Chinese Version Light学术出版中心
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Issue 2 ， 2016
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Measurement of strain coefficient of unequal cross-section FBG sensor based on double optical levers
Abstract：When a single optical lever is used to test the strain coefficients of Fiber Bragg Gratings(FBGs), slip effects may take place in the clamping part between the testing machine and the sensor. To effectively eliminate the slip effects and improve the test accuracy, a measurement system based on double optical levers was established to measure the strain coefficient of a FBG sensor with an elastic stress element by unequal cross sections. In the measurement, two optical lever mirrors were put respectively on the end faces of two fixed ends beside the sensor's elastic stress element. By measuring the relative displacement of two fixed ends, the equivalent strain coefficient of the sensor was obtained by data processing with the curve fitting method and cumulative average method. A simulation model was established, and the experiment and simulation were performed and compared. The results indicate that the equivalent strain coefficient of the sensor nεeff is 0.6817με/pm obtained by the experiment and the precision is 0.91%. Compared to the coefficient 0.6720με/pm from the software simulation, the difference is 1.42%. It is shown that the measurement method satisfies with the requirements for accurately measuring the strain coefficients of complex-structure sensors.Keywords：double optical levers;strain coefficient measurement;Fiber Bragg Grating(FBG) sensor;complex structure- 34
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Published：2020-08-13 -
Scannerless laser active imaging validating system by directly ranging
Abstract：To enhance imaging efficiency, a scannerless laser active imaging system by directly ranging was explored on the basis of an Avalanche Photo Diode(APD) array and a splitting beam illuminating method. A pulse laser was selected to be a light source, and the distant information of a target was obtained by measuring the time-of-flight of laser. A Dammann grating was used for illuminating by splitting beams to improve the usage efficiency of laser energy. Furthermore, a transceiving optical system with a common aperture was adapted to ensure the geometrical alignment between laser foot-prints and pixels of the APD array. Different from the constant threshold discriminator used in reference APD, a time discrimination method in combination of the constant threshold discriminator and the constant fraction discriminator was used to process the echo signal from APD array and to adapt the parametric variation of optical path. Moreover, dedicated time-detecting chip TDC-GP22 was used for each channel to test the interval between starting and stopping pulses, and to obtain the timing resolution of 45 ps.At last, an imaging experiment was conducted by choosing two corner reflectors respectively located in the distance of 19 m and 31 m as cooperative targets and the distant images were given. Result shows that the average distances of the two targets are 19.28 m and 31.54 m, respectively, and the distant errors are 0.28 m and 0.54 m. It concludes that the optical system and design method proposed are feasibility.Keywords：laser active imaging;scannerless imaging;directly ranging;illuminating with splitting beam- 88
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Published：2020-08-13 -
Estimation of detection range for space debris laser ranging system based on efficient echo probability
Abstract：Echo photon number equation is usually used to estimate the detection distance of a space debris laser ranging system. However, it can not exactly determine the minimum recognizable echo number threshold. In this article, a degradation model was proposed by degrading the echo sparsity of measured data to obtain a precision curve and to effectively evaluate the minimum recognizable echo probability with the precision guaranteed, and then to estimate the detection distance of the ranging system. Firstly, the relationship of efficient echo probability and ranging distance was obtained based on the "shutting down" effect of Single Photon Avalanche Diodes(SPADs). After that, the jumping curves of ranging precision and efficient echo probability were drawn based on experimental data. From the "jumping threshold" on "precision plateau" in jumping curves, the minimum recognizable echo probability was calculated and the detection distance for typical space debris with different sizes was obtained. The experiments for three typical space debris with Radar Cross Sections(RCSs) of 3.8840 m2, 6.3912 m2 and 9.8555 m2 were performed. The results show that the minimum recognizable efficient echo probability is 0.02-0.04 with the meter-level precision guaranteed and the maximum detection range for these typical space debris are 820 km, 1520 km and 2250 km correspondingly. This proposed degradation model effectively solves the problem for determining minimum recognizable echo probability, and reduces experimental costs.- 61
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Published：2020-08-13 -
Infrared dual band athermal optical system with common aperture
