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Issue 3 ， 2007
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A refract-reflect telescope with Cooke as compensated lens
Abstract：This paper introduces a new design about refract-reflect telescope using spheric surfaces instead of aspheric mirrors or large fore corrected lens, which lays a small Cook corrected lens behind the second mirror to compensate aberrations. This lens still achieves diffraction limit level in it's full field of 0.5° and F#7, obstruction ratio of 0.42 and MTF 0.45@50pl.The finished assemblage MTF is over 0.4@50pl close to diffraction limit,it is shown that this new configuration can bring up a low cost telescope.Keywords：Cook compensated lens;refract-reflect telescope;spheric primary mirror;spheric second mirror;fore corrected lens- 44
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Published：2020-08-12 -
Fade budgets of PAT link in satellite-to-ground optical communications
Abstract：To achieve enough fade budgets for reliable link in satellite-to-ground optical communications, the expressions for the total probability density functions of signal intensity fluctuation are derived at large zenith angles and small zenith angles considering atmospheric scintillation, static pointing error and pointing jitter and relation of the lost-tracking probability variable with fade budgets is given. Finally, the total probability density function and lost-tracking probability are simulated. Experimental results show that the ratio of the optimal beam divergent angle to the square root of the variance of the pointing jitter for uplink and downlink is 4 and 6; the required fade budget at a lost-tracking probability of 10-3 is 10 dB and 3 dB for uplink and downlink.Keywords：satellite-to-ground optical communication;lost-tracking probability;fade budget;probability density function;intensity fluctuation- 65
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Published：2020-08-12 -
Influence of crab-cantilever on performance of grating moving light modulator
Abstract：The light modulator based on Micro-opto-electro-mechanical System(MEMS) has already become a research focus in projection display field. The structure of Grating Moving Light Modulator (GMLM) supported by four crab-cantilevers is composed of reflection plate, address electrode,four crab-cantilevers and grating plate. In this paper, the influence of crab-cantilevers on GMLM performance was analyzed.The diffraction intensity of GMLM was discussed with Fourier optics, while the grating period number was odd and even integer. Especially, the influence of frame and four crab-cantilevers on GMLM performance was analyzed in detail. The result indicates that frame and crab-cantilever size should be reduced in design for obtaining a higher constrast ratio. Moreover, the relationship between contrast ratio and important structure parameter is shown in figures.Keywords：diffraction grating;Fourier optics;MEMS;grating moving light modulator- 49
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Published：2020-08-12 -
6.5 W LD-pumped 914 nm Nd:YVO4 laser
Abstract：As an important laser active medium, Nd:YVO4 is widely used in LD end-pumped solid-state lasers due to its large stimulated emission cross section, very strong broad absorption band at 809 nm and polarized emission,etc, and it has three useful stimulated emission spectra of 1 064 nm,1 342 nm and 914 nm but the quasi three level of 914 nm spectum and the low thermal conductivity of YVO4 crystal limit the development of its high power laser output. An efficient high power LD-end-pumped continuous-wave (CW) Nd:YVO4 laser has been developed by restraining the high gains at wavelengths of 1 064 nm and 1 342 nm with a simple folded cavity and suitable medium film applied on its three mirrors. An output power of 6.5 W, slope efficiency of 37.9% and optical-to-optical conversion efficiency of 22.4% can be achieved when the pump power is 29 W.Keywords：diode-pumped;solid-state laser;Nd∶YVO4 laser- 67
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Published：2020-08-12 -
Low temperature properties of fiber Bragg grating temperature sensors with two package methods
Abstract：Two package methods of Fiber Bragg Grating(FBG) temperature sensors were introduced. The temperature sensitive factors of the sensors were derived analytically and verified by experiments. The experiment results of two kinds of FBG temperature sensors in identical conditions were compared by analyzing the variety properties of center wavelength from -70℃ to 0℃. From the experimental results,it is shown that the center wavelength of FBG temperature sensor with thin stainless steel tube package falls sharply at -60℃; while there is a very good linearity and preferable repeatability between the center wavelength of FBG with gold package in the temperature change from -70℃ to 0℃, and almost no hysteresis effect. The sensitivities KT of two temperature sensors are 28.2 pm/ ℃ and 21.3 pm/ ℃ respectively during linear change, and they are 2.89 and 2.28 times as large as that of a bare FBG. Their pertinence coefficients are more than 0.999.Keywords：guided and fiber optics;optical fiber Bragg grating;phase mask;package technique;property of low temperature- 66
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Published：2020-08-12 -
Restraining speckle of laser imaging system in accurate measurement
