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Issue 12 ， 2011
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Off-axis three-mirror system based on freeform mirror
Abstract：A freeform off-axis three-mirror system based on a freeform mirror was designed for the long focal length and wide-field off-axis three-mirror system in a space telescope. To obtain a system with a focal length of 4 500 mm, field of view of 11° and the ratio of the total length of system and the focal length in 1/3, the design and performance between traditional off-axis three-mirror system and freeform off-axis three-mirror system were compared. In the designed optical system, the freeform mirror was introduced to the secondary mirror to enhance system optimization and improve the balance capacity for optical aberration. After the comparison and optimization, the relative aperture of 1/9.5 was chosen.In the system, the average of wavefront error of all field of view is better than 0.030λ(λ=632.8 nm), and the average of the Modulation Transform Function(MTF) of all field of view is greater than 0.434(71.4 lp/mm) that is close to the diffraction limitation. Furthermore,the MTF has im- proved more than 5% compared to that of traditional TMA system and the departure of the secondary freeform mirror and theoretical spherical surface is only 1.1λ(λ=632.8 nm). The highly precision testing can be accomplished only by a standard sphere combined with the non-null testing method based on digital mask,which solves the problem of large-aperture convex freeform mirror testing and is helpful for the manufacturing of freeform secondary mirror. The off-axis three-mirror system based on freeform secondary mirror shows its advantages in smaller cubage, better realizability in engineering, better wavefront error and higher MTF.Keywords：optical design;optical remote sensor with long focal length and wide field;off-axis three-mirror system;freeform mirror- 86
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Published：2020-08-12 -
Diagnosis of X-ray polarized spectrum of laser-produced plasma by modified double-crystal method
Abstract：A polarized spectroscopy was designed and manufactured based on the laser-produced plasma experiments to diagnose the X-ray polarization of a laser-produced plasma in 0.2-20 nm. The experiment was performed at the 20 J laser facility in Research Center of Laser Fusion, China Academy of Engineering Physics (CAEP). In the experiment, Poly Ethylene Terephthalate(PET) crystals were used as dispersive elements in the two orthogonal directions and the imaging plates with the effective area of 30 mm×80 mm were taken as detectors. The optical paths of the X-ray beam were about 980 mm and 310 mm from the source to the detectors via the PET crystals, respectively. The X-ray spectrum emitted from the aluminum plasmas was recorded by the image plates. It shows that the polarization of the two Al Ⅻ spectra are about 0.123 3 and 0.148 1 after correcting helium resonance and combination spectrum. The experimental results demonstrate that there is anisotropic phenomenon in the laser-produced plasma, and the proposed method is effective to diagnosis of the polarized spectrum of high-temperature plasma.Keywords：polarized spectrometer;spectral measurement;X-ray diagnosis;laser-produced plasma;polarization- 40
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Published：2020-08-12 -
Accuracy analysis of calibration for imaging spectrometer by using diffuser method
Abstract：The calibration of an imaging spectrometer by using the diffuser method should consider not only the accuracy of calibration instruments,but also the effects of instrument and geometric parameters from the imaging spectrometer on calibration results. According to the calibration principle of imaging spectrometer using the diffuser method, this paper deduces the expression of the collected signal electron number in each spectral channel of the imaging spectrometer by taking the parameters as self-variables, and it analyzes the effects of the incident angle of standard lamp, the distance of standard lamp to the diffuser, the slit direction and the observation incident angle of the imaging spectrometer on the electron number collected by the detector pixels. The results show that when the F number is set to be 3 and 4, the entrance pupil in 0.1-0.2 m, the standard lamp illuminating angle less than 12° and the distance of the standard lamp in 0.5-2 m, the change of the signal electron number can be less than 1%.It satisfies the accuracy need of the calibration by using the diffuser method.Keywords：imaging spectrometer;diffuser method;radiometric calibration;spectral and radiometric characteristics- 51
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Published：2020-08-12 -
Design of improved off-axial TMA optical systems
Abstract：The key design of off-axial Three-mirror Anastigmat(TMA) systems was summarized,and an improved design of the off-axial TMA optical systems was proposed with a new optical structure. By taking two designed systems for examples, the optical elements of the TMA system were reasonably arranged, the secondary mirror was designed as a spherical surface, and the primary and the third mirrors were optimized with high-order aspheric coefficients. Obtained results show that the Modulation Transform Function(MTF) curve of the designed system approaches to the optical diffraction limit with an improved value of 0.6 at the spatial frequency of 50 pl/mm. Compared with the common off-axial TMA optical system, the Strehl ratio can be increased from 0.91 to 0.93. The surface tolerance is relaxed from λ/50 to λ/40, and the assembling tolerances of the primary mirror, second mirror and the third mirror can be relaxed by a factor of 4. The improved design makes the manufacture and assembly of the off-axial TMA optical system much easier, and helps the system to achieve excellent performance in the level of optical diffraction limit. These are beneficial to the popularization of off-axial TMA optical systems.Keywords：space borne remote sensor;optics design;off-axial Three-mirror Anastigmat(TMA) system;optical manufacture;optical assembling- 45
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Published：2020-08-12 -
Stray light suppression of star photoelectric detection system for space target in daytime
Abstract：In consideration of stray light sources of a star photoelectric-detection system, this paper analyzes the generation of the stray light and its transmission characteristics, and proposes how to evaluate the effects of stray light on the photoelectric-detection system. A reasonable suppression scheme for the stray light is provided for guiding the design of opto-mechanical structure of the system. Then the main baffle, baffle vane and the coating technology are used to eliminate the effect of stray light on the opto-mechanical structure. The opto-mechanical structure of the system is simulated by a software and the results show that their Point Source Transmittances (PSTs) before and after eliminating the stray light have been reduced by two orders of magnitude between 10-8 and 10-10. Meanwhile, the obtained detection data in experimental field demonstrate that the scheme can extract a detection im- age with 5 star magnitudes, and the stray light has been suppressed effectively.Keywords：telescope;stray light;photoelectric detection;main baffle;baffle vane;Point Source Transmission(PST)- 51
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Published：2020-08-12 -
Calculation of change of space intersection angle for mapping camera
Abstract：This paper researches the calculation method for the change of space intersection angle of a mapping camera, for the change of the angle should be within 5″ to ensure the reliability of transmitting data in orbit. First, the temperature field was calculated for high and low temperature operating conditions with the I-deas software. Then, the calculated temperature field was input to a structural model as temperature load to complete the temperature mapping from a temperature model to the structural model, namely, from a simple model to a complex model. The thermal-elastic deformation was calculated and the center of optical element deformation was obtained. Finally, the change of space intersection angle of the mapping camera was calculated in two operating conditions with a self-programming software. The results show that the change of intersection angle is below 5″ when the temperature operating condition is changed. It concludes that the calculated method can get the accurate change of intersection angle and the calculated data can benefit to the analysis on the space mapping.Keywords：mapping camera;space intersection angle;temperature mapping;thermal-elastic deformation- 47
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Published：2020-08-12 -
Design of Golay 3 telescope system
Abstract：The primary mirror of a two-reflective system for a telescopy was replaced by a Golay 3 sparse aperture to reduce its weight and volume while remaining high angular resolution. Firstly, the two-reflective system with a spherical primary mirror and a hyperbolic secondary mirror was designed according to the third-aberration theory. Then, the primary mirror was substituted by a Golay 3 sparse aperture,and the relationship between fill factor and sub-mirror radius was analyzed. The whole system was simulated by Zemax software to obtain the Modulation Transform Function(MTF) and the spot diagram of the system. Finally, two silicon correcting lenses were inserted behind the secondary mirror to optimize the radius of the correcting lens and imaging distances and to improve the field of the system. By Zemax simulation, it is shown that the cutoff frequency of the system has been decreased from 114.5 lp/mm to 97.7 lp/mm and to 77.8 lp/mm as the fill factor reduces from 22.2% to 15% and to 10%,respectively. Moreover, inserting the correcting lens in front of the image plane can greatly enlarge the field of the system,which shows the RMS value of maximum spot radius without correcting lens is about 2.5 times larger than that with a correcting lens in the field of 0.3°.Keywords：telescopy;Golay3 sparse aperture;two-reflective system;fill factor;correcting lens- 68
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Published：2020-08-12 -
Fabrication of solar-blind induced transmission filters by ion-beam sputtering methods