Abstract：A set of common aperture athermal catadioptric optical system with infrared dual bands is presented for 320×256 MWIR and LWIR staring focal plane array detectors. The system works at the wavelength of 3.7-4.8μm, 7.7-11.7μm, and the environment temperature of 10-40℃. Its working parameters are the effective focal length of 292 mm, field of view of 1.56°×1.875°, F/# of 1.93 and the cold shield efficiency of 100%. The LWIR system shares the primary mirror, secondary mirror and collimating lens with the MWIR system. The beam splitting of the MWIR and LWIR is achieved by a spectroscope and their aberrations are eliminated by correcting lenses respectively. The design principle, design process and some considering factors in engineering design moment are presented. By choosing appropriate optical materials, mechanical materials and assigning the optical power, the common aperture athermal catadioptric optical system obtains good image quality during 10℃ to 40℃. It shows good imaging quality, good machining ability, easy to be assemble, and suitable for engineering applications.Keywords：optical design;infrared optical system;dual band imaging system;common aperture- 98
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Published：2020-08-13 -
Evaluation of absorption measurement uncertainty of laser calorimeter by exponential method
Abstract：To better understand the absorption characters of fused silica in ultra-violet wavelength, a method to evaluate accurately the measurement uncertainty of a laser calorimeter was explored. The measurement principle of laser calorimeter was introduced firstly, and then the measured absorption data were fitted by the exponential method. After analysis of different effect factors on measuring results, a model for the measurement uncertainty was established, the estimated value and its standard uncertainty of the each input were calculated and the fitting calculation parameters A、γ effecting on absorption measuring results were corrected. By taking the influence of background temperature drift on the measurement uncertainty into account, the influences of linear and nonlinear temperature drifts on the absorption result were simulated by Matlab. The results show that the relative standard uncertainty and relative extended uncertainty of the laser calorimeter are 2.6% and 5.2% respectively. Finally, the absorption measurement was performed for several times by replacing fused silica substrates, and the average values of absorption measuring results for 10 times show the relative standard uncertainty to be 2.3% and relative extended uncertainty to be 4.6%, which are conform to that of evaluated results well.Keywords：measurement technique;laser calorimeter;exponential method;absorption measurement;uncertainty;temperature drift;fused silica- 50
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Published：2020-08-13 -
Polarization-independent 3 dB beam splitter in hole-type silicon photonic crystal
Abstract：A Polarization-independent 3 dB Beam Splitter(PIBS) based on a self-collimation Mach-Zehnder Interferometer(SMZI) in a hole-type silicon photonic crystal(PhC) is proposed and successfully designed. According to theoretical analysis, it shows that the SMZI can implement the polarization-independent beam splitting by utilizing polarization transmission matching method. Then, by changing the path length difference of the SMZI continuously, the same splitting ratio 1:1 of self-collimation beams for both transverse-electric(TE) modes and transverse-magnetic(TM) modes is obtained at the operating frequency of 0.1774c/a based on matching two polarization transmission spectra. This behavior of the PIBS is also numerically demonstrated with the magnetic-field distribution for TE polarization and the electric-field distribution for TM polarization calculated by the time domain finite difference numerical simulation software. The results show that the dimension of the 3 dB PIBS is only 16.7μm×16.7μm when its working wavelength is at 1550 nm. With its small dimensions, simple structure and single silicon material, this 3dB PIBS may have practical applications in future photonic integrated circuits.Keywords：photonic crystal;self-collimation;Mach-Zehnder interferometer;polarization-independent;beam splitter- 40
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Published：2020-08-13 -
Real-time color management for displays
Abstract：On the basis of the high switching speeds of dynamic images, a color management method implemented by hardware was proposed to ensure the consistency of color information of images on different displays. The principle of ICC color management was researched, and a non-uniform look-up table between the RGBs of displays was established based on a look-up table and interpolation method. The color management was realized by three dimensional interpolation with look-up tables and the self-adaptive rendering was obtained by judging the characters of images. Meanwhile, a real-time color management system was designed under a Field-Programmable Gate Array by proposed method. The experiments were performed for two displays. The experimental results indicate that the maximum/average color errors of two displays before and after using this system are 14.56/5.08 and 5.4/1.83ΔEuv unit, and the detail information of images is retained quite well by self-adaptive rendering. It concludes that the system implements higher precision color management for displays and satisfies the requirements for the precision, real time and stabilization.Keywords：display;color management;gamut mapping;Field Programming Gate Array(FPGA)- 50
