-07-03 -
Active disturbance rejection controller of fast steering mirror based on improved dragonfly algorithm
Abstract：To improve the tracking accuracy and anti-interference ability of fast steering mirrors （FSMs） in the photoelectric tracking and pointing systems of space-based laser weapons， an FSM closed-loop control system based on an improved active disturbance rejection controller （IADRC） was presented herein. Owing to the inefficiency of obtaining IADRC parameters via trial and error and the ease of determining local optimal solutions using traditional optimization algorithms， an improved dragonfly algorithm was investigated as the parameter adjustment method of the IADRC. The inertial factors， alignment factors and cohesion factors of the dragonfly algorithm were modified， and the worst elimination strategy and the greedy strategy were introduced in the early and later stages of the algorithm to enhance the exploration and exploitation ability. Finally， a PID controller， an IADRC based on the trial method， a genetic algorithm， a particle swarm optimization algorithm， an initial dragonfly algorithm， and an improved dragonfly algorithm were employed in an FSM to track a high-frequency sinusoidal signal under the vibration of a satellite platform. Results show that when the FSM tracks high-frequency sinusoidal signals， the root-mean-square value of the tracking error in the case of the FSM controlled by the IADRC based on the improved dragonfly algorithm is 7.596 μrad. This is a significant improvement over the tracking accuracies of the FSMs controlled by other five controllers and meets the requirements of FSM tracking accuracy in the field of laser weapons.Keywords：electro-optical countermeasure;laser weapon;fast steering mirror;improved active disturbance rejection control;dragonfly algorithm;parameter optimization- 205
- |
- 41
- |
- 0
Published：2021-07-03 -
Observational adaptive controller for photoelectric tracking platform
Abstract：To solve the incompatibilities between accuracy and high-speed target tracking capability， the control model of a servo system based on a photoelectric platform is established. By analyzing the benefits and limitations of the PID control strategy， an observational adaptive controller （OAC） is designed. First， the OAC employs an adaptive algorithm to improve tracking capability by adjusting the controller parameter values. Moreover， a proposed discontinuous observational projection of OAC controls the adaptive parameter values within the appropriate range that matches the current state. Thus， a state recognition approach is used to reduce the response time and suppress noise enlargement， and linear feedback can ensure robustness to external disturbances. Finally， the OAC adopts the method of arranging the transient dynamics in active disturbance rejection control to restrain the overshoot of the speed loop. Experimental results show that the dynamic error of LOS angular velocity by OAC is 0.05 （º）/s （standard deviation）， which decreases by 53% compared with the proportion control when tracking a target with a velocity of 12 （º）/s. In the case of a target with a speed below 10 （º）/s， the overshoot is controlled within 8% and the dynamic error is less than 0.046 （º）/s. The results indicate that the OAC can improve the tracking accuracy and adaptability of the photoelectric tracking platform.Keywords：Photoelectric seeker;servo system;Adaptive control;Tracking accuracy- 169
- |
- 41
- |
- 0
Published：2021-07-03
Optoelectronic Contermeasures Technology
-
Short coherent light source based on current modulation in semiconductor lasers
Abstract：Traditional interferometers use laser light source， because of the high coherence of laser， there are serious crosstalk in the measurement of parallel plate， prism and other special optical elements.Due to the characteristics of poor collimation， poor stability of light intensity and short coherence length， LED and tungsten lamps are also not suitable for the detection of interferometers with special optical elements. Short-coherent laser source has the advantages of good directivity， high brightness and moderate coherence length， and is an ideal source for detecting interferometers with special components.In order to meet the demand of short coherence interferometer， the coherence of current modulated semiconductor laser source is studied theoretically，the results show that the higher the modulation frequency and the greater the modulation intensity， the shorter the coherence length of the light source.The larger the bias current is， the higher the output power is， but the coherence will also be better， which is not conducive to the generation of short coherent light source. On this basis， a short coherent light source verification system is built to verify the correctness of the relevant theories.A short coherent laser source has been developed，the coherence length of the light source is 80 μm， the sidelobe rejection ratio of the light source decreased to 0.31， the output power of the light source can reach 30 mW， which can meet the requirements of short coherent measurement.Keywords：semiconductor laser;Short coherent light source;Coherent function;Current modulation- 132