Abstract：Solar-blind UV induced Transmission Filters (SBU-ITFs) were fabricated by ion-beam sputtering. Firstly, SBU-ITFs were designed and analyzed theoretically, and the deposition of ZrO2, SiO2 and Al films by ion beam sputtering was optimized. The optical constants of ZrO2 and SiO2 films were derived from the transmitting and reflecting spectra,and the optical constant of Al film was determined by the inversion of the variable incidence ellipsometric spectrum of a sample JGS1/SiO2/Al/SiO2/air(SAS).On the basis of the research, the SBU-ITFs were fabricated by using the three films above and their optical properties were measured. The measurement for SBU-ITFs shows that the peak transmittance of the filter at the 264 nm center wavelength is larger than 60%, the transmittance band width (FWHM) is about 13 nm, and the optical density in the 300-350 nm cutoff spectral region reaches to 2.6.The analysis of the transmittance shows that the main factors affecting the properties of SBU-ITFs are a slower deposition speed for Al film and smaller amount of O2 contents remaining in the chamber during the deposition of Al film.- 43
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Published：2020-08-12 -
Stress transfer performance ofstrain sensing cable
Abstract：In a fiber strain sensing system, strain sensing cable is usually used as a sensing element instead of bare fiber.Therefore, it is necessary to explore the high stress transfer performance of a strain sensing cable.Combining Lame formula and generalized Hooke's law,this paper establishes theoretical models for a tight-jacketed sensing cable and a reinforced sensing cable based on elasticity mechanics and deduces the relationship between the strain of the cable and its stress. Then it does the simulation and experiment on samples of these two typical types of sensing cables by using Brillouir Optical Time-domain Reflectometer(BOTDR) to detect the strain of the cables. The results of theoretical calculation and the experimental measurement show that the linear rates of all the results are more than 97%,and the differences of the slope between the theoretical calculation and the experimental measurement are less than 8%, which proves the models to be effective.The models can provide a basis for stress sensing systems in determining the stress situation for an objective.Keywords：optical fiber sensor;stress transfer model of sensing cable;Elasticity Mechanics- 53
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Published：2020-08-12 -
Detecting performance and overall design of airborne daytime star sensor for navigation
Abstract：The detecting performance of an airborne daytime star sensor for navigation is analyzed and a daytime star sensor prototype is researched. Mathematical models of Signal to Noise-Ratio(SNR) and contrast of a photoelectric imaging system in daytime under noises are established, and calculated results by different focal lengths and different apertures are compared to conclude the influence of system parameters on the detection results and the requirements of optical system.The conclusion shows that the proper relative aperture of optical system is 1/15. A daytime star sensor prototype for tracking stars of magnitude 3 is designed. Tracking images of the polestar from sunrise to noon are acquired by a ground experiment using a F/15 objective, and brightnesses and contrasts of star images at different time are compared. It shows that the contrast of star image has descended from 1.55 at 5:00 a.m. to 1.2 at 12:00 a.m. The minimal degree of modulation is more than 0.03 by calculating with the prototype's parameters, which shows that the optical system with Φ70 mm and F/15 can satisfy the detecting requirements. The theoretic analysis and design is proved to be available, and the research can be a reference for developing of miniaturized and precise airborne daytime navigation star sensors.Keywords：star sensor;daytime star sensing;detecting performance;Contrast;Signal to Noise Ratio(SNR);degree of modulation- 71
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Published：2020-08-12 -
Wear mechanisms of PCD tool in high-speed milling of SiCp/Al composites
Abstract：Milling tests for SiCp/2009Al composites were performed by using Polycrystal Diamond(PCD) tools at the cutting speed of 600-1 200 m/min and the mechanisms of tool wear were investigated. A Scanning Electron Microscope (SEM) was used to examine the machined surfaces and tool wear land,an X-ray diffractometer (XRD) was used to analyze the substances on the machined surface and the laser Raman spectra and Energy Density Spectrometry(EDS) were taken to analyze the elements on the tool wear land. The results show that the tool grain breaking-off, abrasive wear, chipping and the peeling caused by the high frequency impact and the scrapt of SiC particles are the prevalent wear patterns. When high volume fraction materials or heat treated materials are milled, or the milling is at a higher cutting speed, micro-cracks will form on the PCD tools. Furthermore,volume fractions, average sizes of SiC particles, tool grain sizes, cooling and heat treating conditions have significant influence on the tool wear. It concludes that the life of PCD tools is in the range of 70-240 min. The micro-cracks are produced on the tool flank under the combined effects of SiC particle impact, cutting vibration and heat impact. Moreover,the aluminum and copper can be diffused into the tool matrix under the very high cutting temperature and cutting forces and the trivial graphitization is taken place on the PCD tools due to the catalysis of copper in the aluminum matrix.Keywords：particulate reinforced aluminum matrix composite;high-speed milling;Polycrystal Diamond(PCD) tool;wear pattern;wear mechanism- 77
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Published：2020-08-12 -
Dynamic effect in process of stopping capillary by step valve in microchannel
Abstract：The relationship between the dynamic effect of a capillary and the length of microchannel in front of a step valve was researched,then the influence of dynamic effect in the process of stopping the capillary in microchannel formed by hydrophobic and hydrophilic walls on the step valve was analyzed. According to the working principle of the passive valve of capillary and energy conservation law, the critical length in front of the step valve was calculated when the step valve stoped the capillary. The calculated length corresponding to the critical length was obtained by numerical simulation. It shows that when the actual length in front of the step valve is greater than or equal to the calculated length, the valve can stop the capillary effectively. The step valves were fabricated by bonding polydimethylsiloxane (PDMS) to glass. Experiments of stopping the capillary by the step valve were performed in a rectangular microchannel formed by three hydrophobic PDMS walls and one hydrophilic glass wall. For the series of microchannel with a depth of 40 μm and widths from 200 μm to 400 μm, the calculated length in front of the step valve is from 4.531 6 μm to 10.081 μm. In the experiments, the actual length before the step valves for effectively stopping the capillary is in the interval from 10 μm to 2 000 μm. The results show that even if the actual length in front of the step valve is 10 μm, the step valve can also stop the capillary. Therefore, the dynamic effect of the capillary can be ignored in stopping the step valves in the microchannel.Keywords：capillary;microchannel;step valve;dynamic effect- 46
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Published：2020-08-12 -
H type micro-machined resonant pressure sensor based on self-stopped etch technique
Abstract：In order to increase accuracy and reduce temperature drifts of pressure sensors, a micro-machined resonant pressure sensor with H-type doubly-clamped lateral beams was proposed based on electromagnetically driving and differential detection. First, Finite Element Method(FEM) analysis was performed to guarantee the sensitivity and the resolution of the sensor. Then, based on the boron-diffusion self-stopped etch technique, a sensor sample with good uniformity was achieved by a standard bulk Micro-electro-mechanical System(MEMS) process. Finally, the vacuum package of the sensor was accomplished by adhesive bonding using non-photosensitive BCB(Benzocy-clobutene,DVS-BCB-3022-46) and stress isolation. Experimental results show that the nonlinearity is lower than 0.02% in 0 to 120 kPa with a accuracy of 0.05% FS, and the temperature drift is less than 0.05%/℃ in -40 ℃ to 70 ℃.The sensor can suppress temperature drifts and realize pressure measurement in wide measuring range and higher precision.Keywords：Mirco-electro-mechanical pressure sensor;resonant pressure sensor;doubly-clamped lateral beam;differential detection;Adhesive bonding- 57
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Published：2020-08-12 -
Microfabrication of SU-8 cantilever micro-force sensor integrated by copper piezoresistance
Abstract：As the SU-8 cantilever integrated by a metal piezoresistance can achieve a very high force sensitive coefficient due to its low elastic modulus, this paper designs a new type of SU-8 cantilever micro-force sensor integrated by a serpent-shaped copper piezoresistive structure and fabricates a prototype with a double-layer cantilever by a novel processing method. It introduces the design principles and fabrication method for the micro-force sensors and measures its technological parameters.Experimental results show that the SU-8 micro-force sensor has good linearity range in 0-350 μN and its force sensitivity is 0.24 mV/μN and measuring error is 4.06%. It can implement the micro-force detection and has advantages of simpler production process and shorter cycle as compared with a silicon micro-force sensor. Moreover,the force sensor has potential application in biomedical research for the SU-8 with prominent biological compatibility.Keywords：SU-8;metal piezoresistance;micro-force sensor;cantilever- 59
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Published：2020-08-12 -
Influence of bond layer characteristics on strain sensing properties of FBG sensors
Abstract：As material characteristics of a bond layer directly affect the measurement accuracy of Fiber Bragg Grating(FBG) strain sensors,this paper simulates the impact of elastic modulus of the bond layer materials on strain transfer coefficient K according to the bond layer strain transfer model and the formula of strain transfer coefficient K under the premise of determining the structure size parameters. The results show that the strain transfer efficiency of metal is superior obviously to that of the organic adhesive.A contrast test is carried out. Test results indicate that the strain transfer coefficient K of the lead maintains a level of 0.98 while that of epoxy maintains about 0.90,and the former's transfer efficiency has increased by 8.9% as compared with that of the latter.By replacing epoxy with the lead,it can greatly improve the strain measurement precision, and can more fully exert fiber optic sensors' strain measurement ability.Keywords：optical fiber sensing;Fiber Bragg Grating(FBG) sensor;bone layer;elastic modulus;strain transfer coefficient- 49
