Journals >Optics and Precision Engineering
Contents
2010
Volume: 18 Issue 9
27 Article(s)
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Research Article
Sensor demodulation system using PBS and PMF
WANG Kui-ru, ZHANG Jin-long, YU Chong-xiu, LIN Mei-mei, and ZHAO De-xin
A demodulation scheme based on Polarizing Beam Splitters (PBS) and inter-modal polarization interference in Polarization-maintaining Fibers(PMFs)was proposed to implement the wavelength demodulation of fiber Bragg grating sensors and to improve their precisions and stabilities. Using the principle of matrix optics, theA demodulation scheme based on Polarizing Beam Splitters (PBS) and inter-modal polarization interference in Polarization-maintaining Fibers(PMFs)was proposed to implement the wavelength demodulation of fiber Bragg grating sensors and to improve their precisions and stabilities. Using the principle of matrix optics, the mathematic model was established theoretically and the relations of system output signals and Bragg wavelengths of fiber gratings were obtained. The influences of the length of the polarization-maintaining fiber,polarized angles of input light to the principal axis of PMF and the orientation of PBS principal axis on output signals were researched and a method to improve the sensitivity of the system was presented. On the scheme above,an experimental system was set up. The results demonstrate that the scheme is feasible, in which the average precision of the wavelength demodulation is lower than 1 pm and the temperature measurement range is 90 ℃. The demodulation system has higher precision and its stability is better than that of the M-Z interference device..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 9, 1923 (2010)
Development of assembly sagittal focusing crystals with large curvatures
LI Zhong-liang, KANG Le, ZHAO Fei-yun, CHENG Xian-chao, and XU Chao-yin
To improve the performance of beamline for X-ray Absorption Fine Structure (XAFS) in National Synchrotron Radiation Laboratory(NSRL), an idea to reform the current double-crystal monochromator into a sagittal focusing crystal monochromator was proposed. An assembly crystal which cements the silicon strips with the topsTo improve the performance of beamline for X-ray Absorption Fine Structure (XAFS) in National Synchrotron Radiation Laboratory(NSRL), an idea to reform the current double-crystal monochromator into a sagittal focusing crystal monochromator was proposed. An assembly crystal which cements the silicon strips with the tops of titanium stiffening ribs was developed to used as an imaging element of the second crystal of the sagittal focusing monochromator and to minimize the anticlastic curvature and lower the breaking risk of sagittal bent crystal. Based on the parameters of the NSRL-XAFS beamline, a model of assembly crystal was designed and its focusing properties were evaluated by finite element analysis and were measured with a long-trace-profiler. The results indicate that the Full Wave at Half Maximum(FWHM) of beam spot on the sample is decreased to 3 mm from 43 mm(without focusing) in horizon, and the photon density on the sample is increased by one order of magnitude. The results meet the requirements of data quality in current available light sources..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 9, 1930 (2010)
Design of indoor simulation test system for laser warning
WANG Jian-jun, ZHANG Pei-lu, LI Yan, and CUI Shuang
Indoor simulation test systems and their key technologies used in laser warning were investigated. After simulating the actual environment, a simulation test system was established for laser-guided weapons. Firstly, the composition of the simulation test system was introduced, then, by taking the case of laser coding rIndoor simulation test systems and their key technologies used in laser warning were investigated. After simulating the actual environment, a simulation test system was established for laser-guided weapons. Firstly, the composition of the simulation test system was introduced, then, by taking the case of laser coding recognition test for an example, the simulation test methods based on receiving diffuse reflection were discussed and the key factors in the simulation test were specially studied, such as the calculation of laser energy, and the position calibration and energy analysis of diffused screen. Finally, a recognition test of laser pulse code was performed by the diffused laser signal with a pulse energy of 10 mJ. Obtained results show that the detection probability reaches 100%, which proves the feasibility of the simulation test system..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 9, 1936 (2010)
Automatic directional radiometric testing system for large aperture integrating spheres
XIE Ping, WU Hao-yu, ZHENG Xiao-bing, and ZOU Peng
An automatic testing system is developed to test directional radiometric characteristics of large aperture integrating spheres quickly and precisely. The testing system is made up of a scan unit,a trap detector and a control unit. The control unit controls the scan unit fixed with the trap detector to displace accordinAn automatic testing system is developed to test directional radiometric characteristics of large aperture integrating spheres quickly and precisely. The testing system is made up of a scan unit,a trap detector and a control unit. The control unit controls the scan unit fixed with the trap detector to displace according to the set position, then controls the data collector to collect,display and save the data.The system shows its scan ranges of plan uniformity and the directional characteristic are 1 m×1 m and ±60°,respectively. The system is used to test a large aperture integrating sphere with a diameter of 2.5 m,which is automatic and characterized by high precision and efficiency. Obtained results indicate that the plan uniformity is 0.19%, and the maximum offset of Lambert characteristic is 1.03% at ±45°.Currently,the system has been successfully applied to the test of large aperture integrating spheres for many times,and satisfied results are obtained..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 9, 1943 (2010)
