Chinese Version Light学术出版中心
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Issue 3 ， 2016
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Effect of alignment errors of reticle on distortion in lithographic projection lens
Abstract：To meet the requirement of lithographic tool for the distortion in a lithographic projection lens, the distortion of the optical lithography introduced by alignment errors of a reticle was researched. The Legendre polynomials were used to describe the distortion of lithographic projection lens, and then it was taken to analyze and compensate the distortion. Based on the proposed methods, a lithographic projection lens with a Numerical Aperture(NA) of 0.75 and the working wavelength of 193 nm was analyzed. The analysis results show that the combinational tolerances of the reticle tilt error in 1.0μm and the reticle translation error in 0.1 mrad have aroused by uncalibrated distortions of 2113.2 nm and 10.0 nm. The Legendre polynomial was used to fit the distortion to obtain the coefficients of the Legendre polynomial, and then to get the distortion sensitivity of the reticle alignment errors. The distortion sensitivity then was used to perform the tolerance analysis and compensation for the random position errors of the reticle. As the distortion was expected to be less 2 nm, the requirement of the reticle z-direction tolerance is ±2.0μm and those of the reticle x-tilt and y-tilt tolerances are ±22.3μmad and ±55.3μmad, respectively. The results demonstrate that the way proposed is suitable for analyzing and compensating the distortion introduced by reticle alignment errors in lithographic projection lenses.Keywords：Lithography;optical design;lithographic projection lens;optical distortion;Legendre polynomials;tolerance analysis- 57
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Published：2020-08-13 -
Verification of PSIM system based on tunable polarization light source
Abstract：A tunable polarization light source with simple structures and good stability was developed to validate the feasibility of a Polarization Spectral Intensity Modulation(PSIM) experimental system designed by us. A glass stack consisting of two K9 glass pieces was mounted into the tunable polarization light source. By changing the tilt angle of the glass stack, the polarization degree of the partial polarization light output from the system could be adjusted. The working principle of the PSIM was derived, and the calculation method of polarization degree of the output light from the tunable polarization light source was obtained. On the basis of the principle of the PSIM system, a experimental device was built to verify the performance of the PSIM system. The measurement verification experiment was carried out in the laboratory and the different polarization degree spectra output from tunable polarization light source was measured. The results show that the error between the theoretical output of the tunable polarization light source and the measured results of the experiment equipment of PSIM is within 1% when the experiment equipment of PSIM works in its effective working wavelength range, which validates the feasibility of experiment device of PSIM and tunable polarization light source. Meanwhile, it verifies that the tunable polarization light source is expected to be a standard polarization light source and used in the calibration of polarization spectral measuring equipment.Keywords：polarization measurement;tunable polarization light source;Polarization Spectral Intensity Modulation(PSIM) system;design verification- 56
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Published：2020-08-13 -
Measurement of wavefront aberration for high NA objective and some special problems
Abstract：A two-dimension shearing interferometer based on an amplitude chessboard grating was designed to measure the wavefront aberration of a high Numerical Aperture(NA) objective. The principle of Chessboard Grating Lateral Shearing Interferometer(CBGLSI) was researched, and several special problems involved in the measurement of wavefront aberration for the high NA objective were investigated. Firstly, the diffraction efficiencies and diffraction order distribution of the chessboard grating were analyzed by the far-field diffraction function, and the processing method of shearing interferogram was given. According to the projection relation between the spherical pupil coordinates and plane detector coordinates, the influence of pupil coordinates distortion was analyzed. Then, the effect of the nonlinearity of grating formula on systematic errors was analyzed by geometrical ray tracing method. Finally, the relation between the relative irradiance at the objective pupil edge and the numerical aperture was deduced. Experimental results indicate that the measuring repeatability(3σ) of wavefront aberration of a objective with the NA of 0.6 is 3.7 mλ under the same pupil coordinate. Several special problems involved in the measurement of wavefront aberration was discussed, and the results suggest that the influences of pupil coordinate distortion, systematic error due to grating formula, and the irradiance attenuation at pupil edge should be considered when the wavefront aberration of the high NA objective is measured.Keywords：wavefront aberration measurement;shearing interferometer;high Numerical Aperture(NA) objective;lithographic objective- 43
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Published：2020-08-13 -
Characteristics of various packaged reference photovoltaic devices and their conformities to international photovoltaic standards