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Published：2020-08-12 -
Theoretical analysis of double-ball artifact and its applications
Abstract：To ensure high-precision calibration of gear measuring instruments, the international standard ISO / TR 10064-5:2005 recommends a Double-Ball Artifact (DBA) as calibration reference. The DBA employs a high-precision sphere to replace the involute and uses an error compensation technique to obtain a high-precision involute to realize the involate traceability. The theoretical issues relating to the DBA are discussed to provide a theoretical basis for the design and application of the DBA. The error of measurement principle of DBA and its calculation function are given under the conditions of ideal installation and with installed errors for the electronic generative metrology. According to the optimized arc thoughts, the formula of the optimized center distance between the two balls is derived by the least square method. Finally, the error compensation method is described.The DBA software is designed based on the above theory and a DBA is developed with a parameter of module in 2.268 1 mm, number of teeth in 40, and a pressure angle in 20 °.Keywords：gear;gear instrument;gear measurement;Gear Artifact;Double-ball Artifact(DBA)- 50
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Published：2020-08-12 -
Design of digital EMCCD camera with mega pixels
Abstract：A design method for the digital camera based on a back illuminated 1 024 pixel×1 024 pixel Electron Multiplying(EM)CCD image sensor is proposed. The Complex Programming Logical Device(CPLD) is adopted to generate the CCD driver timing and video processing timing, EL7156C pin driver chip is used for standard EMCCD clocks, and a discrete circuit is used for EM clock. By adopting a CCD analog front-end chip VSP2566 with Correlation Double Sampling(CDS) function to sample, the image data of the CCD output are digitized. The design methods of logic timing control, driver circuit, and video processing circuit are introduced. Experiments show that the digital camera circuit can output 16 bit digital image data simultaneously at a speed of 8 frame/s,its optical dynamic range can exceed 70 dB, and the remote programmable control electron multiplication can operate at the gain more than 50 dB. The design has been used in the remote EMCCD imaging system, and also can be applied to the low light level imaging area and radiation diagnosis field.Keywords：high resolution digital camera;Electron Multiplying(EM) CCD;Correlation Double Sampling(CDS);Driver Timing- 58
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Published：2020-08-12 -
Multi-focus fusion algorithm for noisy images
Abstract：This paper attempts to improve the commonly used image multi-focus fusion methods,for they could not identify meaningful image features from noises. An antinoise multi-focus image fusion algorithm is presented. The improved adaptive block-based image fusion algorithm combined with a new focus measure with noise immunity is used to focus the noisy image effectively and to achieve good fusion results. Root Mean Square Error (RMSE) and Mutual Information (MI) are selected to evaluate the fused noisy image with different intensities and comparison experiments are performed.As compared with those of contrast pyramid, wavelet transform and Contourlet transform, the average RMSE of the fused image by the proposed method has been decreased by 4.288 9, 4.479 1 and 4.187 1 respectively, while the average MI increased by 2.366 4,3.282 5 and 2.063 9, respectively. With the noise interference, the proposed method can maintain the useful information of the source images accurately, suppress noise effects effectively and obtain better image fusion quality.Keywords：image fusion;anti-noise property;adaptive block segment;clarity evaluation fuction;genetic algorithm- 46
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Published：2020-08-12 -
Adaptive nonuniformity correction and hardware implementation of IRFPA
Abstract：Infrared Focal Plane Array (IRFPA) is easy to produce a fringe nonuniformity (NU) when it works for long hours or in a changed environment. Aiming at this problem, a dynamic Nonuniformity Correction(NUC) method was proposed in no covering imaging fields and its hardware realization technology was investigated. A scene-based algorithm,Improved Constant Statistics Nonuniformity Correction (ICS-NUC) was presented,in which the fringe NU was reduced by balancing the statistics of vertical channels, and a dynamic NUC was realized by using a forgetting factor in inter-frame iterative process. The ICS-NUC algorithm flow based on an uncooled IRFPA module with BF561 DSP platform was described. Then, two ICS-NUC algorithms,ICS by Average (ICSA) and ICS by Median (ICSM), were implemented on the platform. By these ways, the fringe NU was corrected dynamically, and whole the infrared image quality was improved. The experimental results show that the fringe NU of IR image is reduced after ICS-NUC and the NU of IRFPA module is decreased from 3.43% to 1.82% by ICSA and 0.91% by ICSM,respectively. After continuous operation by four hours, the NU of IRFPA module is still decreased from 5.05% (drifted) to 0.92% by using ICSM.It concludes that the realization of ICS-NUC algorithm on IRFPA module can lay a technical foundation for the following study and applications of high-performance thermal imaging systems.Keywords：Infrared Focal Plane Array (IRFPA);Nonuniformity Correction (NUC);Improved Constant Statistics (ICS);Digital Signal Processor (DSP)- 72
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Published：2020-08-12 -
Spot centroiding algorithm for discrete noise image and its hardware implementation
Abstract：A spot centroiding algorithm immune from noise pixels is proposed to improve the existing centroiding algorithms that can not process images with discrete noise pixels directly, and it is achieved by a Field Programmable Gate Array(FPGA). This algorithm does not depend on noise pre-process or post-process to eliminate noise pixels. Firstly,the algorithm marks the background pixel, noise pixel and the spot pixel, respectively,then each pixel is marked after it is compared with the neighbouring one. At the same time, centroid parameters that belong to the same spot are accumulated, while the real noise pixel is bypassed. Compared with currently existing algorithms, this method takes full advantage of the parallel processing ability of the FPGA. It can extract spot centroid coordinates and eliminate the noise pixel simultaneously when the image pixel is output,the pre-process image is not needed and the storage space is saved. This algorithm is especially suitable for processing the spot image with discrete and high-brightness noises caused by long exposure time.Keywords：noisy image;spot;centroiding algorithm;Field Programming Gate Array(FPGA)- 45
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Published：2020-08-12 -
Local feature description algorithm based on Laplacian
Abstract：In order to balance the robustness and building complexity of a feature descriptor, a local feature description algorithm based on Laplacian is presented. It is analyzed and illustrated that the Laplacian not only has good properties to Euclidian transformation, zoom, and linear brightness changes of an image, but also can characterize the local structure of the image. On the basis of that, a 64-dimension descriptor is built with the response of Laplacian of Gaussian. Finally, the descriptor is used to match feature points with the absolute distance as similarity measurement. Simulation results indicate that the proposed descriptor can obtain better matching results for the image with zoom, rotation, blurring, illumination varying as well as smaller viewpoint changes, and the matching speed is more than 4 times that of Scale Invariable Feature Transformation(SIFT). The proposed feature description algorithm is suitable for matching the images of structured scenes,for it is insensitive to the image transformation with rotation, zoom, luminance varying, compression or small viewpoint changes.Keywords：local feature;feature descriptor;image matching;Laplacian of Gaussian- 66
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Published：2020-08-12 -
Adaptive attitude estimation filtering with low-cost multi-sensors for MAHRS
Abstract：An integrated Micro Attitude Heading Reference System(MAHRS) based on Micro-electro-mechanical System(MEMS) gyroscopes, accelerometers, and magnetic-sensors was researched for Micro Aerial Vehicles (MAV). As traditional algorithms could not keep the attitude accuracy of the MAV during a long-time maneuvering, an adaptive attitude estimation filtering algorithm with low-cost multi-sensors was presented for the MAHRS. Firstly, this algorithm was used to establish the models of acceleration and magnetic-disturbance and took them into a state equation. In this way, it could maintain the attitude accuracy of loads during the long-time maneuvering. Then, this algorithm adopted the federated filter mode to reduce the interaction between acceleration and magnetic disturbance to improve its precision and reliability. Moreover,the algorithm made the estimation variance (P) and measurement variance (R) remain steady adaptively during different maneuvering states. By comparing with other different algorithms for the MAHRS, It shows that the presented algorithm is more accurate and reliable than other algorithms during various maneuvering states.Keywords：Micro-electro-mechanical System(MEMS);magnetic sensor;Micro Attitude Heading Reference System(MAHRS);integrated navigation;adaptive filter;federated filter- 41
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Published：2020-08-12 -
Centroid optimization of Hartmann-Shack wave-front sensor for human eye aberration detection
