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Issue 2 ， 2008
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Evaluation of dynamic imaging quality of space film camera
Abstract：To the visible light and high resolution space film camera, besides the effect of the optical system’s imaging quality and the film resolution, camera’s imaging quality is affected by the device of image shift compensation, the control system of image shift speed and focusing accuracy. By analyzing the imaging theory of the visible light and high resolution space film camera, the imaging quality of complete appliance system is evaluated and the position of imaging plane is exactly calibrated by the MTF method. By contrasting the theoretical value and the experimental data, it is shown that the MTF method which is calculated by FFT etc. of knife edge shadow can be used to evaluate the dynamic imaging quality of the space camera.Keywords：space camera;dynamic imaging;evaluation of imaging quality;Modulation Transfer Function (MTF)- 67
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Published：2020-08-12 -
Design and stability study of the reflector mirror support for the large larse facility
Abstract：This paper analyzed a large aperture reflector mirror support for large larse facility, to which the schemes of adjustable kinematic mounts and integrative design are applied. The design solved some problem such as stability, exact constrain, fast installation and easy adjustment.This paper introduced the structure characteristic and mechanical analysis, the experimental test of sample confirms feasibility of the design.Keywords：laser facility;large aperture reflector mirror support;kinematic mounts;stability- 51
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Published：2020-08-12 -
Testing of weak aspheric surfaces by real-time interferometry
Abstract：A real-time interferometric method for testing asphere was proposed. It can measure aspherical surface of small asphericity without other null optics. When the tested asphere is close to a sphere，a sphere mirror is used as the reference surface. The phase distribution can be obtained by the the digital wavefront interferometer. The surface error was obtained by substracting the theory wavefront error from the phase datum and eliminating the translation error though least-squares fitting. Meanwhile the experiment was carried on with a 350mm aspheric mirror by this method. As results, the PV and RMS of the surface error was 0.387λ and 0.048λ , respectively; the surface map and interferogram were consistent to the surface map and interferogram tested by null compensation; and the difference of PV and RMS error between them was 0.033λ and 0.006λ , respectively. The results conclude that this method is feasible and accurate.Keywords：optical testing;aspheric surface;Interferometry;asphericity;least-squares fitting- 41
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Published：2020-08-12 -
Influence of laser distribution on the Thermal Effect of Nd:YVO4 Crystal
Abstract：Based on the analytical theory of aeolotropy, thermal distortion and temperature field distributions of laser crystal are investigated when Nd:YVO4 crystal with rectangular section is end-pumped by a laser beam of super-Gaussian distribution from a Diode Laser. By analyzing the working characteristics of the Nd:YVO4 laser crystal, a thermal model that accords with the working state of the laser crystal is established taking into account of the distribution and the radius change of laser beam. By using a kind of new solution to the heat conduction equation of the anisotropic medium, general solution expressions of the temperature field and the thermal distortion field of Nd:YVO4 crystal with rectangular section are obtained. Results show that a maximum temperature rise of 243.8C and a maximum thermal distortion of 1.99 m can be obtained in the center of the pump face when the Nd:YVO4 laser crystal is pumped by a Diode Laser with a output power of 15 Watt from the center of end face (the weight percent of neodymium ion doped in the crystal equals 0.5% ), which is in agreement with experimental results. This method can also be applied to the research on the other thermal problems of laser crystal and offer theoretical basis for effectively solving the thermal problems in laser system.Keywords：laser physics;Nd:YVO4 laser thermal analysis;super-Gaussian distribution;rectangular section;aeolotropy- 62
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Published：2020-08-12 -
Design of the laser scan optical system for the Computerized Radiography
Abstract：The Computerized Radiography is an outcome of the rapid development of computer and laser technologies, and one of its core components is the laser scanning optical system. Fθ lens, optical beam expander, and optical scanner in the laser scanning system are discussed in detailed, and some key issues of the scanning system are presented and resolved, such as the influence of the stop position on image quality, factors of influencing spot size, and determination of the form of optical scanner. Finally, the laser scanning optical system is designed by using the ZEMAX software, and good design results are obtained, wherein the spot diameter is smaller than 0.1mm, and focal length and field of view meet linearity relationship. The design results show that on-axis and off-axis aberrations of the designed laser scanning lens are almost equal, and the image quality achieves the diffraction limit.Keywords：laser scanning optical system;Fθ lens;optical design- 48
