Chinese Version Light学术出版中心
Latest Issue
Issue 11 ， 2009
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Selection and Design of Optical System for Spaceborne Hyperspectral Imager
Abstract：The paper outlines the optical systems applied in present hyperspectral imagers. The principle and characteristics of three spectrum-dividing methods with prism, grating and FT(Fourier Transform) are discussed, prism dispersion spectrometer results in high utilization rate of input light energy, but large volume and unreliability limit its application in spaceborne hyperspectral imager, grating dispersion spectrometer has low diffraction efficiency, small volume and stability in space, FT spectrometer only has no more than 50% efficiency due to beam splitter. The paper gives some representative optics adopted by present spaceborne hyperspectral imagers. Finally, an optical system with TMA telescope and two Offner convex grating spectrometer, used in a compact spaceborne hyperspactral imager is designed, small volume, high imaging quality and no spectral distortion make it applicable in spaceborne hyperspectral imager. Enlarging relative aperture of optical system can recuperate low diffraction efficiency.Keywords：hyperspectral imager;Convex Grating;Offner Spectral imaging system- 62
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Published：2020-08-12 -
Robust optimization design of Long Slit Spectrometer’s primary structure
Abstract：In order to minimize the mass of Long Slit Spectrometer (LSS)’s primary structure, and improve the structural response’s robustness, the primary structure was optimized. The effect of structure geometry tolerance and material property tolerance on the structure robustness was analyzed. Accordingly some structure geometry tolerance was altered. The robust optimization model of the LSS primary structure with the constrained conditions of the basic frequency and the objective function of total mass was established. The Monte Carlo simulation and Ant Colony algorithm was applied to solve the optimization model. The optimized structure has reduced about 17.5% in mass than the original design. Although the mass of the optimal robust design is more heavy than the mass obtained by deterministic based optimization, it is insensitive to variations on design variables within a feasible region.- 32
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Published：2020-08-12 -
Study on light scattering property of PS/PMMA
Abstract：Haze and transmittance were two important guide lines characterizing the properties of light scattering materials(LSMs). Compound LSMs with PS as light scattering agent and PMMA as matrix were studied.The results showed that LSMs was obtained with only a little PS dispersed in PMMA. The transmittance of LSMs was 80% on condition that the content of PS was 1%; The haze was could be improved from 50% to 80% with the aid of PMMAPS. The PMMAPS was able to increase the haze of LSMs by improving the compatibility between PMMA and PS. Thus, LSMs with high haze and transmittance can obtained via alteration in the amount of PS and PMMAPS.Keywords：Light scattering;haze;transmittance;PS;PMMA;PMMAPS- 45
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Published：2020-08-12 -
The research on the correction of the aberration in eyes with liquid crystal spatial light modulator
Abstract：Objective: A adaptive optics system (AO) integrates human eye wave-front sensor components and correction components was built and tested. Method: The system uses a Hartman-Shack wave-front sensor (HS-WS) and liquid crystal spatial light modulator (LCSLM) for AO-correction of the dynamic aberrations of the human eye. Result: During testing with a 5D myopic human eye, the AO system corrected ocular aberrations to a residual RMS wave-front error of 0.013(=0.808 nm). Conclusion: The LCSLM can correct the aberration in eyes effectively ,After AO correction the cone of the retina can be seen clearly.- 42
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Published：2020-08-12 -
Analysis and Characteristic Experiment Study of Single Mode Optic Fiber Coupling Sensor
Abstract：Single mode Fiber optic vibration sensor based on coupled fused tapered coupler owns many good characteristics and has been studied recently. The theory of optic fiber coupling sensor is analyzed. According to the relation that the coupler’s coupling ratio is sensitive to the coupled fused part length change and vibration frequency, strain and vibration parameter detection technology are put forward. The strain and vibration experimental system based on micro strain instrument and cantilever is setup and given in detail. Strain response of fiber coupling sensor is investigated and presented through micro strain test. Temperature and transverse interference are shown. The strain response of fiber coupling sensor is excellent. The dynamic experiments of piezoelectric sensor and coupling fiber-optic vibration sensor are accomplished and the good low and high frequency response is approved. The single mode fiber coupling sensor is feasible to measure vibration signal practically, meanwhile, some influence factors including fused part materials, coupler structure, fabrication need resolve for the engineer application in the future.- 50