Abstract：In order to improve the dynamic measurement range and measurement accuracy of the Hartmann-Shack Wavefront Sensor (HSWS) in an adaptive optics system, the centroid detection for a wavefront spot pattern collected by a CCD is researched. The principle of HSWS is introduced and an adaptive centroid detection method by dynamic positioning spot region, dynamic segmenting threshold level and locking optimal detection window is presented according to the structure features of HSWS with 127 units and the distortion characteristics of actual human eye spot pattern.The effects of threshold level selection on human eye spot centriod detection are discussed and the centroid detection accuracy and noise robustness of the method are analyzed through simulation and experiments. Experimental results indicate that selecting the threshold level to be (50±3)% of the total grade amount is more appropriate and the centroid detection error can be decreased by 60% or more as compared with that of other detection methods. By using adaptive centroid detection method in the HSWS of an adaptive optical retina imaging system, human eye aberration can be reduced from 0.728λ to 0.081λ in RMS(λ=785 nm) through a closed loop correction.Moreover, the system can reach the diffraction limit basically and can obtain a retina image. These results show that the adaptive centroid detection method can select different experimental parameters aimed at the characteristics of spots, which makes up the limitations of the general methods.It meets the feasibility and practicability of human eye aberration measurement.Keywords：adaptive optics;Hartmann-Shack wavefront sensor;centroid detection;Human eye aberration- 59
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Published：2020-08-12 -
Real-time correction of imaging nonuniformity for multi-TDICCD mosaic camera on hardware
Abstract：A real-time imaing nonuniformity correction algorithm on a Field Programming Gate Array(FPGA) platform was proposed to modify the imaging nonuniformity of a multi Time Delay Intration(TDI)CCD mosaic camera. Firstly, the definition of Photo Response Nonuniformity(PRNU) and its generation in the multi-TDICCD mosaic camera were introduced. Then, the synthetical correction algorithm was presented,in which the two-point correction method was used in a single channel, gain averaging correction method among multi-channels and the scene-adaptive correction method among multi-TDICCDs. By considering the reliability and the influence of finite word-length of the FPGA, the synthetical correction algorithm was optimized and implemented on the signal processing FPGA platform. Furthermore, a scheme for modifying correction factors and spaceborne calibration were given. The experimental results indicate that the imaging nonuniformity can be decreased from 4.82% to 0.27% for a single TDICCD, and to 0.41% for a 3-TDICCD mosaic camera with the proposed correction algorithm.It also proves that this correction algorithm has high real time performance, good practicality and efficiency, and satisfies the requirements of target projects.Keywords：multi-Time Delay Interation(TDI)CCD mosaic;imaging nonuniformity;real-time correction;Field Programming Gate Array(FPGA)- 64
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Published：2020-08-12 -
Centroid location for space targets based on energy accumulation
Abstract：Sub-pixel positioning technology for CCD images is proposed to improve the astronomical location precision of space targets.The main factors affecting the positioning accuracy of targe centroids, such as image noise, discrete sampling error and window size selection are analyzed. Combining with the CCD imaging characteristics for dispersion spots, a location method for target centroids based on energy accumulation is proposed. This method uses the interpolation technique to reduce the illumination inconsistency between actual sensitive area and discrete sample points,and uses the energy accumulation of dispersion spot to select the efficient target window for optimizing target gray and eliminating random noises. Finally,a squared weighted centroid localization method is taken to calculate the centroid position. Experimental results show that the method has strong anti-interference ability and stability.It can offer a positioning accuracy of 0.01 pixel and is suitable for a low SNR condition.Keywords：astronomical measurement;space target;centroid location;energy accumulation- 48
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Published：2020-08-12 -
Realization of iterative blind image restoration by self deconvolution and increment Wiener filter
Abstract：An iterative blind image restoration algorithm based on Self-deconvolution and Incremental Wiener Filter (SDIWF-IBD) is proposed. The self-deconvolution estimation for a Point Spread Function(PSF) is applied to Iterative Blind Deconvolution(IBD) to estimating exactly the frequency domain of the PSF. The incremental Wiener filter is used in the image estimation of IBD to keep the algorithm convergence steady. To further control the convergency,an in-iterative acceleration is suggested to control the speed of algorithm convergence and reduce total external iteration. Experimental results indicate that more details are recovered in the restoration image with few distortions, and the algorithm is converged to a small error quickly. It concludes that the SDIWF-IBD algorithm has good restoration ability at a fast and controllable convergency speed, and is fit for applications in real-time.Keywords：Iterative Blind Deconvolution(IBD);self-deconvolution;incremental Wiener filter;in-iterative acceleration;algorithm convergency- 51
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Published：2020-08-12 -
FLIR target recognition based on local fuzzy threshold
Abstract：A target recognition method based on local fuzzy thresholds is presented to solve the problems of serious background interference, the absence of reference map for complex terrain objects and the low contrast between the target and the background. Firstly,a multi-threshold algorithm is designed and a saliency map is produced based on the establishment of multi-scale space. Then,the Itti model is improved and a candidate target filtering model is constructed by using the local fuzzy threshold method based on an image fuzzy rate. Finally, the detected results are precisely matched using Integral Nprod to determine the right one. The experimental results indicate that the match rate of the algorithm has increased nearly by 20% and 40% and the time consumption by 75% and 50% as compared with those of Hausdorff distance algorithm and Integral Nprod algorithm,respectively.In conclusions,the new algorithm has the advantages of high match rate, high speed and high accuracy for FLIR targets in complicated backgrounds.Keywords：multi threshold algorithm;local fuzzy threshold;target recognition;Itti model;Nprod algorithm- 44
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Published：2020-08-12 -
Implementation of SLAM by probability hypothesis density filter
Abstract：Traditional Simultaneous Localization and Mapping(SLAM) algorithm is lack of the ability to describe multiple sensor information accurately in a clutter environment, and it is prone to false data association. Therefore,this paper proposes a SLAM algorithm based on Probability Hypothesis Density (PHD) filter to deal with these problems. By taking the sensor observation and environmental map as random finite sets in every time step, a joint target state variable is constructed. Then, with the Probability Hypothesis Density(PHD) filtering, the poses and environmental map of the robot are estimated simultaneously and the PHD filter is realized by a particle filter. To avoid the error caused by cluster, a time-delay particle set outputting approach is proposed for joint target state extracting. The new algorithm can describe the observation uncertainty, loss detecting, false alarm due to a clutter and other sensor information accurately, and also can avoid the data association,by which the system state estimation is closer to real values. The simulation results show that the accuracy of the new algorithm in the vehicle localization and mapping is improved by more than 50% as compared with that of traditional SLAM algorithm. It provides a new solution for SLAM problems in the clutter environment.Keywords：Simultaneous Localization and Mapping(SLAM);random finite set;probability hypothesis density filter;particle filter;target state extraction- 69
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Published：2020-08-12 -
Semi-supervised manifold learning and its application in remote sensing image classification
Abstract：To improve the remote sensing image classification accuracy by incorporating labeled and unlabeled samples, this paper proposed a new manifold learning method, called semi-supervised manifold discriminant embedding (SSMDE). This method constructs two relational graphs through data point labels: A within-class graph and a between-class graph are used to encode the class relation information indicated in the labeled data points, and two weighted matrices are constructed based on the two graphs. Then, we utilize the labeled and unlabeled data points to construct the total scatter matrix to describe the information of all data points. Finally, the projection matrix of SSMDE can be found by solving an optimization problem. SSMDE method can not only take into account the discriminant information of labeled data, but also preserve the global structure information of all data points. The experimental results on both synthetic and remote sensing images show that the proposed method can achieve the classification accuracy rate (92.32%) and the error between the classification results by SSMDE and the Government Statistics are less than 5%, which demonstrates the effectiveness of SSMDE.Keywords：Semi-supervised Manifold Learning- 58
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Published：2020-08-12
Article
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Measurement of particles by optical fiber coupling
Abstract：By using an optical fiber coupling structure, a new particle measuring method through introducing Lorentz classic dispersion formula and multi-wavelength processing was proposed to amend the scattering influence of a sample cell wall and the change of the refractive index. Firstly, the theory of total light scattering for the particle measurement was introduced, and the problems existied in the sample cell and measurement method were studied. Then,the Lorentz dispersion formula was introduced to process the refractive index changes caused by dispersion and the multi-wave length processing was taken to obtain the average particle size and particle size distribution. By establishing an object function,a method based on the genetic algorithm was proposed to implement the inversion of particle refractive index. A new sample cell was designed and manufactured with the end face coupling of optical fiber, and the particle sample dripping placed the end face between two optical fibers was scanned by a spectrometer in multi-wavelengths.Finally, through the algorithm of the computer, the average particle size and particle size distribution were measured. The simulation and experiment result indicates that the average particle size and particle size distribution can be well determined by this method in the case of unknown refractive index.Furthermore, this method has advantages of reliability and stability. When a 2% random noise was put in the transmission extinction measurement values at two wavelengths, the inversion errors of average particle size and refraction index are less than 1% and that of the particle size distribution is less than 5%. It can meet the needs of national standard for mean errors and repeatability errors.Keywords：particle size measurement;particle distribution measurement;optical fiber coupling;multi-wavelength scanning;Lorentz dispersion formula;fiber sample cell;genetic algorithms- 47