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- 5
Published：2020-08-13 -
Calibration of binocular vision measurement system
Abstract：When traditional self-calibration methods are used to calibrate the cameras without scene information, it usually shows lower calibration accuracy. In order to solve this problem, an improved self-calibration method for a binocular vision measurement system was proposed. Without high-accuracy calibration pattern, the proposed method could calibrate intrinsic parameters and rotation matrixes only by using parallel and perpendicular lines to establishing the constraint equation between the camera parameter and the characteristic line. Meanwhile, the translation vector was calibrated by feature points with the known distances between them. The calibration experiment was conducted to verify the proposed method. It shows that the proposed method calibrates the binocular vision measurement system in high accuracy, the accuracy reaches to 0.51%. As the proposed method avoids the difficulties from the high-accuracy calibration pattern needed in the calibration of measuring system, and the complex algorithm and low calibration accuracy in camera self-calibration, it has advantages of easy operating and high accuracy.Keywords：vision measurement;large field of view;stereo vision;binocular vision measurement system;camera calibration- 78
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Published：2020-08-13 -
Design of precise tracking system of laser tracker
Abstract：This paper focuses on the total research of tracking servo control system of a laser tracker and gives a total design scheme. For precise detection of the miss-distance of a tracking target, new detection methods, fine adjusting technologies and digital filtering methods for weak photoelectric signals were explored, by which the detection stability for miss-distance of the tracking target could be better than ±2.0μm. To measure precisely tracking angles, a circular grating data acquisition system was designed, and the digital filtering, angle subdivision and accurate counting as well as data communication modules were achieved. According to the angle data, a tracking error compensation model was established based on harmonic analysis method, and the angle measurement precision was improved to 1.5″ from 3.5″. For tracking servo motor, a mathematical model was established to analyze the special function of current loop in tracking control process, then a three-closed-loop control structure including the current, speed, position and a compound tracking control strategy was proposed. The tracking experiment shows that the tracking distance and the tracking speed are not less than 41.7 m and 2.0 m/s respectively. The technology can also provide a useful reference for the dynamic target tracking, laser communication and so on.Keywords：laser tracker;miss-distance detection;angle measurement;tracking control- 65
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Published：2020-08-13 -
Effect of installation error of parasitic time grating on sensor measuring accuracy
Abstract：To improve the signal quality and angle measuring accuracy of a parasitic time grating sensor, the effect of installation errors of a discrete probe on the angle measuring accuracy of the sensor was researched.The structural components and working principle of parasitic time grating were introduced, and a 3D simulation model of parasitic time grating sensor was built. The Ansoft Maxwell simulation software was used to analyze the influences of different gap sizes between probe and rotor, the size changes of the pitch and yaw angles of the probe on the measurement accuracy of the sensor. Meanwhile, an experimental platform was built by using the 84-level parasitic time grating to verify the actual experiment. The simulation and actual experimental results show that the gap, the pitch angle and yaw angle of the probe in the installation errors all influence the accuracy of the sensor. The influence of gap variation on the measurement accuracy is regular and can be corrected by modeling. The optimal installation gap size of the researched 84-level parasitic time grating is 0.2 mm. Moreover, the modeling method of the pitch and swing angles affecting the accuracy of the sensors is built due to their complex changing principles. The acquired results can be used to research further on the structure optimization, precisely installation and error correction of the sensors and can improve the measurement accuracy of the sensor.Keywords：parasitic time grating;time grating sensor;angle-measuring accuracy;installation error;Ansoft Maxwell;Experimental verification- 66
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Published：2020-08-13 -
Design and experiment of valveless piezoelectric pump with triangular prism bluff body
