2015 Vol. 36, No. 6
Display Method:
2015, 36(6): 823-828.
doi: 10.5768/JAO201536.0601001
Abstract:
In order to resolve the issue of azimuth platform stability depressing, by using the stabilization principle of two-axis two-framework platform, the reason for the stability depressing and the noise caused by secant compensation of azimuth platform were analyzed,which worked in big pitching angle with azimuth gyro of tradition fixing mode. We proposed to install an azimuth gyro and a roll gyro,which were orthogonal, on the azimuth platform to calculate the inertial azimuth angle velocity of line of sight,and realized the controlling method of azimuth stability with big pitching angle. Simulation experiment validates that, the azimuth stability controlling performance of the two-axis two-framework platform with big pitching angle can be advanced and the influence of gyro noise on the controlling performance can be depressed by using the method. Under the same conditions, the peak-to-peak error of azimuth stabilization can reduce form 450 urad to 250 urad.
In order to resolve the issue of azimuth platform stability depressing, by using the stabilization principle of two-axis two-framework platform, the reason for the stability depressing and the noise caused by secant compensation of azimuth platform were analyzed,which worked in big pitching angle with azimuth gyro of tradition fixing mode. We proposed to install an azimuth gyro and a roll gyro,which were orthogonal, on the azimuth platform to calculate the inertial azimuth angle velocity of line of sight,and realized the controlling method of azimuth stability with big pitching angle. Simulation experiment validates that, the azimuth stability controlling performance of the two-axis two-framework platform with big pitching angle can be advanced and the influence of gyro noise on the controlling performance can be depressed by using the method. Under the same conditions, the peak-to-peak error of azimuth stabilization can reduce form 450 urad to 250 urad.
2015, 36(6): 829-835.
doi: 10.5768/JAO201536.0601002
Abstract:
In a world of increasing lightweight design demand, the selection of driving motor influences the size and quality of the overall system directly. The traditional motor selection method can meet our needs in a certain extent, however, there are also many problems that the load analysis is not comprehensive enough and the quantification degree of some influence factors is not deep enough. Therefore, the study on the motor selection method is of great significance for the lightweight design of servo system. This paper analyzed and quantified the load of opto-electronic servo system. For the loads hard to calculate accurately, a method to estimate them was provided. The dynamic characteristics of the motor was checked and the concept of confidence was introduced to help the motor selection.Furthermore, a software for motor selection was designed with Matlab/GUI and used to choose the motor of some opto-electronic pod. And a direct current motor with the confidence of 0.79 was finally chosen.
In a world of increasing lightweight design demand, the selection of driving motor influences the size and quality of the overall system directly. The traditional motor selection method can meet our needs in a certain extent, however, there are also many problems that the load analysis is not comprehensive enough and the quantification degree of some influence factors is not deep enough. Therefore, the study on the motor selection method is of great significance for the lightweight design of servo system. This paper analyzed and quantified the load of opto-electronic servo system. For the loads hard to calculate accurately, a method to estimate them was provided. The dynamic characteristics of the motor was checked and the concept of confidence was introduced to help the motor selection.Furthermore, a software for motor selection was designed with Matlab/GUI and used to choose the motor of some opto-electronic pod. And a direct current motor with the confidence of 0.79 was finally chosen.
2015, 36(6): 836-840.
doi: 10.5768/JAO201536.0601003
Abstract:
According to the design index requirements of a space remote sensors secondary mirror, a lightweight mirror was designed by using the optimization solution function of ANASYS. In the design process, model parameters of the secondary mirror were set as variables and they were solved iteratively through the multi-parameter optimization design function of ANASYS to meet the size of the secondary mirrors under minimum quality and shape deformation. Finally, a secondary mirror mode which could meet design requirement l was got with the lightweight rate of 80.635%, the surface figure root-mean-square(RMS) value of6.953 nm and peak-valley(PV) value of 31.317nm.
According to the design index requirements of a space remote sensors secondary mirror, a lightweight mirror was designed by using the optimization solution function of ANASYS. In the design process, model parameters of the secondary mirror were set as variables and they were solved iteratively through the multi-parameter optimization design function of ANASYS to meet the size of the secondary mirrors under minimum quality and shape deformation. Finally, a secondary mirror mode which could meet design requirement l was got with the lightweight rate of 80.635%, the surface figure root-mean-square(RMS) value of6.953 nm and peak-valley(PV) value of 31.317nm.
2015, 36(6): 841-846.
doi: 10.5768/JAO201536.0601004
Abstract:
In order to enlarge the observation range,adopt the module units and raise the reliability, a multi-functional panoramic sight was designed. By using ballscrew and linear bearing, the lifting at its head was realized so that the observation range of the product could be enlarged. By using gear cluster differential technology, the moving transmission of the mirror was realized so as to guarantee the system reliability. Through driving the Dove prism with a step motor and the cooperation with the absolute value type photoelectric encoder to feedback the angular value position information, the image revolving during panoramic sighting was eliminated, so that the system observation and aiming accuracy and the angle-measuring accuracy could be guaranteed. Engineering practice shows that the panoramic sight can perform the following actions: observation aiming day and night, zooming continuously 3～6 at day, 300 mm lifting at its head, all panoramic sighting in azimuth, the angle-measuring accuracy is no less than 1 mard during continuous rotation.