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Published：2020-08-12 -
Thermal Design of CCD focal plane assembly for attitude-varied space camera
Abstract：In order to keep the temperature of CCD on an attitude-varied space camera within a limited range, a thermal control system of CCD focal plane assembly (CFPA) is designed. A thermal switch, which is the crucial part in the thermal control system, is designed with different kinds of materials. Considering the characteristics of structure of the attitude-varied space camera and its orbit, the scheme of two radiators controlling by thermal switch is presented, and the thermal design of CFPA is stated. Performance of the thermal control system was simulated with the code I-DEAS/TMG. It is shown that the temperature fluctuation of CCD is 12.34℃ on the condition of passive-thermal-control, whereas 1.73℃ on the condition of both passive-thermal-control and active-thermal-control. The thermal control system could meet the requirement of mission, the thermal design is effective and reasonable.Keywords：attitude-varied space camera;CCD focal plane assembly;thermal design;thermal switch- 67
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Published：2020-08-12 -
Experimental study on the affection of sidelobe of FBG on the multiplex demodulation result
Abstract：Based on the demodulating theory of FBG, the demodulation affection of reflection sidelobe on the fiber Bragg grating strain sensor is analyzed. The phenomenon that bandwidth of reflection spectrum largens, the peak value falls, and the reflection sidelobe augment when the performance of FBG sensor degenerates by theoretical deduction and simulation. Then the effect of reflection sidelobe and the loss of link connection on the FBG multiplex demodulation result are analyzed in detailed, aiming at the problem that the solution of using floating demodulation threshold and restraining reflection sidelobe are presented. The experimental results show that, the theory is validity and the method is feasibility, and the accuracy of measuring strain result is greatly improved.Keywords：fiber Bragg grating;strain sensor;series multiplexing;sidelobe- 44
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Published：2020-08-12 -
The model and errors analysis of Ion Beam Figuring in Aspheric Optics
Abstract：Abstract: We presented the motion model formulas of the ion source subsystem when the ion bean figuring (IBF) facility is used to figure aspheric optics, and also other optics. The de-convolved process of dwell time function was transferred to a linear matrix equation, which could be easy to optimize to get the optimized dwell time resolution. By the analysis of the located errors, we proposed that the final figure errors caused by the located errors of the ion source five-axis motion subsystem could be attributed to a coefficient factor, The best way to assure the IBF process stable and the spared cost is that we should take both the ion beam material removal function and the located errors into account to design the five-axis system accuracy, Only emphasis on the located errors is not economical method.Keywords：ion beam figuring;aspheric optics;located errors analysis;dwell time matrix equation- 57
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Published：2020-08-12 -
Experiments of second harmonic generation of 9.3 μm pulsed CO2 lasers
Abstract：Experiments results of mid-infrared 4.65m radiation with second harmonic generation (SHG) in AgGaSe2 crystals from a 9.3m pulsed TEACO2 laser are introduced. Based on the principles of nonlinear optics and laser frequency doubling, the pulsed TEA CO2 laser was improved for its output beam quality which made it the whole way to meet the basic requirements of pumping laser source in frequency doubling experiment and then took this laser source as fundamental wave to perform the research works for the SHG. Results show that the same AgGaSe2 crystals made by the different manufacturers displays the different surface damaged characteristics, but the resemblance to them is bulk damaged threshold values higter than surface one. The frequency-doubled maximal single pulse energy 12.9 mJ and average power 940 mW were obtained.- 74
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Published：2020-08-12 -
Optical System Design of Three Line Array Stereoscopic Mapping Camera
Abstract：The size and structure of three line array stereoscopic mapping camera is mainly determined by the optical system. It is necessary for certain the miniaturization, lightening and high reliability of the camera. Kinds of optical system configurations are analyzed and compared by the requirements of the optical system. Telecentric system is adopted to meet the requirement of stereoscopic mapping. The MTF value of each lens is close to the diffraction limit at Nyquist frequency of 77 lp/mm. The tested result shows the MTF of each optical system can reach to 0.43 at Nyquist frequency of 77 lp/mm, which can meet the requirements of precision for the mapping camera.- 61
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Published：2020-08-12 -
Image distortion rectification and resolution test of Photon-counting imaging detector with wedge-and-strip anode
