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Focal plane wave-front sensing algorithm for high-contrast imaging

Science China(physics,Mechanics & astronomy) 2009年第8期52卷 1284-1288页

作者： DOU JiangPei1,2,3,REN DeQing1,2,4,ZHU YongTian1,2 & ZHANG Xi1,2,3 1 National Astronomical Observatories/Nanjing Institute of Astronomical Optics & Technology,Chinese Academy of Sciences,Nanjing 210042,China 2 Key Laboratory of Astronomical Optics & Technology,Nanjing Institute of Astronomical Optics & Technology,Chinese Academy of Sciences,Nanjing 210042,China 3 Graduate university of Chinese Academy of Sciences,Beijing 100049,China 4 physics & astronomy department,california state university northridge,18111 nordhoff street,northridge,california 91330-8268,usa National Astronomical Observatories/Nanjing Institute of Astronomical Optics & Technology Chinese Academy of Sciences Nanjing China Key Laboratory of Astronomical Optics & Technology Nanjing Institute of Astronomical Optics & Technology Chinese Academy of Sciences Nanjing China Graduate university of Chinese Academy of Sciences Beijing China physics & astronomy department California State University Northridge Northridge USA

High-contrast imaging provided by a coronagraph is critical for the direction imaging of the Earth-like planet orbiting its bright parent star.A major limitation for such direct imaging is the speckle noise that is induced from the wave-front error of an optical *** derive an algorithm for the wave-front measurement directly from 3 focal plane *** 3 images are achieved through a deformable mirror to provide specific phases for the optics *** introduce an extra amplitude modulation on one deformable mirror configuration to create an uncorrelated wave-front,which is a critical procedure for wave-front *** simulation shows that the reconstructed wave-front is consistent with the original wave-front theoretically,which indicates that such an algorithm is a promising technique for the wave-front measurement for the high-contrast imaging.

关键词： high-contrast imaging multi-image algorithm speckle nulling technique wave-front sensing

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An iterative wavefront sensing algorithm for high-contrast imaging systems

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Research in astronomy and Astrophysics 2011年第2期11卷 198-204页

作者： Jiang-Pei Dou 1,2,De-Qing Ren 1,2,3 and Yong-Tian Zhu 1,2 1 National Astronomical Observatories/Nanjing Institute of Astronomical Optics & Technology,Chinese Academy of Sciences,Nanjing 210042,China 2 Key Laboratory of Astronomical Optics & Technology,Nanjing Institute of Astronomical Optics & Technology,Chinese Academy of Sciences,Nanjing 210042,China 3 physics & astronomy department,california state university northridge,18111 nordhoff street,northridge,california 91330-8268,usa National Astronomical Observatories / Nanjing Institute of Astronomical Optics & Technology Chinese Academy of Sciences Nanjing 210042 China Key Laboratory of Astronomical Optics & Technology Nanjing Institute of Astronomical Optics & Technology Chinese Academy of Sciences Nanjing 210042 China physics & astronomy department California State University Northridge 18111 Nordhoff Street Northridge California 91330-8268 USA

Wavefront sensing from multiple focal plane images is a promising technique for high-contrast imaging ***,the wavefront error of an optics system can be properly reconstructed only when it is very *** paper presents an iterative optimization algorithm for the direct measurement of large static wavefront errors from only one focal plane *** first measure the intensity of the pupil image to get the pupil function of the system and acquire the aberrated image on the focal plane with a phase error that will be *** we induce a dynamic phase on the tested pupil function and calculate the associated intensity of the reconstructed image on the focal *** algorithm will then try to minimize the intensity difference between the reconstructed image and the aberrated test image in the focal plane,where the induced phase is a variable of the optimization *** simulation shows that the wavefront of an optical system can theoretically be reconstructed with high precision,which indicates that such an iterative algorithm may be an effective way to perform wavefront sensing for high-contrast imaging systems.

关键词： techniques: image processing -- methods: numerical -- planetarysystems

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Stochastic parallel gradient descent based adaptive optics used for a high contrast imaging coronagraph

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Research in astronomy and Astrophysics 2011年第8期11卷 997-1002页

作者： Bing Dong De-Qing Ren Xi Zhang physics ＆ astronomy department California State University Northridge CA 91330-8268 USA National Astronomical Observatories/Nanjing Institute of Astronomical Optics ＆ Technology Chinese Academy of Sciences Nanjing 210042 China

An adaptive optics （AO） system based on a stochastic parallel gradient descent （SPGD） algorithm is proposed to reduce the speckle noises in the optical system of a stellar coronagraph in order to further improve the contrast. The principle of the SPGD algorithm is described briefly and a metric suitable for point source imaging optimization is given. The feasibility and good performance of the SPGD algorithm is demonstrated by an experimental system featured with a 140-actuator deformable mirror and a Hartrnann-Shark wavefront sensor. Then the SPGD based AO is applied to a liquid crystal array （LCA） based coronagraph to improve the contrast. The LCA can modulate the incoming light to generate a pupil apodization mask of any pattern. A circular stepped pattern is used in our preliminary experiment and the image contrast shows improvement from 10^-3 to 10^-4.5 at an angular distance of 2A/D after being corrected by SPGD based AO.

关键词： instrumentation: adaptive optics -- methods: laboratory -- techniques: image processing coronagraph

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