In order to enlarge the observation range,adopt the module units and raise the reliability, a multi-functional panoramic sight was designed. By using ballscrew and linear bearing, the lifting at its head was realized so that the observation range of the product could be enlarged. By using gear cluster differential technology, the moving transmission of the mirror was realized so as to guarantee the system reliability. Through driving the Dove prism with a step motor and the cooperation with the absolute value type photoelectric encoder to feedback the angular value position information, the image revolving during panoramic sighting was eliminated, so that the system observation and aiming accuracy and the angle-measuring accuracy could be guaranteed. Engineering practice shows that the panoramic sight can perform the following actions: observation aiming day and night, zooming continuously 3～6 at day, 300 mm lifting at its head, all panoramic sighting in azimuth, the angle-measuring accuracy is no less than 1 mard during continuous rotation.
2015, 36(6): 847-851.
doi: 10.5768/JAO201536.0601005
Abstract:
Phase-shifting interferometry is an important measurement method for surface topography, but the depth measuring range is limited by the wavelength.A four-wavelength interference measurement system for surface topography was proposed.Through rotating the filters, 4 light sources with different wavelengths were switched out from LED light, and the single wavelength interference was conducted in turn. A data processing method for multiple wavelength interference images was put forward, which used the algorithm of elliptic fitting and the combination of varied scales to achieve wide-range highprecision surface topography measurement on the condition of calculating the phase point-by-point and frame-by-frame. Experimental results show that under the measurement depth expanded to nearly 41 times, the relative measurement error of surface roughness of square wave specimen with multiple grooves is only 4.09%,compared to the data calibrated by China Institute of Metrology. Therefore, the system can realize high-precision measurement for surface topography in a certain range.
Phase-shifting interferometry is an important measurement method for surface topography, but the depth measuring range is limited by the wavelength.A four-wavelength interference measurement system for surface topography was proposed.Through rotating the filters, 4 light sources with different wavelengths were switched out from LED light, and the single wavelength interference was conducted in turn. A data processing method for multiple wavelength interference images was put forward, which used the algorithm of elliptic fitting and the combination of varied scales to achieve wide-range highprecision surface topography measurement on the condition of calculating the phase point-by-point and frame-by-frame. Experimental results show that under the measurement depth expanded to nearly 41 times, the relative measurement error of surface roughness of square wave specimen with multiple grooves is only 4.09%,compared to the data calibrated by China Institute of Metrology. Therefore, the system can realize high-precision measurement for surface topography in a certain range.
2015, 36(6): 852-856.
doi: 10.5768/JAO201536.0601006
Abstract:
In order to improve the practical level of two-photon 3D optical storage technology,the information storage system was built based on DVD servo technology and two-photon absorption technology. The radial basis function (RBF) neural network self-adjusting proportional-integral-derivative (PID) control algorithm was used to built the simulation model of PID control system based on the transfer function of DVD pick-up head.The parameters of PID controller were adjusted online by the ability of the RBF neural network self learning and global nonlinear strong approximation and simulated by Matlab. It is proved that the settling time of the step response of the system is shortened to 0.25s and the overshoot of the system reduces to almost zero after applying the RBF neural network adaptive PID control algorithm.
In order to improve the practical level of two-photon 3D optical storage technology,the information storage system was built based on DVD servo technology and two-photon absorption technology. The radial basis function (RBF) neural network self-adjusting proportional-integral-derivative (PID) control algorithm was used to built the simulation model of PID control system based on the transfer function of DVD pick-up head.The parameters of PID controller were adjusted online by the ability of the RBF neural network self learning and global nonlinear strong approximation and simulated by Matlab. It is proved that the settling time of the step response of the system is shortened to 0.25s and the overshoot of the system reduces to almost zero after applying the RBF neural network adaptive PID control algorithm.
2015, 36(6): 857-863.
doi: 10.5768/JAO201536.0601007
Abstract:
According to the validation requirements of the field test, a large aperture optical system with precisely zooming was designed, in order to provide target imaging simulation from near field to far field to test and evaluate the system performance. The system has two parts: zoom system and projection system. Based on the requirements of beam aperture and image size on the unit to be tested, and with the precondition of pupil connection and aperture matching principle, the optical parameters of projection system and zoom system were calculated and the image quality was optimized. The zoom system works between 8 m ~12 m in far-infrared band with a 16x zoom ratio. The large-aperture projection system has a 300mm aperture. Simulation experiment results show that, the image position is stable and the modulation transfer function (MTF) curve of each focal length is close to the diffraction limit during zoom process, which could meet the test requirement exactly.
According to the validation requirements of the field test, a large aperture optical system with precisely zooming was designed, in order to provide target imaging simulation from near field to far field to test and evaluate the system performance. The system has two parts: zoom system and projection system. Based on the requirements of beam aperture and image size on the unit to be tested, and with the precondition of pupil connection and aperture matching principle, the optical parameters of projection system and zoom system were calculated and the image quality was optimized. The zoom system works between 8 m ~12 m in far-infrared band with a 16x zoom ratio. The large-aperture projection system has a 300mm aperture. Simulation experiment results show that, the image position is stable and the modulation transfer function (MTF) curve of each focal length is close to the diffraction limit during zoom process, which could meet the test requirement exactly.