Abstract：A photon-counting imaging detector with wedge-and-strip anode (WSA) can record position information on single photon or particle of incidence, and can acquire objective’s two-dimensional image. They have been widely applied in fields such as biochemistry science, space science, analytical instrumentation, and so on. In this paper, we give a detail description on a detector prototype built by us firstly, including its configuration and operating principle; then imaging distortion of such detector is analyzed, correction methods are proposed and distortion-free images are obtained. After that, the resolution tests are taken using the USAF1951 resolution target which is placed in front of the detector. The acquired image shows that the element 6th in group 2nd of USAF1951 target can be differentiate by human’s naked eyes. At last, in order to remove the subjectivity error produced by human eyes observation and ensure the measurement accuracy, the imaging modulation value is computed. The computed results is that, for the element 6th in group 2nd of USAF1951, its imaging modulation can reached 57% and 37% in vertical and horizontal respectively. This result indicated that, our detector prototype can differentiate the element 6th in group 2nd absolutely, this corresponds to 7.13linepair/mm, i.e., the spatial resolution can arrive at 0.14mm.Keywords：wedge-strip anode;photon-counting imaging;resolution chart;imaging modulation- 37
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Published：2020-08-12 -
Influence of mid- and high-frequency errors from optical manufacture on fractional encircled energy
Abstract：In view of the primary mirror of large optical system, with the relation between full frequency errors and fractional encircled energy (FEE), the mathematical model between the root-mean square gradient (GRMS) errors of mid- and high-frequency errors and FEE was established by assuming that the surface error is stationary Gaussian random progress, and the numerical computation and actual surface profile data of the model was validated. It is found the FEE almost declines in exponential form with the increasing of GRMS of the mid- and high-frequency errors and the various frequency errors transform the edge energy of the ideal intensity distribution to the centre and wider domain of the intensity distribution and the energy transfer curve vibrates again and again with the increasing of GRMS. And the influences on FEE are less than 5% when the GRMS of the mid- and high-frequency errors are less than 12nm/mm and 30nm/mm respectively under the special optical diameter and can be used to control the influence of mid- and high-frequency error on FEE and provide the support for the further finishing and figuring of the optical surface profile.Keywords：optical transmitting system;mid-frequency error;high-frequency error;fractional encircled energy;RMS Gradient- 35
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Published：2020-08-12 -
The SNR analysis of SBUV-ICCD
Abstract：The noise source and characteristic of Solar Blind Ultraviolet Intensified Charge Coupled Device (SBUV-ICCD) was analyzed. When SBUV-ICCD is working, the gain will be set to so high that the single p-e (photo-electronic) response diffuses into neighbor pixels in CCD. So we made the assumption that the system of SBUV-ICCD was linear and shift invariant, imported photo-electronic pulse response into the calculation of SNR, got the module of SNR using the principle of Fourier Transformation. When calculating the p-e response, we fitted it with planar gaussian function after we measured data directly instead of traditional ways, it will be more simple and applicable. The influence of gain on SNR was analyzed. At last the module was validated when we compared SNR between the value measured practically and calculated based on the module.Keywords：ICCD;SNR;Photo-Electronic Pulse Response- 38
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Published：2020-08-12 -
Research On Rational Harmonic Mode-Locked Phenomenon Of Passively Mode-Locked Erbium-Doped Fiber Laser
Abstract：It is analyzed that the theory of rational harmonic mode-locked and the transmission characteristic of nonlinear amplifying loop mirror(NALM),furthermore, we put emphasis on investigation of the passively mode-locked Erbium-doped fiber laser on correlative experimentation. We found that not only the steady harmonic mode-locked pulse phenomenon but also rational harmonic mode-locked pulse phenomenon took place on pulse experiment of Figure-Eight Shape passively mode-locked fiber laser. It is demonstrated that the pulse train belongs to the repetition rate of 3th-order,5th-order and 6th-order rational harmonic mode-locked pulse train by analyzing the repetition rate of pulse train.Keywords：Erbium-doped fiber laser;passively mode-locked;rational harmonic mode-locked;Nonlinear amplifying loop mirror- 44
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Published：2020-08-12 -
The studies on Hadamard mini-spectrometer based on 2D multi-micro-silicon-slits matrices
