A low noise and relatively high dynamic range CMOS active pixel sensor (APS) using a variable-gain column amplifier is presented and analyzed. On this signal path there are a pixel source follower, a switched-capacitor, noise-cancelling, variable-gain amplifier, and a correlated double sample (CDS) circuit in each column. The using of high gain for the column amplifier reduces input-referred random noise, but it may reduce the dynamic range of this device at meanwhile. In this paper, we present a detail analysis for the noise and the dynamic range with the variable gain of the column amplifier. It is revealed that the total random read noise can be analyzed in three parts: the first part is from the pixel circuit, including the pixel-related fixed-pattern noise, reset noise and pixel source follower amplifier noise; the second part is from the column circuit, including the column-related fixed-pattern noise and the column amplifier noise; and the third part is from the output amplifier in the chip-level circuit. The analysis suggests that the noise components from the pixel and column can be significantly cancelled by the double-stage column noise canceller, and the noise components from the output amplifier in the chip-level circuit, are the major noise source and can be greatly reduced if the signal is amplified before this noise is added. Both the analysis and measured result indicate that we can achieve a low input-referred noise and keep a relatively high dynamic gain by choosing a proper column amplifier gain.
{"title":"The optimization of noise and dynamic range with variable-gain column amplifier in CMOS image sensors","authors":"R. Deng, Jin-jin Yu, Yong P. Chen","doi":"10.1117/12.900975","DOIUrl":"https://doi.org/10.1117/12.900975","url":null,"abstract":"A low noise and relatively high dynamic range CMOS active pixel sensor (APS) using a variable-gain column amplifier is presented and analyzed. On this signal path there are a pixel source follower, a switched-capacitor, noise-cancelling, variable-gain amplifier, and a correlated double sample (CDS) circuit in each column. The using of high gain for the column amplifier reduces input-referred random noise, but it may reduce the dynamic range of this device at meanwhile. In this paper, we present a detail analysis for the noise and the dynamic range with the variable gain of the column amplifier. It is revealed that the total random read noise can be analyzed in three parts: the first part is from the pixel circuit, including the pixel-related fixed-pattern noise, reset noise and pixel source follower amplifier noise; the second part is from the column circuit, including the column-related fixed-pattern noise and the column amplifier noise; and the third part is from the output amplifier in the chip-level circuit. The analysis suggests that the noise components from the pixel and column can be significantly cancelled by the double-stage column noise canceller, and the noise components from the output amplifier in the chip-level circuit, are the major noise source and can be greatly reduced if the signal is amplified before this noise is added. Both the analysis and measured result indicate that we can achieve a low input-referred noise and keep a relatively high dynamic gain by choosing a proper column amplifier gain.","PeriodicalId":355017,"journal":{"name":"Photoelectronic Detection and Imaging","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131525022","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A novel focusing method of the remote sensing camera is proposed in this paper. To evaluate the quality of the image obtained by the aerial camera, an assessing function was constructed based on the Wavelet transform. And the characteristic of the CCD mosaicing structure was taken use to solve the problem that the evaluating values can not be compared for the images captured by the aerial camera are variable. On the basis of the wavelet evaluating function, the quality of the image was assessed. Then the CCD mosaicing structure was utilized to perform auto-focusing process, a simulation was made to validate the novel method in the end. There are three major contributions in the paper. Firstly, the weights of the wavelet coefficients in the evaluating function were set according to the characteristic of the Wavelet transform and human vision system (HVS). By those, the assessing result is close to our subjective feel and insensitive to noise. Secondly, in order to make the function adaptive to images with different high-frequency components, the properties of the wavelet basis were analyzed. By comparing the evaluating effect of different images, the wavelet basis with the best effect is symlet2 and the level of decomposing is three. Finally, by making use of the CCD mosaicing structure, the problem that auto-focusing of the aerial camera can't use digital images processing directly was solved, and the region with the highest frequency component was chosen as the evaluating area so as to improve the sensitivity of the function.