Abstract：Three factors of restraining speckle noise in detection system,coherence, phase difference and polarization of the incident ray,were analyzed in detail, and the relations between these factors and speckle contrast were also presented. Calculation results show that when coherence length is less than 1 mm, speckle contrast is reduced to 0.5, which is advantageous to obtaining excellent measuring accuracy and keeping good details for a image. On the basis of theoretical analysis, the solution and optimization to reduce speckle was proposed to restrain speckle noise, improve illumination quality and enhance accuracy of measurement.Keywords：accurate measurement;laser imaging;speckle;coherence;Polarization;Contrast- 87
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Published：2020-08-12 -
Effects of low power laser irradiation on characteristics of transient outward potassium current of neurons
Abstract：Based on the acutely isolated rat hippocampal CA3 pyramidal neurons irradiated by a semiconductor laser with wavelengh 670 nm and power 5 mW, the current characteristics of transient outward potassium channel were investigated using the whole-cell patch clamp technique. The experiments reveal that low power laser decreases the amplitudes of transient outward potassium current (IA) in a voltage-dependent and reversible manner. The percentage of current inhibition is up to (40.13±5.19)% (n=10) depolarizing to +50 mV in laser irradiating 5 min. The maximal activation current densities of control group, irradiation group and recovery group are (398.55±36.49)pA/pF, (238.62±30.78)pA/pF (n=10, P<0.01) and (354.08±35.16)pA/pF (n=10, P>0.05), respectively. Laser irradiation markedly affect the activation and inactivation process of IA. The half-activation voltage and the slope factor of the steady activation curve change under the laser's exposure. The former alters from (-27.05±4.53) mV to (-2.10±3.14) mV (n=10, P<0.01) and the latter from (-26.71±6.15) mV to (-20.70±4.38) mV (n=10, P<0.05). The half-inactivation voltage also changes from (-70.49±7.21) mV to (-81.27±6.26) mV (n=10, P<0.01) and the slope factor of the inactivation curves from 9.47±3.54 mV to 9.58±3.02 mV (n=10, P>0.05). The results indicate that the effect of low power laser on hippocampal neurons could change the current characteristics of transient outward potassium channel of membrane of neurons, and then affect the formation and firing of action potentials. Moreover, physiological function of neurons is adjusted as a result of low power laser irradiation, which might contribute to the restoration and regeneration of injured neurons.Keywords：transient outward potassium current;patch clamp technique;low power laser irradiation;biologic effect;neurons- 52
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Published：2020-08-12 -
Mirror form grinding of free-form surface of reflector mould core
Abstract：In order to assure form accuracy and surface roughness of optic free-form surface of injection mould core, form grinding of free-form surface was conducted in CNC precision grinder by use of precisely dressed and trued arc-shaped coarse diamond grinding wheel to realize effective mirror grinding. The form truing principle of arc-shaped diamond grinding wheel was investigated to establish number control mode of arc-truing, and wheel path algorithm for equal- envelope-height grinding was established to realize CNC grinding of free-form surface. Then, formation of super-smooth ground surface was theoretically analyzed in connection with grinding parameters and wheel topography. The theoretical analysis shows that super-smooth ground surface of nanometer order can been produced by increasing wheel rotating speed, decreasing wheel moving speed and improving wheel topography. Experimental results show that surface roughness of Ra<10 nm may be obtained by use of dressed and trued wheel with wheel moving speed in less than 15 mm/min, and no brittle cracks on microscopic ground surface. The form accuracy of PV < 10 μm and the surface roughness of Ra<20 nm can be obtained when machining the free-form surface of high-speed steel.Keywords：reflector mould core;diamond grinding wheel;CNC grinding;surface roughness;form accuracy- 68
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Published：2020-08-12 -
Estimation of aerial camera parameters based on ground control points with equal elevation
Abstract：To make a low cost aerial CCD camera locate a ground target accurately, a new estimating technique using four known ground control points with equal elevation for estimating camera parameter is presented,in which the focal length and external parameters of an aerial camera carried by a parachute, including position and pose angles relative to the world reference frame, can be estimated according to a single aerial image.In this paper,we use direct linear transformation algorithm to compute the homographic matrix between the known ground control points with equal elevation and the corresponding points on the image plane, then establish the relationships between the homographic matrix and the collinearity equations, and finally give the mathematic models for computing the intrinsic and extrinsic parameters of the aerial camera. Two experiments are carried out to examine the effectiveness of the proposed algorithm with indoor simulation control points and outdoor real control points, respectively. The experiment results show that the presented technique can get the camera parameters with relative error of 2% by given the 3-dimension coordinates of four known ground control points and the 2-dimension coordinates of the corresponding image points. The estimated parameters can meet the need of geo-location.Keywords：ground control point with equal elevation;aerial camera;homography matrix;collinearity equation- 51
