2014 Vol. 7, No. 6
2014, 7(6): 879-888.
doi: 10.3788/CO.20140706.0879
Abstract
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Abstract:
In this paper, we take for space-based surveillance as research background, and mainly focus on opto-electrical acquisition tracking and pointing(ATP) control technology. For multi degree of freedom control process including adjusting posture and changing trajectory control of satellite and opto-electrical tracking frame control, physics model of spaced surveillance, opto-electrical ATP control system scheme on satellite and television tracking precision are analyzed respectively. By these analyses, we not only have a clearer understanding of multi stage, multi task and multi mode switching control, but also obtain a more comprehensive understanding of key technologies involved. These analyses have a certain guiding role for design of opto-electrical ATP control system on satellite.
In this paper, we take for space-based surveillance as research background, and mainly focus on opto-electrical acquisition tracking and pointing(ATP) control technology. For multi degree of freedom control process including adjusting posture and changing trajectory control of satellite and opto-electrical tracking frame control, physics model of spaced surveillance, opto-electrical ATP control system scheme on satellite and television tracking precision are analyzed respectively. By these analyses, we not only have a clearer understanding of multi stage, multi task and multi mode switching control, but also obtain a more comprehensive understanding of key technologies involved. These analyses have a certain guiding role for design of opto-electrical ATP control system on satellite.
2014, 7(6): 889-896.
doi: 10.3788/CO.20140706.0889
Abstract:
The definition and structure of Internet of Things are introduced. The application and prospection of optical communication technique(optical fiber and wireless communications) in internet of things are discussed from perceiving and network direction. The optical fiber communication, near field wireless communication and mobile communication are a basis for development of Internet of Thing. Uniform and standardized treaty and technical standard must be estallished to solve critical and difficult problems in the future development.
The definition and structure of Internet of Things are introduced. The application and prospection of optical communication technique(optical fiber and wireless communications) in internet of things are discussed from perceiving and network direction. The optical fiber communication, near field wireless communication and mobile communication are a basis for development of Internet of Thing. Uniform and standardized treaty and technical standard must be estallished to solve critical and difficult problems in the future development.
2014, 7(6): 897-910.
doi: 10.3788/CO.20140706.0897
Abstract:
Firstly, the basic concepts and theories of super-resolution restoration method are introduced. Secondly, some applications focused on common method of super-resolution restoration are summarized. Their theoretical basis, advantages and disadvantages, and scope of applications are exhaustively analyzed. Finally, the future development of super-resolution restoration method is prospected. Overall, the super-resolution restoration methods are divided into frequency domain method and space domain method. Frequency domain recovery method is simple in principle and easy in calculation. But its motion model is shift model and doesn't have a general. Meanwhile it is difficult to use the priori information of the image to help super-resolution restoration. With space domain recovery method, a complex motion model can be easily established considering almost all of the imaging degradation factors, including noise, down sampling, fuzzy caused by non-zero aperture, degradation of optical system, and motion blur. As the same time, we could also add more perfect priori knowledge. Compared to the frequency domain method, space domain super-resolution restoration model is more close to actual degradation processes and is currently the most widely used super-resolution restoration method.
Firstly, the basic concepts and theories of super-resolution restoration method are introduced. Secondly, some applications focused on common method of super-resolution restoration are summarized. Their theoretical basis, advantages and disadvantages, and scope of applications are exhaustively analyzed. Finally, the future development of super-resolution restoration method is prospected. Overall, the super-resolution restoration methods are divided into frequency domain method and space domain method. Frequency domain recovery method is simple in principle and easy in calculation. But its motion model is shift model and doesn't have a general. Meanwhile it is difficult to use the priori information of the image to help super-resolution restoration. With space domain recovery method, a complex motion model can be easily established considering almost all of the imaging degradation factors, including noise, down sampling, fuzzy caused by non-zero aperture, degradation of optical system, and motion blur. As the same time, we could also add more perfect priori knowledge. Compared to the frequency domain method, space domain super-resolution restoration model is more close to actual degradation processes and is currently the most widely used super-resolution restoration method.