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Published：2020-08-12 -
Sub-mirror’s imaging quality study of segmented mirror synthetic aperture optics
Abstract：Exit pupil wavefront of segmented mirror synthetic aperture optics is discrete, and much different from traditional systems’. Theory of wave aberration and diffraction optics should be introduced to evaluate imaging quality simultaneously. By using the diffraction integral, two methods are used to evaluate imaging quality, which one is fit the exit pupil wavefront to Zernike polynomial directly and calculate the complex amplitude distribution, and the other way is calculate the complex amplitude distribution of each sub-exit-pupil individually, and overlap them in image plane. A segmented mirror system with three sub-mirrors primary is built, and the wavefront is obtained by ZYGO GPI interferometer, include overall exit pupil wavefront and each sub-exit-pupil wavefront. The two methods are compared and the result shows that the latter way is more precision but complex; on the other hand, the former way can satisfy the required precision and more simple, when the system exit pupil wavefront is near the diffraction limit.Keywords：synthetic aperture optical system;segmented mirror;Aberration;error analysis;wavefront- 69
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Published：2020-08-12 -
A refract-reflect telescope with meniscus corrector
Abstract：The deficiencies of the popular mass-produced telescopes of the Schmidt-Cassegrain design include their low aperture ratio and narrow spectral range. The novel systems for Cassegrain telescopes with a meniscus corrector proposed here are free of these deficiencies. Two such systems are described: a system with corrector lenses made from the same material and a system with corrector lenses made from different materials. The systems are technologically convenient (all the surfaces are spherical) and are distinguished by small lens diameters (down to 1/3 of the effective aperture), compactness, a high aperture ratio (up to 1:6.5-1:7), high-quality aberration correction, and a broad spectral range (400-1100 nm), which is sufficient for working with modern photographic materials and CCD arrays.Keywords：meniscus corrector;refract-reflect telescope;spheric primary mirror;spheric second mirrors;no fore corrected lens- 48
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Published：2020-08-12 -
Internal Model control for Electro-Optical Tracking System Based on Sampled-data Control Theory
Abstract：In this paper, a kind of two-degree-of-freedom internal model controller for electro-optical tracking servo system is presented. By converting the design of controller to a H∞ optimization problem, the system can obtain good robust performance. Considering the dynamic behavior between sampling time and multi-rate signals in system, the sampled-data control techniques such as jump transform, lifting and so on are used to the synthesis of robust controller. The simulation results show that the designed internal model controller not only can guarantee good attenuation of disturbance as well as the tracking performance, but also can finally satisfy speed control requirement for high-performance linear servo systems. By this way, the works in this paper give a new method to design the controller for servo system of electro-optical tracking.Keywords：electro-optical;servo system;internal control;robust control;sampled-data- 73
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Published：2020-08-12 -
Temperature Errors Compensation for Digital Closed-Loop Fiber Optic Gyroscope Using RBF Neural Networks
Abstract：In order to supress temperature errors of digital closed-loop fiber optic gyroscope (FOG), a scheme based on radial basis function (RBF) neural networks was designed for temperature errors compensation and its applied scale factor error model and bias error model were investigated. First, based on the distribution of FOG’s temperature errors, a scheme, which combined scale factor error compensation and bias error compensation, was designed for temperature errors compensation. A multiscale analysis algorithm of signal feature extraction was used to preprocess original testing data for higher modeling accuracy. Then two RBF neural network models were developed and their learning algorithm was improved to avoid over-fitting. Finally, the effects of the models’ input vectors on the models’ scale are discussed as well. Analysis of simulation results indicate that residaul mean square (RMS) of the scale factor error model is 0.73 and the RMS of the bias error model is 0.051 . It can satisfy the requirements of real-time temperature compensation for middle and high precision FOG.Keywords：Fiber optic gyroscope;neural network;Temperature errors;error model;error compensation- 32
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Published：2020-08-12 -
The detect capability analysis of land based photoelectricity image system