- |
- 20
- |
- 0
Published：2021-07-03 -
Surface microstructure design of viewing angle deflection film based on extended light source
Abstract：To make a liquid crystal display used in the cockpit meet the special viewing angle requirements of the viewer， we designed a new type of optical film for deflecting the maximum brightness of the liquid crystal display from the frontal direction to a specific direction according to the position of the viewer. Using an extended light source， we propose a segment-weighted method for designing microstructures wherein the light from the different positions of the extended light source has different energy levels. The simulation results show that the horizontal viewing angle is unchanged， the vertical viewing angle is deflected by -15°， the light transmittance is 84.7%， and the half-brightness viewing angle range was （-38.4°， 4.4°）. An actual sample was fabricated using a maskless direct-write lithography process， and an effect test was performed. The test results show that the maximum vertical brightness was deflected from 0° to -16° and the half-brightness viewing angle is changed from （-23.8°， 27.4°） to （-43°， 9.4°） compared with the traditional backlight viewing angle. The transmittance is 83.0%， which meets the requirements of deflected viewing angle and brightness.Keywords：liquid crystal display;extended light source;segment-weighted method;surface microstructure;viewing angle deflection- 100
- |
- 20
- |
- 1
Published：2021-07-03 -
Improvement of phase unwrapping method for dual-frequency projection fringe
Abstract：To address the problem of abrupt changes during the phase unwrapping of fringes using the dual-frequency heterodyne method， we proposed an improved method in this study. First， the fractional part of the fringe order at a frequency was calculated based on the heterodyne principle， and the actual value of the current decimal part was calculated based on the phase principal value of the grating fringe corresponding to the frequency of the fringe order. Second， the difference between the decimal parts of the above two values was determined using a set threshold based on the inherent error of the phase principal value. Finally， the absolute phase was corrected by adding or subtracting the cycle number of the intermediate parameter based on the determination results. By adding Gaussian noise with different mean values and variances to the phase shift diagram of the simulated dual-frequency fringe pattern， and comparing the phase diagrams before and after correction， the correction rate of the improved method for phase jump errors was analyzed. In addition， the practical effect of the method was verified through actual measurement experiments of samples. The experimental results indicate that the improved method yields a correction rate of over 90% for absolute phase jump errors， with a high practicability and immunity to noise.Keywords：optical three-dimensional measurement;dual-frequency fringe;fringe order;phase unwrapping;phase jump;error correct- 162
- |
- 25
- |
- 2
Published：2021-07-03 -
Monocular vehicle pose estimation based on 3D model
Abstract：Vehicle pose estimation is an important component of intelligent transportation systems. However， the complex scenes and loss of depth information are challenging problems in the estimation. This paper proposes a method that combines monocular pose estimation and a 3D vehicle model to estimate vehicle pose. First， a multi-scale vehicle are normalized， and then the coordinates of key points are predicted in the form of a vector field to increase the accuracy of the pose estimation for the truncated and occluded vehicle. Furthermore， a distance-based loss function for the vector field and key point error minimization voting method is established to further improve the accuracy of the pose estimation algorithm. In addition， we propose a synthetic vehicle pose estimation dataset with rich annotation information. The verification results show that the average position and angle errors of our algorithm are 0.162 m and 4.692°， respectively. Our method provides significant improvements over existing methods and has considerable practical application value.Keywords：monocular vision;vehicle pose;three-dimensional model;vector field;key point- 115
- |
- 23
- |
- 2
Published：2021-07-03
Modern Applied Optics
-
Piezoelectric inertial actuator with “forward-forward” motion mode