2015, 36(6): 864-867.
doi: 10.5768/JAO201536.0601008
Abstract:
During the designing process for large diameter catadioptric infrared, the aberrations of primary and secondary mirrors are calibrated separately, which makes the precise alignment difficult. For this problem,an assistant alignment lens used for infrared optical system was designed, which could compensate the aberrations to accomplish system alignment with high-precision. The manufacture precision of assistant alignment lens was exactly controlled to reduce error caused by itself in manufacturing process.The designed wave aberration data of system is 0.14 and the practical data is 0.3 after operated using ZYGO interferometer. At last, the secondary imaging lens was used in stead of assistant alignment lens.The result shows that the image quality of the optical system can satisfy the demand of infrared search and tracking system.
During the designing process for large diameter catadioptric infrared, the aberrations of primary and secondary mirrors are calibrated separately, which makes the precise alignment difficult. For this problem,an assistant alignment lens used for infrared optical system was designed, which could compensate the aberrations to accomplish system alignment with high-precision. The manufacture precision of assistant alignment lens was exactly controlled to reduce error caused by itself in manufacturing process.The designed wave aberration data of system is 0.14 and the practical data is 0.3 after operated using ZYGO interferometer. At last, the secondary imaging lens was used in stead of assistant alignment lens.The result shows that the image quality of the optical system can satisfy the demand of infrared search and tracking system.
2015, 36(6): 868-872.
doi: 10.5768/JAO201536.0601009
Abstract:
One important parameter of single wall carbon nanotubes (SWCNTs) to be measured is chiral index. Chiral indices not only contain information about diameter and chiral angle, but also indicate electronic properties of SWCNTs. Generally, near infrared photoluminescence fluorescence spectrometer is a widely used method for chiral indices identification. However, there is no standard calibration procedures for this kind of fluorescence spectrometer, resulting in a lack of comparability between the results measured by various instruments. Based on this kind of fluorescence spectrometer, the principle and configuration of fluorescence spectrometer were briefly introduced, and the calibration procedures were discussed including excitation light path calibration and emission light path calibration.The method was to calibrate the excitation wavelength and emission wavelength to the 467 nm and 1 053 nm using standard xenon lamp spectrum and standard laser glass spectrum respectively. After calibration, chiral indices of SWCNTs were measured using calibrated instrument and ultraviolet-visible-near infrared spectrometer, and the results both are (11, 1)，(8, 7)，(10, 3)，(9,5)，(11, 3)，(8, 6)，(9,2)，(7, 6)，(8, 4)，(7, 5)，(10,2). The comparison results indicate that the calibration procedures are accurate.
One important parameter of single wall carbon nanotubes (SWCNTs) to be measured is chiral index. Chiral indices not only contain information about diameter and chiral angle, but also indicate electronic properties of SWCNTs. Generally, near infrared photoluminescence fluorescence spectrometer is a widely used method for chiral indices identification. However, there is no standard calibration procedures for this kind of fluorescence spectrometer, resulting in a lack of comparability between the results measured by various instruments. Based on this kind of fluorescence spectrometer, the principle and configuration of fluorescence spectrometer were briefly introduced, and the calibration procedures were discussed including excitation light path calibration and emission light path calibration.The method was to calibrate the excitation wavelength and emission wavelength to the 467 nm and 1 053 nm using standard xenon lamp spectrum and standard laser glass spectrum respectively. After calibration, chiral indices of SWCNTs were measured using calibrated instrument and ultraviolet-visible-near infrared spectrometer, and the results both are (11, 1)，(8, 7)，(10, 3)，(9,5)，(11, 3)，(8, 6)，(9,2)，(7, 6)，(8, 4)，(7, 5)，(10,2). The comparison results indicate that the calibration procedures are accurate.
2015, 36(6): 873-879.
doi: 10.5768/JAO201536.0601010
Abstract:
In order to solve the problems of tedious data transmission among multi-software and slow optimization in designing the lens for uniformity with extended sources,according to the sequential ray tracing, Fresnel formula and luminance compensation, we proposed a rapid optimization method by using only one software, Matlab. The method can closely combine ray tracing, illumination fitting and feedback optimization.What is more, we can optimize the lighting system fast and accurately. In order to verify the feasibility of the system, we designed a compact uniform lens of which the h/d is equal to 2.5:1. The results show after giving parameters of the source and target plane, the system optimization time is only 8 min;the uniformity and efficiency in the target plane significantly improve by 86.75% and 88.42%,respectively.
In order to solve the problems of tedious data transmission among multi-software and slow optimization in designing the lens for uniformity with extended sources,according to the sequential ray tracing, Fresnel formula and luminance compensation, we proposed a rapid optimization method by using only one software, Matlab. The method can closely combine ray tracing, illumination fitting and feedback optimization.What is more, we can optimize the lighting system fast and accurately. In order to verify the feasibility of the system, we designed a compact uniform lens of which the h/d is equal to 2.5:1. The results show after giving parameters of the source and target plane, the system optimization time is only 8 min;the uniformity and efficiency in the target plane significantly improve by 86.75% and 88.42%,respectively.