Measurement of packaging-induced strain in high power diode laser bar
WANG Ye, ZHANG Yan, QIN Li, LIU Yun, and WANG Li-jun
As the strain caused by the packaging process of a diode laser influences on the output power, wavelength and the reliability of the high power diode laser bar, this paper researches the measurement of packaging-induced stain in the laser. On the basis of the variation of polarization degree of the output lights in theAs the strain caused by the packaging process of a diode laser influences on the output power, wavelength and the reliability of the high power diode laser bar, this paper researches the measurement of packaging-induced stain in the laser. On the basis of the variation of polarization degree of the output lights in the diode laser can reveal the variation of band edges of the quantum wells in active region of the diode laser bar, it deduces the dependence of the polarization degree of laser outputs on the packaging-induced stain by using electro-luminescent spectroscopy. The strain in active region of a 800 nm GaAsP/GaInP high power diode laser bar is studied and the experimental results are in good agreement with the theoretical simulation. Furthermore, the experimental results are compared with the original strain in active region of the diode laser bar, and it is found that the bar is compressed by the copper heat sink during the packaging process, and the packaging strain is induced in the active region. The packaging-induced strain at the center of the laser bar is higher than the one at the edges. Moreover, the experimental strain of the bar shows more variation apparently, which can be considered as that the defects are created in the indium solder layer fabricated by electrolytic deposition method. In the experiment, the maximum strain is 1.370×10-3 and the defect density is 40.8%.Obtained results demonstrate that the polarization degree measurement of the diode lasers can reveal the defects and the packaging-induced strains of diode lasers accurately and can well evaluate their qualities..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 9, 1951 (2010)
Reflected temperature compensation method and its experimental verification
YANG Zhen, ZHANG Shi-cheng, and YANG Li
According to the theory of infrared radiation and principles of temperature measurement using infrared imagers, a reflected temperature compensation method was proposed to compensate the effect of environmental radiant on the infrared temperature measurement. The principles and implementary methods of reflected temperaAccording to the theory of infrared radiation and principles of temperature measurement using infrared imagers, a reflected temperature compensation method was proposed to compensate the effect of environmental radiant on the infrared temperature measurement. The principles and implementary methods of reflected temperature compensation were introduced, and the theoretical calculation formula was obtained. Through the relevant experiments, it was indicated that the method can be used to compensate the reflective energies of the high-temperature objects under the condition that measured objects are arounded by high-temperature objects. The selection of infrared mirror is related to the surface of a measured object. If the measured object can be regarded as Lambertian, the aluminum foil can be chosen as the infrared mirror; if the measured material is non-Lambertian, the infrared mirror should be replaced by a material that has a similar structure with the measured object surface. After temperature compensation, it can be more accurate to measure the surface temperature of the Lambertian and the measuring error is within 2%; Furthermore, the accuracy of the temperature measurement is also greatly improved for the non-Lambertian and the measuring error is not more than 5%. Experimental results show that the method is simple and of high accuracy,and is applicable to the most of infrared imagers..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 9, 1959 (2010)
Design of high channel-count optical fiber filters based on sampled Bragg grating with discrete linear chirp structure
TU Xing-hua, LIU Feng-qing, and XU Ning
A novel approach to obtain multi-channel comb filters with various channel bandwidths is presented based on a sampled Bragg grating. A kind of high-channel-count comb filter with channel spacings of 50 GHz, 100 GHz and 200 GHz is then fabricated respectively by design of a discrete-chirped sampled Bragg grating structuA novel approach to obtain multi-channel comb filters with various channel bandwidths is presented based on a sampled Bragg grating. A kind of high-channel-count comb filter with channel spacings of 50 GHz, 100 GHz and 200 GHz is then fabricated respectively by design of a discrete-chirped sampled Bragg grating structure like a ladder in grating period. This kind of optical fiber filter is characterized by multiple equalized bands with flat-top steep-edge and high transmittance and its inter-channel isolation is more than 28 dB, in-band insertion loss is less than 0.1 dB and phase response is between 5~30 ps in the 3 dB bandwidth. By using proposed approach, the holographic phase mask with discrete-chirped coefficients can be easily prepared in low costs and good repetition. Furthermore, by changing the optical fiber parameters, the optical fiber filters with different channel bandwidths can be implemented in high stability and repetition, which has a good potential in the high-speed optical communication systems and optical interconnects..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 9, 1965 (2010)