Abstract：To solve the problem of backward motion existing in traditional piezoelectric inertial actuators， we designed an inertial piezoelectric linear actuator on the basis of the converse wiring method of double vibrators. The actuator operates in the “forward-forward” motion mode of the converse wiring method， which， in principle， completely eliminates the problem of backward motion. First， to better understand the motion characteristics of the actuator， we performed an in-depth analysis of the working principle of the actuator with the converse method and preliminarily developed a theoretical model. Next， we designed and fabricated a prototype and built an experimental system to perform a series of experiments to explore the motion performance of the actuator in the direct wiring mode （traditional wiring mode） and the converse wiring mode （proposed wiring mode）. The experimental results indicated that the backward/forward rate reached 0 under the forward-forward motion mode， the energy conversion efficiency increased from 2.16% to 2.60%， the average speed increased from 6.08 μm/s to 7.88 μm/s， the maximum deviation was 0.12 μm， and the standard deviation was 0.035 6. In general， the designed actuator has high stability and energy conversion efficiency， and completely solves the problem of backward motion， thus showing that it has great application potential in cell manipulation and other micromanipulation fields.Keywords：piezoelectric actuator;asymmetric clamping;no backward motion;converse wiring method;cell manipulation- 168
- |
- 28
- |
- 1
Published：2021-07-03 -
Failure analysis of electro-thermal micro-actuator under effect of process error
Abstract：In order to study the failure probability of a V-shaped electro-thermal micro-actuator， an uncertainty analysis of the temperature at the center of the actuator， where the highest temperature is located is performed based on its process error. The actuators that were fabricated at the same time are first measured. Then， the parameters are obtained when the width and resistivity satisfy the normal distribution. Moreover， the finite element model （FEM） of the actuator is established and validated by experiment， which ensures that the sample data used in the uncertainty analysis is accurate. According to the distribution of width and electrical resistivity and the non-intrusive polynomial chaos expansion （NIPCE）， the Hermite orthogonal polynomial is chosen for the chaos expansion. Its coefficient is obtained by the Gauss numerical integration method. Finally， the chaos polynomial model of the temperature is validated by the Monte Carlo simulation. The results show that the stochastic distribution of the highest temperature on the actuator is accurate， which is obtained by using the chaos polynomial model. The main distribution and mean value of the highest temperature increases with an increase in the voltage. Similarly， the probability of temperature failure of the actuator also increases with an increase in the voltage. When an 18 V voltage is applied， the failure probability of the actuator is 91.5%.Keywords：electro-thermal actuator;machining error;uncertainty;chaos polynomial;failure probability- 82
- |
- 13
- |
- 2
Published：2021-07-03 -
Fast calibration method of robot tool coordinate
Abstract：To address the problem of low precision or low efficiency in the calibration of a robot tool coordinate system， a fast calibration method of the tool coordinate system by a laser tracker is proposed. First， the structure of the robot end flange is analyzed based on the relative position relationship of each point on the flange. The laser tracker is used to calibrate the position of the tool coordinate system based on the principle of the geometric method. Second， the robot is controlled to move along the X- and Z-axes of the tool coordinate system， and the posture of the tool coordinate system is calibrated based on the relative position and posture relationship between the tool coordinate system and the flange end coordinate system. Finally， the calibration method based on the distance constraint proposed in previous studies is used to calibrate the tool coordinate system， and the accuracy is compared with that of the geometric method proposed in this paper. The experimental results show that the accuracy of the proposed calibration method can reach 0.692 mm， which is equivalent to that of the distance constraint method. Meanwhile， in the geometric method， the robot does not need to be moved； it only needs to measure six points at its end， to calibrate the position of the tool coordinate system. In addition， after the robot end is replaced with a new tool， the position of the new tool coordinate system can be obtained by measuring one point only. It shows that the proposed geometric method for a robot tool coordinate system calibration has high efficiency and high precision.Keywords：robot;tool coordinate system;geometric method;flange;laser tracker- 127
- |
- 20
- |
- 2
Published：2021-07-03 -
Deployment and Implementation of data cloud processing system for double-flank gear rolling test based on Javaweb