Abstract：In combination of the rapid prototyping of 3D printing technology, a valveless piezoelectric pump in the micro-electromechanical system with a triangular prism bluff body was designed and fabricated.For the pump, a piezoelectric vibrator was used as its exciting source and a triangular prism bluff as its valve without moving parts. The working principles, theoretical flow and the vibration characteristics of vibrator were analyzed, and its flow expression was derived. Then, the flow resistance characteristics of triangular prism bluff body was simulated by using finite element method. On the basis of interior pressure distribution and flow speeds in the import and export of the pump, the flow resistances in positive and negative directions were analyzed qualitatively.Finally, an experimental prototype for the valveless piezoelectric pump was fabricated by using a 3D printing machine, and some experiments on flow resistances and flow rates of the pump were measured. The results show that the triangular prism bluff body has different flow resistances in positive and negative directions. The maximum flow rate of the piezoelectric pump obtained is 29.8 ml/min under peak-to-peak voltage of 550 V(8 Hz). The experimental results validate that the pumping performance of the valveless piezoelectric pump with triangular prism bluff body is excellent.Keywords：valveless piezoelectric pump;triangular prism;bluff body;flow resistance measurement;Flow rate measurement- 56
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Published：2020-08-13 -
Dual mode control for electro-optical tracking systems
Abstract：A dual mode control technology in combination of fuzzy control method with lag-lead compensation method was introduced to improve the response speed, anti-jamming performance and to reduce the overshoot of an electro-optical tracking system. The operation principles of fuzzy control method and lag-lead compensation method were introduced respectively. Based on the advantages of two methods mentioned above, the dual mode control system was designed. Then the MATLAB was used to perform the simulation experiments for the dual mode control system and corresponding actual experimental verification. The simulation results show that dual mode control technology reduces the overshoot of the system, improves the response speed of the system effectively and has a much better capability in anti-jamming as compared with the lag-lead compensation method. Furthermore, the actual experiment of the dual mode control technology was performed on an electro-optical tracking platform, the experiments by 180°step for azimuth subsystem and 60°step for elevation subsystem were carried out.The results show that the overshoots of both azimuth and elevation subsystems reach 0%, meanwhile their adjusting time and precision of steady state are improved. It concludes that the dual mode control method is characterized by faster responding speeds, small overshoot and higher capability in anti-jamming.Keywords：electro-optical tracking system;Dual mode control;fuzzy controller;lag-lead compensation- 61
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Published：2020-08-13 -
Electrochemical mechanical polishing of thin film solar cell flexible stainless steel substrate
Abstract：A novel method integrating electrochemical machining with mechanical action was proposed to polish the flexible metal foil to satisfy the requirements of thin-film solar cell flexible stainless steel substrate for lower surface roughness,higher light reflection rate and lower harmful impurity. Firstly,a compound cathode was designed and manufactured for machining flat surfaces,meanwhile its mechanism on the material removal was analyzed. Then,the electrochemical corrosion behaviors and friction effects were analyzed based on the Faraday law and adhesion friction theory, by which the match action between electrochemical corrosion and mechanical action was resolved. Finally,taking the 304 stainless steel sized 50 mm×50 mm×0.3 mm as the workpiece,an experiment was conducted to demonstrate above analysis. The results show that the surface roughness has changed from Ra124 nm to Ra10 nm and the reflection rate changed from 56.8% to 62.4% after polishing time of 20 min. Moreover, a metal oxide layer(Fe2O3,Cr2O3) is formed, which blocks the diffusion of Fe and Cr. These results indicate that the method proposed has higher efficient and economical to process thin film solar cells with flexible stainless steel foils.Keywords：composite electrochemical polishing;thin-film solar cell;flexible substrate;stainless steel foil;material removal;adhesion friction;reflectivity- 48
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Published：2020-08-13 -
Morphologic control of wet anisotropic silicon etching
Abstract：For fabrication of microaccelerometers with beam-mass structures, an anisotropic wet silicon etching technology based on ternary TMAH(tetramethyl ammonium hydroxide) solutions containing Triton and IPA was proposed and corresponding etching characteristics was investigated. The underlying mechanism between two kinds of additives(the Triton and IPA) and its effect on the wet silicon etching were analyzed. The appropriate ratio of additives was chosen to control the etching morphology. By a combined action of two kinds of additives, a mirror-like finish surface(Ra≈1 nm) and high reduction of undercutting(the ratio of undercut at the convex corner less than 0.8) were achieved synchronously. The experimental results show that the etched morphology has been dramatically improved by the ternary solutions. Furthermore, the reasons affecting the etched morphology were discussed, and the underlying mechanism on hydrophobic silicon surface, surface tension adjustion and the reciprocity between surfactant and alcohol were used to explain the new etched characteristics. Finally, by taking fabrication of a spring-mass structure for an example, the proposed method is verified by obtaining a very smooth cantilever and a complete mass structure without convex corner compensation. As compared to some other fabrication techniques, this method is very simple, easy to operate and useful in improving the quality of devices.Keywords：silicon;wet etching;morphological control;ternary solution;surface roughness;convex corner- 63