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Published：2020-08-12 -
Analysis on ground random vibration response of large-scale precision mirror mount
Abstract：Aiming at the stability problem of large-scale precision mirror mount caused by random vibration in the ICF (Inertial Confinement Fusion) facility, the finite element model of a mirror mount was established. The PSD measured on the install base level of the mount as the excitation, the random vibration response of the mount was analyzed with the PSD module of ANSYS. The analyzed results are in good agreement with the experiment values, and the actual vibration of installment base level meets the stability requirements of mirror mount.Keywords：large-scale precision mirror frame;finite-element analysis;random vibration- 54
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Published：2020-08-12 -
Mechanical property of sagittal focusing crystal and effect of slope error on incidence angle
Abstract：The principle of dynamically bending of the crystal in a sagittal focusing monochramator by flexural hinge-based bender was presented and the geometric parameters of bender and crystal were optimized. Then the mechanical properties of bender and crystal were analyzed with Finite Element Method. Finally, the effect of slop error on the incident angle was calculated. The analyzed results indicate that the acceptance angle of the monochromator increases from 1 mrad to 3 mrad, and the horizontal width (FWHM) of the spot on the sample reduces from 12.5 mm to 2.5 mm after replacement.The anticlastic curvature caused by bending is 1 700 times as long as the sagittal curvature, and the incident angle error is only 2.2 μrad. The Von Mize stress on the bender is about 800 MPa. When Beryllium-Cu is selected as the material of the bender, the linear relationship between the curvature of crystal in 0.57~1.72 m and the driving forces in 8~2.67 N is obtained. The analyzed results also indicate that the designing parameters are achievement in that the flux and photo intensity are increased and the requirement of fast and tunable scanning on the XAFS measurement is satisfied at the same time.Keywords：sagittal focusing;double crystal monochromator;flexural hinge;bender;slope error- 44
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Published：2020-08-12 -
Research on driving system and controlling means of PZT
Abstract：A controlling means of PZT driving system was introduced in detail. By application of DLL library for PZT power supply and Timer control of VB, the real-time programmable output of control voltage was realized. According to the nonlinearity and hysteresis of PZT, the polynomial curves of the round-trip voltage and displacement of PZT were charted, and the relational expression of voltage with displacement was obtained by MATLAB. The research supplies further scientific ways to amend and reduce the effect of nonlinearity and hysteresis error, and can improve the positioning accuracy of the system.Keywords：PZT;controlling means;hysteresis;nonlinearity- 74
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Published：2020-08-12 -
Piezoelectric type nozzle flapper valve and its control method
Abstract：A novel piezoelectric type nozzle flapper hydroelectric servo valve was developed and its control method was researched. A double nozzle baffle amplifier was designed as the prestage actuator of the double nozzle flapper hydroelectric servo valve by the low cost bimorph bend component, then the principle of the novel piezoelectric type nozzle flapper hydroelectric servo valve was introduced. Finally, for the hysteresis and creep nonlinearities of the piezoelectric component and time variation factors of the system, a single nerve-cell adaptive PSD intelligent control method was presented. Experimental results show that the overshoot and the setting time of the step respond under the PID control method is 7.9% and 0.13 s, respectively, but the overshoot and the setting time of the step respond under the proposed control method is 2.4% and 0.07 s. It is proved that the proposed control method is validaty. Experimental results also indicate that the novel piezoelectric type nozzle flapper hydroelectric servo valve has advantages in simple structure, low cost and high precision, it can meet the need of high precise control system in the recent period.Keywords：bimorph;nozzle flapper hydroelectric servo valve;nonlinearity;single nerve-cell adaptive PSD control- 49
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Published：2020-08-12 -
Application of high-speed camera to characteristic measurement of MAV
Abstract：In order to measure the dynamic characteristics of high rotating MAV with weak signal and big interference, a new measurement way based on the high speed camera was presented. Being different from the traditional way measured only in theory, this kind of new way can measure angle of high rotating object accurately in camera speed of 15 000 frame/s. In this experiment, two angles, the blade angle and connecting rod angle,is need to measured in four steps, the angles are disposed for the convenience of next step, then the MAV are taken pictures in two different angles, front and side.For gaining the required angles, the pictures are saved and analyzed using MATLAB software by four different kinds of detecting ways, including checking the edge of the image and fitting curve. Finally, the relationship between the motor voltage, pitch angle and the distorting angle of the connecting rod in the eight groups of curves are achieved by corresponcling to the angles and voltage. The precision of the angles is analyzed,which is proved that this way is effective.Keywords：angle measurement;high speed camera;MATLAB;edge checking;MAV- 51