FY-3A multi-detector radiometric calibration for infrared band of medium resolution spectral imager
HU Xiu-qing, ZHANG Li-yang, ZHENG Zhao-jun, ZHANG Yong... and HUANG Xiao-xian|Show fewer author(s)
As the FY-3A Medium Resolution Spectral Imager(MERSI) takes a cross-track scanning by 40 detectors in a thermal Infrared Window band,its radiometric calibration is more complicate than those of traditional single detectors. Therefore,this paper investigates a multi-detector radiometric calibration method for the MERSI.As the FY-3A Medium Resolution Spectral Imager(MERSI) takes a cross-track scanning by 40 detectors in a thermal Infrared Window band,its radiometric calibration is more complicate than those of traditional single detectors. Therefore,this paper investigates a multi-detector radiometric calibration method for the MERSI. Firstly, the operational calibration algorithm for the IR band of MERSI based on onboard blackbody detector-by-detector is proposed to eliminate the radiometric response difference strips.Then,based on the radiance ratios of each detector to reference detector at different blackbody temperatures, this algorithm conducts the normalization processing for SRF-different bias (spectral normalization)to alleviate the image strips by radiometric mechanism. To verify the accuracy of MERSI calibration,the inter-calibration between MERSI and Moderate-resolution Imaging Spectroradiometer(MODIS) is performed by using Simultaneous Nadir Observation (SNO).Experiments show that the difference of their brightness temperatures is about 1.0 K,which may come from their different bandwidths..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 9, 1972 (2010)
Coordinate measurement of steep conformal optics
JIA Li-de
The measurement of conformal optics is always difficult to perform in the field of ultra-precise manufacturing and measuring. In this paper, a coordinate measuring method based on stitching profile was proposed for the conformal optics. By proposed method, the profile of the conformal optics was divided into several seThe measurement of conformal optics is always difficult to perform in the field of ultra-precise manufacturing and measuring. In this paper, a coordinate measuring method based on stitching profile was proposed for the conformal optics. By proposed method, the profile of the conformal optics was divided into several sections with some overlap points, then the every local profile was measured by adjusting the attitude of the measured workpiece, which was completed by the relative movement between the measuring system and the measured workpiece in rotation and transition. Furthermore, an algorithm based on the least square was used to stitch the local profile and to reconstruct the global profile. After those, a mathematical model of the method was established and an iteration algorithm was put forward. An experimental setup was built and the corresponding measurement and data processing software were written with VC and MATLAB, respectively. Finally, an ellipse with a diameter of 120 mm and a length/diameter of 1.2 was tested. Simulations and experiments indicate that the method is practical and simple, and can reconstruct the global profile accurately..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 9, 1981 (2010)
Optical design of cross-dispersed echelle spectrograph
TANG Yu-guo, SONG Nan, Bayanheshig, CUI Ji-cheng, and CHEN Jin-yong
In order to acquire high resolution spectra in a wider spectral range, the echelle based spectrographs were researched. The general theories of the echelle gratings and the echelle spectrographs were introduced briefly, and the distinction between echelle spectrograph and common plane grating spectrograph was analyzed In order to acquire high resolution spectra in a wider spectral range, the echelle based spectrographs were researched. The general theories of the echelle gratings and the echelle spectrographs were introduced briefly, and the distinction between echelle spectrograph and common plane grating spectrograph was analyzed and compared. A high-resolution echelle spectrograph of Czerney-Turner(C-T) structure was designed by using principles of optical imaging and aberration,and its wavelength ranges were set to be 200-500 nm which were the most intensive ranges of atomic spectra. To simplify the calculation work, the aberration of 350 nm wavelength beam was eliminated.Furthermore, the incident beam was set to work at a quasi-Littrow angle to acquire high diffraction efficiency. As a cross-disperser, a catadioptric prism was used to separate the overlapped diffraction orders,therefore, a two-dimensional spectral surface was obtained by CCD. The optical system shows the merits of flat field and point-to-point imaging, and its resolution could be 2 000-15 000 in the whole wavelength ranges. This instrument is aimed to research on the absorption and emission spectra of atoms, and can improve its performance by replacing different detectors and adding peripheral circuits and software..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 9, 1989 (2010)
Measurement of nano-particles by dynamic light scattering based on spectral estimation
YANG Hui, ZHENG Gang, and WANG Ya-jing