{"title":"A digital auto-focusing method based on CCD mosaicing for aerial camera","authors":"Yan Wang, Yang Liu, Xing-lin Chen","doi":"10.1117/12.900175","DOIUrl":"https://doi.org/10.1117/12.900175","url":null,"abstract":"A novel focusing method of the remote sensing camera is proposed in this paper. To evaluate the quality of the image obtained by the aerial camera, an assessing function was constructed based on the Wavelet transform. And the characteristic of the CCD mosaicing structure was taken use to solve the problem that the evaluating values can not be compared for the images captured by the aerial camera are variable. On the basis of the wavelet evaluating function, the quality of the image was assessed. Then the CCD mosaicing structure was utilized to perform auto-focusing process, a simulation was made to validate the novel method in the end. There are three major contributions in the paper. Firstly, the weights of the wavelet coefficients in the evaluating function were set according to the characteristic of the Wavelet transform and human vision system (HVS). By those, the assessing result is close to our subjective feel and insensitive to noise. Secondly, in order to make the function adaptive to images with different high-frequency components, the properties of the wavelet basis were analyzed. By comparing the evaluating effect of different images, the wavelet basis with the best effect is symlet2 and the level of decomposing is three. Finally, by making use of the CCD mosaicing structure, the problem that auto-focusing of the aerial camera can't use digital images processing directly was solved, and the region with the highest frequency component was chosen as the evaluating area so as to improve the sensitivity of the function.","PeriodicalId":355017,"journal":{"name":"Photoelectronic Detection and Imaging","volume":"25 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131754689","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
R. Xu, Zhiping He, Zehong Zhang, Zhong-qian Fu, Jianyu Wang
Acousto-optic tunable filter (AOTF) is an electronically tunable optical filter which can make optical beams passing through the acousto-optic (AO) crystal manipulated by suitable frequency generated acoustic waves. In view of the advantages of AO devices such as compact, solid-state, easily integrated, extremely fast response and tunable wavelength output, the AOTF spectrometers have been widely applied in space-based instruments. Considering the operation of the devices in the naturally occurring space radiation environment is one of the major space qualification issues nowadays, the research on characteristics of AOTF in the space radiation environment is significant. Focusing on the space radiation effects on AOTF, especially for radiation environment that lunar exploration infrared imaging spectrometer based on AOTF needs to carry on, the space radiation characteristics of AOTF has been studied through the radiation experiments and the AOTF performance tests. In this paper, some details of AOTF performance tests like detecting principle, method, equipments and performance indicators are introduced firstly. Then the radiation experiment of AOTF is described, while the measured data such as optic transmission, the relationship between diffraction efficiency and driving power, diffraction efficiency and driving frequency, diffraction wavelength and driving frequency relations before and after experiment are analyzed comparatively next. Finally the experimental results are presented and evaluated.