Abstract：This paper focuses on analysis of the origins of measuring transfer errors of standard solar cells and the uncertainty to international photovoltaic standards from the International Electrotechnical Commission(IEC). Six kinds of commercial packaged PV devices were chosen randomly, and their properties including temperature responsibility, spectral response and surface reflection effect were measured and evaluated based on the IEC standards, The results demonstrate that the structure of packaged PV device affects its cooling effect and temperature measurement accuracy, so that to leads to the instability of temperature and short-circuit current(Isc). The variation coefficients are 0.12% for the temperature and 0.04% for the Isc. Moreover, the spectral responses with and without white bias lights all reflect the linearity feature of incident light intensity for the Isc, in which the spectral responses were quantified by defining a spectral mismatch factor. The influence of surface reflection on Isc was analyzed by measuring Isc at different incident angles, and the ΔIsc caused by the surface reflection was deduced to be up to 0.21% by fitting with a cosine function. The results provide the important guidance for the manufacture, selection and application of the packaged PV devices in photovoltaic industry.Keywords：solar cell;measurement standard of solar cell;standard solar cell;temperature stability;spectral response;linearity;surface reflection- 64
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Published：2020-08-13 -
Process and properties of selective laser sintering ultrahigh molecular weight polyethylene
Abstract：The effects of different processing parameters in Selective Laser Sintering(SLS) and subsequent heat treatment on the mechanical properties of Ultrahigh Molecular Weight Polyethylene(UHMWPE) specimens were investigated. By adjusting the different processing parameters, such as scanning space, scanning speed and laser power, the density, tensile strength and breaking elongation of UHMWPE specimens fabricated by SLS were described, then the mechanical properties of the UHMWPE specimens with and without heat treatments were compared. The experimental result demonstrates that the relative density, tensile strength and the breaking elongation have a positive correlation with the laser power and have a negative correlation with the scanning space and scanning speed. After heat treating, the mechanical properties of the UHMWPE specimens are improved obviously and the relative density, tensile strength and the breaking elongation are 95.12%, 24.08 MPa, and 334.82 MPa respectively. These results suggest that the mechanical properties of UHMWPE specimens fabricated by SLS is weaker than that fabricated by molding. Process optimization can not get the ideal performance, but the mechanical property can be enhanced to meet the requirements after heat treatment.Keywords：laser technology;Selective Laser Sintering(SLS);Ultrahigh Molecular Weight Polyethylene(UHMWPE);mechanical property;relative density- 60
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Published：2020-08-13 -
Optical system of high contrast dynamic star simulator based on LCOS splicing technology
Abstract：The dynamic star simulator based on Liquid Crystal on Silicon(LCOS) splicing technology has low contrast, and it can not provide all effective targets for the star sensor in star map recognition. Thus a method for improving the contrast of the dynamic star simulator by suppressing stray lights was put forwarded. The influence of the polarization degree on stray light was discussed in detail, and the function of the polarization degree and the angle of incidence was derived.The optical system for stray light suppression was designed, including a lighting source designed by combination of a Compound Parabolic Concentrator(CPC) and a telescopic system, a 1/4 wave plate with combination of multi-prisms, and a collimating system with field angle greater than 11°. The MTF of the collimating system is greater than 0.7 when the edge frequency is 601p/mm and the field angle is less than ±5°. The experiments show that the angle distance error between stars of the high contrast dynamic star simulator based on LCOS splicing is less than 18", and its stray light energy is reduced by 2.38 times as compared with those of conventional star simulators. These results indicate that the high contrast dynamic star simulator based on LCOS splicing can not only reduce the background noise of dynamic star simulator effectively, but also can improve the recognition rate of star map. Consequently, it meets the requirements of dynamic star simulator in all magnitude levels for high dynamic characteristics and high precisions.Keywords：optical system design;Liquid Crystal on Silicon(LCOS) splicing technology;star simulator;stray light;polarization degree;star map recognition- 104
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Published：2020-08-13 -
Thin ring gauge artifact for probing error evaluation of multi-sensor coordinate measuring machine