A new dynamic light scattering analysis method based on modern power spectral estimation was proposed to resolve problems on lower resolution and variance, and power spectrum leakage in the current dynamic light scattering software.The modern power spectrum estimation algorithm and measurement system were studied. FirsA new dynamic light scattering analysis method based on modern power spectral estimation was proposed to resolve problems on lower resolution and variance, and power spectrum leakage in the current dynamic light scattering software.The modern power spectrum estimation algorithm and measurement system were studied. Firstly, the photon correlation spectroscopic theory and the scattering spectrum estimation of dynamic light scattering measurement were introduced. Then, the dynamic scattering spectrum based on modern power spectrum estimation was descripted in detail, and the order of p was calculated particularly. Furthermore, the measurement system was described,in which the hardware components included optical systems and signal processing system and the software showed the development process. Finally, a experiment was carried out on the latex particle sample solution with the particle diameters of 30, 50, 100 nm and solution transmission of 96%. The results show that the average values of the measurement error and repeatability error are 1.88% and 1.62%, respectively,which can achieve the national standard that the measurement and repeatability errors should be less than 2%, respectively..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 9, 1996 (2010)
Projected fringe profilometry for profile measurement of high reflective surface
JIANG Hong-zhi, ZHAO Hui-jie, LI Xu-dong, and LI Dong
An improved non-contact optical measuring method, projected fringe profilometry, is proposed to realize the 3-D structure measurement of high reflective surfaces. The reflection characteristics of high reflective surfaces and their effects on phase computation are analyzed, and it is pointed out that the failure reasonAn improved non-contact optical measuring method, projected fringe profilometry, is proposed to realize the 3-D structure measurement of high reflective surfaces. The reflection characteristics of high reflective surfaces and their effects on phase computation are analyzed, and it is pointed out that the failure reason of the traditional projected fringe profilometry is the mismatch of the range of reflection intensity with the dynamic range of the measuring camera. Then, the techniques of light-dark fringe projection,multi-exposure time image acquisition and image synthesis are introduced to match the measuring range of intensity of camera with the range of reflection intensity. The feasibility and useable range of the method are analyzed. Finally, the processes of fringe projection and image acquisition in the improved profilometry are given. Experimental results indicate that the improved profilometry is able to handle the problems of fringe image saturation and dark images.Moreover,it has obtained 3-D data cloud more than 99.6%, and solve the problem of loss of 3-D data. In conclusions, the improved method can measure the 3-D profiles of high reflective surfaces with non-contact methods..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 9, 2002 (2010)
Parameter correction of thermal analysis for space camera based on center composite design
CHEN Li-heng, WU Qing-wen, DONG Ji-hong, and XU Shu-yan
A method to correct thermal calculation parameters based on the Center Composite Design (CCD) was presented for enhancing the thermal analysis accuracy of a space camera. Firstly, the CCD was introduced,and the thermal tests of second mirror and baffle for the space camera were summarized. The finite element mode of thA method to correct thermal calculation parameters based on the Center Composite Design (CCD) was presented for enhancing the thermal analysis accuracy of a space camera. Firstly, the CCD was introduced,and the thermal tests of second mirror and baffle for the space camera were summarized. The finite element mode of the thermal tests was established and the thermal analysis was dealt with by a software code TMG at different load cases. The parameters of thermal analysis were designed by means of the CCD,then they were taken as the different load cases for the thermal analysis. The regression equations about the highest temperature of second mirror,free convection coefficient and the contact coefficient of heat transfer were fitted according to the results of thermal analysis. The final thermal calculation parameters were obtained by solving the regression equations based on the test results. Finally, the thermal analysis was dealt with again by the parameters that had been solved. The results show that the calculation results of parameters corrected are in agreement with the results of thermal test well,and the relative error is 2%. Moreover,the method can be applied to the thermal analysis of other space cameras and shows a good universality..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 9, 2009 (2010)
Performance testing of attitude control wheel under ceramic bearing support and grease lubricating for micro-small satellites
BAI Yue, CAO Ping, GAO Qing-jia, HUANG Dun-xin, and WU Yi-hui