{"title":"The research on characteristics of acousto-optic tunable filter by space radiation experiment","authors":"R. Xu, Zhiping He, Zehong Zhang, Zhong-qian Fu, Jianyu Wang","doi":"10.1117/12.902425","DOIUrl":"https://doi.org/10.1117/12.902425","url":null,"abstract":"Acousto-optic tunable filter (AOTF) is an electronically tunable optical filter which can make optical beams passing through the acousto-optic (AO) crystal manipulated by suitable frequency generated acoustic waves. In view of the advantages of AO devices such as compact, solid-state, easily integrated, extremely fast response and tunable wavelength output, the AOTF spectrometers have been widely applied in space-based instruments. Considering the operation of the devices in the naturally occurring space radiation environment is one of the major space qualification issues nowadays, the research on characteristics of AOTF in the space radiation environment is significant. Focusing on the space radiation effects on AOTF, especially for radiation environment that lunar exploration infrared imaging spectrometer based on AOTF needs to carry on, the space radiation characteristics of AOTF has been studied through the radiation experiments and the AOTF performance tests. In this paper, some details of AOTF performance tests like detecting principle, method, equipments and performance indicators are introduced firstly. Then the radiation experiment of AOTF is described, while the measured data such as optic transmission, the relationship between diffraction efficiency and driving power, diffraction efficiency and driving frequency, diffraction wavelength and driving frequency relations before and after experiment are analyzed comparatively next. Finally the experimental results are presented and evaluated.","PeriodicalId":355017,"journal":{"name":"Photoelectronic Detection and Imaging","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115165840","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this paper, the low-frequency vibrational modes of crystalline benzoic acid (BA) have been investigated by terahertz time-domain spectroscopy (THz-TDS) and theoretical simulations based on the linearity combination of atomic orbital within the Density Functional Theory (DFT) as well as ab initio molecular orbital method at second-order Moller-Plesset Perturbation Theory (MP2) level for single molecule and dimer. Experimentally, a series of prominent absorption features of pure benzoic acid relevant to intra- and inter-molecular vibrational modes have been obtained below 4 THz at room temperature. For the theoretical simulations, geometry-optimization results of bond lengths and dihedral angles in both BA monomer and dimer are very close to experimental neutron diffraction measurements. Furthermore, the simulation results demonstrate absorption profile centered at 1.89 THz contains low-frequency modes of Ph-COOH twisting due to intramolecular motion and cogwheel owing to intermolecular motion. All the intra- and inter-molecular vibrational modes measured have also been assigned.
{"title":"Low-frequency vibrational modes of benzoic acid investigated by terahertz time-domain spectroscopy and theoretical simulations","authors":"Hui Yan, W. Fan, Zhuan-ping Zheng","doi":"10.1117/12.900322","DOIUrl":"https://doi.org/10.1117/12.900322","url":null,"abstract":"In this paper, the low-frequency vibrational modes of crystalline benzoic acid (BA) have been investigated by terahertz time-domain spectroscopy (THz-TDS) and theoretical simulations based on the linearity combination of atomic orbital within the Density Functional Theory (DFT) as well as ab initio molecular orbital method at second-order Moller-Plesset Perturbation Theory (MP2) level for single molecule and dimer. Experimentally, a series of prominent absorption features of pure benzoic acid relevant to intra- and inter-molecular vibrational modes have been obtained below 4 THz at room temperature. For the theoretical simulations, geometry-optimization results of bond lengths and dihedral angles in both BA monomer and dimer are very close to experimental neutron diffraction measurements. Furthermore, the simulation results demonstrate absorption profile centered at 1.89 THz contains low-frequency modes of Ph-COOH twisting due to intramolecular motion and cogwheel owing to intermolecular motion. All the intra- and inter-molecular vibrational modes measured have also been assigned.","PeriodicalId":355017,"journal":{"name":"Photoelectronic Detection and Imaging","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121859880","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A novel algorithm of motion blur image restoration based on PSF half-blind estimation with Hough transform was introduced on the basis of full analysis of the principle of TDICCD camera, with the problem that vertical uniform linear motion estimation used by IBD algorithm as the original value of PSF led to image restoration distortion. Firstly, the mathematical model of image degradation was established with the transcendental information of multi-frame images, and then two parameters (movement blur length and angle) that have crucial influence on PSF estimation was set accordingly. Finally, the ultimate restored image can be acquired through multiple iterative of the initial value of PSF estimation in Fourier domain, which the initial value was gained by the above method. Experimental results show that the proposal algorithm can not only effectively solve the image distortion problem caused by relative motion between TDICCD camera and movement objects, but also the details characteristics of original image are clearly restored.