Abstract：A thin ring gauge artifact is designed to evaluate the probing errors of a multi-sensor Coordinate Measuring Machine(CMM) equipped with an imaging probe and a touch probe. This artifact is defined with a sharp edged hole in a metal plate. It has the features of both 2D circle and 3D ring gauge, the effective height of the hole is only 0.1 mm and the roundness is 0.5μm. It is suitable to measure the touch probe as well as imaging probe. As the height effect of the hole for the imaging probe is eliminated, the artifact also could be used in the touching measurement. Moreover, the designed cone structure ensures the stability of the artifact, so the deformation could not be happened when it is used in the touching measurement. The artifact is used in the evaluation of the probing errors of a combinend probing system equipped with the imaging probe and the touch probe, and the results show that the artifact has implemented the calibration of the probing errors. Finally, according to ISO 10360-9, parameters including combined size error, form error and location error are calculated and the method based on coordinate transform is applied to correction of location errors and optimization of systematic parameters.Keywords：multi-sensor coordinate measurement machine;imaging probe;touch probe;thin ring gauge artifact;measurement uncertainty- 75
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Published：2020-08-13
Modern Applied Optics
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A microfluidic inertial switch with response characteristics to high acceleration
Abstract：On the basis of micro communicating vessels, a novel microfluidic inertial switch with excellent response characteristics to a high acceleration over 30000g was proposed. Brine was selected as the working-fluid due to its conductivity and non-toxicity. The mechanism of droplet separation was discussed, and the channel structure of the switch was designed. Then, the working principle of the switch was theoretically analyzed and modeled. Finally, by the combination of Computational Fluid Dynamics(CFD) simulation technology and a prototype experiment, the structure and functions of the switch were verified. The results show that fluid dispersion problem has been avoided even under the 30000g high step acceleration, and the bigger acceleration amplitude leads to the shorter response time. By the review of the experiment results, the height difference of the two liquid-gas interfaces of the brine can be realized at the initial state and the static acceleration threshold of the prototype is between 134.6g to 152.3g, which is agreed well with its theoretical counting acceleration threshold 142.7g. The experiments indicate that the micro communicating vessels efficiently improve the anti-dispersion ability of the microfluidic inertial switch. It separates the acceleration amplitude and shows good latching function and higher response characteristics to the high acceleration.Keywords：microfluidic inertial switch;micro acceleration switch;micro communicating vessel;anti high acceleration- 65
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Published：2020-08-13 -
Effect of oil velocity on sensitivity of micron metal particle detection by inductive sensor
Abstract：To improve the sensitivity of a planar inductive microfluidic chip, the relationship between the oil velocity and the signal amplitude was researched. The working principle of the planar inductive microfluidic chip was introduced, the effect of the oil velocity on the detection signal amplitude was analyzed theoretically and the related formula were derived. Then, the experimental verification was performed by the control variable method. The iron particles with diameters from 80-85μm were used as the samples, the velocity of oil was set from 0.02 ml/min to 0.10 ml/min, an experiment was carried out. The obtained data illustrate that the signal amplitude decreases with the improvement of oil velocity, and the relationship between the oil velocity and signal amplitude is linear after fitting. When other conditions are invariant, the sensitivity has been significantly improved with the velocity decreased, and the maximum can catch about 87.5%.It suggests that the experiment data agree with the theoretical ones well and the signal amplitude can be improved by decreasing the oil velocity. The conclusion is valuable for the sensitivity improvement of microfluidic chips.Keywords：particle detection;flow velocity detection;microfluidic chip;marine hydraulic oil;oil velocity- 64
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Published：2020-08-13 -
Lapping of sapphire wafers by CVD diamond coated tools
Abstract：Three kinds of Chemical Vapor Deposition(CVD) diamond coated tools with different surface morphologies(including spherical structure crystal, incisive pyramid crystal and quadrangular prism crystal) were prepared by Hot Filament Chemical Vapor Deposition(HFCVD) method to improve the lapping efficiency of CVD diamond coated tools in sapphire wafer processing. The influences of process parameters such as diamond coating grain morphology, lapping load, velocity of operating platform and lapping time on the removal rates and surface roughnesses were researched The results show that the diamond coating grain morphology has great impact on the material removal rate and surface roughness. Moreover, the diamond coated tool with spherical crystal structure has a lower tangential force, while the diamond coated tool with quadrangular prism structure offers a higher tangential force. When the diamond coated tool with quadrangular prism structure is selected to lap sapphire wafers, and the process parameters are lapping load in 0.15 MPa, the velocity of operating platform in 100 r/min and lapping time in 3 min, the maximum material removal rate reaches to 0.397μm/min and the surface roughness is 0.354μm. It concludes that the CVD diamond coated tools are suitable for machining and lapping sapphire wafers and can remove the scratches on the surface of sapphire wafers and improve their surface qualities.Keywords：Chemical Vapor Deposition(CVD) diamond coating;lapping;sapphire;grain morphology- 72