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Published：2020-08-13 -
Analysis of detection signal for magnetostrictive displacement sensor
Abstract：The detecting voltage signal of a magnetostrictive displacement sensor was experimentally studied to improve its detection accuracy. The effects of waveguide wire materials, driving pulse currents, and detecting coil parameters on the detecting voltage signal were analyzed and confirmed. The detecting coil was designed optimally and the parameters for the magnetostrictive displacement sensor were determined. The research shows since the Fe-Ga waveguide has a larger magnetostrictive coefficient and remarkable Weidmann effect, it improves the electric-magnetic-mechanical conversion efficency and obtains more detecting voltage signals. Based on the experimental results, a new type of magnetostrictive displacement sensor with the Fe-Ga waveguide wire was fabricated and its performance was compared with that of a magnetostrictive displacement sensor with the Fe-Ni waveguide wire. The research shows that the detecting signal for the magnetostrictive displacement sensor with the Fe-Ga waveguide wire is obviously enhanced and the signal-to-noise ratio is improved significantly as compared with that with the Fe-Ni waveguide wire. Moreover, the detecting voltage signal amplitude for the magnetostrictive displacement sensor with the Fe-Ga wire increases 40 mV and its detection precision may be 2 times that of the sensor with the Fe-Ni wire.Keywords：displacement sensor;magnetostriction;Fe-Ga material;waveguide wire- 51
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Published：2020-08-13 -
RPY modeling and error calibration of flexible measuring arm
Abstract：An adaptive error calibration method was proposed to complete parameter calibration and error compensation to realize the high accuracy test for a 1P3R flexible measuring arm. Firstly, a kinematic model of 1P3R flexible measuring arm was built based on RPY theory and a differential method was used to deduce the error model of system. Then, the real number encoding was performed based on the theory of Markova chain convergence. Adaptive control factors were added to Genetic Algorithm(GA) to improve population diversity and the quantity of the best individual. Finally,the calibration accuracy and convergence performance of a normalized GA, a general GA and least square method were compared and analyzed and the results were used to verify the feasibility and effectiveness of the proposed method. It shows that the accuracy of the normalized GA has been enhanced from 3.1μm to 5.2μm just after 328 generation searching, and its convergence velocity is 2.3 times that of the general GA. Moreover, the convergence of least square method is stopped after 20 generations and its calibration accuracy is only 18.4μm. Experiments indicate that normalized GA is characterized by some advantages of fast convergence speed, high calibration accuracy and better stability. It is suitable for measuring these kinds of flexible measuring arms in high accuracy.Keywords：flexible measuring arm;RPY theory;normalized Genetic Algorithm(GA);error calibration- 55
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Published：2020-08-13 -
Suppression of random vibration response of optical satellite by matching honeycomb stiffened plates' structural parameters
Abstract：To implement the optimal matching of structure parameters, a new idea was proposed to improve the vibration environments of optical satellites. As the random response of a honeycomb panel was far beyond the normal range in a satellite vibration test, adding several enforced ribs on this panel was proposed to reduce the response. The function of the enforced rib in reducing the response of simply supported honeycomb panel was researched. The characteristics of honeycomb panel structure in the optical satellite were introduced, and the random excitation load of the optical satellite and dynamic response of the honeycomb panel under this load were also discussed. According to the entire satellite structure, a method to reduce the honeycomb response by adding H enforced ribs on the panel was proposed. In order to study the function of the enforced rib, the finite element method was used to verify the random vibration of the honeycomb panel model with a size of 1000 mm×1000 mm×30 mm. The analysis results show that the H enforced ribs reduce the response of the honeycomb panel obviously. Finally, the satellite finite element model was improved by the vibration test results and its dynamical analysis and optimization was performed. The analysis results show that the response has reduced to 40%, being an acceptable level, which verifies that the H enforced rib is a good choice to reduce the response of simply supported honeycomb panels on optical satellites.Keywords：optical satellite;honeycomb panel;random vibration;vibration test;H enforced rib- 68