In order to solve the problems on lightweight, efficient support and lubricating for the attitude control wheel in a micro-small satellite, a method using grease lubricated ceramic bearing to support and lubricate the attitude control wheel was proposed. The static frication torque, power loss, anti-temperature, anti-vIn order to solve the problems on lightweight, efficient support and lubricating for the attitude control wheel in a micro-small satellite, a method using grease lubricated ceramic bearing to support and lubricate the attitude control wheel was proposed. The static frication torque, power loss, anti-temperature, anti-vibration and life of the wheel using ceramic bearing support and grease lubricating were analyzed through experiments. The results show that the static frication torque and power loss of the ceramic bearing under grease lubricating are less than those of all-steel bearings,and the starting characteristics of the proposed wheel are very well at the temperature from -30 ℃ to 50 ℃. Moreover, the vibration resistance performances of the wheel under the testing conditions equal to the conditions when a satellite is launched perfectly. After the vibration testing, the wheel has been tested for four years under a vacuum degree of 0.02 Pa and a rotation speed of 5 000 min/s and results show the variations of current are less than 1%,which proves that the life of the attitude control wheel has more than four years and can meet the lightweight and life requirements of micro-small satellites in space..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 9, 2016 (2010)
Design of resonant MEMS temperature sensor
MA Hong-yu, HUANG Qing-an, and QIN Ming
In order to realize meteorologic temperature measurement based on frequency outputs, a resonant micro-temperature sensor with a bilayer cantilever was proposed. According to the working principle that the resonant frequency of the microcantilever will be shifted due to the thermal expansion coefficient mismatch betweenIn order to realize meteorologic temperature measurement based on frequency outputs, a resonant micro-temperature sensor with a bilayer cantilever was proposed. According to the working principle that the resonant frequency of the microcantilever will be shifted due to the thermal expansion coefficient mismatch between the two-materials,the temperature variation could be detected by driving the cantilever and detecting the resonant frequency with piezoelectric excitation and detection. The structure of the temperature sensor was designed according to the front side fabrication process of silicon. Then, the resonant modes, detectable models and the effect of temperature on these models were analyzed by means of finite element method. The resonant characteristics were also researched with a polytech laser Doppler vibrometer. The results indicate that the 2nd resonant model of the cantilever has the largest Q factor about 150 as compared with other resonant models. Furthermore, the higher mode, particularly the 2nd resonant model is more suitable for detecting the resonant frequency of the temperature sensors by utilizing ZnO as piezoelectric materials and it can offer a relative higher sensitivity about 20 Hz/℃ and temperature coefficient of frequency about 1.9×10-4/℃. These results show that the sensor can satisfy the requirements of meteorologic temperature measurement and has the advantages of high electrical stability, high sensitivity and simple signal transmission interface..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 9, 2022 (2010)
Precision of row frequency of scientific grade TDICCD camera
MA Tian-bo, GUO Yong-fei, and LI Yun-fei
In view of practical projects, this paper analyzed the influence of the precision of row frequency on the image quality of a TDICCD camera systematically by taking scroll imaging for an example. Firstly, the expression of the image motion of each pixel was deduced when the camera was scroll imaging, and the relationshiIn view of practical projects, this paper analyzed the influence of the precision of row frequency on the image quality of a TDICCD camera systematically by taking scroll imaging for an example. Firstly, the expression of the image motion of each pixel was deduced when the camera was scroll imaging, and the relationship between scroll angle and image motion velocity was established. Based on this, the Modulation Transfer Function(MTF) was used to evaluate the image quality. The influence of image motion mismatching on the MTF was analyzed in detail, and the dependence of image quality on the precision of row frequency was calculated. The results show that the bigger the scroll angle and the integral number of TDICCD are, the higher the precision of required row frequency is. Contrarily, the precision of row frequency is not required strictly. In engineering application(the scroll angle is 35°), when the integral numbers of the camera are 64 and 96, the precision of row frequency should be no less than 0.54% and 0.36% respectively for MTFmatch≥0.95, which meets the need of the system. Comparing the experimental results with the calculation analysis, it is proved that the analyzed results are correct and can provide the useful references for engineering application and designing..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 9, 2028 (2010)
Design of inner frame vibration absorbing system for optoelectronic pod
GAN Zhi-hong
In order to observe the dynamic processing of missile launching by a optoelectronic pod, an inner frame vibration absorbing system for the optoelectronic pod was developed. Firstly, the working environments and working principles of the pod were analyzed, and the necessity to damp the vibration of inner frame was pointIn order to observe the dynamic processing of missile launching by a optoelectronic pod, an inner frame vibration absorbing system for the optoelectronic pod was developed. Firstly, the working environments and working principles of the pod were analyzed, and the necessity to damp the vibration of inner frame was pointed out. The characteristics of vibration absorbing systems were discussed and how to eliminate the shaft gas was given. A module driving shaft was designed, which combined the thicknesses of torque motor and bearings to decrease the shafting space and to increase the space of effective load. Finally, an inner frame vibration absorbing system was designed. By module combination, the system is more flexible and universal. Furthermore, by using the independent appliance and carrying horizontally forward the inner frame into the outside frame, the system is easy to assemble and adjust greatly. A vibration experiment on the optoelectronic pod with an inner frame vibration absorbing system was carried out in a test field and a simulated target was also observed, obtained results indicate that the pod has a good working condition and the video image of target is clear and fluid. The tracking experiment shows that the tracking error is less than 1 mrad..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 9, 2036 (2010)