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Published：2020-08-13 -
Micro-measurement of SU-8 photoelastic performance
Abstract：The photoelastic performance of SU-8 photoresist is related to extending its applications to the field of MEMS(Micro-electronic-mechanical System). Therefore, this paper designs a micro-measuring path to obtain the stress-optical coefficient of the SU-8, and implements the measurement experiment of SU-8 photoelastic performance. Firstly, based on the photoelastic mechanism, the micro-measuring optical path was designed and the formulas for the calculation of SU-8 stress-optical coefficient were deduced. Then,, the experiment devices for photoelastic microscopic measurement were built according to the designed optical path, and the tensile test of SU-8 specimen was conducted in the scope of the half order of a single photoelastic fringe. Finally, through extracting the values of the light intensity from the experimental photographs by Matlab, the light intensity of monochromatic light penetrated throught the SU-8 specimen under different tensile forces were measured and the value of SU-8 stress-optical coefficient was calculated. The experimental results and the calculation of measurement formulas show that the stress-optical coefficient of SU-8 is(3.007±0.149)×10-11 m2/N, greater than that of normal optical glass and other materials commonly used in MEMS fields, such as silica. The experimental results can lay a foundation for the design and manufacturing of micro-grippers and micro-probes made from the SU-8 materials and used for the force measurement through photoelastic mechanisms.Keywords：optical measurement;micro-measurement;photoelastic analysis;SU-8 photoresist;stress-optical coefficient- 57
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Published：2020-08-13 -
Lateral support of thin meniscus mirror
Abstract：Thin meniscus mirrors with a lateral support in either equal weight vertical support or equal-angle vertical push-pull always generate bending aberrations badly. To eliminate the bending deformations, this paper analyzes the structure characteristics of the thin meniscus mirrors and proposes two kinds of lateral support models including equal-angle push-pull shear and unequal-angle push-pull shear for the thin meniscus mirrors. By increasing the axial forces on lateral supports to balance the force components, the tangential force, radial force and axial force of the lateral support are expressed for both lateral support modes. The parameters of a 1.23 m thin meniscus mirror are optimized, and the results show that the parameter β(determines the contribution of tangential forces to weight support) of a 16-point lateral support system is 0.75. After applying axial shear component to the 16-point equal-angle push-pull lateral support, the mirror deformation(RMS) is reduced from 1259.1 nm to 3.4 nm, showing a better support surface. The equal-angle push-pull shear lateral support mode is successful in reducing deformation without active correction, but it has a major disadvantage in a great force difference between lateral support points. Considering uniformity and practicality for lateral support mechanism, the 16-point unequal-angle push-pull shear lateral support mode is used to achieve 4.6 nm deformation(RMS) with axial active correcting by the maximum active force of only-1.01 N.Keywords：thin meniscus mirror;lateral support;equal weight vertical support;equal-angle vertical push-pull;equal-angle push-pull shear;unequal-angle push-pull shear- 70
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Published：2020-08-13 -
Large-scale spatial angle measurement based on inertial reference
Abstract：For measuring a large-scale spatial angle during large equipment assembly, a large spatial angle measurement method based on an inertial reference was proposed and a corresponding measurement system was designed. On the basis of auto-collimation principle, a two-dimensional galvanometer was used in the measurement system to aim the direction of measured axis. A gyroscope and a photoelectric encoder were adopted to measure the vector coordinates of each measured axis in inertial coordinate system. Then, the spatial angle between measured axes was calculated by their vector coordinates in the public reference. The mathematical model of large-scale spatial angle measurement was built and the measurement uncertainty of the measurement system was analyzed and calculated. Finally 14", a prototype was established and the simulated measurement experiment was carried out by the prototype in laboratory. Experimental results show that the measurement error is, which meets the requirements of large-scale spatial angle measurement. The method overcomes difficulties that the measuring reference is difficult to be built and transmitted in measuring large-scale spatial angles and makes the measurement process more flexible and efficient.Keywords：Large-scale measurement;spatial angle measurement;coordinate measurement;inertial reference;autocollimation- 57
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Published：2020-08-13 -
Multi-scale numerical prediction of flow-induced thermal conductivity variation in micro-injection molded heat sink