2015, 36(6): 880-887.
doi: 10.5768/JAO201536.0602001
Abstract:
Moving object detection is a key step in the system of intelligent visual surveillance. A randomized background nonparametric modeling algorithm was proposed for object fast detection application. In the initialization stage, a set of values were randomly taken in the neighborhood of the current pixel. In the update stage, a reasonable randomized updating and background samples propagation mechanism were introduced, which could restrain the scene noise effectively. In the post-processing stage, a foreground optimized filter based on the integral image was designed to further remove the noises and fill the holes of the objects. Experimental results show that the performance of the proposed algorithm is significantly superior to other similar algorithms. It can further restrain noise and has high detection precision. In addition, for 320240 pixel format video stream, the computing of the proposed detection algorith can reach up to 120 fps, which can fully meet the requirement of the real-time application system.
Moving object detection is a key step in the system of intelligent visual surveillance. A randomized background nonparametric modeling algorithm was proposed for object fast detection application. In the initialization stage, a set of values were randomly taken in the neighborhood of the current pixel. In the update stage, a reasonable randomized updating and background samples propagation mechanism were introduced, which could restrain the scene noise effectively. In the post-processing stage, a foreground optimized filter based on the integral image was designed to further remove the noises and fill the holes of the objects. Experimental results show that the performance of the proposed algorithm is significantly superior to other similar algorithms. It can further restrain noise and has high detection precision. In addition, for 320240 pixel format video stream, the computing of the proposed detection algorith can reach up to 120 fps, which can fully meet the requirement of the real-time application system.
2015, 36(6): 888-892.
doi: 10.5768/JAO201536.0602002
Abstract:
We introduced the dispersion compensation principles of dispensation compensation fiber (DCF) and fiber Brag grating (FBG), compared their advantages and disadvantages, proposed adding the FBG into the end in traditional optical fiber transmission systems. We designed a transmission system with a capacity of 40Gbit/s by using Optisystem software and studied three dispersion compensation schemes. If the FBG dispersion compensation was used only, its Q value was 3.745 and its bit error ratio (BER) was 7.41942e-5 with the optical signal transmission of 400 km. The scheme of DCF static mixed compensation and the combination scheme of static and dynamic dispersion compensation were simulated,and the Q value and BER of the two schemes for transmission of the same distance were compared. It is proved that the scheme combined the static with the dynamic compensation can improve the optical transmission performance.
We introduced the dispersion compensation principles of dispensation compensation fiber (DCF) and fiber Brag grating (FBG), compared their advantages and disadvantages, proposed adding the FBG into the end in traditional optical fiber transmission systems. We designed a transmission system with a capacity of 40Gbit/s by using Optisystem software and studied three dispersion compensation schemes. If the FBG dispersion compensation was used only, its Q value was 3.745 and its bit error ratio (BER) was 7.41942e-5 with the optical signal transmission of 400 km. The scheme of DCF static mixed compensation and the combination scheme of static and dynamic dispersion compensation were simulated,and the Q value and BER of the two schemes for transmission of the same distance were compared. It is proved that the scheme combined the static with the dynamic compensation can improve the optical transmission performance.
2015, 36(6): 900-904.
doi: 10.5768/JAO201536.0602004
Abstract:
Modern space telescopes use conic surfaces rather than sphere surfaces in optical systems to avoid the unnecessary aberration brought by sphere surfaces. Geometric parameters of conic surfaces include the vertex radius and aspheric coefficient (e2), they are significant to the performance of the telescopes. As the coordinate measuring machine (CMM) is widely used, the measurement for the geometric parameters of conic surface is much more convenient. We introduced a new algorithm for calculating vertex radius and e2 based on the data measured by the CMM through a few steps: measuring the coordinates, finding the axis and calculating the normal aberration theory. According to the simulation and experiment, the error of vertex radius is less than 0.01%, the error of e2 is less than 0.0002,which can meet the demands for most measurements.
Modern space telescopes use conic surfaces rather than sphere surfaces in optical systems to avoid the unnecessary aberration brought by sphere surfaces. Geometric parameters of conic surfaces include the vertex radius and aspheric coefficient (e2), they are significant to the performance of the telescopes. As the coordinate measuring machine (CMM) is widely used, the measurement for the geometric parameters of conic surface is much more convenient. We introduced a new algorithm for calculating vertex radius and e2 based on the data measured by the CMM through a few steps: measuring the coordinates, finding the axis and calculating the normal aberration theory. According to the simulation and experiment, the error of vertex radius is less than 0.01%, the error of e2 is less than 0.0002,which can meet the demands for most measurements.
2015, 36(6): 893-899.
doi: 10.5768/JAO201536.0602003
Abstract:
In view of the problems that the translation and small angle rotation motion always exist between adjacent frames when the handheld mobile camera is filming video sequence, and it is easily affected by noise and illumination changes,we put forward a kind of real-time robust digital image algorithm based on optimized oriented features from accelerated segment test (FAST) and rotated binary robust independent elementary features (BRIEF) (ORB) feature matching algorithm.Firstly the adjacent frame images were preprocessed to enhance image clarity and to avoid noise interference;secondly the oriented FAST operator was used to detect feature points and the rotated BRIEF was used to describe feature points, then the neighbor hamming distance was adopted to match the ORB feature point pairs; thirdly the cascaded filter was used to remove the false matching points; finally the iterative least squares method(ILSM) was used to fit model parameters,then the motion compensation was done to achieve digital image stabilization. Standard image matching test and digital image stabilization experimental results show that the run time of compensation for each frame by the electric image stabilization method based on improved ORB algorithm is faster than 0.1 s, the positioning accuracy can reach sub-pixel level, this method can effectively compensate the translation and rotation movement between the adjacent frames, and is not sensitive to noise and illumination changes, has strong robustness. After image stabilization processing,the real scene shooting video quality obviously improves and the peak signal-to-noise ratio (PSNR) increases by an average of 10 db.