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Published：2020-08-12 -
Spectral calibration of imaging spectrometer with convex grating
Abstract：A spectral calibration facility consisting of a monochromator and a collimator was established to calibrate the Offner imaging spectrometer with a convex grating designed by ourselves. The self-designed software for sampling and processing spectral data was used to calibrate the Offner imaging spectrometer and analyze obtained data. Calibrated results show that the calibration facility has a compact conformation,better commonality and high calibration precision,and its spectral range is better than 400-800 nm and spectral resolution is superior to 10 nm,which can satisfy the calibration need in practice.Keywords：imaging spectrometer;convex grating;spectral calibration;collimated monochromatic calibration- 48
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Published：2020-08-12 -
Strain Sensing Properties of FBG Sensors Influenced by Bond Layer Characteristics
Abstract：As an important strain transfer part to FBG, material characteristics of bond layer directly affect the measurement accuracy of FBG strain sensors. According to the bond layer strain transfer model and the formula of strain transfer coefficient K, under the premise of determining the structure size parameters, simulate the impact on strain transfer coefficient K by elastic modulus of bond layer materials, the results show that strain transfer efficiency of metal is superior obviously to organic adhesive.The contrast test has been carried out, the test results indicate that the Pb’s strain transfer coefficient K maintains the level of 0.98 while epoxy’s maintains about 0.90, Pb’s transfer efficiency increases by 8.9%.to epoxy. Replacing epoxy.with Pb can greatly improve the strain measurement precision, and can more fully exert fiber optic sensors’ excellent strain measurement ability.Keywords：FBG sensors- 30
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Published：2020-08-12 -
Infrared characteristics of the wall temperature for a single microtube during in-tube flow boiling
Abstract：In this paper, a boiling heat transfer test unit was designed and built, while the characteristics of boiling heat transfer of refrigerant in a single microtube was researched. The wall temperature of microtube was measured by TH5104 infrared thermography. The test piece was a single stainless circular tube whose external diameter (do) was 1.22mm, internal diameter (di) was 0.86mm, and length was 200mm. The infrared photography tested and recorded the wall temperature of the microtube with heat flux ranging from 65kW/m2 to 231kW/m2 at different mass flux from 1726kg/m2.s to 8635kg/m2.s. Experimental results were analyzed and discussed. The wall temperature distribution along the axial direction varies obviously. For the flow boiling in horizontal microtube, there was a large temperature difference along the whole tube during the evaporation of fluid in micro tube. Whether the difference of wall temperature is positive or negative is relative to the heat flux. And the variation of the wall temperature was affected by the heat flux, flow patterns of working fluid and heat transfer model. The more complex the flow pattern is, the more severely the wall temperature varies.Keywords：wall temperature- 36
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Published：2020-08-12 -
Research on calculation method for change of space intersection angle of mapping camera
Abstract：In order to ensure the reliability of transmitting datum on orbit, the change of space intersection angle of mapping camera is required in the scope of 5 seconds. In this paper, the calculation method is studied for the change of space intersection angle of mapping camera. First, the temperature field was calculated for high and low temperature operating condition with I-deas software. Then, the calculated temperature filed was input in structural model as temperature load. The temperature mapping was done from temperature model to structural model, namely, from simple model to complex model. The thermal-elastic deformation was calculated and the center of optical element deformation was got. Finally, the change of space intersection angle of mapping camera was calculated in two operating condition with self-programming software. The results show that the change of intersection angle is below when the temperature operating condition is changed. In a word, the calculated method can get the accurate change of intersection angle. The calculated data can benefit to the analysis on earth.Keywords：thermal-elastic deformation- 70
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Published：2020-08-12 -
Design of Golay3 telescope system
Abstract：In order to reduce the weight and volume of telescope system while remaining high angular resolution, the primary mirror of the two-reflective system is replaced by Golay3 sparse aperture, and the telescope is evaluated and optimized using Zemax sofeware. Firstly a two-reflective system is designed according to third-aberration theory with a spherical primary mirror and a hyperbolic secondary mirror; then the primary mirror is substituted by Golay3 sparse aperture, the relationship between fill factor and sub-mirror’s radius is analyzed, the whole system is simulated by Zemax sofeware to obtain the system’s MTF and the spot diagram. Finally, two Silicon correcting lens are inserted after the secondary mirror to improve the system’s field by optimizing correcting lens’ radius and imaging distances. By Zemax simulation, it is found that the system’s cutoff frequency decreases from 114.5 lp/mm to 97.7lp/mm and to 77.8lp/mm as the fill factor reduces from 22.2% to 15% and to 10%; moreover, the insertion of correcting lens before the image plane can greatly enlarge the system’s field, the RMS value of maximum spot radius without correcting lens is about 2.5 times larger than the one with correcting lens in the field of .Keywords：correcting lens- 38
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Published：2020-08-12 -
Research on Airborne Navigation Daytime Star Sensor Detecting Performance and Its Experiment
Abstract：Detecting performance of airborne daytime star sensor for navigation is analyzed and its experiment is researched in this paper. Mathematical models of SNR (Signal-Noise-Ratio) and contrast of photoelectric imaging system in daytime under noise are established, and calculated results by different focal lengths and different apertures are compared to conclude the influence of system parameters and requirements of optical system, and conclusion is get that the proper relative aperture of optical system is 1/15. Overall design of daytime star sensor prototype for tracking stars of magnitude 3 or brighter is put forward. Tracking images of polestar from sunrise to noon are acquired by ground experiment using a F/15 objective, and brightness and contrast of star images at different time are compared. The contrast of star image descends from 1.55 at 5:00 a.m. to 1.2 at 12:00 a.m. The minimal degree of modulation is always more than 0.03 by calculating with the prototype’s parameters, which shows the Φ70mm, F/15 optical system can satisfy the detecting requirements. Processing result by frames cumulating and filtering is showed in this paper. The theoretic analysis and design is proved to be available, and the research in this paper can be a reference to developing of miniaturized and precise airborne daytime navigation star sensors.Keywords：degree of modulation- 39
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Published：2020-08-12 -
Research of a new-style off-axis three-mirror system
Abstract：In order to realize the long focal length wide-field off-axis three-mirror system in space telescope, the mathematical model of optical freeform mirror was disscussed, the design of new-style freeform off-axis three-mirror system based on freeform mirror was studied. The system required a focal length of 4500 mm, field of view of 11°,the ratio of the tatal length of system and the focal length is 1/3. The design and performance comparison between traditional off-axis three-mirror system and new-style freeform off-axis three-mirror system whose secondary mirror is freeform mirror were complished. In the new-style optical system, the freeform mirror was introduced to the secondary mirror, the variable of optimization was increased, and the balance capacity of optical aberration was enhanced. After the comparison and optimization, the relative aperture of 1/9.5 was chosen, the average of wavefront error of all field of view was better than 0.030λ(λ=632.8nm), and the average of the MTF of all field of view was greater than 0.434(71.4lp/mm) which reached the diffraction limitation. The MTF was improved more than 5% compared to the traditional TMA system. During the design and optimization, the realizability of the manufacture technology was disscussed, the departure of the secondary freeform mirror and theoretical spherical surface was only 1.1λ, the highly precision testing was complished only by standard sphere and non-null testing method based on digital mask, the problem of large-aperture convex freeform mirror testing was solved, it is helpful for the manufacturing of freeform secondary mirror. The results indicates that the new-style off-axis three-mirror system based on freeform secondary mirror has a series of advantages of smaller cubage, better realizability in engineering, better wavefront error and higher MTF, and it can meet the requirement of space remote sensing optical system.Keywords：freeform mirror- 47
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Published：2020-08-12 -
New design of the off-axial TMA optical system