2014, 7(6): 911-916.
doi: 10.3788/CO.20140706.0911
Abstract:
An automatic localization method of light strips in multi-planar structures is proposed in order to solve the problem that it is difficult to distinguish light strip regions of irregular surface in rudder angular measurement based on the vision system of line-structured light. Firstly, the sub-pixel centers of curvilinear structures are extracted by Steger algorithm. Secondly, pieces of line segments are detected and labeled using line constraints and distance constraints to calculate the distances and orientations of points. Finally, different planes are located according to light strips positions. Experimental results show that the presented method is convenient and effective.
An automatic localization method of light strips in multi-planar structures is proposed in order to solve the problem that it is difficult to distinguish light strip regions of irregular surface in rudder angular measurement based on the vision system of line-structured light. Firstly, the sub-pixel centers of curvilinear structures are extracted by Steger algorithm. Secondly, pieces of line segments are detected and labeled using line constraints and distance constraints to calculate the distances and orientations of points. Finally, different planes are located according to light strips positions. Experimental results show that the presented method is convenient and effective.
2014, 7(6): 917-924.
doi: 10.3788/CO.20140706.0917
Abstract:
To deal with the effect of flutter of carrying platform on remote sensing camera, motion estimation algorithm can be used to the image sequences taken by auxiliary high-speed array CCD camera during exposure to estimate the vibration. Pixel binnng is proposed to compensate the time of exposure and to improve the brightness and contrast as well as SNR of the images. And a region selection algorithm is used to select the image region by which we can estimate the displacement using gray projection algorithm. The experiment results show that the error is 1 pixel by utilizing the improved algorithm, which greatly enhance the accuracy and stability.
To deal with the effect of flutter of carrying platform on remote sensing camera, motion estimation algorithm can be used to the image sequences taken by auxiliary high-speed array CCD camera during exposure to estimate the vibration. Pixel binnng is proposed to compensate the time of exposure and to improve the brightness and contrast as well as SNR of the images. And a region selection algorithm is used to select the image region by which we can estimate the displacement using gray projection algorithm. The experiment results show that the error is 1 pixel by utilizing the improved algorithm, which greatly enhance the accuracy and stability.
2014, 7(6): 925-930.
doi: 10.3788/CO.20140706.0925
Abstract:
In order to investigate the influence of aggregation and surface effect on the optical properties of ZnS nanoparticles, SiO2 is used to modify the surface of ZnS nanoparticles. The optical properties of the synthesized ZnS and ZnS/SiO2 nanoparticles are both studied for making a comparison. According to the absorption spectra recorded by an ultraviolet-visible spectrophotometer, the band gap edge red-shifts from 333 nm to 360 nm. To analyze the emission properties, the fluorescence spectra of the solution and the powders containing the ZnS or ZnS/SiO2 nanoparticles are both collected. It is found that the light emission of the ZnS nanoparticles in the violet to blue region is enhanced obviously when SiO2 is introduced. When the samples are excitated by a xenon lamp, the integrated fluorescence intensity of the ZnS/SiO2 nanoparticles is enhanced by 17.5 times. However, a much smaller enhancement is found in the measurement for the solution samples. The fluorescence is only 1.1 times higher after coating ZnS nanoparticles by SiO2. The inhibition of the aggregation between the ZnS nanoparticles by the SiO2 coated layer is supposed to be responsible for the enhancement, which is confirmed by the photoluminescence data where a 325 nm He-Cd laser is used as the excitation source.
In order to investigate the influence of aggregation and surface effect on the optical properties of ZnS nanoparticles, SiO2 is used to modify the surface of ZnS nanoparticles. The optical properties of the synthesized ZnS and ZnS/SiO2 nanoparticles are both studied for making a comparison. According to the absorption spectra recorded by an ultraviolet-visible spectrophotometer, the band gap edge red-shifts from 333 nm to 360 nm. To analyze the emission properties, the fluorescence spectra of the solution and the powders containing the ZnS or ZnS/SiO2 nanoparticles are both collected. It is found that the light emission of the ZnS nanoparticles in the violet to blue region is enhanced obviously when SiO2 is introduced. When the samples are excitated by a xenon lamp, the integrated fluorescence intensity of the ZnS/SiO2 nanoparticles is enhanced by 17.5 times. However, a much smaller enhancement is found in the measurement for the solution samples. The fluorescence is only 1.1 times higher after coating ZnS nanoparticles by SiO2. The inhibition of the aggregation between the ZnS nanoparticles by the SiO2 coated layer is supposed to be responsible for the enhancement, which is confirmed by the photoluminescence data where a 325 nm He-Cd laser is used as the excitation source.