Abstract：This studies on Hadamard mini-spectrometer based on 2D multi-micro-silicon-slits matrices is presented. Multi-micro-silicon-slits matrices is produced by MEMS technique. Offner optical structure is used in the system. The phenomenon of diffraction is analysed by using the software of Matlab. The set of experiments run with the system compare the performance of Hadamard circle-S (N=23) and single silt. Feature of the presented device are for example the throughput advantage (up to the factor of 3.10).Keywords：Hadamard spectrometer;micro-silicon-slits matrices;throughput;resolution- 69
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Published：2020-08-12 -
An experimental study in small-holes EDM by current dividing
Abstract：The paper presents a new method of electrical discharge machining for small-holes in which critical value of machining can be less than primitive EDM system generates. In this study, the characters of small-holes EDM in area equalization by current dividing were studied. The research outcomes provided a foundation for small-holes EDM in area equalization by current dividing. After that, experiments to verify the stability and feasibility of EDM in area equalization by current dividing were carried out and analyzed. The results of the experiments show that drilling speed and discharge gap decrease a little，but electrodes wear .increases slightly. There is a consistency in processability between single and double electrodes, and the method helps to control the dimension precision. In a word, it is that the method in EDM by current dividing in the condition of process stability is a novel method in small-holes.Keywords：EDM;small-holes;area equalization;current dividing- 30
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Published：2020-08-12 -
WIRE ELECTROCHEMICAL MICRO-MACHINING BY USING IN SITU FABRICATED WIRE ELECTRODE
Abstract：Wire electrochemical micromachining (WEMM) is proposed as a new method of micro fabrication in this paper. Effects of the diameter of wire electrode on the machining accuracy of WEMM are investigated theoretically. In situ fabrication of wire electrode is proposed in this study to fabricate micro meter scale wire electrode. The tungsten wire electrode with the diameter of 5μm is electrochemically in situ fabricated for the production of micro structures. Micro blades with the slit width of 20μm and micro sharp-angles structure with the radius of 1μm are machined experimentally.Keywords：Wire electrochemical micro-machining;Wire electrode;In situ fabricated- 34
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Published：2020-08-12 -
Study of stale platform adaptive inverse control
Abstract：Stable platform is a complicated nonlinear system. The common PID control can not meet the requirement of high precision and fast response. The adaptive inverse control was introduced in the system of stable platform. Based on it , the system utilize its character of open circle to improve system capability. In the model building to object model and object inverse model, the NARX network is used. The algorithm uses the least square method instead of least square(LMS) to identify the parameters and design the control. The simulation results show several advantages of this control strategy, such as sensitive response, non-overshoot, good anti-disturbance, and minimal stable error, and showed dynamic/static performance was superior to those of conventional PID method.Keywords：stable platform;adaptive inverse control;LMS algorithms- 54
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Published：2020-08-12 -
Design on wavefront coding system for measuring the crack width in concrete structure
Abstract：It is very important to measure the width of cracks in concrete for monitoring the status of buildings and avoiding fatal damages of concrete structure. In order to remedy some defects such as the difficulty of accurate focusing and the image’s blur because of field curvature or less depth of field in the handy system for measuring the crack width in concrete structure which designed before based on the traditional optical imaging technology, a new system based on wave-front coding which can extend the depth of focus is designed. First, the normalized parameter of a cubic phase plate and the relationship between it and its corresponding real design parameters are discussed. Then a handy measuring system design based on wavefront coding with CODE V is completed. Finally, the cubic phase plate is made and a preliminary experiment is done. Experimental results indicate that the depth of field of the wavefront coding system based on a single lens can be extended to 15mm when resolving power is 50mm and F number is 6, which is 4.5 times of that in theory at the same F number. The system can satisfy the requirements of depth of field and imaging for measuring the width of cracks in concrete.Keywords：Concrete structure;Crack width;Depth of field;Wavefront coding;Cubic phase plate;Measuring system- 53
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Published：2020-08-12 -
Design for the focusing mechanism of space remote sensor