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Published：2020-08-13 -
Dynamic linearity calibration system for accelerometers with high measurement range
Abstract：A dynamic linearity calibration system, dual warhead Hopkinson bar,was designed to calibrate the dynamic linear parameters of a micro accelerometer with high measurement range accurately. On the basis of one-dimension stress wave theory and elastic wave superposition principle, the influences of the dual warhead Hopkinson bar with different sizes on the required acceleration signals were analyzed. The ANSYS/LS-DYNA was employed to simulate the shock effect of the dual warhead Hopkinson bar under different design conditions. According to analysis and simulation on different factors, the design parameters were determined. Then, a dynamic linearity calibration system(dual warhead Hopkinson bar) for accelerometers with the diameter of 30 mm and the length of 1200 mm was designed. The dual warhead Hopkinson bar was used in the dynamic linearity calibration of an accelerometer with high measurement range. The results indicate that the dynamic linear error of the accelerometer is within 5%, which verifies that the dual warhead Hopkinson bar designed is feasible for dynamic linearity calibration of the accelerometers with higher measurement ranges,and the calibration results satisfy the requirements of shock calibration.Keywords：accelerometer;Hopkinson bar;dual warhead;dynamic linearity calibration;ANSYS/LS-DYNA;stress wave- 45
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Published：2020-08-13 -
Three-dimensional coordinate evaluation method of gear errors
Abstract：A three-dimensional coordinate evaluation method for gear errors was explored to eliminate the influence of positioning error of a measurement instrument on the measurements and evaluations of a gear and to improve the measuring accuracy. The traditional two-dimensional gear error evaluation method was analyzed, and then the gear error evaluation model was changed from two-dimensional evaluation model into three-dimensional evaluation model. In the three-dimensional evaluation model, the measurement points of gear error were not required in the characteristic surface, and error measurement and evaluation of gear could be realized in a three-dimensional space. Furthermore, to improve the efficiency of three-dimensional evaluation algorithm of gear errors, three-dimensional data were reduce to two-dimensional data by using spiral dimensionality reduction method, and the error evaluation of two-dimensional measurement data were carried out. By taking the in-site measurement system with laser tracker for megagear as an experimental object, the profile error of a 4 level standard gear was measured, and obtained results were compared with that of the traditional two-dimensional gear error estimation method and the evaluation results from the InvolutePro software of German ZEISS company. The experimental results indicate that the traditional two-dimensional evaluation method has a bigger error, but the proposed three dimensional evaluation method can obtain the same evaluation results with the software of InvolutePro of German ZEISS company, and the algorithm precision reaches 0.1μm. The results verify that proposed three dimensional evaluation method is correct. It eliminates the influence of instrument positioning precision on gear error measurement and improves the measurement precision of gear measuring instruments.Keywords：gear measurement;positioning error;three-dimensional evaluation;spiral dimensionality reduction method- 56
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Published：2020-08-13 -
Micro-mechanical behavior and machining property for tripler plane of KDP crystal
Abstract：To reveal the micro elastic-plastic mechanic behavior and the machining property of tripler plane of a potassium dihydrogen phosphate(KDP) crystal, the nano-indentation process was researched. An anisotropic mechanical model for the tripler plane of KDP crystal was established. Then the nano-indentation numerical simulation based on Smoothed Particle Hydrodynamics(SPH) method was performed and the nano-indentation experiments were accomplished. The results indicate that the correlation coefficient between the experimental load-indentation depth curve and the simulation one is 0.996328, showing a higher goodness of fit and verifying the correctness of the mechanical model. Moreover, the yield strength of tripler plane of the KDP crystal is 240 MPa. Because of the anisotropy property of the material, the stress inside the workpiece is irregular arc shape distribution, and the relationship between the magnitude of load and the influence depth of equivalent stress is an approximate linear increasing. The distribution shape of equivalent plastic strain on the material surface is similar to the geometrical shape of the indenter projective plane, which verifies that the reflection effect exists. When the load is lower than 2 mN, the differences of the residual stress's depths among the indenters are less than 0.2μm. As the load increases gradually, the differences are widening. The research results provide theoretical supports for machining the tripler planes of KDP crystals in high efficiency and low damage.Keywords：potassium dihydrogen phosphate(KDP) crystal;tripler plane;nano-indentation;Smoothed Particle Hydrodynamics(SPH);numerical simulation- 42