{"title":"The algorithm of motion blur image restoration based on PSF half-blind estimation","authors":"Da-ke Chen, Zhe Lin","doi":"10.1117/12.895528","DOIUrl":"https://doi.org/10.1117/12.895528","url":null,"abstract":"A novel algorithm of motion blur image restoration based on PSF half-blind estimation with Hough transform was introduced on the basis of full analysis of the principle of TDICCD camera, with the problem that vertical uniform linear motion estimation used by IBD algorithm as the original value of PSF led to image restoration distortion. Firstly, the mathematical model of image degradation was established with the transcendental information of multi-frame images, and then two parameters (movement blur length and angle) that have crucial influence on PSF estimation was set accordingly. Finally, the ultimate restored image can be acquired through multiple iterative of the initial value of PSF estimation in Fourier domain, which the initial value was gained by the above method. Experimental results show that the proposal algorithm can not only effectively solve the image distortion problem caused by relative motion between TDICCD camera and movement objects, but also the details characteristics of original image are clearly restored.","PeriodicalId":355017,"journal":{"name":"Photoelectronic Detection and Imaging","volume":"145 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132785213","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Acousto-Optical Tunable Filter (AOTF) is an electronically tunable optical filter based on Acousto-optic effect and has its own special compared with other dispersive parts. Because its characteristics of electronic tunable spectral selection, rapid response and simple structure, imaging spectrometer based on AOTF is a useful high-spectral technology, especially in deep space exploration applications. This paper introduces two imaging spectrometers, a VIS-NIR Imaging Spectrometer (VNIS) built as a payload instrument for lunar detection and a whiskbroom imaging spectrometer (WIS) with programmable spectral sampling. VNIS provides programmable spectral selection from 0.45 to 2.4 μm and includes two channels, a V-NIR hyper-spectral imager (0.45 to 0.95μm) and a SWIR spectrograph (0.9 to 2.4μm), with a spectral overlap of 0.05μm. WIS is a kind of scanning, spectral programmable imaging spectrometer, includes a scanning mechanism and a programmable spectral selection spectrometer. In the end, the prospects in deep-space exploration application are discussed.
{"title":"Imaging spectrometer based on AOTF and its prospects in deep-space exploration application","authors":"Zhiping He, R. Shu, Jianyu Wang","doi":"10.1117/12.902420","DOIUrl":"https://doi.org/10.1117/12.902420","url":null,"abstract":"The Acousto-Optical Tunable Filter (AOTF) is an electronically tunable optical filter based on Acousto-optic effect and has its own special compared with other dispersive parts. Because its characteristics of electronic tunable spectral selection, rapid response and simple structure, imaging spectrometer based on AOTF is a useful high-spectral technology, especially in deep space exploration applications. This paper introduces two imaging spectrometers, a VIS-NIR Imaging Spectrometer (VNIS) built as a payload instrument for lunar detection and a whiskbroom imaging spectrometer (WIS) with programmable spectral sampling. VNIS provides programmable spectral selection from 0.45 to 2.4 μm and includes two channels, a V-NIR hyper-spectral imager (0.45 to 0.95μm) and a SWIR spectrograph (0.9 to 2.4μm), with a spectral overlap of 0.05μm. WIS is a kind of scanning, spectral programmable imaging spectrometer, includes a scanning mechanism and a programmable spectral selection spectrometer. In the end, the prospects in deep-space exploration application are discussed.","PeriodicalId":355017,"journal":{"name":"Photoelectronic Detection and Imaging","volume":"106 7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133294262","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Promising Crystals of Generating THz have been discussed according as the theory of solid state physics. We found that PbB4O7 (PTB) crystal has probability of generating about 3.12THz, and Bi4Ge3O12 (BGO) crystal has probability of generating and 2.7, 3.7, 6.0 and 10.8THz radiation.