In view of the problems that the translation and small angle rotation motion always exist between adjacent frames when the handheld mobile camera is filming video sequence, and it is easily affected by noise and illumination changes,we put forward a kind of real-time robust digital image algorithm based on optimized oriented features from accelerated segment test (FAST) and rotated binary robust independent elementary features (BRIEF) (ORB) feature matching algorithm.Firstly the adjacent frame images were preprocessed to enhance image clarity and to avoid noise interference;secondly the oriented FAST operator was used to detect feature points and the rotated BRIEF was used to describe feature points, then the neighbor hamming distance was adopted to match the ORB feature point pairs; thirdly the cascaded filter was used to remove the false matching points; finally the iterative least squares method(ILSM) was used to fit model parameters,then the motion compensation was done to achieve digital image stabilization. Standard image matching test and digital image stabilization experimental results show that the run time of compensation for each frame by the electric image stabilization method based on improved ORB algorithm is faster than 0.1 s, the positioning accuracy can reach sub-pixel level, this method can effectively compensate the translation and rotation movement between the adjacent frames, and is not sensitive to noise and illumination changes, has strong robustness. After image stabilization processing,the real scene shooting video quality obviously improves and the peak signal-to-noise ratio (PSNR) increases by an average of 10 db.
2015, 36(6): 905-908.
doi: 10.5768/JAO201536.0603001
Abstract:
Polarization measurement error may be caused by achromatic /4 wave-plate due to the retarder error and different absorption coefficients for the light oscillating along the fast axis and slow axis of wave-plate. We studied the system-level calibration effect of achromatic /4 wave-plate in full-polarized charge coupled-device (CCD) camera based on the radiometric model by using the integrating sphere and the high-precision auxiliary rotation polarizer. Experimental result shows that there are the variation of the retarder and absorption coefficients of achromatic /4 wave-plate for the different operating wavelengths and bandwidths in full-polarized CCD camera. The achromatic effects of 650 nm (phase retardation 88.90) and 750 nm (phase retardation 88.90) are better than that of 850 nm (phase retardation 84.33) of our achromatic /4 wave-plate in full-polarized CCD camera. The phase retardation precision in our system-level calibration is better than 0.8 through the analysis of phase retardation standard error.
Polarization measurement error may be caused by achromatic /4 wave-plate due to the retarder error and different absorption coefficients for the light oscillating along the fast axis and slow axis of wave-plate. We studied the system-level calibration effect of achromatic /4 wave-plate in full-polarized charge coupled-device (CCD) camera based on the radiometric model by using the integrating sphere and the high-precision auxiliary rotation polarizer. Experimental result shows that there are the variation of the retarder and absorption coefficients of achromatic /4 wave-plate for the different operating wavelengths and bandwidths in full-polarized CCD camera. The achromatic effects of 650 nm (phase retardation 88.90) and 750 nm (phase retardation 88.90) are better than that of 850 nm (phase retardation 84.33) of our achromatic /4 wave-plate in full-polarized CCD camera. The phase retardation precision in our system-level calibration is better than 0.8 through the analysis of phase retardation standard error.
2015, 36(6): 909-912.
doi: 10.5768/JAO201536.0603002
Abstract:
The distance between the charge couple-device (CCD) and the micro lens array is one of the assembling errors which affects the accuracy of HartmannShack wavefront detector. The correction of this motion assembly parameter can effectively reduce the wavefront detector error. The relationship between the subaperture spot centroid shift amount,caused by the spherical wavefront passing through the micro lens, and the structural parameters of wavefront sensor was derived theoretically. By utilizing the relationship, it is able to work out the actual distance from the CCD to the micro lens array and improve the calculation of the slope of wavefront. Experiments verified the rationality of theoretical derivation, and the actual assembly parameter calibrated is 24.2 mm. The wavefront was reconstructed by the calibrated parameter, the relative error can reduce by 20.4%. Experiment results show that the calibration method can effectively improve the measurement accuracy of wavefront sensor.
The distance between the charge couple-device (CCD) and the micro lens array is one of the assembling errors which affects the accuracy of HartmannShack wavefront detector. The correction of this motion assembly parameter can effectively reduce the wavefront detector error. The relationship between the subaperture spot centroid shift amount,caused by the spherical wavefront passing through the micro lens, and the structural parameters of wavefront sensor was derived theoretically. By utilizing the relationship, it is able to work out the actual distance from the CCD to the micro lens array and improve the calculation of the slope of wavefront. Experiments verified the rationality of theoretical derivation, and the actual assembly parameter calibrated is 24.2 mm. The wavefront was reconstructed by the calibrated parameter, the relative error can reduce by 20.4%. Experiment results show that the calibration method can effectively improve the measurement accuracy of wavefront sensor.