Abstract：The objects on the ground imaging on the CCD through the photoelectricity system are affected by a lot of factors such as the characteristic of objects and atmosphere and CCD capability and optical system. This paper introduced the analysis and estimate in theory for the ability of the land based photoelectricity image system. And the author had a detailed analysis and estimation for the detect capability of the optical system. At last, it proved the necessary and accuracy of the analysis through reality cases.Keywords：photoelectricity system;CCD;optical system;detect capability- 40
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Published：2020-08-12 -
Investigation of the Influence of Processing Parameter on Replication Fidelity of Microstructured Parts
Abstract：High replication fidelity is a prerequisite of high quality plastic microstructured parts in injection molding. But, there’s not an economical and practical method to evaluate and improve the replication fidelity until now. Based on part weight evaluation, this paper studied a new method of replication fidelity improvement. In order to improve replication fidelity of microstructured parts, this paper took micro lens array as the application case and the part weight as quantitative assessment index of replication fidelity, studied the effects of processing parameters(melt temperature, mold temperature, injection time, packing pressure and packing time) on the part weight of microstructured parts in injection molding by experiment. The results showed that the increase of melt temperature and mold temperature could make the packing pressure transfer to micro cavity more effectively through runner system, and increasing the part weight; The higher the part weight, the better the filling of the microstructures. In conclusion, part weight can be used to evaluate the replication fidelity of microstructured parts primarily; investigation of the influence of processing parameter on the part weight can be used to improve the replication fidelity of microstructured parts.Keywords：Microstructured parts;replication fidelity;Injection Molding;processing parameters;part weight- 49
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Published：2020-08-12 -
A kind of workspace with universal characteristics of Gough-Stewart manipulator and its analytical resolution
Abstract：In the design of pose and position fine adjustment instrument about secondary mirror in optical telescope, aiming at drawing a comparison between different designs of the Gough-Stewart platform, a new concept Universal Workspace is proposed, its analytic method is also discussed in detail. Universal Workspace is the intersection of movement ranges in 36 special directions with the strut-length qualification. The merits of Universal Workspace are as follows, Firstly, the Universal Workspace can be described in Image directly without any additional changes such as reduce dimension from 6 to 3. Secondly, figure of the Universal Workspace is simple and regular revolving solid. Thirdly, analytic solution is the boundary of Universal Workspace, and the solution is exclusive. Compared a performance index between several designs, the results indicate that, despite of the distinct differences of mechanism parameters between different designs, the Universal Workspaces have the universal characteristic, that is Universal Workspaces are all similar simple and regular revolving solids which makes the same performance index comparable within the scope of Universal Workspace, and the results of comparison lays a foundation for further optimal design.Keywords：Secondary mirror of telescope;Adjustment instrument of pose and position;Gough-Stewart parallel manipulators;workspace;Analytical resolution- 42
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Published：2020-08-12 -
The study of complex control in digital-leading for photoelectric platform
Abstract：The principle and working function of the photoelectric platform is introduced in the article. The classical control method of the velocity loop and the position loop is also described in the article. For improving the tracing precision of the system . the complex control in the digital-leading system of the photoelectric platform is put foreward. The principle and limitatiion of the feedforward control is depicted in the article.. and the article particularly describes the design method of the feedforward control in the system .the experiment result is provided. The results show that the digital-leading tracing precision of the system is improved with the feedforward control and it does not change the closed-loop property of the system- 52
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Published：2020-08-12 -
Study of the polymer flow profile in micro hot embossing