Abstract：The development of the optical system of the off-axial three-mirror-anastigmat (TMA) has been restricted for a long time by the current design level, and the difficulties in manufacture and test. In this paper, an improved design of the off-axial TMA optical system is proposed, with a new optical structure, and two design examples are provided. The optical elements of the TMA system are reasonably arranged, the secondary mirror is designed as spherical surface, and the primary and the third mirror are optimized with high-order aspheric coefficients. The MTF curve of the designed system approaches that of the optical diffraction limit, with an improved value of 0.6 at the spatial frequency of 50pl/mm. Compared with the normal off-axial TMA optical system, the Strehl ratio can be elevated from 0.91 to 0.93. The surface tolerance is relaxed from λ/50 to λ/40, and the assembling tolerance of the primary mirror, the second mirror and the third mirror can be relaxed by a factor of 4. The improved design makes the manufacture and the assembly of the mirrors of the off-axial TMA optical system much easier, and helps to achieve excellent performance of the system in the level of optical diffraction limit. These are beneficial to the popularization of the off-axial TMA optical system.Keywords：optical manufacture and assembling- 51
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Published：2020-08-12 -
Modified Double-crystal Diagnosis for X-ray Polarid Spectrum of Laser-produced Plasma
Abstract：To diagnose X-ray polarization of laser-produced plasma in a wavelength of 0.2 ~ 20 nm, a novel polarized spectroscopy is designed and manufactured based on spatial resolution in laser-produced plasma experiments. The experiment was carried out at the 20J laser facility of Research Center of Laser Fusion, China Academy of Engineering Physics (CAEP). In the experiment, PET crystals are used as dispersive elements in the two orthogonal directions. The imaging plates, the effective area of 30 mm×80 mm, are taken as detectors. And the long optical paths of the X-ray beam are about 980 mm and 310mm from the source to the detectors via the PET crystals, respectively. The X-ray spectrum emitted from the aluminum plasmas was recorded by the image plates. It is calculated that the polarization were respective about 0.1233 and 0.1481 of the two Al Ⅻ spectrum by correcting helium resonance and combination spectrum. The experimental results demonstrate that there is anisotropic phenomenon in laser-produced plasma. This is an effective technique to diagnose the polarid spectrum of high-temperature plasma.Keywords：laser-produced plasma- 32
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Published：2020-08-12 -
Design of Mega Pixels Digital EMCCD Camera
Abstract：A design method of digital camera around a back illuminated 1024×1024 pixels EMCCD image sensor is proposed. A CPLD is adopted to generate the CCD driver timing and video processing timing. The EL7156C pin driver chip is used for standard EMCCD clocks, and a discrete circuit is used for EM clock. Adopting a CCD analog front-end chip VSP2566 with CDS function to sample and digitize the CCD output into 16bits digital image data. The design method of logic timing control, driver circuit, and video processing circuit is introduced. The digital camera circuit can output 16 bits digital image data simultaneously at the speed of 8 frames per second. Experimental results show that the optical dynamic range can exceed 70dB, and the remote programmable control electron multiplication can operate at the gain more than 0.1e/ADU. The design has used in the remote EMCCD imaging system, which can be applied in the low light level imaging area and radiation diagnosis field.Keywords：Driver Timing- 41
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Published：2020-08-12 -
Fabrication of solar-blind induced transmission filters by ion-beam sputtering methods
Abstract：本文对采用离子束溅射沉积方法制备“日盲”紫外诱导透射滤光片进行了研究。首先对“日盲” 紫外诱导透射滤光片进行理论设计与分析，然后分别对离子束溅射方法沉积ZrO2、SiO2 和Al 薄膜工艺进行了优化。利用反射与透射光谱反演解析获得了ZrO2 和SiO2 薄膜的光学常数，利用JGS1/SiO2/Al/SiO2/air（简称SAS）样品的变角度椭偏光谱反演精确获得了Al 薄膜的光学常数。在此基础上，采用上述三种薄膜材料优化制备了“日盲”紫外诱导透射滤光片，测量了滤光片的光谱性能。对光谱性能的分析表明，滤光片的峰值波长位于264nm，峰值透过率大于60.0%，透过峰带宽（FWHM）约为13nm，在300-350nm 波段的截止度达到了2.6OD，制约离子束溅射制备“日盲”紫外诱导透射滤光片性能的主要因素是Al 金属膜的溅射沉积速率以及沉积Al 膜时腔体中残余的O2 含量。Keywords：induced transmission- 27
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Published：2020-08-12 -
Analysis of Stress Transfer Performance of Strain Sensing Cable
Abstract：In a fiber strain sensing system, strain sensing cable is usually used as sensing organ instead of bare fiber. High stress transfer performance of strain sensing cable is required to provide qualified accuracy and sensitivity. In a strain sensing system which contains strain sensing cable, the detected strain is the strain of the fiber. This strain can’t directly reflect the actual stress on the sensing cable. This paper has established theoretical models of tightly jacketed sensing cable and reinforced sensing cable based on elasticity mechanics, combining Lame formula and Generalized Hooke's Law. Meanwhile, this paper has proceeded simulation experiment on samples of these two typical types of sensing cables, using BOTDR to detect the strain of the cables. The results of theoretical calculation match the experimental measurement, the linear rate of all the results are more than 97%,the differences of the slope between theoretical calculation match the experimental measurement are less than 8%, which proves the model in this paper is effective.Keywords：Elasticity Mechanics- 37
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Published：2020-08-12 -
Effect of the Parameter of Imaging Spectrometer on the Accuracy of Calibration Using Diffuser Method
Abstract：Using the diffuser method to calibrate the imaging spectrometer, not only the calibration instrument is needed to be considered ,but also the incident angle of the standard lamp, the distance of the standard lamp to the diffuser, the slit direction , the observation incident angle and the parameter of the imaging spectrometer are needed to be considered. The expression of the collected signal electron number in each spectral channel of the imaging spectrometer detector pixels about the above parameters was deduced according to the principal of the calibration of imaging spectrometer using diffuser method in this paper. And the effect of the incident angle of the standard lamp, the distance of the standard lamp to the diffuser, the slit direction and the observation incident angle on the electron number collected by the detector pixels was discussed. The results indicate that F number of 4 and 3, the entrance pupil in the range of 0.1m~0.2m, the standard lamp illuminating angle is less than 12?, the angle changes 0.5?, the distance of the standard lamp is in the range of 0.5~2m, the distance changes 1mm, make the change of the signal electron number less than 1%. Satisfying the need above can make the accuracy of the calibration using diffuser method higher.Keywords：spectral and radiometric characteristics- 52
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Published：2020-08-12 -
Stray Light Analysis of Solar Photoelectric Detection System on Space Target
Abstract：Abstract: Most conventional spacious solar photoelectric-detection systems suffer from unexpected stray light. This paper demonstrates the effects on photoelectric detection system bring out by stray light. On this foundation, build up evaluation index of stray light system, to search the reasonable programme to eliminating stray light. A detailed telescope system geometry model was created, and scatter models were created for telescope and enclosure components. By the means of designing the structure of main baffle, baffle vane and the coating technology. In order to verify the prosperity of structure that designed, we utilize software to analysis opto-mechanical model before and after eliminating stray light. The simulations shown that point source transmittance (PST) of the system was thus reduced by up to two orders of magnitude between 10-8 and 10-10. Meanwhile, the experiment obtained clean detection data which satisfies the system requirements. Stray light has been suppressed effectually, and so measurement precision was improved from detection graphics.Keywords：PST- 56
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Published：2020-08-12
Modern applied optics
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Compensation of signal for reflective grating engraved on steel ring
Abstract：In order to improve the measuring accuracy of a steel ring reflective grating,a grating signal compensation system is designed. The system is used to compensate the signal amplitude,DC voltage and the phase of the grating, respectively, for which two grating signals have a better orthogonality. First, according to the sampling method for steel ring reflective grating signals, an electronic processing system is created. And then several compensation algorithms are established aiming at the signal amplitude,DC voltage and the phase.By taking the steel ring reflective grating with 8 192 lp/mm as a platform and the results of testing precision as a basis of adjudication,the proposed signal compensation system is verified. The results show that the precision compensated has been improved by 2.28″ with an increasing magnitude of 50%.Obtained results prove that the signal compensation system is feasible.Keywords：steel ring encoder;reflective grating;sensor;Lissajou diagram;signal compensation- 53
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Published：2020-08-12 -
Pre-stressed six-axis force/torque sensor based on Stewart platform
Abstract：A pre-stressed six-axis force/torque measurement method based on a Stewart platform was established to extend its measuring range. Compared to the traditional Stewart six-axis force/torque sensor,the principle of the pre-stressed Stewart six-axis force/torque measurement was analyzed. Then, structure design of the sensor was finished. By using the ANSYS software, a finite element model for the pre-stressed Stewart six-axis force/torque sensor was established. According to this model, the vibration modal was analyzed, and the natural frequencies and vibration modes were obtained. Finally, principle of the sensor calibration was analyzed, and the sensor coupling matrix was calculated according to the data of a static calibration experiment. Experimental results indicate that this pre-stressed Stewart six-axis force/torque sensor has the measuring ranges of 0~3 000 N for the force and 0~300 N·m for the torque, and its measuring accuracy is better than 7.5% of the actual data. It shows its advantages in wide measuring range, easy to decoupling and convenient for assembly.Keywords：Stewart parallel structure;six-axis force/torque sensor;decoupling matrix- 48
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Published：2020-08-12 -
Design and microfabrication of polymer micro-force sensor integrated piezoresistive