2015, 36(6): 913-917.
doi: 10.5768/JAO201536.0603003
Abstract:
In order to calibrate the strain stretch coefficient of Bragg grating strain measurement system simply and precisely, on the basis of the analysis of the demodulation principle of the measurement system, we proposed the method for using inverse piezoelectric effect of lead zirconate titanate (PZT) to calibrate the system and carried out the calibration experiment on the 8 strain measurement channels. The relationship curves of the strain and the phase difference between demodulation signals were obtained by the linear fitting of the experimental data of each channel,and the strain sensing coefficient of each channel was determined by the relationship curves. Analysis shows that the coefficients of the calibration relative error is within 0.002 m/（）, the results have higher accuracy.
In order to calibrate the strain stretch coefficient of Bragg grating strain measurement system simply and precisely, on the basis of the analysis of the demodulation principle of the measurement system, we proposed the method for using inverse piezoelectric effect of lead zirconate titanate (PZT) to calibrate the system and carried out the calibration experiment on the 8 strain measurement channels. The relationship curves of the strain and the phase difference between demodulation signals were obtained by the linear fitting of the experimental data of each channel,and the strain sensing coefficient of each channel was determined by the relationship curves. Analysis shows that the coefficients of the calibration relative error is within 0.002 m/（）, the results have higher accuracy.
2015, 36(6): 918-922.
doi: 10.5768/JAO201536.0603004
Abstract:
An assembling method for off-axis parabolic mirror of a high-precision polarimeter based on ellipse detecting was put forward. Using the reversing light path, the light field diaphragm could be imaged to be a focusing spot on camera. The ellipse detecting means based on least square method was adopted to trace the focusing spot and get the moving track of the center of the spot,so as to measure the shift-error of the optic axis. A special assistant-software was developed to control camera and process image. The spots moving track was shown on the software interface, thus technicians can judge how to adjust mirrors position according to how the track is changing. It is verified that this method can guide technician assembling effectively and the shift-error of the optic axis can be detected out accurately. Finally, the assembling error is corrected from 1.33 to 0.3 which meets requirement.
An assembling method for off-axis parabolic mirror of a high-precision polarimeter based on ellipse detecting was put forward. Using the reversing light path, the light field diaphragm could be imaged to be a focusing spot on camera. The ellipse detecting means based on least square method was adopted to trace the focusing spot and get the moving track of the center of the spot,so as to measure the shift-error of the optic axis. A special assistant-software was developed to control camera and process image. The spots moving track was shown on the software interface, thus technicians can judge how to adjust mirrors position according to how the track is changing. It is verified that this method can guide technician assembling effectively and the shift-error of the optic axis can be detected out accurately. Finally, the assembling error is corrected from 1.33 to 0.3 which meets requirement.
2015, 36(6): 923-930.
doi: 10.5768/JAO201536.0603005
Abstract:
Based on the plate theory, using the tiny changes of interference pattern under the stress deformation on Newtons rings, we put forward an nondestructive optical vitreous stress measurement method based on the optical interference theory.We theoretically deduced the analytic formula between the curvature radius of Newtons rings and the stress,by using a designed pressure applying device which could be reasonably installed on the Newtons ring device, experimentally studied the transformation relation between the applied stress and the interference pattern, eventually proved the feasibility of the stress measurement method based on interference technique with Newton s ring through theoretical analysis and experimental comparison.Using this system to measure the stress of the optical glass sample, the minimum error between the measurement results and the actual stress is 0.8%.
Based on the plate theory, using the tiny changes of interference pattern under the stress deformation on Newtons rings, we put forward an nondestructive optical vitreous stress measurement method based on the optical interference theory.We theoretically deduced the analytic formula between the curvature radius of Newtons rings and the stress,by using a designed pressure applying device which could be reasonably installed on the Newtons ring device, experimentally studied the transformation relation between the applied stress and the interference pattern, eventually proved the feasibility of the stress measurement method based on interference technique with Newton s ring through theoretical analysis and experimental comparison.Using this system to measure the stress of the optical glass sample, the minimum error between the measurement results and the actual stress is 0.8%.
2015, 36(6): 931-936.
doi: 10.5768/JAO201536.0603006
Abstract:
To acquire the overall light intensity value of lighted visual aid to indicate temporary runway closure and the relationship between device visible distance and the air turbidity T,the virtual points were used to calculate the overall light intensity of the device. Compared with the superposition method, this method can upgrade the accuracy. Then, the relationship between the air turbidity T and the runway visual range (RVR) was built, according to the Rayleigh and Mie scattering formulas. And the point light stadia formula was corrected. The new way makes it meaningful by considering the relationship between incident wavelength and RVR. Through calculation, we know that the visible distance varies from 280 m to 370 m under the lowest operational standards,which can guide pilots to find it and fly again safely. The equation gives a calculation method to judge the visibility of lighted visual aid to indicate temporary runway closure,also it proves that the device can meet the visibility requirement theoretically. The correction of the calculation method was tested by experiments primarily.
To acquire the overall light intensity value of lighted visual aid to indicate temporary runway closure and the relationship between device visible distance and the air turbidity T,the virtual points were used to calculate the overall light intensity of the device. Compared with the superposition method, this method can upgrade the accuracy. Then, the relationship between the air turbidity T and the runway visual range (RVR) was built, according to the Rayleigh and Mie scattering formulas. And the point light stadia formula was corrected. The new way makes it meaningful by considering the relationship between incident wavelength and RVR. Through calculation, we know that the visible distance varies from 280 m to 370 m under the lowest operational standards,which can guide pilots to find it and fly again safely. The equation gives a calculation method to judge the visibility of lighted visual aid to indicate temporary runway closure,also it proves that the device can meet the visibility requirement theoretically. The correction of the calculation method was tested by experiments primarily.