Abstract：To understand the relationship of the mold structure with the flow profile, the Deform-2D code was used to simulate the micro hot embossing process. The mold duty ratio, the ratio of the mold width to the polymer thickness (ROWT), the concave mold, the convex mold and the non symmetric mold with respect to the polymer flow profile were systematically studied for the first time. The numerical simulation results show that with the decrease of the duty ratio, the flow profile of the polymer changes from single peak to dual peak, from craggedness to flatness and when ROWT is more than 1.5, the flow profile becomes dual peak. The simulation results were verified by the relative experiments. Compared with the results of nearly no pattern height difference when embossing with the convex mold, the micro pattern height has distinct difference when the concave mold is used. The optimization strategy of the mold topological structure was proposed to improve the polymer filling efficiency. With the help of some flow barriers located at the edge of the mold, the polymer flow speed at the boundary can be decreased and the effective filling will be enhanced. The numerical results show that this optimization strategy can increase the polymer filling speed in hot embossing process.Keywords：hot embossing;flow profile;polymer;finite element method- 31
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Published：2020-08-12 -
Mixed Preisach hysteresis model and its properties research
Abstract：It is difficult to find suitable Preisach function for the classical Preisach model identified by the parametric strategy for the piezoceramic actuator which has complex construction. To improve the modeling accuracy, this paper presents an average hysteresis model as the compensation of the classical Preisach model, based on which a mixed Preisach model is defined as the weight sum of the classical Preisach model and the average hysteresis model. The weight parameter called hysteresis degree is used to describe the badness of the hysteresis linearity. As the classical Preisach model, the mixed Preisach model has the wiping-out and congruency properties which compose the representation theorem. The neural network is applied to accomplish the identification of the two models. It is experimentally proven that the predicted error of the mixed Preisach model reduces 1.77 compared with the classical Preisach model when driven by the triangle voltage and 1.26 when driven by the decay sinusoid voltage.Keywords：piezoceramic actuator;hysteresis;Preisach model- 44
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Published：2020-08-12 -
Optical testing of Dynamic characteristic of Vibrating Wheel Micromechanical Gyroscope
Abstract：To evaluate the dynamic characteristic of vibrating wheel micromechanical gyroscope, an optic testing system based on high speed camera system combining with microscope and digital image correlation technique is setup. A sequence of real time images of tested object are recorded and saved by high speed camera (32000fps) equipped microscope, then the corresponding image correlation method for angular vibrating characteristic was applied to figure out movement displacement of vibrator, and the dynamic characteristic of vibrator such as nature frequency, damp coefficient and quality factor can be obtained. As experimental results shown, the precision of image correlation will approach 0.01 pixel, the measurement error was less than 0.01%. This testing system realizes a high precision dynamic characteristic measurement for vibrating wheel micromechanical gyroscope, and it also provides an available method to research dynamic characteristic of microstructure.Keywords：high speed camera;image correlation;vibrating wheel micromechanical gyroscope;natural frequency;quality factor- 55
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Published：2020-08-12 -
Study on satellites formation design in unperturbed eccentric orbits
Abstract：Satellites formation design in unperturbed eccentric reference orbit was presented. Relative motion problem was discussed in RAC coordinate system. The relationship of orbital element differences and deputy satellite coordinates in RAC was established using the sensitivity matrix in RAC, and arithmetic of formation design in eccentric orbit was also deduced. Using the arithmetic, chief-deputy same trace formation flying orbit was designed. Simulation shows that the position error is measured by millimeter, and velocity error is measured by millimeter/second. The precision of the arithmetic can satisfy the need of formation flying mission.Keywords：Formation flying;Eccentric orbit;Orbit design- 64
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Published：2020-08-12 -
Study on Simultaneous Area Measurement for Multiple Image Objects Based on a Geodesic Active Contour
Abstract：A novel scheme to the area measurement of multiple image objects is proposed. This scheme is suitable for the simultaneous and exact measurement of multiple objects’ areas with different shape. A geodesic active contour is applied and this scheme consists of two steps. Firstly, the active contour converges to the object’s contour edge from an initial position via the iteration of level set functional . Secondly, for the convergent active contour, a sub-pixel area measurement and counting the number of internal pixels of image objects are applied to compute every object’s area simultaneously. Experiments indicate this scheme’s measurement repetition error can decrease to 0.5%. Compared to conventional area measurement schemes, this scheme is highly efficient (i.e., simultaneous measurement of multiple objects’ areas) and highly accurate.Keywords：visual detection;Image measurement;area computation;geodesic active contour- 71