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Published：2020-08-13 -
Stellar image registration based on mutual information in object area
Abstract：A measuring algorithm based on mutual information in an object area was proposed to register stellar images with noises, pseudo stars, sparse stars and the rotation between the images. Firstly, a stellar image was segmented to extract star points in the stellar image and the star points were processed with binarization. Then, on the basis of the mutual information model, the Powell algorithm was used to guide the search of the best transformation parameters in the object area by taking the maximal mutual information as the aim function. Furthermore, the star segmentation method suitable for the proposed stellar registration algorithm was analyzed and the feasibility of the proposed algorithm was verified. The proposed algorithm was compared with normal mutual information registration algorithm, and the results show that the time consuming is relative to the number of stars in image, and the speed up ratio is up to 3.4 times that of the normal mutual information registration algorithm when the image size is 1000×1000. Experimental results demonstrate that the proposed algorithm achieves a high precision stellar registration with noises, pseudo stars, sparse stars and rotation. The average error of 50 groups of real stellar images is 0.1382 pixel. It concludes that the algorithm meets the requirements of space target detection for image registration.Keywords：stellar image;star object area;mutual information;image registration- 49
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Published：2020-08-13 -
Automatic printed circuit board wire detecting method of cone beam CT image
Abstract：The CT image of Printed Circuit Board(PCB) exists problems in grey inhomogeneity, changeable and irregular wire shapes, so it is difficult to be detected efficiently. This paper proposes an automatic PCB wire detecting method based on superpixel segmentation. The comparably top-hat transform based on a guided filtering was used to preprocess images and to improve the interclass difference of different regions and the subsequent superpixel segmentation results. Then, the graph-based segmentation algorithm was selected to achieve the wire positioning. Finally, the wire region was identified by using the geometry and grayscale distribution features of the wire to implement the wire detection. The experiments for the PCB CT images with inhomogeneity grey, multi-wire and multi-scales were performed. The results show that the algorithm is able to overcome the intensity inhomogeneity of PCB CT image and achieves a better result with a detection rate more than 90%. It concludes that the algorithm satisfies higher precision and strong anti-jamming requirements for automatic detection of the wires of PCBs and has high application values.Keywords：CT Image;Printed Circuit Board(PCB);wire detection;top-hat transformation;superpixel segmentation- 63
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Published：2020-08-13 -
Calculation of overlapping pixels in interleaving assembly for CCD focal plane of space camera
Abstract：The focal plane of a wide-field space camera is comprised of several staggered Charge Coupled Device(CCD) detectors.To eliminate the gap in imaging field of the space camera,this paper proposes an analytic calculation method for overlapping pixels applied to multiple maneuvering angle modes. The imaging characteristics of CCD interleaving assembly and the reason that imaging gaps appear were analyzed. Then, the calculation model for overlapping pixels was established by combining space coordinate transformation with a collinearity equation. The dynamic mathematical relationship of the image point, camera center and the ground point was established. The overlapping pixels between adjacent CCDs were calculated by tracing the locus of image point on the image plane. With an engineering example, the influence of maneuvering angle, subastral latitude and the field location of the space camera on overlapping pixels was calculated and analyzed and the maxmum number of gap pixels calculating among different working situations were considered as mechanical assembly numbers. The result shows that the theoretical error of the number overlapping pixels is less than 1 pixel. Comparing with scrolling imaging, the pitching imaging needs more number of assembly pixels. The computing model can be applied to other space cameras of different types, and the overlapping pixels can be calculated at any attitude mode.Keywords：space camera;Changed Coupled Device(CCD);interleaving assembly;overlapping pixel;collinearity equation- 71
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Published：2020-08-13 -
Evaluation of MTF for FY-2G middle infrared band based on moon observation and image restoration