2015, 36(6): 937-941.
doi: 10.5768/JAO201536.0604001
Abstract:
The favourable physical properties of SiC make it a potential material for use as containment layer in new generation nuclear reactors. The material will thus be exposed to high temperatures and fluences from fission products. The impact of increasing neutron fluence at constant irradiation temperature (800 ℃) on the properties of neutron-irradiated 3C-SiC was investigated, employing infrared reflectance spectroscopy and atomic force spectroscopy. A relation was found between the neutron fluence and the surface morphology of the irradiated 3C-SiC. The varying surface morphology also affected the dielectric parameters of the SiC.
The favourable physical properties of SiC make it a potential material for use as containment layer in new generation nuclear reactors. The material will thus be exposed to high temperatures and fluences from fission products. The impact of increasing neutron fluence at constant irradiation temperature (800 ℃) on the properties of neutron-irradiated 3C-SiC was investigated, employing infrared reflectance spectroscopy and atomic force spectroscopy. A relation was found between the neutron fluence and the surface morphology of the irradiated 3C-SiC. The varying surface morphology also affected the dielectric parameters of the SiC.
2015, 36(6): 942-947.
doi: 10.5768/JAO201536.0604002
Abstract:
According to the measuring requirements of mount quality for flexible printed circuit (FPC), starting from the designs of the hardware and software subsystems, an automatic mount quality inspection system based on machine vision was developed. The use of self-designed arc frame was utilized to simplify the process of calibration and reduce the influence of hardware on image acquisition. On the basis of laser triangulation method, the Laplacian of Gaussian operator and ultimate threshold segmentation methods were introduced to distinguish between centre and scattered area for the scattered light spot. And then the centric region was separated out by morphological closing operation. Meanwhile, the invariance of spatial moments was applied to ellipse fitting whose central position was converted to the change of stiffener on thickness that was easier to make observation. The results show that the fluctuation of spot center location is 1.15 pixels. Furthermore, the maximum error of location is only 0.82 pixels. And if the structure element of closed operation is 8, it can further improve the detection accuracy and efficiency.
According to the measuring requirements of mount quality for flexible printed circuit (FPC), starting from the designs of the hardware and software subsystems, an automatic mount quality inspection system based on machine vision was developed. The use of self-designed arc frame was utilized to simplify the process of calibration and reduce the influence of hardware on image acquisition. On the basis of laser triangulation method, the Laplacian of Gaussian operator and ultimate threshold segmentation methods were introduced to distinguish between centre and scattered area for the scattered light spot. And then the centric region was separated out by morphological closing operation. Meanwhile, the invariance of spatial moments was applied to ellipse fitting whose central position was converted to the change of stiffener on thickness that was easier to make observation. The results show that the fluctuation of spot center location is 1.15 pixels. Furthermore, the maximum error of location is only 0.82 pixels. And if the structure element of closed operation is 8, it can further improve the detection accuracy and efficiency.
2015, 36(6): 948-954.
doi: 10.5768/JAO201536.0604003
Abstract:
In order to obtain the optimum deposition processes of monolayer LaTiO3 films, monolayer LaTiO3 films were prepared by electron-beam thermal evaporation technique. The influence of experiment parameters on laser damage properties of LaTiO3 films was investigated. Experiment results show that the greatest influence on the laser-induced damage threshold (LIDT) of LaTiO3 films process conditions is the deposition temperature, followed by the gas pressure, the last is the electron beam current. The optimum deposition processes of LaTiO3 films are obtained: the deposition temperature is 175 ℃, the gas pressure is 2.010-2 Pa, the electron beam current is 120 mA(8 KeV). It is proved that the LaTiO3 films prepared under the optimum processes conditions has nice laser damage characteristics and the optimum processes conditions possess stability and repeatability. The laser-induced damage threshold of LaTiO3 films is 16.9 J/cm2(1 064 nm，10 ns).
In order to obtain the optimum deposition processes of monolayer LaTiO3 films, monolayer LaTiO3 films were prepared by electron-beam thermal evaporation technique. The influence of experiment parameters on laser damage properties of LaTiO3 films was investigated. Experiment results show that the greatest influence on the laser-induced damage threshold (LIDT) of LaTiO3 films process conditions is the deposition temperature, followed by the gas pressure, the last is the electron beam current. The optimum deposition processes of LaTiO3 films are obtained: the deposition temperature is 175 ℃, the gas pressure is 2.010-2 Pa, the electron beam current is 120 mA(8 KeV). It is proved that the LaTiO3 films prepared under the optimum processes conditions has nice laser damage characteristics and the optimum processes conditions possess stability and repeatability. The laser-induced damage threshold of LaTiO3 films is 16.9 J/cm2(1 064 nm，10 ns).
2015, 36(6): 955-958.
doi: 10.5768/JAO201536.0605001
Abstract:
In order to study the output performance of pyrotechnic-pumped laser, the fireworks pump source and laser crystal rod matching experiments were researched in the pyrotechnic-pumped laser, and the fiber coupling output experiment of pyrotechnic-pumped laser was completed. The experimental results show that the output of pyrotechnic-pumped laser reaches more than 4.82 J,which satisfies the need for energy output of pyrotechnic-pumped laser initiation system;the fiber coupling output of pyrotechnic-pumped laser reaches more than 2.87J,and the efficiency of fiber coupling device reaches more than 50%, it can provide important technical support for the initiation systems used for the ejection of fighter hatch and pilot seat.