Abstract：To address the data processing problem of double-flank gear rolling tests in a cloud platform， in this study， the evaluation of radial composite deviations， deployment of cloud data processing systems， and design of cloud data processing software are investigated. The cloud platform for a cloud data processing system of a double-flank gear rolling test adopts the architecture of “Linux+Tomcat+MySQL+Java” and employs Java Web technology. Herein， the method of deploying a web application in a cloud platform is presented， the cloud data processing system of the double-flank gear rolling test is designed， and the data interaction between the client and cloud， and that between the instrument and cloud are realized. The key aspects of the software design include the network IP address， front-end access interface of the data processing software for the double-flank gear rolling test， database， and evaluation of radial composite deviations. Furthermore， the cloud processing system interface is presented， and evaluation experiments of radial composite deviations are conducted. Radial composite deviations can be obtained through the evaluation of the measurement data from the instrument end. For the sample of the measured product gear， the radial composite deviation was 32.7 and tooth-to-tooth radial composite deviation was 9.5 μm， with a grade 8 accuracy in accordance with the standard GB/T 38192-2019. Therefore， this study is expected to serve as a reference for the development of cloud data processing technology for precision instruments.Keywords：gear metrology;double flank gear rolling test;cloud platform;cloud data processing;Javaweb- 113
- |
- 21
- |
- 1
Published：2021-07-03
Micro/Nano Technology and Fine Mechanics
-
Spectral feature extraction of hyperspectral remote sensing images based on kernel class pair-weighted criterion
Abstract：To extract efficient nonlinear discriminant features when foreign objects， with similar spectra and outlier classes， are present in hyperspectral remote sensing images （HRSIs）， a kernel class pair-weighted （KCP-weighted） criterion is proposed. First， we derive a class pair form of the kernel linear discriminant analysis （KLDA） criterion， viz. the kernel class pair （KCP） criterion， in which the kernel-between-class and kernel-within-class scatter matrices are both expressed in the form of class pairs. Then， the KCP-weighted criterion is proposed to weight the kernel-between-class and kernel-within-class scatter matrices of each class pair according to their separability in a kernel space. The KCP-weighted criterion can ensure that the separabilities of class pairs are balanced in the KCP-weighted feature subspace. Finally， the K-nearest neighbor and minimum distance classifiers are used to evaluate the feature extraction performance. Experimental results of two real HRSIs show that， compared with the original space and KLDA methods as well as the kernel weighted pairwise Fisher criterion， the presented KCP-weighted criterion can effectively improve the overall terrain classification rate while reducing the dimensionality of the data.Keywords：kernel linear discriminant analysis;kernel class pair-weighted criterion;feature extraction;hyperspectral remote sensing images- 141
- |
- 24
- |
- 0
Published：2021-07-03 -
A novel image fusion method with fractional saliency detection and QFWA in NSST
Abstract：In traditional infrared and visible image fusion algorithms， some research problems such as inadequate detail texture information and insufficient edge information retention. Therefore， a non-subsampled shearlet transform （NSST） image fusion method based on fractional saliency detection and improved quantum fireworks algorithm is proposed. First， an NSST decomposition is performed for infrared and visible images， and the saliency detection is also executed on the basis of the fractional differential enhancement for low-frequency components， and then fusion is carried out according to the rules of the saliency map matching degree. The high-frequency subbands are merged by the gradient variation and gray difference weighting strategy. Second， the quantum fireworks algorithm is improved， and the high- and low-frequency fusion parameters are optimized by the improved quantum fireworks algorithm. Finally， the best fusion image can be generated. The experiment results showed that the saliency detection based on fractional differential enhancement can achieve good visual saliency. Moreover， the improved quantum fireworks algorithm has strong optimization ability and high convergence efficiency. As a result， the fusion image obtained by the proposed method effectively integrates the detailed information into the infrared and visible images. Compared with the existing methods， the proposed method realizes a better fusion effect with strong self-adjustment ability without any human intervention.Keywords：infrared and visible image fusion;non-subsampled shearlet transform;fractional differential;saliency detection;quantum fireworks algorithm- 185
- |
- 330
- |
- 3
Published：2021-07-03 -
Application of structured light coding measurement technology in Mars high-resolution camera