Abstract：Various piezoresistive micro-force sensors were developed for a demand on perception and measurement in the field of MEMS. Doped semiconductor silicon material is commonly used in piezoresistive micro-force sensor production. SU-8 cantilever integrated metal piezoresistive achieves very high force sensitivity coefficient due to low elastic modulus. We designed a new type of SU-8 cantilever micro-force sensor integrated serpent-shaped copper piezoresistive structure and samples with double cantilever were fabricated by a kind of novel processing. Experimental results show that SU-8 micro-force sensor has good linearity ranged from 0 to 350 μN with a sensitivity of 0.24 mV/μN and error of 4.06%. It can satisfy micro force detection, and compared to silicon micro-force sensor, SU-8 micro-force sensor has simpler production process and shorter cycle. Besides, SU-8 is winning for its prominent biological compatibility leading to a more extensive application prospect in biomedical research.Keywords：cantilever- 40
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Published：2020-08-12 -
Fundamental of double-ball artifact
Abstract：Abstract: To ensure high-precision calibration of gear measuring instruments, the international standard ISO / TR 10064-5:2005 recommends a Double-Ball Artifact (DBA) as calibration reference. The DBA employs a high-precision sphere instead of the involute, by means of error compensation technique, to reach high-precision involute for traceability. The theoretical issues relating to the DBA are discussed in this paper to supply theoretical basis of the design and application of DBA. The error of measurement principle of DBA and its calculation function are given under the conditions of ideal installation and being installed with error for the electronic generative metrology; according to the optimized arc thoughts, the formula of optimized center distance of two ball is derived by the least square method; finally, this paper describes the error compensation method. The DBA software was designed based on the above theory and a DBA was developed with parameters of module 2.2681mm, number of teeth 40, and pressure angle 20 °.Keywords：Gear Artifact- 34
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Published：2020-08-12 -
PCD Tool Wear Mechanisms in the High-speed Milling of SiCp/Al Composites
Abstract：Objective: Tool wear and the mechanisms were investigated when high-speed milling SiCp/2009Al composites. Method: Milling tests were performed using PCD tools in the cutting speed range of 600-1200m/min. The scanning electron microscope (SEM) was used to examine the machined surfaces and tool wear land. XRD was used to analyze the substances on the machined surface and Laser Raman and EDS were used to analyze the elements on the tool wear land. Result: The results show that tool grain breaking-off, abrasive wear, chipping and peeling were the prevalent wear patterns. When milling the high volume fraction material or the heat treated material, or milling with higher cutting speed, micro-cracks will form on the PCD tools. Volume fraction, average size of SiC particles, tool grain size, coolant and heat-treatment have significant influence on the tool wear. Conclusion: The tool life of PCD tools was in the range of 70-240min. The very high-frequency impact and scrape of SiC particles were the main mechanisms for the above wear patterns. The micro-cracks were produced on the tool flank under the combined effects of SiC particle impact, cutting vibration and heat impact. The aluminum and copper had diffused into the tool matrix under the very high cutting temperature and cutting forces. Trivial graphitization had taken place on the PCD tools due to the catalysis of copper in the aluminum matrix.Keywords：wear mechanisms- 44
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Published：2020-08-12 -
High performance Micro-machined Resonant Pressure Sensor
Abstract：In order to increase accuracy and reduce temperature drift, a micro-machined resonant pressure sensor based on electromagnetically driven H-type doubly-clamped lateral beams and differential detection is proposed in this paper. First, FEM analysis was carried out to guarantee the sensitivity and resolution of the sensor. Then based on the boron-diffusion self-stopped etch technique, the sensor samples were achieved by standard bulk MEMS process, which were of good uniformity. Finally, the vacuum package of the sensor was accomplished by adhesive bonding using non-photosensitive BCB (DVS-BCB-3022-46) and stress isolation. Experimental results indicate that the nonlinearity is lower than 0.02% in the range of 0~120kPa，with the accuracy 0.05% FS, and the temperature drift is less than 0.05%/℃ in the range of -40℃ to 70℃.Keywords：Adhesive bonding- 34
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Published：2020-08-12 -
Study on analysis of dynamic effect in process of stopping capillary by step valve in microchannel
Abstract：Abstract:In order to analyze the dynamic effect in the process of stopping the capillary by the step valve in microchannel formed by hydrophobic and hydrophilic walls, the relationship between the dynamic effect of the capillary and the length before the step valve was researched. First, when the step valve stops the capillary, the critical length before the step valve is calculated according to the working principle of the passive valve of capillary and energy conservation law. Then we obtained the calculated length corresponding to the critical length by numerical simulation. When the actual length before the step valve is greater than or equal to the calculated length, the valve can stop the capillary effectively. The step valves are fabricated by bonding polydimethylsiloxane (PDMS) to glass. Experiments of stopping the capillary by the step valve were performed in the rectangular microchannel formed by three hydrophobic PDMS walls and one hydrophilic glass wall. For the series of microchannel with the depth of 40μm and width from 200μm to 400μm, the calculated length before the step valve is from 4.5316μm to 10.081μm. In the experiments, the actual length before the step valves for effectively stopping the capillary is in the interval from 10μm to 2000μm. Experimental results show that even if the actual length before the step valve is 10μm, the step valve can also stop the capillary. Therefore, the dynamic effect of the capillary can be ignored in the stopping process of the step valves in the microchannel.Keywords：dynamic effect- 28
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Published：2020-08-12
Micro/nano technoloy and fine mechanics
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A Solution to SLAM Problem Based on Probability Hypothesis Density Filter
Abstract：The traditional SLAM algorithm model is lack of the ability to describe multiple sensor information accurately in the clutter environment, and is prone to false data association. To deal with this problem, a novel SLAM algorithm based on the probability hypothesis density (PHD) filter is proposed. It models the sensor observations and environmental map as random finite sets in every time step, and constructs joint target state variable. The new algorithm estimates the robot’s poses and environmental map simultaneously through the PHD filter, and the PHD filter is realized by particle filter. To avoid the error caused by cluster algorithm, it uses a time-delay particle set outputting approach in joint target state extracting. The new algorithm model can depict the observation uncertainty, loss detecting, false alarm due to clutter and other sensor information more naturally and accurately, it also avoids the data association, the system state estimation is closer to real values. The simulation results show that the accuracy of the new algorithm in vehicle localization and mapping is improved by more than 50% compared with traditional SLAM algorithm. This algorithm provides a new solution to SLAM problem in the clutter environment.Keywords：target state extraction- 48
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Published：2020-08-12 -
FLIR Target Recognition Algorithm Based on Local Fuzzy Threshold
Abstract：A new target recognition method based on local fuzzy threshold is presented to solve the problems of serious background interference, the absence of reference map for complex terrain object and low contrast between target and background. Firstly, multi-threshold algorithm is designed and saliency map is plot based on the establishment of multi-scale space. Secondly, Itti model is improved and candidate target filtering model is constructed by using local fuzzy threshold method based on image fuzzy rate. Lastly, the detected results are precisely matched using Integral Nprod to determine the right one. The results of the experiments indicate that the match rate of the algorithm increases nearly 20% compared with Hausdorff distance algorithm and time consumption decrease 75%,and increases nearly 40% compared with Integral Nprod algorithm and time consumption decreas 50%.The new algorithm has the advantages of high match rate, high speed and high accuracy for FLIR target in complicated background.Keywords：Nprod algorithm- 23
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Published：2020-08-12 -
Centroid optimization algorithm of Hartmann-Shack wave-front sensor for human eye aberration detection
Abstract：In order to improve the dynamic measurement range and measurement accuracy of Hartmann-Shack Wavefront Sensor (HSWS) in adaptive optics system, the study of centroid detection for wavefront spot pattern collected by CCD is proposed. This paper introduces the principle of HSWS and presents an adaptive centroid detection method of dynamic positioning spot region, dynamic threshold level segmentation and optimal detection window locking, according to the structure features of Hartmann-Shack wavefront sensor of 127 units and distortion characteristics of the actual human eye spot pattern. Paper discusses the effects of threshold level selection on human eye spot centriod detection and analyses the centroid detection accuracy and noise robustness of the method through simulation and experiments. Experimental results indicate that selecting the threshold level as (50±3)% of total grade amount is the most appropriate and the centroid detection error can be decreased by 60% or more compared with other detection methods. The adaptive centroid detection method is used in HSWS of the adaptive optics retina imaging system, human eye aberration can be reduced from 0.728λ to 0.081λ in RMS(λ=785nm) through close loop correction, and moreover, the system can reach the diffraction limit basically and get retina image. These results show that the adaptive centroid detection method can selecte different experimental parameters aimed at the characteristics of spots, and make up for the limitations of the general methods, and then it can meet the feasibility and practicability of human eye aberration measurement.Keywords：Human eye aberration- 33