{"title":"Search promising crystal of generating THz wave","authors":"Bi-hui Hou, Yali Wang, Wei Hao, Guoqing Liu, Bingxin X. Yang","doi":"10.1117/12.900330","DOIUrl":"https://doi.org/10.1117/12.900330","url":null,"abstract":"Promising Crystals of Generating THz have been discussed according as the theory of solid state physics. We found that PbB4O7 (PTB) crystal has probability of generating about 3.12THz, and Bi4Ge3O12 (BGO) crystal has probability of generating and 2.7, 3.7, 6.0 and 10.8THz radiation.","PeriodicalId":355017,"journal":{"name":"Photoelectronic Detection and Imaging","volume":"52 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134254673","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The rotation angle of a mounted polarizer in front of a camera has a direct effect on imaging quality and therefore this paper presents a rapid computation method for a polarizer's optimal rotation angle on an airborne optical platform. The computation contains four steps. First, we construct a world coordinate system and a camera coordinate system that both adopt the center of a code disc as their common origin. Second, we take the origin of the world coordinate system as a start point, intercept a unit segment along the sunlight direction and compute the endpoint coordinates of the unit segment in the world coordinate system. Third, by mapping the relation from the world coordinate system to the camera coordinate system, we compute the above endpoint coordinates in the camera coordinate system. Fourth, we project the above segment towards a disc code plane, compute the angle between the projected line and the reference of the code disc, and take the resultant angle distance as a polarizer's optimal rotation angle of airlight rejection utilizing polarization filtering. Experiment results indicate that our computation method of a polarizer's optimal rotation angle can be applied to airlight rejection on an airborne optical platform.
{"title":"Computation for polarizer's optimal rotation angle on airborne optical platform","authors":"Bin Feng, Zelin Shi","doi":"10.1117/12.900139","DOIUrl":"https://doi.org/10.1117/12.900139","url":null,"abstract":"The rotation angle of a mounted polarizer in front of a camera has a direct effect on imaging quality and therefore this paper presents a rapid computation method for a polarizer's optimal rotation angle on an airborne optical platform. The computation contains four steps. First, we construct a world coordinate system and a camera coordinate system that both adopt the center of a code disc as their common origin. Second, we take the origin of the world coordinate system as a start point, intercept a unit segment along the sunlight direction and compute the endpoint coordinates of the unit segment in the world coordinate system. Third, by mapping the relation from the world coordinate system to the camera coordinate system, we compute the above endpoint coordinates in the camera coordinate system. Fourth, we project the above segment towards a disc code plane, compute the angle between the projected line and the reference of the code disc, and take the resultant angle distance as a polarizer's optimal rotation angle of airlight rejection utilizing polarization filtering. Experiment results indicate that our computation method of a polarizer's optimal rotation angle can be applied to airlight rejection on an airborne optical platform.","PeriodicalId":355017,"journal":{"name":"Photoelectronic Detection and Imaging","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133087979","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
With the development of terahertz related technologies, the terahertz imaging technology will show its greater practical value in more areas. In this paper, we describe a terahertz imaging system that uses a single pixel detector in combination with a series of random masks to enable high-speed image acquisition. The image formation is based on the theory of compressed sensing (CS). When the scene under view is compressible by an algorithm like JPEG or JPEG2000, the CS theory enables us to stably reconstruct an image of the scene from fewer measurements than the number of reconstructed pixels. In this manner, we achieve sub-Nyquist image acquisition. CS theory mainly includes signal sparse representation, encoding measurement and reconstruction algorithm. CS combines sampling and compression into a single non-adaptive linear measurement process. Rather than measuring pixel samples of the scene under view, we measure inner products between the scene and a set of test functions. CS permits the reconstruction of a N-by-N pixel image using much fewer than N2 measurements. This approach eliminates the need for raster scanning of the object or the terahertz beam, while maintaining the high sensitivity of a single-element detector. We demonstrate the concept using a backward wave oscillator (BWO) which is a continuous-wave terahertz source and get a preliminary test result.