Abstract：Introduce a kind of focusing structure of space remote sensor, including harmonic drive and screw, line guide rail, compensate traditional focusing structures. According to the resistance torque calculation determined the motor’s model. Calculating the resolution of focusing structure is 0.43μm. The structure was experienced dynamic environment testing with whole machine, and compared focus precision after dynamic environment testing. The testing data indicate that the line tilt was less than 20″ and the displacement error was less than 5μm, met the requirement .Experimental results proved that this focusing structure was compact, high rigidity , well precision, meets using demand.Keywords：focusing structure;resistance torque;focus resolution;dynamic environment testing- 39
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Published：2020-08-12 -
Design and Implementation of an FPGA-Based Self-Repairing AMB controller for Space MSFW
Abstract：Magnetically suspended flywheel (MSFW) serves as actuator in the high precision attitude control of spacecrafts such as satellites.Magnetically suspended flywheel (MSFW) for space application requires fault-tolerant and highly adaptive real-time controller. Field programmable gate array (FPGA) , owing to its high reliability and flexibility, offers a flexible platform the development of space applications. This paper use the idea of on-chip hardware and software co-design and presented an FPGA-based digital controller with LEON soft core processor subsystem for active magnetic bearing (AMB) of space MSFW. A prototyping platform is designed to test algorithms and verify system performance. At last, a self-repairing FPGA-based AMB controller is proposed, which in theory can significantly improve system reliability.- 38
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Published：2020-08-12 -
3D Laser measurement and evaluation for brittle / ductile mode cutting of micron/nanometer-scale V-shaped groove
Abstract：Due to the difficulty of measurement and evaluation of machined micron/nanometer-scale V-shaped groove, a single-point diamond turning was employed to machine the V-shaped groove of optic glass in micron/nanometer-scale and then a non-contact laser measure technology was used to analyze the topography of machined V-shaped groove. The aim is to analyze the micron/nanometer-scale machinability of V-shaped groove and find out the evaluation method for its machining precision. First, brittle/ductile mode cutting of V-shaped groove was conducted by using a single-point diamond turning. Then, the machined V-shaped groove was measured by 3D laser meter and then by using the measured data points, the evaluation mode of form error PV and tip arc-radius of V-shaped groove was established. Finally, the effect of sub-micron-scale cutting depth was investigated on the form error PV and the tip arc-radius. The results show that there exists a critical cutting depth transferred from brittle mode cutting to ductile mode cutting in sub-micron-scale space. In ductile mode cutting, the diamond tool tip can be replicated to the workpiece, producing the sub-micron-scale V-shaped groove with the cutting depth of 0.386μm and less, the form error PV of 0.103μm and the tip arc-radius of 0.182μm. In addition, the form error PV of V-shaped groove may maintain a stable value in ductile mode cutting, but greatly increased with the increase of cutting depth in brittle mode cutting; on decreasing the cutting depth, the tip arc-radius decreases in ductile mode cutting and also is reduced to critical borderline and less for the formation of V-shaped groove. It is concluded that the form error PV and the tip arc-radius can be employed to evaluate the machining precision and micro-scale of V-shaped groove by processing 3D data derived from non-contact laser measurement.Keywords：V-shaped groove;brittle/ductile mode cutting;Laser measurement;form error PV;tip arc-radius- 48
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Published：2020-08-12 -
Strapdown Inertial Navigation System Error Model and Simulation Analyse
Abstract：In order to get the accuracy of short-time navigation of strap-down inertial navigation system (SINS), navigation error mathematic model is established, and the effect of inertial devices error on navigation accuracy of system is analyzed. With strap-down inertial navigation mechanism, aiming at the characteristic of short-time navigation, navigation equation of carrier in navigation coordinate is predigested. Attitude error of carrier is deduced by installation error of inertial devices and equivalent zero-shift of gyroscopes. Combing with navigation equation, attitude error equation and error of inertial devices, mathematic model of velocity error and position error is derived. Based on the error mathematic model, state-space model and block diagram of error model are established. Module of error model, which is combined with strap-down inertial navigation algorithm to calculate navigation data in ground within 150s, is built in Matlab/Simulink. The experimental results show that relative system error of x-axes of navigation coordinate is less than 20%, and that of y-axes and z-axes is less than 5%, respectively. Simulation results also show that the change of accelerometer accuracy influences the SINS navigation error basically.Keywords：SINS;error model;system simulation- 41
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Published：2020-08-12 -