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Published：2020-08-12 -
Real-time correction of the non-uniformity for multi-TDICCD mosaic camera on FPGA
Abstract：To solve the non-uniformity problem of multi-TDICCD mosaic camera, a real-time non-uniformity correction algorithm was proposed and implemented on FPGA platform. Firstly, the definition of PRNU and the reason of non-uniformity in multi-TDICCD mosaic camera imaging were introduced. Secondly, the synthetical correction algorithm was presented, which was two-point correction method in single channel, gain averaging correction method among multi channels, scene-adaptive correction method among multi TDICCDs. Finally, considering the reliability and the influence of finite word-length of FPGA, the synthetical correction algorithm was optimized, and implemented on signal processing FPGA platform. Furthermore, the correction parameters could be modified after spaceborne calibration when necessary. The experimental results indicate that the non-uniformity can be decreased from 4.82% to 0.27% for one TDICCD, and to 0.41% for 3-TDICCD mosaic camera with the proposed correction algorithm, which proves that this correction algorithm has high real time performance, good practicality and efficiency, and satisfies the requirements of target project.Keywords：FPGA- 35
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Published：2020-08-12 -
IRFPA Adaptive Nonuniformity Correction and Hardware Implementation
Abstract：It is easy for infrared focal plane array (IRFPA) to produce fringe nonuniformity (NU) when works for long hours or the environment changes violently. Aiming at this problem, a dynamic nonuniformity correction without covering the imaging field and hardware implementation technology was investigated. A scene-based algorithm - improved constant statistics NUC (ICS-NUC) was presented. The fringe NU was reduced by balancing the statistics of vertical channels, and a dynamic NUC was realized by using forgetting factor in inter-frame iterative process. An ICS-NUC algorithm flow based on an uncooled IRFPA module with BF561 DSP platform was described. Then, two ICS-NUC algorithm - mean filter ICS (ICSA) and median filter ICS (ICSM) – were implemented on the platform. It was very effective on correcting the fringe NU dynamically, and the whole infrared image quality was increased. The experiment showed that the fringe NU of IR image was reduced after ICS-NUC. The NU of IRFPA module UR was decreased from 3.43% to 1.82% (ICSA) and 0.91% (ICSM). After 4 hours continuous operation, the NU of IRFPA module UR was still decreased from 5.05% (drifted) to 0.92% (using ICSM). The implementation of ICS-NUC algorithm on IRFPA module laid a technical foundation for the following study and applications of high-performance thermal imaging systems.- 29
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Published：2020-08-12 -
Space Target Centroid Location based on Energy Accumulate Method
Abstract：In order to effectively improve the precision of the astronomical determination of space target, sub-pixel positioning technology research is very important for CCD exploration images. This article firstly systematic analysis of the main factors which affect the positioning accuracy, such as image noise, discrete sampling error and window selection etc.. Combining with the CCD imaging characteristics, a target centroid location method which based on energy accumulation is proposed. This method using interpolation technique to reduce the inconsistency which caused by the difference between the actual sensitive area light intensity and discrete sample points, and then by energy accumulation of diffuse plaque to adaptive selection the correct target window, by gray optimizing for the target to reducing random noise effect, finally using squared weighted centroid localization method to get the high precision position. Experimental results show that the method has strong anti-interference ability and stability, positioning accuracy can reach 0.01 pixels. It is suitable for low SNR condition.Keywords：Energy Accumulate- 48
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Published：2020-08-12 -
Research on multi-focus noisy image fusion
Abstract：Noise is often introduced during the image acquisition and image transfer process. The presence of noise affects image detail feature detection. The existing image multi-focus fusion methods could not identify meaningful image features from noise. An antinoise multi-focus image fusion algorithm is presented for image fusion. The improved adaptive block-based image fusion algorithm combined with a new focus measure with noise immunity solves the problem of noisy image fusion effectively and achieves good fusion results. Root Mean Square Error (RMSE) and Mutual Information (MI) are selected to evaluate the fused image with noise of different intensity. Experimental results show that compared with contrast pyramid, wavelet transform and Contourlet transform, the average RMSE of the fused image by the new proposed method is lower 4.0924, 4.1268 and 4.0735 respectively, while the average MI is higher 2.0376，2.5875 and 1.3638 respectively. The useful information of the source images can be maintained accurately with the noise interference outperforming other conventional methods in terms of fusion quality and noise reduction in the fused output.Keywords：genetic algorithm- 58
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Published：2020-08-12 -
A Local Feature Description Algorithm Based on Laplacian
Abstract：In order to balance the robustness and building complexity better, a local feature description algorithm based on Laplacian is presented. It is analyzed and illustrated that Laplacian not only has good properties to image Euclidian transformation, zoom, and linear brightness changes, but also can characterize the local structure of the image. On the basis of that, a 64 dimensions descriptor is proposed and built with the response of Laplacian of Gaussian. Some measures such as partitioning the feature point neighborhood with its domain orientation as the starting point and normalizing the feature vector are taken to make the descriptor keep invariant with image rotation and luminance changes. Finally, the descriptor is used to match feature points with the absolute distance as similarity measurement. Simulation results indicate that the proposed descriptor performs better in the case of image zoom, rotation, blurring, illumination varying as well as smaller viewpoint changes, and the matching speed is at least 4 times of SIFT. The proposed feature description algorithm is suitable for exigent real-time performance requirement areas and matching the images of structured scene, between which there is the transformation of rotation, zoom, luminance varying, compression or smaller viewpoint changes.Keywords：Laplacian of Gaussian- 44
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Published：2020-08-12 -
Iterative blind image restoration algorithm based on self deconvolution and increment Wiener filter
Abstract：An iterative blind image restoration algorithm based on self-deconvolution and incremental Wiener filter (SDIWF-IBD) is purposed. The self-deconvolution method for PSF estimation is applied to IBD to extract the Fourier estimation of PSF exactly. To keep algorithm convergence steady, incremental Wiener filter is used in image estimation step of IBD. Furthermore, in-iterative acceleration is suggested to control the speed of algorithm convergence and reduce total external iteration. Experimental results indicate that, more detail is recovered in restoration image with few distortions, and algorithm converges to a small error quickly. So, the SDIWF-IBD algorithm has good restoration ability in fast and controllable convergency speed, which is fit for application in real-time.Keywords：algorithm convergency- 55
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Published：2020-08-12 -
Spot centroinding algorithm for discrete noise image and FPGA implementation
Abstract：With currently existing spot centroiding algorithm, image with discrete noise pixel cannot be processed directly. In this paper, a new centroiding algorithm and its FPGA implementation that is immune to noise pixel is proposed. This algorithm does not depend on noise pre-process or post-process to eliminate noise pixel. Background pixel, noise pixel and spot pixel is marked differently. Each pixel is marked after it is compared with neighbouring pixel. At the same time, centroid parameters that is belong to same spot is accumulated, while noise pixel is bypassed. Compared with currently existing algorithm, this method takes full advantage of the parallel processing ability of FPGA. Centroid coordinates extracting and noise pixel eliminating runs simultaneously with picture output. The extra memory for picture pre-process is not needed and storage space is saved. This algorithm provides an effective way to process high-brightness image with discreet noise spot that is caused by long exposure time.Keywords：FPGA- 64
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Published：2020-08-12 -
A PR Adaptive Attitude Estimation Filtering Algorithm with Low-cost Multi-Sensor for MAHRS
Abstract：An integrated micro attitude heading reference system(MAHRS) was researched for micro aerial vehicles (MAV) based on the MEMS gyroscopes, accelerometers, and magnetic-sensors. Due to the fact that the traditional algorithm can not keep the attitude of MUAV accurate during a long-time maneuvering, a PR adaptive attitude estimation filtering algorithm with low-cost multi-sensor for MAHRS was presented. Firstly, this algorithm modeled the acceleration and magnetic-disturbances and took them into state equation, in this way the algorithm could maintain the attitude accurate during a long-time maneuvering; Secondly, this algorithm adopted the federated filter mode to reduce the impacts between acceleration and magnetic disturbance in order to improve the precision and reliability; Thirdly, this algorithm made the estimation variance (P) and measurement variance (R) adaptive to remain steady during different maneuvering states. Compared with other different algorithms which were used for the MAHRS, the simulation results showed that this algorithm presented was more accurate and reliable than other algorithms during various maneuvering states.Keywords：federated filter- 30
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Published：2020-08-12
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