2014, 7(6): 931-935.
doi: 10.3788/CO.20140706.0931
Abstract:
La1.6(MoO4)3:Eu0.43+ nancrystal is synthesized by combustion method and the interaction between the phonon-dopant-lattice and luminescence properties of this nanocrystal are investigated. It is shown by X-ray diffraction that the powders are crystallized in a single phase annealed at 500~900 ℃. It is found that the excitation of the Mo6+-O2- charge transfer band(CTB) can result in the emissions of Eu3+ ion, which indicates that energy transfer takes place from CTB to Eu3+ ions. Two one-phonon sidebands locate at 1=469 nm and 2=426 nm in the excitation spectra which are due to Mo=O and MoOMo expand and contract vibration modes, respectively, with phonon energies of 1 202 cm-1 and 767 cm-1. The Huang-Kun factors S1=0.055 and S2=0.037 describing the interaction intensity between phonon and lattice are determined. The optical properties of La1.6(MoO4)3:Eu0.43+ would be able to provide the experimental foundation to reveal the properties of high conductivity and negative thermal expansion(NTE) with the trivalent ions.
La1.6(MoO4)3:Eu0.43+ nancrystal is synthesized by combustion method and the interaction between the phonon-dopant-lattice and luminescence properties of this nanocrystal are investigated. It is shown by X-ray diffraction that the powders are crystallized in a single phase annealed at 500~900 ℃. It is found that the excitation of the Mo6+-O2- charge transfer band(CTB) can result in the emissions of Eu3+ ion, which indicates that energy transfer takes place from CTB to Eu3+ ions. Two one-phonon sidebands locate at 1=469 nm and 2=426 nm in the excitation spectra which are due to Mo=O and MoOMo expand and contract vibration modes, respectively, with phonon energies of 1 202 cm-1 and 767 cm-1. The Huang-Kun factors S1=0.055 and S2=0.037 describing the interaction intensity between phonon and lattice are determined. The optical properties of La1.6(MoO4)3:Eu0.43+ would be able to provide the experimental foundation to reveal the properties of high conductivity and negative thermal expansion(NTE) with the trivalent ions.
2014, 7(6): 936-941.
doi: 10.3788/CO.20140706.0936
Abstract:
In order to achieve both wide field of angle and high resolution in one imaging device, we propose a method which combines detectors arrays mosaic technique and monocentric imaging lens. This paper first introduces the scheme of detectors mosaic of four lens systems, and next there is a thorough discussion of advantages by adopting monocentric objective lens. After that, a completed lens design prescription is presented as well as the related specifications. In the final part, evaluation of the imaging quality is discussed along with the tolerance sensitivity analysis. The finished system has 120 FOV and 100 mm focal length. As depicted, the contradiction between wide field of angle and long-focus has been figured out excellently by the monocentric mosaic imaging system which can complete ultra-high resolution imaging and has great advantage compared with other imaging devices.
In order to achieve both wide field of angle and high resolution in one imaging device, we propose a method which combines detectors arrays mosaic technique and monocentric imaging lens. This paper first introduces the scheme of detectors mosaic of four lens systems, and next there is a thorough discussion of advantages by adopting monocentric objective lens. After that, a completed lens design prescription is presented as well as the related specifications. In the final part, evaluation of the imaging quality is discussed along with the tolerance sensitivity analysis. The finished system has 120 FOV and 100 mm focal length. As depicted, the contradiction between wide field of angle and long-focus has been figured out excellently by the monocentric mosaic imaging system which can complete ultra-high resolution imaging and has great advantage compared with other imaging devices.
2014, 7(6): 942-948.
doi: 10.3788/CO.20140706.0942
Abstract:
This paper introduces the multi-band spectral fusion technology of laser receiving and color TV confocal-window. A continuous zoom lens with focal length of 20-450 mm and angel of vision from 13.6810.26~0.610.46 is adopted. Under the condition of concentrated or parallel light, the contrast tests are implemented respectively using cubic prism or flat glass to separate light. Results show that when using cubic prism under concentrated light in the big angel of vision of 13.6810.26, with the biggest light incident angle, serious color deviation and image color distortion occur. With the decrease of angel of vision and light incident angle, the degree of image color distortion declines, and almost disappears when getting closed to the small angel of view of 0.610.46 gradually. However, under the condition of using flat glass and parallel light to separate light, continuous zoom lens can not only meet the requirement of optical aberration in the whole range field of view, but also solve the color deviation problem occurred in cubic prism, which shows a regular image color. Under the restrict limitation of room size, the MTF of color TV optical system reaches 0.3 at 108 lp/mm and the design result meets the requirement of engineering application.