The research on the measurement of the aircraft attitude by electro-optical theodolite
Abstract：The paper studies electro-optical theodolite method of measuring the aircraft attitude. Firstly, Single Station theodolite was introduced in a measured distance from the aircraft posture information. An exhaustive approach was used to access to the aircraft axis of the feature points and the location in the space was used to obtain space posture parameters. Secondly, the multi-station theodolite was introduced to get the information of the aircraft flight attitude by method of using all things to the intersection. Two-dimensional image to obtain objective axis by fitting algorithm using Hough transform. And then, Calculate the vertical distance of the origin to the target of the central axis and the origin to the target of the central axis of the angle between the normal and the X-axis obtaining the linear equation in the two-dimensional plane. Two-dimensional axis of the target image and the camera system's optical center only identified a space plane. The aircraft yaw axis angle and pitch angle can be obtained by getting the space axis using things to the intersection method. Experimental results show that the two yaw angle error in the calculating method is 0.28% and the pitch angle deviation is 1.1%.In this paper, the mathematical model is correct and the algorithm is reasonable in extracting effective parameters of the aircraft's attitudeKeywords：electro-optical theodolite;the aircraft attitude;Hough transform;things to the intersection method- 44
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Published：2020-08-12 -
Floating particle recognition in ampoules based on wavelet packet energy spectrum and SVM
Abstract：A method based on wavelet packet energy spectrum feature extraction and support vector machine recognition is presented in this paper to solve the problem of recognizing the floating and suspending impurities in ampoules. Firstly, the impurity zone’s image is obtained through image sequence difference and points detection division. Then, a 1-D signal can be obtained through adding the ROI row by row in axis direction of an ampoule. The 1-D signal was decomposed by wavelet packet, and the independent primary components in wavelet packet feature vector are extracted using PCA, and the wavelet packet energy spectrum of the independent primary components is taken as the feature of impurity types. As the input vector of support vector machine, the sample features can be classified rapidly by sequential minimal optimization method through training. Different types of core functions and corresponding parameters are selected for training and testing in the experiments. The results of experiments show that the recognition period of SVM decrease by 60% and the recognition precision is improve by 35%, as compared to the BP network. This method can meet the requirement on feature extraction and rapid recognition for the floating particles in production.Keywords：wavelet packet energy spectrum;feature extraction;support vector machine;type recognition;primary component analysis- 29
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Published：2020-08-12 -
A method of simulation and testing closed-loop driving cell of aerospace drift angle in real time
Abstract：Abstract: For testing the function, the performance and the reliability of driving cell of adjusting drift angle in real time, A method using FPGA was given, which can test the driving cell of adjusting drift angle. Using this method and the technology of computer, the testing system for the driving cell of adjusting drift angle was developed. The system sample the driving signals with high speed AD into the FPGA. And after analyzing the signals, the information of control impulse was formed. At the same time, the system simulates the coder to feedback the information to the driving cell, And immediately send the information of control impulse and the information of the coder simulated into the computer system to test. The system test the driving cell of adjusting drift angle, which work frequency equal to 1.2kHz, the lest interval of coder feedback equal to 10ms, the warp of feedback less than ±1 code. The experimental results show that the testing system can exactly monitor the state of the driving cell and detect the various of error of driving cell. It totally satisfies the requirements for the closed-loop testing of the driving cell of drift angle in real time- 38
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Published：2020-08-12 -
On Calibration Technology of Airborne Lidar(Updata)
Abstract：Calibration of interior origination element biases between laser scanner and navigation system is essential for Lidar before survey applications. First, control areas are detected and ascertained through laser intensity map. Then the control points are calculated with laser footprint measurements average within control area. Equations include biases and navigation parameters based on control points are set up for optimal estimation. The General Least Squares method with white technology is adopted to handle coupling measurement noise covariance and give optimal estimation of biases under least squares principle. Experiment results shows this algorithm can restrain imprecise coefficient matrix error cause by navigation system. With assumption that relax small angle and measurement noise increased, algorithm is superior to traditional method in general. This confirms algorithm satisfy the calibration requirement with both precision and robust.Keywords：airborne LiDAR;Interior origination element calibration;General Least Squares estimation;Control area- 50