Abstract：To further increase the thermal conductivity of polymer composites, a multi-scale numerical prediction method was applied to investigation of the CF flow induced orientation in micro-injection molded polyamide/carbon fibers(PA66/CFs) micro heat sink as well as its influence on the thermal conductivity of composites. Firstly, the Moldflow was used to determine the orientation tensor of the CF, the Comsol Multiphysics was used to develop the corresponding micro cell of the composite, and an orthogonal experiment method was utilized to study the effects of processing parameters including melt temperature, mold temperature, maximal injection pressure and injection flow rate, on the thermal conductivity. Then, on the basis of prediction data analysis, the optimal combination of the injection molding processing parameters was obtained. Finally, the optimal combination results were confirmed using simulated experiment, which verified the feasibility of the proposed multi-scale numerical prediction method. The results show that the influential parameters in descending order of importance are melt temperature, injection flow rate, maximal injection pressure, and mold temperature. Moreover, the obtained optimal combination of the investigated factors is identified as the melt temperature of 360℃, mold temperature of 70℃, maximal injection pressure of 220 MPa and the injection flow rate of 3×10-4 cm3/s. In addition, the maximal variation of the flow-induced thermal conductivity is determined as 0.36 W/(m·K), which is 1.5 times that of polymer matrix. The findings in the present work provide theoretical basis and data supports for further increasing the thermal conductivity of polymer composites from a new viewpoint of processing control.Keywords：polymer composite;micro heat sink;injection molding;thermal conductivity;multi-scale numerical prediction- 46
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Published：2020-08-13 -
MEMS gyro denoising by EMD-HOS method
Abstract：For the nonlinear and non-stationary signals existing in a MEMS(Micro-electronic-mechanic system)gyro, a denosing method based on the Empirical Mode Decomposition/High Order Statistic(EMD/HOS) was proposed. Firstly, the MEMS gyro signals were captured, and they were decomposed into a cluster of intrinsic mode function(IMF) based on the proposed EMD/HOS sift process. The IMF peak values were estimated by using Bootstrap technology, respectively, to verify its Gaussianity and the Gaussian components were filtered directly. Then the variance algorithm was used to calculate the Hurst exponent of the IMF. According to the Hurst exponent, the threshold was calculated and the each IMF was processed by soft threshold technology. Finally, the remained IMFs after threshold processing were reconstructed to implement the signal denoise. Moreover, the Allan variance algorithm was introduced to analyze the gyro noise, and the characteristic of gyro noise could be observed via the curve of related time and root Allan variance. The conclusion is that EMD-HOS and soft threshold technology decrease the noise of MEMS obviously, the SNR is increased by 5.6 dB, and each indicator of MEMS; gyro noise is improved almost by one order.Keywords：MEMS gyro;signal denoising;Empirical Mode Decomposition(EDM);High Order Statistic(HOS);Intrinsic Mode Function(IMF);soft threshold;Hurst exponent- 53
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Published：2020-08-13 -
Active disturbance rejection control of speed governing system for PMSM
Abstract：A first-order Active Disturbance Rejection Controller(ADRC) with an arc-hyperbolic sine function was presented to increase the tracking precision of the Sinusoidal Pulse Width Modulation(SPWM) speed governing system of a Permanent Magnet Synchronous Motor(PMSM). A mathematical model for the velocity loop of the PMSM was studied. Then a first-order tracking differentiator and a second-order extended state observer were designed respectively and their convergences were analyzed by using the Lyapunov function. The first-order ADRC of the velocity loop was constructed, and the asymptotic stability of the first-order ADRC error system was verified. Finally, the designed first-order ADRC was used as the rotating speed adjuster of the SPWM, and the SPWM speed governing system with the ADRC was analyzed. Simulation experiments demonstrate that the speed step response adjustment time of the SPWM speed governing system with the ADRC is 0.15s, the steady error is less than 0.28 r/min, and the maximum sine tracking error is 17 r/min. As compared with a PI controller, the governing system with the ADRC is characterized by fast and stable step response, smaller stable error and no overshoot. Moreover, it shows better sine tracking performance and smaller tracking errors.Keywords：Permanent Magnet Synchronous Motor(PMSM);first-order Active Disturbance Rejection Controller(ADRC);arc-hyperbolic sine function;speed governing system;asymptotic stability- 60
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Published：2020-08-13 -
Linear analysis and practical tests of fixation mechanisms in space robotic arm