Abstract：Structured light coding measurement technology is typically adopted in the measurement of the three-dimensional topographies of components of the Mars high-resolution camera. Conventional structured light coding measurement technology employs the method of sine phase shift symmetry in combination with the Gray code， which easily produces periodic dislocation errors， significantly affecting the measurement accuracy. To eliminate the periodic dislocation error in principle， in this study， we propose an asymmetric structured light coding measurement technology. First， the concept of region encoding for four-step sinusoidal phase-shifting is proposed. Then， the sinusoidal phase-shifting is combined with cyclic code asymmetrically. Given that the cyclic code and region code vary with time， the cyclic dislocation error is reduced from one cycle to one pixel owing to the dual constraint of the cyclic code and region code. The simulation measurement results of the 3ds Max and the physical measurement results indicate that in comparison with the conventional measurement technology， the maximum measurement error of the asymmetric structured light coding measurement technology is relatively reduced by an order of magnitude， and the mean square measurement error is relatively reduced by 70%. The asymmetric structured light coding measurement technology effectively eliminates periodic misalignment errors and substantially improves the three-dimensional measurement accuracy.Keywords：3D measurement;encoding of structured light;asymmetric combination;cycle dislocation errors- 129
- |
- 33
- |
- 2
Published：2021-07-03 -
Calibration of cross structured light based on linear space rotation
Abstract：Aiming at the rapid and high-precision calibration of cross structured light in the measurement of complex surface features， we propose a cursor calibration method for the cross structured light based on linear space rotation. We used the Otsu thresholding algorithm to select the best threshold for extracting the area where the light bar was located， and the Steger algorithm based on the Hessian matrix and the least square method were able to extract and fit the center of the light strip. After the construction of feature point pairs in the image and the target plane， the random sample consensus （RANSAC） algorithm was used to solve the homography matrix， and a straight line was transformed to obtain the linear equation of the light bar in the target plane. The straight line was then converted into the camera coordinate system. From the rotation transformation relationship of the space straight line around any axis， the light strips were rotated around the projection centerline， and the two straight lines before and after the rotation were plane fitted to solve the light plane equation parameters. The results showed that the average error when using this method to measure the distance between the target centers was 0.023 mm and that the root mean square error was 0.026 mm. This method can achieve higher measurement accuracy and can avoid multiple movements of the target plane.Keywords：cross structured light;light plane calibration;homography matrix;linear space rotation transformation;computer vision- 118
- |
- 25
- |
- 0
Published：2021-07-03 -
Enhancement method of oceanic front features in SAR images based on nonpolarized components
Abstract：Owing to the sea surface motion， relatively low NRCS of the sea surface， and influence of the sea state， the oceanic front features in SAR images tend to be weak； this causes difficulties in subsequent applications. Therefore， it is imperative to develop methods for enhancing oceanic front features. The sea surface echoes received by SAR can be decomposed into Bragg scattering components and nonpolarized components. This paper proposes a method for enhancing oceanic front features based on these nonpolarized components. First， dual co-polarization （VV and HH） radar data are calibrated. To address the problem of noise enhancement during the extraction of nonpolarized components， the calibrated results are filtered. Subsequently， we calculate the Bragg model polarization ratio. Finally， the nonpolarized components are extracted based on the polarization difference and polarization ratio to enhance the oceanic front features. In this study， the ALOS PALSAR data are processed. Quantitative analyses are performed by calculating the peak-to-background ratio （PBR） and the equivalent number of looks （ENL）. The experimental results indicate that the PBR increased by more than 15% and the ENL increased by more than 30%， as compared with those for dual-polarization images. These experimental results prove the effectiveness of the proposed method， serving as the basis for subsequent applications.Keywords：oceanic front;nonpolarized components;features enhancement- 242
- |
- 512
- |
- 0
Published：2021-07-03 -
Multi-scale vehicle and pedestrian detection algorithm based on attention mechanism
Abstract：In complex and dynamic traffic scenes， accurate and timely detection of dynamic vehicle and pedestrian information by driver-less cars is particularly important. However， problems such as rapid camera movement， large scale changes， target occlusion， and light changes are encountered in unmanned driving scenarios. To overcome these challenges， this paper proposes a multi-scale target detection algorithm based on attention mechanism. Based on the YOLOv3 network， multi-scale local area features were fused and stitched by adding an improved spatial pyramid pooling module， so that the network could learn target features more comprehensively. Next， a spatial pyramid was used to shorten the information fusion and construct the YOLOv3-SPP+-PAN network. Finally， an efficient attention mechanism-based target detector， SE-YOLOv3-SPP+-PAN， was designed. Numerical results from the simulated system indicate that the SE-YOLOv3-SPP+-PAN network proposed herein achieved an improvement of 2.2% in mean average precision over the YOLOv3 network while retaining superior real-time reasoning-speed performance. This proves that the proposed SE-YOLOv3-SPP+-PAN network is more efficient and accurate than YOLOv3 is， and thus， it is more suitable for target detection in complex intelligent driving scenarios.Keywords：computer vision;vehicle and pedestrian detection;neural network;attention mechanism- 226