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Published：2020-08-12 -
Rotary Varifocal Mechanism Driven By Ultrasonic Motor
Abstract：Varifocal is a common function in optical system, and the agency performing it is called Varifocal Mechanism. However, the traditional varifocal mechanism has several disadvantages, when moving a group of zoom lens along or across the optical axis, such as large occupation of room, complicated configuration, long time consumption, disable in self-lock when power off ,etc. In order to improve the performing of the varifocal mechanism, our research institution has developed a novel rotary varifocal mechanism driven by Ultrasonic Motor, and the test on it was successfully conducted which proved the availability of this mechanism. Moreover, this mechanism can realize several varifocal at one time, instead of two. The experiment suggested that this new varifocal mechanism realized the largest rotating angle with no error 0.432′, and corresponding ray displacement error in imager was less than 0.034mm when photo pixel was 30μm and focal length of optical system was 300mm , that less than the length of one pixel.Keywords：varifocal mechanism;rotation;ultrasonic motor;optical- 38
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Published：2020-08-12 -
Image Restoration Based on Hopfield Neural Network and Wavelet Domain HMT Model
Abstract：In order to solve the problem of unable to compress the noise and protect the details both well at the same time in the traditional image restoration algorithm based on Hopfield neural network, a new algorithm based on the modified Hopfield neural network of continuous state change and the wavelet domain hidden Markov tree (HMT) model is presented. The wavelet domain HMT model is utilized as the prior information about the statistical relationship between the image wavelet coefficients, and is introduced into the neural network model as the regularization term, the final restoration image is obtained using the energy convergence property of Hopfield neural network. Further more, a highly-parallel weight matrix determination algorithm is proposed, the weight values are computed batch by batch through the operator operation to the pattern images, in order to avoid the multiplication of large scale matrices. Experimental results demonstrate that, for either real image or artificial image, the visual quality of the restoration result is improved evidently, and the ISNR improves more than 0.3dB compared to the traditional algorithms. The objective of compressing the noise and protecting the details at the same time is reached.Keywords：image restoration;Hopfield neural network;wavelet domain hidden Markov tree model;weight matrix- 38
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Published：2020-08-12 -
2-D attitude measurement of object based on covariance matrix
Abstract：Aiming at large amount of computation, a new method of 2-D object attitude measurement based on covariance matrix is presented. Firstly, binary the image and calculate the center of object. Then, compute covariance matrix of the object area. Finally, get the ellipse area defined by covariance matrix, and compute the length and orientation of both axes. The ratio of corresponding axes is the scale change, and the orientation difference of corresponding axes is the rotation angle. The experimental results show that the presented method can calculate the rotation and scale change fast and accurately, the angle error is within , and the scale error is within ,while the computation time is 1/16 of that of log-polar method.Keywords：covariance matrix;attitude measurement;ellipse- 41
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Published：2020-08-12 -
Precise Measurement of Circles in Industrial Computed Tomography Image
Abstract：It is significant to detect circles, obtain the parameters，which can be applied to industrial computed tomography（CT） image measurements as well as the reverse engineering. A method to precisely measure circles in industrial CT image has been developed based on Facet sub-pixel edge detection and improved algorithm for calculation of probability of circles exitence. To overcome the defects of long-time calculation and memory consuming in the current method of existence probability map for detecting circles, the present method first makes sure the potential range of the center of a circle, and store the message which meet the required numerical values in the chain. By applying the method to the measurement of 10 circles in an image obtained from an industrail CT system with its spatial resolution as 2.0lp/mm, the result shows that this method has greatly improved the calculation rate, and the circles measurement accuracy is better than 0.5%.Keywords：Facet model;reverse engineering;probability of existence;computed tomography;Image measurement- 54