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Published：2020-08-12 -
Research on correction method for CCD pixel response non-uniformity
Abstract：In the application of machine vision, it is implicitly assumed that the pixel grey level out of from CCD reflects the feature of object. So, in almost all cases, a correction of pixel grey level is neglected. But due to the occurrence of dark current and non-uniformity in CCD, the grey level of different pixel has deviation for same irradiance, for this reason, in optics precision measurement, the grey level of each pixel on CCD should be corrected, in order to accurately characters object feature. After analyzing the cases which ware related to the pixel non-uniformity, an algorithm based on least square method is introduced for correcting pixel non-uniformity. Simulation shows that the method presented is effective to correct CCD non-uniformity grey level.Keywords：CCD;non-uniformity;correcting grey level;least square method- 47
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Published：2020-08-12 -
Study on Signal-noise Ratio Model of the Laser Active Imaging System
Abstract：To judge performance of laser active imaging system, based on system imaging process, the signal-noise ratio model of laser active imaging system was built by analysing target and background reflection character, atmosphere backscattering character, range gating character, the performance of laser and receiver, By using of solid laser of wavelength 0.532μm,ICCDcamera, sync control range gating plate based on CPLD technology ,the experiment was done. finally the signal-noise ratio mode was verified.- 52
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Published：2020-08-12 -
The Multi-User Access Based on Cross-Layer CSMA of Wireless Sensor Network Spreading Communication System
Abstract：Wireless sensor network (WSN) is an asynchronous communication network based on limited energy nodes working in a bad communication circumstance. This paper discusses an improved CSMA in a spread communication WSN system, analyses the possibility of connecting MAC layer and physical layer to reduce system collision and realize multi-user access with little increase of system complexity. The main idea is adjusting the phase of sending signal according to the phase of listened signal so that the received signal of different user has different phase which can be used to distinguish them out.Keywords：WSN;Spreading System;Multi-User- 42
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Published：2020-08-12 -
An Improved Adapted Genetic Algorithm For Image Segmentation In Real-time
Abstract：To determine the optimal threshold in image automatic segmentation, a new thresholding method is proposed. In the method, the genetic algorithm carries on the global optimization to get the threshold rapidly, and the computational method of the crossover probability and mutation probability of the Adapted Genetic Algorithm(AGA) is improved. The improved AGA can guarantee that the multifamily of population and the astringency of the algorithm, and overcom the problems of a poor astringency and a premature occurrence in Simple Genetic Algorithm(SGA). Using the AGA to optimize the 2-D Fisher evaluation function that is taken as a threshold criteria, the best threshold is obtained. Then the image is segmented using this best threshold. Taking the TMS320VC5416 as the core processor, an embedded multi-objects measurement platform is built, and the multi-objects image fast segmentation and real-time measurement are realized in the platform. The experimental results show that the AGA has a good convergence rate and stability, also can not only ensure the accuracy of the image segmentation, but also shortened the time of image segmentation.Keywords：AGA;image segmentation;Fisher criterion;2-d histogram- 48
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Published：2020-08-12 -
A Fast Method for Implicit Surface Reconstruction based on RBF from 3D Scattered Points
Abstract：In this paper, we describe a fast method for arbitrary surface reconstruction from 3D scattered points based on RBF (radial basis functions) implicit surface model. According to the properties of 3D data from laser scanners, such as non-uniform, large scattered and topology unknown, we emphasize the importance of data simplification and surface geometry preserving. The crucial idea is based on the difference of nearest normal vectors and covariance matrix. We transform global implicit function into local RBF models by the partition of unity method with K-d tree data structure and the weight coefficients of local model are directly derived from solving a linear system. To smooth final surface model, these local shape functions are blended together in overlapping domains. Experiment results show that the proposed approach is not only easy, fast to implement in reconstruction from large scattered point, but also with good accuracy.Keywords：reconstruction from 3D scattered points;data preprocess;radial basis functions;implicit surface- 49
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Published：2020-08-12 -
Application of wavelet neural network in removing CCD noise in digital images