In order to study the output performance of pyrotechnic-pumped laser, the fireworks pump source and laser crystal rod matching experiments were researched in the pyrotechnic-pumped laser, and the fiber coupling output experiment of pyrotechnic-pumped laser was completed. The experimental results show that the output of pyrotechnic-pumped laser reaches more than 4.82 J,which satisfies the need for energy output of pyrotechnic-pumped laser initiation system;the fiber coupling output of pyrotechnic-pumped laser reaches more than 2.87J,and the efficiency of fiber coupling device reaches more than 50%, it can provide important technical support for the initiation systems used for the ejection of fighter hatch and pilot seat.
2015, 36(6): 959-964.
doi: 10.5768/JAO201536.0605002
Abstract:
In order to validate the sea surface reflectance model stressed by wind and calculate the accuracy of zero-wind calibration by sea surface return, the intensity and velocity characters of sea surface return were analyzed. For the intensity characters, we compared the sea surface reflectance model to the Doppler lidar observation data, with the consideration of the contribution from subsurface reflectance, and a good consistent was showed with the local sea surface windspeed in the result referring to the windspeed of QuikSCAT sea surface. For the velocity characters, we simulated the sea wave shape with considering the vertical and horizontal movement and calculated the sea surface velocity information.The zero-wind correction accuracy for Doppler lidar with the temporal integral measurement was less than 0.2 m/s.
In order to validate the sea surface reflectance model stressed by wind and calculate the accuracy of zero-wind calibration by sea surface return, the intensity and velocity characters of sea surface return were analyzed. For the intensity characters, we compared the sea surface reflectance model to the Doppler lidar observation data, with the consideration of the contribution from subsurface reflectance, and a good consistent was showed with the local sea surface windspeed in the result referring to the windspeed of QuikSCAT sea surface. For the velocity characters, we simulated the sea wave shape with considering the vertical and horizontal movement and calculated the sea surface velocity information.The zero-wind correction accuracy for Doppler lidar with the temporal integral measurement was less than 0.2 m/s.
2015, 36(6): 965-970.
doi: 10.5768/JAO201536.0605003
Abstract:
Based on sufficient investigation of the advantages and disadvantages of several laser tuning methods, aiming at the shortcomings in tuning range, tuning speed, tuning linearity, etc., we proposed a new laser frequency tuning technology based on piezoelectric ceramic. In this method, the fiber Bragg grating(FBG) was stuck to the piezoelectric ceramics, and the driving voltage of the piezoelectric ceramics was adjusted to driven the Bragg grating telescoping, so as to achieve the wavelength (ie frequency) tuning. Meanwhile, the nonlinearity between piezoelectric ceramics input voltage and output displacement was corrected by using the fitting software in virtual instrument to make the system exhibit a linear frequency tuning, in order to improve the measurement accuracy. Experiment results show, when the drive voltage of piezoelectric ceramics changes to 126 V, the 0.8 nm (ie 100 GHz) tuning range can be realized.
Based on sufficient investigation of the advantages and disadvantages of several laser tuning methods, aiming at the shortcomings in tuning range, tuning speed, tuning linearity, etc., we proposed a new laser frequency tuning technology based on piezoelectric ceramic. In this method, the fiber Bragg grating(FBG) was stuck to the piezoelectric ceramics, and the driving voltage of the piezoelectric ceramics was adjusted to driven the Bragg grating telescoping, so as to achieve the wavelength (ie frequency) tuning. Meanwhile, the nonlinearity between piezoelectric ceramics input voltage and output displacement was corrected by using the fitting software in virtual instrument to make the system exhibit a linear frequency tuning, in order to improve the measurement accuracy. Experiment results show, when the drive voltage of piezoelectric ceramics changes to 126 V, the 0.8 nm (ie 100 GHz) tuning range can be realized.
2015, 36(6): 971-975.
doi: 10.5768/JAO201536.0605004
Abstract:
When the TV sight of airborne EO device is viewing the backlighting object, the brightness changes dramatically, which can produce image blooming,so the system is unable to capture useful details.Aiming at the problem, we proposed a scheme to solve the image blooming by utilizing the laser auxiliary illumination. When the equipment observed the backlighting object, the designator illuminated a laser of a certain frequency to irradiate the object,meanwhile, the exposure time of camera was reduced so as to decrease the illumination. Experiment shows that the TV system can format a image of laser irradiation，the histogram difference of the image edge is about 55,which meets the demand of edge detection, and the edge information can be distinguished.
When the TV sight of airborne EO device is viewing the backlighting object, the brightness changes dramatically, which can produce image blooming,so the system is unable to capture useful details.Aiming at the problem, we proposed a scheme to solve the image blooming by utilizing the laser auxiliary illumination. When the equipment observed the backlighting object, the designator illuminated a laser of a certain frequency to irradiate the object,meanwhile, the exposure time of camera was reduced so as to decrease the illumination. Experiment shows that the TV system can format a image of laser irradiation，the histogram difference of the image edge is about 55,which meets the demand of edge detection, and the edge information can be distinguished.
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