- |
- 64
- |
- 4
Published：2021-07-03 -
Template matching with multi-feature co-occurrence matrix
Abstract：Accurately identifying the target object in complex scenes （such as those involving partial occlusion， cluttered backgrounds， imbalanced illumination， and nonrigid deformations） is one of the difficulties involved in the study of template matching. To overcome the problem of precise matching under these conditions， we propose a co-occurrence matrix template matching algorithm based on multi-feature fusion. First， we extracted the color feature， depth feature， and HOG feature of the image. Thereafter， PCA and K-means clustering were used to realize multi-feature fusion. This method employs the co-occurrence matrix as its similarity measurement； this is different from traditional methods that directly use distance calculations. Finally， the matching score was calculated as the weighted sum of the probability of each window. Moreover， the region with the highest score was regarded as the best matching area. The area under the curve score of our algorithm was 0.658 6， which was 7.9%， 8.1%， and 20.2% higher than those of DDIS-D， DDIS-C， and BBS， respectively. The experimental results showed that multi-feature fusion is an effective approach for exploiting image information. With the aid of the co-occurrence matrix， the method can capture the similarities in image textures. Moreover， this measurement focuses on the co-occurrence statistics alone， rather than the actual pixels； this overcomes the impact of complex scenes on matching. The proposed method also achieves higher matching accuracy and better robustness than traditional methods.Keywords：image processing;template matching;multi-feature fusion;co-occurrence matrix- 202
- |
- 153
- |
- 2
Published：2021-07-03 -
Corrosion depth detection of tank top based on ultrasonic guided waves
Abstract：The method of inspecting and evaluating an oil storage tank currently focuses on the bottom and outer wall of the tank， and the roof the tank does not typically receive sufficient attention. However， the complicated structure and the unique physical and chemical environment lead to corrosion of the roof， which in severe cases may result in sudden failure or fire. Estimating the extent of corrosion of a tank roof is therefore of great significance. A new method based on the Lamb-wave reflection/transmission amplitude ratio is proposed to evaluate the corrosion depth. By analyzing the nonlinear modulation of guided waves in corroded materials， the relationship between corrosion depth and the reflected and transmitted wave amplitudes is obtained. Then， using the attenuation characteristics of guided waves， a theoretical expression for the ratio of reflected and transmitted signal amplitudes is derived. Numerical analysis and electrochemical corrosion experiments verified the relationship between the corrosion depth and the amplitude ratio. Using realistic experimental parameters and assuming a plate thickness of 3 mm， it is noted that guided wave attenuation factors （- 87
- |
- 19
- |
- 1
Published：2021-07-03 -
RUL prediction of aero-engine based on residual self-attention mechanism
Abstract：In this study， the remaining useful life （RUL） prediction algorithm based on the residual self-attention mechanism is employed to address the shortcomings of traditional neural networks in the context of multi-dimensional data high-resolution feature recognition and high-precision signal extraction. The structural characteristics of a convolutional neural network and long short-term memory （LSTM） neural network are compared and analyzed， whereby their limitations are revealed in terms of their long-sequence information feature correlation and local feature extraction abilities. Furthermore， as part of our research on the self-attention mechanism， we introduce a double-layer residual network to suppress the spread of the error function back propagation， following which we construct a deep learning method for the convolutional memory residual self-attention mechanism. Simulation analyses of the typical aviation aero-engine degradation experiment data set show that the proposed method can effectively establish the relationship between the monitoring data and engine health status. The obtained value of the key evaluation index， namely， the mean square error （MSE） of the RUL prediction， is 225. When compared with that of the traditional self-attention mechanism， the MSE in this case is reduced by 17.9%， which verifies the feasibility and effectiveness of the proposed method.Keywords：Residual self-attention mechanism;neural network;Remaining useful life;aero-engine- 141
- |
- 24
- |
- 0
Published：2021-07-03
Information Sciences
Loading...
0