Abstract：The stiffness characteristics of fixation mechanisms of a space robotic arm show nonlinear, and it should be processed in linearity by equivalence method in the dynamic analysis on the whole-system. A method based on six-dimensional stiffness equivalence for linearizing fixation mechanisms was proposed and related analysis and tests were performed as well. A nonlinear model of a single preloaded fixation mechanism was created and corresponding stiffness information of the fixation mechanism was acquired through nonlinear analyses. Then the above information was offered to BUSH elements to simulate the fixation mechanism. The modal analysis and frequency response of whole model for the robotic arm was carried out. The results indicate that the first three natural frequencies of the whole system are 89 Hz, 92 Hz, 96 Hz and the maximum relative error between analysis results and test results is 3%. Moreover, the frequency response analysis results of different components are consistent with that of the test results and maximum relative error is 8%, which verify the effectiveness of the above method. The method takes the coupling of stiffness in different directions into account, and avoids processing the contact surfaces of the fixation mechanisms one by one, showing a stronger practical engineering value.Keywords：robotic arm;fixation mechanism;contacting analysis;dynamic analysis;stiffness equivalence;BUSH element- 62
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Published：2020-08-13
Micro/Nano Technology and Fine Mechanics
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Measurement of vertical target dispersion with target-hitting sequence for barrage weapons
Abstract：A kind of three space target structure based on four linear TDI-CCD(Time Delay and Integration CCD) cameras is put forward to measure the target-hitting parameters and to obtain the vertical target dispersion for barrage weapons when multiple projectiles hit the target at the same time. With measurement, two CCD cameras intersect to form the vertical target I, and the target surface is perpendicular to the scheduled ballistic direction. Target surface Ⅱ and Ⅲ are formed by a CCD camera respectively, and a certain angle between target I and Ⅱ is formed in vertical direction, which is the same as that between target I and Ⅲ in horizontal direction. Combined with the geometry of three dimensional target surfaces, the imaging time and imaging angle of the flying projectile on the four linear CCD cameras, the vertical target coordinate and projectile's flying speed are calculated. Meanwhile, based on the relationship of imaging position and the constraint of flying velocity among three target surfaces, the space-time distribute parameters of multiple projectiles are deduced, such as target-hitting sequence, velocity, nutation angle and the target coordinates. Simulation and experiment show that the matching rate of multiple targets among three target surfaces reaches to 100%. The test method effectively eliminates the false target-hitting coordinate when multiple projectiles impact the target simultaneously and calculates precisely multiple projectile parameters all at once.Keywords：barrage weapon;three CCD space target surface;vertical target dispersion;target-hitting sequence;multiple target space-time match- 79
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Published：2020-08-13 -
Calibration of installation angle for high accuracy shipboard star sensor
Abstract：Ship attitude measurement accuracy based on star sensors is relative to the calibration accuracy of the installation angle between star sensor and ship desk. This paper introduces the coordinate system of the shipboard star sensor and the definition of installation angle. Then, it establishes a model to correct the atmospheric refraction of the sensor and proposes a calibration method for installation angle of the high accuracy shipboard star sensor. When the space TT & C ship docks in shipyard, shipboard theodolite determines the course of the ship by shooting the azimuth mark, and star sensor obtains the ascension and declination of the stars in the field of view by star recognition to construct the star reference vectors with respect to inertial space. After correction of precession, nutation, pole shift and ship position, the star reference vectors with respect to Inertial Navigation System(INS) horizontal coordinate system are obtained. According to the atmospheric refraction correction model, each star in the field of view corrects its pitch angle and reconstructs its star reference vector with respect to INS horizontal coordinate system. Finally, star sensor installation matrix is calculated based on the principle of attitude determination algorithm, and then three installation angles are solved. Experiment results show that the calibration accuracy of azimuth and pitch using proposed method reach less than 10". The proposed method is based on the higher pointing accuracy of the star sensor and improves automatic programming and measuring accuracy of ship attitudes.Keywords：star sensor;ship attitude;installation angle;calibration- 55
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Published：2020-08-13 -
Improved KAZE feature matching algorithm with viewpoint change robustness
Abstract：The KAZE algorithm is sensitive to image view changes, so that it is not capable of the correct match between images with large view-point differences. This paper proposes a PKAZE(Perspective-KAZE) algorithm which is robust to the viewpoint changes. Firstly average second-order gradient values in the neighborhood region of key-points extracted by ordinary KAZE descriptors were calculated to extend the original KAZE feature descriptor to be a new 80-dimension one. Then, a perspective transform model was used to warp the image pairs to be matched in a series of different perspective angles. New KAZE feature descriptors were extracted on transformed image pairs and were matched later. Finally, five simulated image pairs with the most correct match numbers that are in top five simulated image pairs were selected as initial matching results, and the Random Sample Consensus(RANSAC) algorithm was used to remove false