Vision measuring system for soft-landing drop test of unmanned lunar explorer
CHAO Zhi-chao, JIANG Guang-wen, HUANG Wei, SONG Shi-jun, and YU Qi-feng
A measuring system based on computer vision was developed to measure the movement parameters of a unmanned lunar explorer at a soft-landing test, such as the 3D pose, 3D velocity of explorer and the working strobe of snubber. Firstly, some opposite-vertical-angle marks were painted on the surface of the explorer, and tA measuring system based on computer vision was developed to measure the movement parameters of a unmanned lunar explorer at a soft-landing test, such as the 3D pose, 3D velocity of explorer and the working strobe of snubber. Firstly, some opposite-vertical-angle marks were painted on the surface of the explorer, and their 3D coordinates were measured by a high-precision total station. Then, a series of images were taken by a high speed digital camera during the soft-landing test of explorer. Finally, the above parameters could be obtained by processing serial images of the explorer and 3D coordinates of the marks with the mono-vision method. The system is compact and easy to be operated. The theoretical analysis and experiments for the measurement precision of the system were performed. The results indicate that accuracies of pose angle, velocity and working strobe in measurements are 4′, 0.02 m/s and 4 mm, respectively,which can satisfy the requirements of movement parameter measurements in the soft-landing tests for unmanned lunar explorers..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 9, 2044 (2010)
D esign of large-array CCD real-time display system
WANG Ming-fu, YANG Shi-hong, and WU Qin-zhang
As the CCD camera based on CameraLink interface can not display images without a dedicated data acquisition card and system computer, a kind of simple and real-time image display system was designed for a 4 008×5 344 array CCD camera based on CameraLink interface. Two SDRAMs were used in the system to storage imagAs the CCD camera based on CameraLink interface can not display images without a dedicated data acquisition card and system computer, a kind of simple and real-time image display system was designed for a 4 008×5 344 array CCD camera based on CameraLink interface. Two SDRAMs were used in the system to storage images alternately, and the main logical function was accomplished in a Spatan3 family Field Programming Gate Array(FPGA) from Xilinx Company. The image data from CameraLink were storaged in a SDRAM by stitching and BIN processing,meanwhile,the image data read from another SDRAM at a speed of 25 frame/s(50 field /s) were convert to standard TV analog signals by a digital-to-analog encoder chip ADV7300 to display in an analog monitor. The verification results show that the system can real-time display the images of the large-array digital aerial camera with different resolutions and their details at a speed of 3.6 frame /s,and also can adjust the brightness of the images to get a good observation according to the weather conditions. The designed system only contains one PCB board and one alanog monitor and has been used in a CCD digital aerial camera with the 4 008×5 344 array successfully..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 9, 2053 (2010)
Target localization based on LSSVR in wireless sensor networks
ZHANG Xiao-ping, LIU Gui-xiong, and ZHOU Song-bin
In consideration of the direct influence of Received Signal Strength Indicator(RSSI) fluctuation on the target localization accuracy in wireless sensor networks (WSN), the basic principle of target localization using Least Square Support Vector Regression(LSSVR) is discussed. Then, the characteristics of LSSVR modelingIn consideration of the direct influence of Received Signal Strength Indicator(RSSI) fluctuation on the target localization accuracy in wireless sensor networks (WSN), the basic principle of target localization using Least Square Support Vector Regression(LSSVR) is discussed. Then, the characteristics of LSSVR modeling are analyzed for given and variable detection sensors, respectively. Furthermore, a method for Target Localization based on Adaptive LSSVR Modeling (TL-AML) in WSN is proposed. By considering localization accuracy and real-time performance comprehensively, LSSVR models are built for locating target at initial time, and at follow-up time it is used to decide whether new models need to be built or not according to the inclusion relation between detection nodes and sensor nodes. The performance of TL-AML is verified based on CC2430 WSN experiment platform. Results show that the Root Mean Square Error (RMSE) of target localization based on TL-AML has reduced by 34%~37% and 60%~65% as compared with those of MLE and LSE,respectively. When modeling parameters are taken in reasonable value ranges, the localization accuracy of TL-AML is improved evidently compared with MLE and LSE. Moreover,the consuming time of TL-AML is 0.2~0.4 s,If LSSVR modeling is needed. Otherwise, the consuming time is only about 0.04 s. The results indicate that TL-AML method can weaken the influence of RSSI fluctuation on the accuracy of target localization and has good real-time target localization accuracy..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 9, 2060 (2010)