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Published：2020-08-12 -
Design calculation and analysis of half corner-filleted flexure hinge
Abstract：A half corner-filleted flexure hinge was introduced.Based on the Castigliano’s second theorem, closed-form equations were formulated for compliances of half corner-filleted flexure hinge and precision of rotation was also evaluated in terms of compliances. Experimental results show the effect of two-dimensional geometric parameters on the performance of a half corner-filleted flexure hinge,it is coincident well with the finite element analysis. Compared with symmetric corner-filleted flexure hinge, the performance of flexure hinge can be evaluated in terms of flexibility, precision of rotation and sensitivity to axial effects. Experiment results can provide some theoretic foundations for flexure hinge design.Keywords：half corner-filleted flexure hinge;compliance;precision of rotation;finite element- 63
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Published：2020-08-12 -
3D feature extract method for tool wear based on grating projection
Abstract：Image detection method for carbide tool wear based on laser grating projection is presented. Phase information in undesformed areas that belongs to object shadow and data regression with the least-squares iteration are used to obtain phase distribution parameters on the ideal reference plane. For unnecessary to collect deformed grating images of object reference plane, it reduces operation steps and takes no solution for the phase of object reference plane. Experiments show that the method realizes the on-line measurement by detecting the parameters during the time slots caused by replacing tools of numerical control machine. Also, the measurement data of maximum width, maximum area, circumference and maximum depth in z direction of wear region come to the results that measurement standard deviation and relative accuracy are no more than 0.01. Therefore, this method is a precise 3D profilometry of wear area.Keywords：laser technique;CCD;grating projection;tool wear;3D profilometry- 49
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Published：2020-08-12 -
Regression analysis of wavefront fitting using Zernike polynomial
Abstract：A new method of wavefront fitting based on regression analysis of normal equation is proposed using Zernike polynomials. By stepwise regression, the optimum combination of Zernike mode is obtained and the method is verified by computer simulated wavefront. Computer simulations show that the PV and RMS relative fitting errors are only 1.11% and 0.07%,respectively.Keywords：information processing technique;laser interferometry;wavefront fitting;stepwise regression;Zernike polynomial- 89
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Published：2020-08-12 -
Image fusion binarization method based on SOFM neural network
Abstract：An image fusion binarization method based on Self-organization Feature Map(SOFM) neural network is presented. The characteristic and the learning algorithm of SOFM neural network are introduced. The first threshold of the image is derived from the clustering characteristic of SOFM, and it is treated as a initialization of the circulated iteration method to obtain the second threshold of the image. The binarization for the original image is carried on using the second threshold to obtain the first fusing image. Then, the binarization for the original image is performed more again using the improved Bernsen method to obtain the second fusing image. Finally, two fusing images are merged based on the minimum principle of image gray values to get the final binarization image. This method can effectively eliminate the ghost and can also separate the characters very well. Experimental results show that the method is effective, and its binarization effect surpasses Bernsen method and Ostu method obviously, moreover it has good compatibility.Keywords：image fusion;binarization;Threshold;SOFM neural network;pixel- 88
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Published：2020-08-12 -
Optimization of spatial filter matrix
Abstract：The key techniques of spatial filter matrix used in large laser facility such as super-long-distance beam transmission, beam control, beam quality control, stability of supporting structure, adjustment accuracy of all coupling glasses, stability of glass mounts, off-axis adjustment are studied. This paper surveys current technology of spatial filters, determines the specifications of the system, and finally provides a comprehensive solution for the structure design of spatial filter by using "Pro/E" software program in the 3-D simulation model of spatial filter matrix. The key components and specifications are analyzed carefully, and new structure design and techniques are employed. The rigidity, strength, and vibration modes of the structure are analyzed using "ANSYS" software program. The structure has been optimized by bidirectional embedding of finite element method and CAD. To seek the proof for the equipment structural flexibility, it has been tested with a slight shock to check the components and units, which has significant influence on the structure stability.Keywords：high-power solid state laser facility;spatial filter;stability;simulation;bidirectional embedding- 54
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Published：2020-08-12 -