Abstract：For improving the spatial resolution of FY-2G middle infrared band, this paper proposes a method to extract the edge from a moon image and to calculate the Modulation Transfer Function(MTF). It implements image restoration based on the image quality evaluation parameters and improves the image space resolution. Firstly, a moon visual position algorithm was designed based on the image navigation of FY-2 to search the moon image in the FY-2G full disk image. By using one-order differential and extreme value matching, the MTF evaluation value of FY-2G middle infrared band was calculate out by Fourier transform. Using the calculated MTF, the full disk image was restored by a Wiener filter. By using the pixel average gradient, power spectral components and image information entropy as evaluation functions, the reasonable filter parameters were determined. Finally, the high resolution image after MTF restoration was obtained. The experiments indicate that the MTF calculation is correct, image restoration is effective, and the spatial resolution has been improved greatly. Moreover, it ensures the consistency of image energy before and after restorations.Keywords：FY-2 satellite;middle infrared band;moon observation;Modulation Transform Function(MTF) evaluation;image restoration- 51
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Published：2020-08-13 -
Design of one-step carry-free adder with three-rotator structure
Abstract：The research of optical adders for modern optical computers suffers from hardware implementation difficulties, limited qualitative inputs and so on, so this paper designs and complements a new optical adder. It is a three-rotator structure one-step adder with carry-free based on Modified Signed-Digit(MSD) addition theory and symmetry MSD coding technology. The paper describes the main optical structure design and programs of the adder in detail, gives the abstract structure of the three rotator, designs the optical structure of the control optical path, and offers specific programs of circuit implementation. The adder can easily be achieved, does not limit inputs, and can implement thousands of data-bit addition by a parallel model in a single step. Finally, specific experiments are designed to verify above optical structures and circuit scheme, and the carry-free binary addition of 13 data-bits is completed. Experimental results show that the principle of the one-step carry-free adder design is correct, the circuit scheme is reasonable, and it has great potential in the numerous data bit parallel computing.Keywords：three rotator structure;one-step carry-free adder;optical path;circuit;MSD addition- 67
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Published：2020-08-13 -
Adaptive scale object tracking with kernelized correlation filters
Abstract：As most of tracking-by-detection methods have not dealt with the scale estimation problem in target tracking, this paper proposes a scale estimation strategy based on the tracking-by-detection framework. Meanwhile, it designs an adaptive scale tracking algorithm based on kernelized correlation filters. The algorithm uses a kernel function to solve the regularized least square classifier to obtain the kernelized correlation filters. Then it completes the target position and scale detection by online learning the kernelized correlation filters, and updates the filters in online. To verify the feasibility of the proposed algortihm, ten groups of benchmark video sequences are tested and obtained results are compared with those of five kinds of tracking algorithms. The experimental results show that the proposed approach improves the performance by 6.9% in the average distance precision as compared to the best one of the other five excellent existing tracking algorithms. It is robust to scale changing, illumination variation, partial occlusion, pose variation, rotation, fast motion and other complex scenes.Keywords：kernelized correlation filter;object tracking;adaptive scale;regularized least square classifier- 41
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Published：2020-08-13 -
Moving object detection by optical flow method based on adaptive weight coefficient
Abstract：To set and update weight coefficients of Horn-Schunck optical flow method adaptively, the influencing rules of weight coefficients on Horn-Schunck optical flow method is researched. An optical flow method based on adaptive weight coefficients and Fuzzy C-Means(FCM) clustering is proposed. Firstly, it computes varying curves of optical flow total values with different weight coefficients. Then, by combining two levels of FCM clusterings, it finds the optimal weight and the convergence point of Horn-Schunck optical flow method based on fixed number of iterations. By which the optimal weight coefficient is obtained adaptively. Finally, the feasibility of the method is verified based on standard video sequence. The result shows that the optical flow images estimated by the optimal weight obtains evident movement targets with little noise as compared with other weight coefficients and its running time is 0.1060 s, useful ratio is 0.5956, and End-point Error is 0.8011. It achieves the best or the next-best performance.Keywords：moving object detection;Horn-Schunck optical flow method;fuzzy C-means clustering;adaptive weight coefficient- 63
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Published：2020-08-13
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