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Published：2020-08-12 -
Parameter identification of the point spread function in noisy and blur images
Abstract：For motion blur and defocus blur, we propose a robust bispectrum-based method to estimate the blurred parameters in noisy images. At first we calculate the bispectrum of a standard test image. Then we use curve fitting to get the function relations between statistics characteristic in bispectrum and degraded parameters. Finally, the BP neural network, which is trained by the aforementioned function relations, can accomplish the blurred parameters recognition in other noisy image. The experimental results show our method is effective in certain ranges. When SNR is 25dB，the tolerance of blurred parameters recognized is less than 0.5 pixel.Keywords：point spread function (PSF);noisy image;bispectrum;curve fitting;BP neural network- 42
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Published：2020-08-12 -
A novel video de-noising method based on 3D wavelet transform and block Context model
Abstract：In this paper, a video de-noising method based on 3D wavelet transform and block Context model(3DWTBCM) is proposed. There is a strong correlation between the frames of video sequence, and this correlation can be utilized by de-noising in 3D wavelet domain. In order to take advantage of the characteristic of the coefficients in 3D wavelet domain and noise distribution, wavelet coefficients are partitioned into subblocks firstly according to local relativity of these coefficients, then Context model is used in the corresponding subblock. The wavelet coefficients in each block are divided into several parts according to their energy distribution by 3D Context model and each part is estimated by its independent energy distribution and a suitable threshold is got. Experimental results show that 3DWTBCM achieves better de-noising performance than hierarchical 2D de-noising methods and its PSNRs improves more than 1.5dB averagely compared with common 3D de-noising methods. In terms of visual quality, 3DWTBCM can effectively preserve the video detail when de-noising the wavelet coefficients and is especially adequate to process the video frames with acute movement and plenty of texture.Keywords：video de-nosing;3D wavelet transform;blocks;3D Context model- 45
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Published：2020-08-12 -
Hyperspectral Image Lossless Compression Based on Optimal Recursive Bidirection Prediction
Abstract：This paper presents a hyperspectral image lossless compression algorithm based on optimal recursive bidirection prediction. At first, different compression model for each band is chosen according to its spectral correlation factor. If the spectral correlation factor is less than 0.9, bzip2 compression model is chosen. Otherwise, single band optimal previous prediction is performed on the reference band and optimal recursive bidirection prediction is performed on the non-reference band and the residual images are coded by JPEG-LS. Our experimental findings are reported using the algorithms designed in this paper applied to Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data. The result shows that the average compression ratio is 3.217, which is 0.09-1.374 higher than the other lossless compression algorithms.Keywords：hyperspectral image;lossless compression;bidirection prediction- 59
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Published：2020-08-12 -
Fusion of GFP fluorescent and phase contrast image using a SWT based variable-transparency method
Abstract：It is valuable to merge the green fluorescent protein (GFP) fluorescent image and its corresponding phase contrast image for the localization of the protein and sub-cellular structures. When ARSIS concept based methods which have been successfully applied to merge remote sensing images are used for the fusion of GFP fluorescent and phase contrast images, there may exist many artifacts. To overcome this limit, a variable-transparency concept is proposed to design a set of functions based on visual effects. After each pixel is assigned the multi-scaled transparency, original images can be synthesized from their results of stationary wavelet transform (SWT). Firstly 30 groups of images are used to estimate parameters involved in the function set and then 117 groups are assessed by means of qualitative tests. Quantified indexes which are related with the fused product and original images, such as the quality index Q and the high frequency correlation coefficient HPCC, are respectively calculated for inside and outside of the fluorescent area. Results demonstrate that compared with common algorithms, including the transparency method, the chessboard method and the SWT substitution method, this proposed algorithm can keep the interactive user-transparency and improve the definition of the fused product while reduce the interruption from the dark background of fluorescent images.Keywords：image fusion;transparency;ARSIS concept;phase contrast image;GFP fluorescent image- 27
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Published：2020-08-12
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