This paper introduces the multi-band spectral fusion technology of laser receiving and color TV confocal-window. A continuous zoom lens with focal length of 20-450 mm and angel of vision from 13.6810.26~0.610.46 is adopted. Under the condition of concentrated or parallel light, the contrast tests are implemented respectively using cubic prism or flat glass to separate light. Results show that when using cubic prism under concentrated light in the big angel of vision of 13.6810.26, with the biggest light incident angle, serious color deviation and image color distortion occur. With the decrease of angel of vision and light incident angle, the degree of image color distortion declines, and almost disappears when getting closed to the small angel of view of 0.610.46 gradually. However, under the condition of using flat glass and parallel light to separate light, continuous zoom lens can not only meet the requirement of optical aberration in the whole range field of view, but also solve the color deviation problem occurred in cubic prism, which shows a regular image color. Under the restrict limitation of room size, the MTF of color TV optical system reaches 0.3 at 108 lp/mm and the design result meets the requirement of engineering application.
2014, 7(6): 949-955.
doi: 10.3788/CO.20140706.0949
Abstract:
The single-channel demonstration is adopted to validate the rationality and feasibility of CO2 detector optical system. Atmosphere spectrum is tested by experiment with the mode of sun light and diffuser. The spectrum calibration of the single-channel demonstration is carried out in lab. The matching calculation of two spectral position obtained from above two ways is carried on by using spectral matching algorithm. The result shows that the absorption peak point deviation is less than 0.006 nm in the line depth stable position, which could meet accuracy requirement of algorithm. This way can not only verify the validity of the matching algorithm, but also the rationality and feasibility of optical system design. The research provides the theoretical and practical optical reference data for spectrometer design in the future.
The single-channel demonstration is adopted to validate the rationality and feasibility of CO2 detector optical system. Atmosphere spectrum is tested by experiment with the mode of sun light and diffuser. The spectrum calibration of the single-channel demonstration is carried out in lab. The matching calculation of two spectral position obtained from above two ways is carried on by using spectral matching algorithm. The result shows that the absorption peak point deviation is less than 0.006 nm in the line depth stable position, which could meet accuracy requirement of algorithm. This way can not only verify the validity of the matching algorithm, but also the rationality and feasibility of optical system design. The research provides the theoretical and practical optical reference data for spectrometer design in the future.
2014, 7(6): 956-961.
doi: 10.3788/CO.20140706.0956
Abstract:
An imaging keratometer by the aid of modern optoelectronic technology is proposed to improve the accuracy of measurement. The optical system consists of an annular object, a first imaging subsystem, a second imaging subsystem, and a CCD detector. First, the first imaging subsystem and second imaging subsystem are designed and optimized by ZEMAX, and two subsystems are connected by a semitransparent mirror. Then we perform optimization of the whole optical system of imaging keratometer. Finally, the simulation of the illumination of the annular image is accomplished by TracePro. The result shows that the measurement range of this imaging keratometer is about 30D to 60D(5.5 mm to 11 mm in radius of curvature), and the accuracy is about 0.072D in the case of the radius of curvature of 7.8 mm.
An imaging keratometer by the aid of modern optoelectronic technology is proposed to improve the accuracy of measurement. The optical system consists of an annular object, a first imaging subsystem, a second imaging subsystem, and a CCD detector. First, the first imaging subsystem and second imaging subsystem are designed and optimized by ZEMAX, and two subsystems are connected by a semitransparent mirror. Then we perform optimization of the whole optical system of imaging keratometer. Finally, the simulation of the illumination of the annular image is accomplished by TracePro. The result shows that the measurement range of this imaging keratometer is about 30D to 60D(5.5 mm to 11 mm in radius of curvature), and the accuracy is about 0.072D in the case of the radius of curvature of 7.8 mm.