Abstract：Objetive: Nonlinearity of camera response function makes for complexity of CCD noise model and makes the traditional filter inefficient, so a wavelet neural network filter is proposed to remove CCD noise in digital images. Method: First, by analyzing the CCD noise model we find out the reason for the CCD noise model’s complexity---nonlinearity of camera response function and image intensity. Second, on the basis of analyzing ANS filter, two factors affecting the filter---filter window and image intensity are found. wavelet neural network (WNN) is used to approach the photon transfer curve (PTC) , classify the image according to the noise parameter and assign the coefficient, and then suited nonlinear filters are used to remove noise , at last all filters’ output are combined for the final output. Result: Experimental results indicate that WNN-NANS filter has a better filtering effect and increases the SNR（24.65）. Conclusion: Because of good approach to nonlinearity, neural network is combined with nonlinear ANS (Adaptive noise smoothing) filter for a new filter-WNN-NANS (neural network-nonlinear adaptive noise smoothing) filter. Experiment results show that the WNN filter is more efficient in noise removal, edge reservation and SNR.Keywords：image process;CCD noise;Nonlinear filter;Wavelet neural network;ANS (Adaptive noise smoothing) filter- 47
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Published：2020-08-12 -
Research of UV Endoscopic System Based on Embedded Computer
Abstract：After keeping on working for a long time, insulating materials will aging or damage that may cause corona discharge or fault in the special internal environment of the electric equipment. These potential faults which are difficult to be found may cause the electric equipments damage, even grave accident. The paper introduces a new electric endoscopic system which based on the technology of embedded system, ultraviolet discharge detection and image acquisition. The paper presents the theory of ultraviolet discharge detection, the block diagram of hardware platform, the process of running embedded Linux and Qtopia file system, the method of image acquisition by USB camera and, then showing the flow chart of system application program. At last, the simulant experiment been done proves the new electric power endoscopic system is useful in detecting electric power equipment, which can also provide important information of the equipment.Keywords：Electric equipment;Ultraviolet detection;image acquisition;Endoscopic system;Embedded computer- 67
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Published：2020-08-12 -
A high-accurate dimension measurement method based on sequential partial images
Abstract：In order to realize the high-accurate vision measurement of large scale machine parts, the problem that at present, the range of vision measurement is too small must be solved and the effects of image distortion on measurement accuracy must be managed to get rid of; Accordingly, a vision measurement method based on dimension characteristics of sequential partial images is proposed. Firstly, the transition distribution modality of part image edges and its effects on measurement accuracy are analyzed. To get rid of the effects, a method of edge pixel compensation is proposed, which availably improve measurement accuracy. Then, taken the dimension measurement of straight edge parts as prototype, the vision measurement method based on dimension characteristics of sequential partial images is introduced. This method consists of three steps. First, take the images of small areas in the part and produce the sequential partial images which overlap at adjacent margins one by one. Second, apply the cross-correlation matching technique and the bilinear interpolation algorithm to obtain the dimension characteristic lines of the adjoining sequential images in sub-pixel level. On the basis of it, extract the dimension characteristic of each partial image and perform sum and compensation of these sizes to get the dimension of the part. The experiment shows that, applying the edge pixel compensation method to the single image of general scale parts, the relative error is within 0.008%; applying the sequential image measurement method to large scale parts, the relative error is within 0.01%. These indicate that the edge pixel compensation method can effectively get rid of the effects of unbeknown exact location of the real edge on measurement accuracy; by limiting the image area in the center position of the photosurface, the sequential image measurement method can be used to measure large scale parts with small distortion images. It has the advantage of small error accumulation. The measurement accuracy meets the need of the accurate measurement. Edge pixel compensation method and sequential image measurement method novelly promote the precision of machine vision measurement and can be applied to the precise auto-measurement of sheet metal parts. The thought of “dividing the whole into pieces and sum the pieces making the whole” is of great value for extending the application of machine vision measurement.Keywords：vision measurement;image processing;Sequential images;Edge compensation;feature matching- 69
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Published：2020-08-12
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