External field stitching technology for high speed target measuring and its implementation
WANG Min, SONG Li-wei, QIAO Yan-feng, and YU Yi
As a single high-speed camera can not meet the requirements of high-speed target measurement for large fields, high frame rates, high resolutions and large volume data processing，the high speed target measuring technology completed by external field stitching was researched. On the basis of analysis and comparison of eAs a single high-speed camera can not meet the requirements of high-speed target measurement for large fields, high frame rates, high resolutions and large volume data processing，the high speed target measuring technology completed by external field stitching was researched. On the basis of analysis and comparison of external field stitching methods, a ultimate scheme of external field stitching with external fields from four cameras was proposed. In the scheme, two cameras were mounted at one side along the horizontal axis of a 'T' type tracking frame and the others were at the other side. A prototype of external field stitching measuring system made of four lenses with 10°field-angle was designed,and its actual stitching field of view is 40 ° (horizontal) × 10 ° (vertical).When the parallax is 360 mm, the complete image can be obtained for the target over 247 m away from the cameras without blind spots..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 9, 2069 (2010)
Rebinned BPF reconstruction for helical cone-beam CT with half-cover scaning
ZOU Xiao-bing, and ZENG Li
As the conventional scan mode in helical cone-beam CT limits the field of view of the CT system, this paper analyzes the half-cover scanning of helical cone-beam CT and presents a new reconstruction method combined the Backprojected Filter(BPF) reconstruction and the cone-beam CT with half-cover scanning.This scanning As the conventional scan mode in helical cone-beam CT limits the field of view of the CT system, this paper analyzes the half-cover scanning of helical cone-beam CT and presents a new reconstruction method combined the Backprojected Filter(BPF) reconstruction and the cone-beam CT with half-cover scanning.This scanning method only demands more than half of cross section to be covered by X-ray beam at each view angle,and the width of the planar detector is about half of the conventional helical cone-beam CT, so that the cost of planar detector is saved.By combing the fan projection and 2D BPF, this paper researches a rebinned-weighted BPF algorithm for half-cover helical cone-beam CT,in which the projection data are firstly rebinned to half-cover fan-beam data, and then the weighted BPF are used in reconstruction. The results validate that reconstruction time with rebinned-weighted BPF algorithm has reduced to 3/5 that of the conventional helical FDK algorithm. Furthermore, the reconstructed value is more closed to the real value than that of FDK algorithm with large helical pitchs, and the MSE has reduced by half..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 9, 2077 (2010)
Calibration of inner orientation elements for camera by means of star points
LIU Wei-yi, DING Ya-lin, JIA Ji-Qiang1, and LIU Bo
To implement the single or batch calibrations of mapping cameras, a calibration method to find the inner orientation elements of the camera by star points was presented. The principles and calculation steps of the method were introduced, and the experimental process was described in detail. The method was based on a hoTo implement the single or batch calibrations of mapping cameras, a calibration method to find the inner orientation elements of the camera by star points was presented. The principles and calculation steps of the method were introduced, and the experimental process was described in detail. The method was based on a hole imaging and it established a relationship between celestial coordinate and pixel coordinate by the conversions of different coordinate frames to obtain the inner orientation elements. In comparison to the precision angle measurement method based on the collimator and precision rotating platform, this method greatly simplifies the calibration steps and requires no expensive experimental equipment. Finally, the calibration precision was analyzed, and the effects of noise disturbance and known errors of inner orientation elements on calibration results were discussed. Obtained results indicate that the principal point precision and principal distant precision are better than 3 μm(1/3 pixel) and 7 μm(1 pixle),respectively,which meets the requirement of calibration precision..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 9, 2086 (2010)
Detection of point targets in space-based infrared images
MENG Xiang-long, ZHANG Wei, CONG Ming-yu, CAO Yi-ming, and BAO Wen-zhuo
In order to research the on-board data processing for infrared (IR) scan images in Geostationary Earth Orbit (GEO) satellite, processing flows of data processors in the Phase Ⅱ and DSP-Ⅰ satellites for U.S. Defense Support Program (DSP) are discussed. A point target detection algorithm for IR scan images is proposed baIn order to research the on-board data processing for infrared (IR) scan images in Geostationary Earth Orbit (GEO) satellite, processing flows of data processors in the Phase Ⅱ and DSP-Ⅰ satellites for U.S. Defense Support Program (DSP) are discussed. A point target detection algorithm for IR scan images is proposed based on a two-channel filter to suit for space conditions. Firstly, the background prediction is modeled by a mean filter to suppress background clutters, and the adaptive threshold is determined on the residual image after the background elimination. Then, the peak detection is used to detect the peaks in IR images to reduce probability of false alarm originating from the adaptive threshold. Finally, the target identification algorithm using fusion technique is performed for the data from two channels. Experiments show that the proposed algorithm can get high detection probability and low false-alarm probability, and is easy and convenient for real-time operation. The obtained results indicate that the detection probability reaches 99.3% (the false alarm probability is 1.3×10-3) when the input Signal-to-Noise ratio (SNR) is no less than 6. The real-time analysis of the algorithm shows that the data processing capability can achieve 56.45 Mb/s. The proposed algorithm can meet the need of space-based data processing..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 9, 2094 (2010)