Fast gray projection algorithm and its application to electronic image stabilization
Abstract：By analysing the gray projection algorithm and correlation function curves for detecting motion vector in image sequence in electronic image stabilization technique, a fast searching algorithm on the basis of single peak characteristic is proposed, and compared with the full-search method which can cause time delay. By selecting two points, a and b within the search coverage , calculating and comparing their correlation measure, also judging the search direction, a new search coverage is confirmed, which is one half of the old one in size of coverage. Repeating this steps, the motion vector of image sequence frames can be obtained quickly. Experimental results show that when the size of the original searching coverage is 2n+1, its operation load is n+2 instead of 2n+1 of the full-search method, which reduces the computational load greatly. This method has been applied to ship-borne electronic image stabilizer and confirmed in high calculation speed and high accuracy on the test result.Keywords：electronic image stabilization;gray projection algorithm;motion vector;searching coverage- 73
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Published：2020-08-12 -
Implementation of coefficient of Haar wavelet filter by single-mode-fiber coupler
Abstract：A design of wavelet filter of waveguide is given using single-mode-fiber coupler as a basic unit to implement a coefficient. The couplers with various power divisions are designed, then, these couplers are combinated appropriately. Their solutions are proved to be accurate, integrated easily and parameter-stable. The geometry features relevant to coefficient implementation of fused single-mode-fiber coupler, the coupling behavior of the taper region with gradually changing cross section and the uniform coupling region are discussed. Finally, a 3 dB coupler is given to implement the coefficient of Haar wavelet transform filter successfully by simulation with an error less than 3%. This result verifies the correction and the effectiveness of the design.Keywords：optical fiber coupler;optical wavelet;Haar wavelet- 46
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Published：2020-08-12 -
Mark image geometric distortion calibration in alignment system for multilevel imprint lithography
Abstract：A distortion model based on cubic polynomial is established concerning various linear and nonlinear distortions in the alignment system based on video image for multi-level imprint lithography and a calibration technique based on controlled points is adopted to solve the model. By minimizing the error object function, the indeterminate coefficients of the distortion model are obtained. The calibration results are evaluated by the standard deviation of calibration error, and the results show that the fitting error is 0.22 μm. By introducing distortion correction based on this model, the alignment error due to image geometric distortion in the alignment system is reduced from 2.5 μm to 0.25 μm, which meets the requirement of precise positioning of alignment marks.Keywords：image distortion;calibration;alignment;imprint lithography- 63
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Published：2020-08-12 -
Nonlinear target tracking method based on optimized wavelet features
Abstract：For tracking in complicated environment,a nonlinear target tracking method based on optimized wavelet features is proposed. Gabor wavelet network (GWN) is used to describe the features of the object. GWN includes a set of wavelets, and each of their parameters is computed by optimization procedure. The tracking framework is based on optimized particle filter and each particle figures a set of possible motion parameters. L-M optimization is then employed to drive the particles to the local peak values,and tracking with optimized particle filters is robust and efficient as a result of multimodality. The tracking result shows that the algorithm is robust to illumination variation and noise, and it also has the strong ability of tracking under local occlusion. Compared with standard particle filter method, the average tracking error of the proposed algorithm is within 1 pixel, which has been reduced by 50%.Keywords：particle filter;Gabor wavelet network;L-M optimization;visual tracking- 62
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Published：2020-08-12 -
Application of threshold denoising based on wavelet packet decomposition to vehicular CAN-bus
Abstract：In order to identify the correct failure code in a vehicular CAN-bus disturbed by the unforeseen damage of the controllers, application of threshol denosing based on wavelet packet decomposition was proposed here. The disturbed signal was decomposed into the multiscale wavelet domain by minimal Shannon entropy criteria. Then, the threshold based on Stein's unbiased risk estimation was used to eliminate the noise in the high frequency coefficients and the double criteria,and holding frequency singleness and little energy losses were used to set the threshold of the low frequency coefficients. Finally, the denoised signal was achieved by the invert WPD. Experimental results show that the S/N radio of the denoising technique in proposed method has been increased 1/3 over that of tranditional method,which can effectively get the correct facult-code while the some controller is damaged in CAN bus.Keywords：WPD;best tree;mixed threshold;risk function;CAN bus- 54
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Published：2020-08-12
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