matching pairs in initial results. The matching experiments were performed on several image groups. The experimental results show that the proposed algorithm is more robust to the viewpoint changes as compared with the common KAZE, Scale Invariant Feature Transform(SIFT) and Speed Up Robust Feature(SURF) algorithms. The correct rate of proposed algorithm is 2-10 times that of the Perspective Scale Invariant Feature Transform(PSIFT) and 2-7 times that of the Affine Scale Invariant Feature Transform(ASIFT). Furthermore, the proposed algorithm is not only robust to the viewpoint changes for simulated images, but also robust to the large view-point difference images in a real 3D complex scene. These results verify that the algorithm has a very good practical value.Keywords：image matching;feature matching;KAZE algorithm;second-order gradient;perspective transform;nonlinear scale space- 92
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Published：2020-08-13 -
Spatial error concealment algorithm based on adaptive edge thresholding and directional weight
Abstract：In wireless transmission, H.264/AVC compressed video stream shows poorer image reconstruction quality due to the data losing, so this paper presents a spatial error concealment algorithm based on adaptive edge thresholds and directional weights. This algorithm uses Sobel gradient operator in image edge detection to detect the edge of adjacent macroblocks. Then it sets adaptively gradient threshold according to the specific information of adjacent macroblock in the damaged macroblock. Finally, it makes the direction weighted interpolation for the damaged macroblock implement the image reconstruction. Experiments show that the algorithm is simple and practical. It not only retains the advantages of the weighted average algorithm and conceals the errors of the images with different edge information intensities. The Peak Signal to Noise Ratio of the algorithm has improved 0.2-3.8 db as compared to that of the Multi-Directional Interpolation algorithm in different probability events of data losing for Real-time Transport Protocol(RTP). This algorithm improves the quality of image restoration and has a higher application value.Keywords：H.264/AVC;error concealment;adaptive edge threshold;direction weight;Sobel gradient operator- 72
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Published：2020-08-13 -
Image motion analysis and compensation for aerial scanning camera during turning flight
Abstract：The image motion calculation and compensation for an aerial scanning camera in turning imaging was researched to improve its imaging quality. The geometrical modeling and velocity vector decomposition were utilized to establish the image motion computation model of turning imaging according to the imaging principle of the aerial scanning camera. The mean compensation method for forward turning imaging motion was proposed based on the established model. The forward image motion compensation analysis on the turning imaging indicates that the maximum residual of forward image motion compensation is 2.22μm at the focal length of camera in 500 mm, exposure time in 0.01 s, speed height ratio in 0.02 rad/s, the longitudinal field of view in 10°, and the angular velocity in 1(°)/s and that is 3.36μm at the angular velocity in 1.5(°)/s. Moreover, the latitudinal image motion compensation analysis on the turning imaging indicates that the latitudinal image motion value increases as the magnitude of longitudinal field of view increased, and the value reaches 3μm while the exposure time is 0.005 s, the latitudinal field of view is 30°, the angular velocity is 1(°)/s and the longitudinal field of view is 4.5°. The imaging experiment of test turning flight obtains excellent image quality without geometric distortion and proper forward image motion compensation, which verifies the validity of the proposed image motion compensation method for turning imaging.Keywords：aerial camera;turning imaging;scanning imaging;image motion computation;image motion compensation- 68
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Published：2020-08-13 -
TSK classifier based on fuzzy(C+P) means clustering and SP-V-SVM
Abstract：To obtain a TSK(Takagi-Sugeno-Kang) classifier with well generalization performance and a capability of rule adaptive deduction, the method based on the FCPM(Fuzzy(C+P) Means) clustering and the SP-V-SVM(Support Vector Machine) is proposed to construct the TSK classifier. The method firstly clusters train data by FCPM clustering algorithm, and then identifies the centers and widths of the Gaussian membership functions of the antecedent part in TSK classifier based on the clustering result. Finally it uses the SP-V-SVM algorithm with the group sparsity constraints to learn the parameters of the consequent part of the fuzzy rule to improve the generalization performance. Moreover, the attribute reduction capacity of the SP-V-SVM algorithm is used to reduce the number of fuzzy rules and to make the TSK classifier compacted. The classification error and the number of fuzzy rules of the proposed algorithm are compared with several standard data sets from UCI and IDA repository, and results show that the proposed TSK classifier not only gets better performance but also has a few number of fuzzy rules and is suitable for structuring compact fuzzy classifying systems.Keywords：TSK(Takagi-Sugeno-Kang) classifier;fuzzy rule;rule deduction;Fuzzy(C+P) Means(FCPM)clustering;SP-V-Support Vector Machine(SP-V-SVM)- 70
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Published：2020-08-13 -