{"title":"Single-pixel terahertz imaging via compressed sensing","authors":"Ya-qin Zhao, Liangliang Zhang, Guoteng Duan, Xiaohua Liu, Cunlin Zhang","doi":"10.1117/12.900486","DOIUrl":"https://doi.org/10.1117/12.900486","url":null,"abstract":"With the development of terahertz related technologies, the terahertz imaging technology will show its greater practical value in more areas. In this paper, we describe a terahertz imaging system that uses a single pixel detector in combination with a series of random masks to enable high-speed image acquisition. The image formation is based on the theory of compressed sensing (CS). When the scene under view is compressible by an algorithm like JPEG or JPEG2000, the CS theory enables us to stably reconstruct an image of the scene from fewer measurements than the number of reconstructed pixels. In this manner, we achieve sub-Nyquist image acquisition. CS theory mainly includes signal sparse representation, encoding measurement and reconstruction algorithm. CS combines sampling and compression into a single non-adaptive linear measurement process. Rather than measuring pixel samples of the scene under view, we measure inner products between the scene and a set of test functions. CS permits the reconstruction of a N-by-N pixel image using much fewer than N2 measurements. This approach eliminates the need for raster scanning of the object or the terahertz beam, while maintaining the high sensitivity of a single-element detector. We demonstrate the concept using a backward wave oscillator (BWO) which is a continuous-wave terahertz source and get a preliminary test result.","PeriodicalId":355017,"journal":{"name":"Photoelectronic Detection and Imaging","volume":"112 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116587122","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In the conventional method, the structural parameters of primary mirror are usually optimized just by the requirement of mechanical performance. Because the influences of structural parameters on thermal stability are not taken fully into account in this simple method, the lightweight optimum design of primary mirror usually brings the bad thermal stability, especially in the complex environment. In order to obtain better thermal stability, a new method about structure-thermal optimum design of tracking primary mirror is discussed. During the optimum process, both the lightweight ratio and thermal stability will be taken into account. The structure-thermal optimum is introduced into the analysis process and commenced after lightweight design as the secondary optimum. Using the engineering analysis of software ANSYS, a parameter finite element analysis (FEA) model of mirror is built. On the premise of appropriate lightweight ratio, the RMS of structure-thermal deformation of mirror surface and lightweight ratio are assigned to be state variables, and the maximal RMS of temperature gradient load to be object variable. The results show that certain structural parameters of tracking primary mirror have different influences on mechanical performance and thermal stability, even they are opposite. By structure-thermal optimizing, the optimized mirror model discussed in this paper has better thermal stability than the old one under the same thermal loads, which can drastically reduce difficulty in thermal control.
{"title":"Thermal optimum design for tracking primary mirror of Space Telescope","authors":"Haichao Pan, P. Ruan, Fu Li, Hongwei Wang","doi":"10.1117/12.899606","DOIUrl":"https://doi.org/10.1117/12.899606","url":null,"abstract":"In the conventional method, the structural parameters of primary mirror are usually optimized just by the requirement of mechanical performance. Because the influences of structural parameters on thermal stability are not taken fully into account in this simple method, the lightweight optimum design of primary mirror usually brings the bad thermal stability, especially in the complex environment. In order to obtain better thermal stability, a new method about structure-thermal optimum design of tracking primary mirror is discussed. During the optimum process, both the lightweight ratio and thermal stability will be taken into account. The structure-thermal optimum is introduced into the analysis process and commenced after lightweight design as the secondary optimum. Using the engineering analysis of software ANSYS, a parameter finite element analysis (FEA) model of mirror is built. On the premise of appropriate lightweight ratio, the RMS of structure-thermal deformation of mirror surface and lightweight ratio are assigned to be state variables, and the maximal RMS of temperature gradient load to be object variable. The results show that certain structural parameters of tracking primary mirror have different influences on mechanical performance and thermal stability, even they are opposite. By structure-thermal optimizing, the optimized mirror model discussed in this paper has better thermal stability than the old one under the same thermal loads, which can drastically reduce difficulty in thermal control.","PeriodicalId":355017,"journal":{"name":"Photoelectronic Detection and Imaging","volume":"38 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117164677","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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