2014, 7(6): 962-968.
doi: 10.3788/CO.20140706.0962
Abstract:
In order to realize the simulation of autonomous landing on planets based on optical navigation and to satisfy the need of ground-based testing for system navigation algorithms, a scheme of simulator based on commercial projector's projection system is suggested. The idea of optical system design are described especially and the design results are given. First, the working principle and components of system are introduced. Then the optical specifications of projective lens and imaging lens are fixed based on the simulator's technology demands, projector and CCD selected. Finally, the optical system layouts, aberration curves, spot diagrams and modulation transfer functions(MTF) are showed. Simulation results indicate that the symmetry of spot diagrams is well to satisfy the demand of image processing and judgments, and the design value of MTF is close to 0.6 at the Nyquist frequency(91 lp/mm) and the imaging performance of system is good. The design results can be used for the following manufacture of simulator for autonomous landing on planets based on optical navigation.
In order to realize the simulation of autonomous landing on planets based on optical navigation and to satisfy the need of ground-based testing for system navigation algorithms, a scheme of simulator based on commercial projector's projection system is suggested. The idea of optical system design are described especially and the design results are given. First, the working principle and components of system are introduced. Then the optical specifications of projective lens and imaging lens are fixed based on the simulator's technology demands, projector and CCD selected. Finally, the optical system layouts, aberration curves, spot diagrams and modulation transfer functions(MTF) are showed. Simulation results indicate that the symmetry of spot diagrams is well to satisfy the demand of image processing and judgments, and the design value of MTF is close to 0.6 at the Nyquist frequency(91 lp/mm) and the imaging performance of system is good. The design results can be used for the following manufacture of simulator for autonomous landing on planets based on optical navigation.
2014, 7(6): 969-974.
doi: 10.3788/CO.20140706.0969
Abstract:
This research demonstrated an innovative and integrated approach to design 3D compound eye optical structure which composed of seven sub-systems, and to improve image quality of marginal FOV. For every sub-system, it is an unattached optical system with cross light path, which consists of a mircolens array layer, an aperture stop array, and integrating freeform lens which are used to make images of different mircolens onto a plane image sensor. It's easier for this structure to get better image quality for marginal FOV by reducing the maximum light deviation angle. The theoretic FOV can be as large as 180. In the meantime the requirment for fabricating accuracy is not very high. The feasibility of the proposed structure is validated with optical software.
This research demonstrated an innovative and integrated approach to design 3D compound eye optical structure which composed of seven sub-systems, and to improve image quality of marginal FOV. For every sub-system, it is an unattached optical system with cross light path, which consists of a mircolens array layer, an aperture stop array, and integrating freeform lens which are used to make images of different mircolens onto a plane image sensor. It's easier for this structure to get better image quality for marginal FOV by reducing the maximum light deviation angle. The theoretic FOV can be as large as 180. In the meantime the requirment for fabricating accuracy is not very high. The feasibility of the proposed structure is validated with optical software.
Manufacturing and testing of rectangular off-axis aspheric mirror with double-swing polishing method
2014, 7(6): 975-981.
doi: 10.3788/CO.20140706.0975
Abstract:
A kind of manufacturing and testing method for rectangular off-axis aspheric lightweight mirror is introduced. In order to overcome the corner effect, double-swing polishing(DSP) method is proposed. A DSP machine is made to achieve satisfying manufacturing result. The DSP and the 4-pole method are successfully applied for manufacturing optical system in the spectrometer. Four rectangular off-axis aspheric mirrors with the largest size of 266 mm110 mm are polished, and the final surface precision figures are better than 0.020(RMS, @633 nm). Manufacturing result shows that the double-swing polishing method improves the polishing efficiency and reduces the optical surface medium frequency error.
A kind of manufacturing and testing method for rectangular off-axis aspheric lightweight mirror is introduced. In order to overcome the corner effect, double-swing polishing(DSP) method is proposed. A DSP machine is made to achieve satisfying manufacturing result. The DSP and the 4-pole method are successfully applied for manufacturing optical system in the spectrometer. Four rectangular off-axis aspheric mirrors with the largest size of 266 mm110 mm are polished, and the final surface precision figures are better than 0.020(RMS, @633 nm). Manufacturing result shows that the double-swing polishing method improves the polishing efficiency and reduces the optical surface medium frequency error.