Design of chaotic one-way hash function based on orbit perturbation
LI Pei-yue, GU Li, SUI Yong-xin, and YANG Huai-jiang
On the basis of analysis on the pseudo-random perturbation policy and Variable Parameter Compensation(VPCM) policy for digital chaotic system, a method to design the chaotic one-way hash function based on the orbit perturbation is proposed. In order to improve the security of short message hashing, the message is paddeOn the basis of analysis on the pseudo-random perturbation policy and Variable Parameter Compensation(VPCM) policy for digital chaotic system, a method to design the chaotic one-way hash function based on the orbit perturbation is proposed. In order to improve the security of short message hashing, the message is padded to be a multiple of 64 byte. Then,the length fixed perturbation of 64 bytes length is chosen,and the perturbation together with the padded message are mapped to the perturbation space of digital chaotic system.Finally, the digital chaotic system is iterated multiple times by using the elements of the perturbation space as inputs, and a hash value with 160 bit length is extracted from the results. The proposed algorithm uses the logistic mapping as the chaotic mapping, of which the computational complexity is lower than the one that has a reasonable high dimension. As the orbit perturbation is introduced the algorithm,its security is higher than that of common one. The results indicate that the algorithm is sensitive to the initial message comparatively and shows good confusion and diffusion properties. Moreover, the fix-point operations with 256 bits are used in the proposed algorithm, and it is easy to be completed by software or hardware..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 9, 2101 (2010)
Signal processing for confocal probe based on time difference
QIU Zu-rong, WEI Fang-kun, XIE Li-qin, LI Xing-hua, and XIAO Gong-jian
The displacement measured by a confocal probe based on time difference method is an one-to-one mapping to the time difference between the two peaks in a photo-electric signal. In order to calculate the time difference accurately, the characteristics of photo-electric signal output from an improved probe was analyzed anThe displacement measured by a confocal probe based on time difference method is an one-to-one mapping to the time difference between the two peaks in a photo-electric signal. In order to calculate the time difference accurately, the characteristics of photo-electric signal output from an improved probe was analyzed and then the defects in the current signal processing method were pointed out.A processing method named similar pattern analysis was persented to calculate the time interval between the two peaks. Experimental data show that in the data acquisition system with sampling frequency of 2 MHz, the standard deviation of time difference by using the similar pattern analysis is 0.33 μs,which is better than 3.37 μs by using the maximum value method. With the similar pattern analysis, it is easy to implement the signal pre-processing. The calculated results are accurate and stable and are not influenced by the changes of laser intensity and ambient light interference..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 9, 2109 (2010)
Restoration of field curved image from line camera and its applications in foreign fiber detecting
WANG Ji, and LU Wen-kai
To eliminate the spatially variant blurs caused by a field curvature from a camera and to improve the resolutions and the measuring precisions of images, a 1D image restoration method was proposed to overcome the influence of field curvature on an image from the camera used in industrial inspections. On analysis of theTo eliminate the spatially variant blurs caused by a field curvature from a camera and to improve the resolutions and the measuring precisions of images, a 1D image restoration method was proposed to overcome the influence of field curvature on an image from the camera used in industrial inspections. On analysis of the spatially variant blur matrix, the Point Spread Functions(PSFs) of a partial region were estimated and then the blur matrix of whole image field was computed by shifting and interpolation. On the basis of the blur matrix, the restored matrix which was unrelated to the observed signal was obtained by the constrained least square algorithm. In inspection, the restored image could be obtained by multiplying the acquired signals with restored matrix. This method has been applied in foreign fiber detecting systems and verified by real images containing fine fibers. Obtained results show that this method can improve the image resolution and enhance the difference between background and irregular points by 10%. Therefore, it improves the detecting accuracies for images..
Optics and Precision Engineering
- Publication Date: Sep. 19, 2021
- Vol. 18, Issue 9, 2116 (2010)
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