Recognition of seedlings in mechanical transplanting processing by Morphological image detection
Abstract：How to discover and remedy the damaged seedlings quickly in batch processing seedlings by automatic transplanting technology was researched. A recognition method of seedlings in mechanical transplanting processing based on machine vision was proposed. Based on the characteristics of mechanical transplanting seedlings, the method was used to measure soil matrix intact rate of seedlings by comparison of the image areas between soil matrix and benchmark. By which the samples were qualified or not could be judged. Then, the image characteristics processed by morphological image processing method in mechanical transplanting seedlings were described from the theory and practice and an online testing system for recognition of mechanical transplanting seedlings was designed. Finally, the manipulator transplanting seedling method based on morphological image detection and the common image detection method were compared. Experimental results indicate that the morphological detection method proposed in this paper for a seedling tray containing 72 holes increases the detection rate by 6.6%, and unqualified detection rate by 54.5%. At the same time, the average time that processes one seeding is about 1.82 s. It is shown that the proposed method is reliable, short time-consuming, satisfied with the requirement of real-time processing.Keywords：morphology;Image detection;mechanical transplanting;seedling- 46
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Published：2020-08-13 -
Video quality objective assessment combined contrast sensitivity characteristics of human visual system
Abstract：In combination of the perceiving characteristics of human eyes for brightness, chroma, contrast and moving targets, an objective assessment method of video quality based on contrast sensitivity characteristics of a human visual system was proposed. In the method, the video was divided into spatial and time domains to be described. The features of image were extracted from four aspects, brightness, chroma, contrast, and target motion based on the perceiving characteristics of human eyes and their intensities were computed. Then, the contrast sensitivity values of human eyes were used as the weight factors of the intensity to sum and to construct the model of human eye perception content of the video. Finally, original and distorted videos respectively perceived by imitating eyes with this model, and the intensity differences of the pixels and the motion vectors between arbitrary corresponding units of two videos were computed. By taking the intensity differences as the scores of video quality objective evaluation, the objective evaluation model for video quality was constructed by them. The experiments were carried out with 6 source videos and 48 test videos proposed by LIVE database, and the 5 classic video quality evaluation models recommended by the Video Quality Expert Group(VQEG) were compared with the proposed model. The results show that the linear correlation coefficient between video quality evaluated by the proposed model and the subjective evaluation results reaches 0.8705. They have good consistency, and evaluation effects are better than those of other 5 classical models.Keywords：human visual system characteristics;video quality assessment;brightness;chroma;Contrast;correlation coefficients- 65
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Published：2020-08-13 -
Infrared image segmentation based on graph cut of fast recursive fuzzy 2-partition entropy
Abstract：Most of existing Graph Cut(GC) algorithms have not considered the fuzzy feature, poorer segmentation precision and lower operating efficiency of infrared images sufficiently. So this paper proposes an infrared image segmentation method based on the GC of fast recursive fuzzy 2-partition entropy to implement the automatic segmentation of an infrared image in complex backgrounds. The information of the maximum fuzzy entropy from a Region of Interest(ROI) was used to set the likelihood energy of the GC. The ROI containing the maximum image information was detected by the iterative condition scheme based on the local fuzzy entropy values to ensure the completeness of the extracted target information. To improve the searching efficiency of the maximum fuzzy entropy, a recursive algorithm with time complexity O(n2) was presented to convert the computation of fuzzy entropy into a recursive process, and all the values of recursive entropy function were cached for the succeeding exhaustive optimization. For certain ROI, the likelihood energy of the GC energy function was set by the maximum fuzzy 2-partition membership functions of the ROI. By this way, the fuzzy feature of the infrared image can be considered sufficiently. The experimental analysis of the proposed algorithm on visual results, running time, misclassification error as well as F values were compared to those of several common algorithms. A plenty of experimental results indicate that the segmentation precision of proposed algorithm is up to 95% and the running time is 72% shorter than those of compared algorithms. It satisfies the requirements of automatic infrared image segmentation for higher precision, rapid speed, as well as stronger robustness.Keywords：infrared image;image segmentation;fuzzy partition entropy;recursive algorithm;graph cut- 67
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Published：2020-08-13
Information Sciences
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