2014, 7(6): 982-988.
doi: 10.3788/CO.20140706.0982
Abstract:
The whole process of space heat flux analysis, heat flux simulation and programmable load for thermal test is expatiated for a given space optical remote sensor working in sun-synchronous orbit. Firstly, space heat flux simulation process of space optical remote sensor is summarized. Secondly, calculation methods of solar radiation, earth albedo and earth infrared radiation are introduced. Thirdly, the space total absorbed heat flux for the given space optical remote sensor is calculated, and the average heat flux of the sunlit area and the shaded area is gained. Finally, the space heat flux simulation method and tactic of thermal test are confirmed, and open-loop control program of programmable power is written using LabVIEW language, and space transient heat loads of thermal test are accurately applied. The results of test indicate that the deviations of applied heat load are within 2.5%, and the deviations which can meet the requirements of thermal test.
The whole process of space heat flux analysis, heat flux simulation and programmable load for thermal test is expatiated for a given space optical remote sensor working in sun-synchronous orbit. Firstly, space heat flux simulation process of space optical remote sensor is summarized. Secondly, calculation methods of solar radiation, earth albedo and earth infrared radiation are introduced. Thirdly, the space total absorbed heat flux for the given space optical remote sensor is calculated, and the average heat flux of the sunlit area and the shaded area is gained. Finally, the space heat flux simulation method and tactic of thermal test are confirmed, and open-loop control program of programmable power is written using LabVIEW language, and space transient heat loads of thermal test are accurately applied. The results of test indicate that the deviations of applied heat load are within 2.5%, and the deviations which can meet the requirements of thermal test.
2014, 7(6): 989-995.
doi: 10.3788/CO.20140706.0989
Abstract:
When the spatial telescope tracks the target on the orbit, move and rotation will occurr between the visual axis of the telescope and target(namely pointing deviation and oscillation) due to all kinds of factors in space. In order to compensate above errors, the arm compensation mechanism is designed to compensate the errors between the visual axis and the target. Because the size and weight of the arm compensation mechanism are restricted severely, and the size of the telescope is huge and its weight is more than 3 000 kg, this configuration results in lower stiffness of the system. In order to satisfy higher machinery stiffness required by the control system, the feasibility is analyzed to improve system stiffness through forcing preload on bearing after the system configuration is confirmed. This paper studies on the relationship among bearing preload, bearing stiffness and system stiffness, and the relationship curve between bearing preload and system natural frequency is obtained. The analysis proves that forcing an appropriate preload to bearing can improve system stiffness on the condition that the system configuration is confirmed, and it is also an effective method to confirm the optimum bearing preload.
When the spatial telescope tracks the target on the orbit, move and rotation will occurr between the visual axis of the telescope and target(namely pointing deviation and oscillation) due to all kinds of factors in space. In order to compensate above errors, the arm compensation mechanism is designed to compensate the errors between the visual axis and the target. Because the size and weight of the arm compensation mechanism are restricted severely, and the size of the telescope is huge and its weight is more than 3 000 kg, this configuration results in lower stiffness of the system. In order to satisfy higher machinery stiffness required by the control system, the feasibility is analyzed to improve system stiffness through forcing preload on bearing after the system configuration is confirmed. This paper studies on the relationship among bearing preload, bearing stiffness and system stiffness, and the relationship curve between bearing preload and system natural frequency is obtained. The analysis proves that forcing an appropriate preload to bearing can improve system stiffness on the condition that the system configuration is confirmed, and it is also an effective method to confirm the optimum bearing preload.
2014, 7(6): 996-1002.
doi: 10.3788/CO.20140706.0996
Abstract:
In order to ensure the imaging quality of sweep aerial remote sensor, the precise assembling of TDI CCD is researched. Firstly, the working principle of sweep aerial remote sensor and TDI CCD is introduced. Secondly, degradation in the Modulation Transfer Function(MTF) of TDI CCD caused by the angle between TDI direction of TDI CCD and image motion in the direction of pendulum swing is discussed. And the calculated results demonstrate that precise assembling is indispensable to TDI CCD in sweep aerial remote sensor. Finally, the method of precise assembling of TDI CCD in sweep aerial remote sensor is provided. The assembling and adjusting results show that the assembled method of TDI CCD can give very high precision, and the MTF at Nyquist frequency of TDI CCD caused by the assembling error is 0.999 9, when the stages of TDI CCD are 200.
In order to ensure the imaging quality of sweep aerial remote sensor, the precise assembling of TDI CCD is researched. Firstly, the working principle of sweep aerial remote sensor and TDI CCD is introduced. Secondly, degradation in the Modulation Transfer Function(MTF) of TDI CCD caused by the angle between TDI direction of TDI CCD and image motion in the direction of pendulum swing is discussed. And the calculated results demonstrate that precise assembling is indispensable to TDI CCD in sweep aerial remote sensor. Finally, the method of precise assembling of TDI CCD in sweep aerial remote sensor is provided. The assembling and adjusting results show that the assembled method of TDI CCD can give very high precision, and the MTF at Nyquist frequency of TDI CCD caused by the assembling error is 0.999 9, when the stages of TDI CCD are 200.
2014, 7(6): 1003-1011.
doi: 10.3788/CO.20140706.1003
Abstract:
In order to realize the high precise wavefront test of large-aperture collimator and evaluate its wavefront quality, the method of differential pentaprism scanning wavefront detection is proposed in this paper. This method is the optimization of pentaprism scanning detection. Firstly, the information of wavefront curvature is obtained by measuring wavefront slope change to reconstruct the wavefront. The title and defocus error instructed by inaccurate calibration of center of mass are eliminated. Secondly, the differential pentaprism scanning wavefront detection system is established to verify the feasibility of this method. Lastly, the error analysis is given. The error analysis shows that the testing precise of this method is 10.54 nm. The experimental results show that the repeatability precisions of wave peak and valley value(PV) and root mean square(RMS) are increased by 74.41% and 125.81% compared with pentaprism scanning method. This method basically meets the requirements of high accuracy and good stability for collimator wavefront detection, which can be used to evaluate the quality of collimator wavefront.
In order to realize the high precise wavefront test of large-aperture collimator and evaluate its wavefront quality, the method of differential pentaprism scanning wavefront detection is proposed in this paper. This method is the optimization of pentaprism scanning detection. Firstly, the information of wavefront curvature is obtained by measuring wavefront slope change to reconstruct the wavefront. The title and defocus error instructed by inaccurate calibration of center of mass are eliminated. Secondly, the differential pentaprism scanning wavefront detection system is established to verify the feasibility of this method. Lastly, the error analysis is given. The error analysis shows that the testing precise of this method is 10.54 nm. The experimental results show that the repeatability precisions of wave peak and valley value(PV) and root mean square(RMS) are increased by 74.41% and 125.81% compared with pentaprism scanning method. This method basically meets the requirements of high accuracy and good stability for collimator wavefront detection, which can be used to evaluate the quality of collimator wavefront.
2014, 7(6): 1012-1018.
doi: 10.3788/CO.20140706.1012
Abstract:
We use a type of interferometer with space phase-shifting technique to measure the optical surface of the concave aspheric mirror in this paper. By using polarized elements and multi-image collected in synchronism we implement the phase-shifting process, and we adopt the phase unwrapping algorithm based on discrete cosine transform(DCT) onto the interferograms that we measured. For the discontinuous phase distribution, we adopt the un-weighted least square method to optimize the objective function, and finally reconstruct the wavefront surface of the measured optical surface. This type of interferometer has the capacity of anti-vibration, and can optimize the algorithm in the digital image processing procedure, so we can get the measured surface shape rapidly and steadily, and it is no need for high performance hardware. This approach can be used as optical measurement out of laboratory conditions, and we can get high measuring precision under the condition of disturbance existing.
We use a type of interferometer with space phase-shifting technique to measure the optical surface of the concave aspheric mirror in this paper. By using polarized elements and multi-image collected in synchronism we implement the phase-shifting process, and we adopt the phase unwrapping algorithm based on discrete cosine transform(DCT) onto the interferograms that we measured. For the discontinuous phase distribution, we adopt the un-weighted least square method to optimize the objective function, and finally reconstruct the wavefront surface of the measured optical surface. This type of interferometer has the capacity of anti-vibration, and can optimize the algorithm in the digital image processing procedure, so we can get the measured surface shape rapidly and steadily, and it is no need for high performance hardware. This approach can be used as optical measurement out of laboratory conditions, and we can get high measuring precision under the condition of disturbance existing.
