6 August 2014 A coronagraph based on two spatial light modulators for active amplitude apodizing and phase corrections
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Almost all high-contrast imaging coronagraphs proposed until now are based on passive coronagraph optical components. Recently, Ren and Zhu proposed for the first time a coronagraph that integrates a liquid crystal array (LCA) for the active pupil apodizing and a deformable mirror (DM) for the phase corrections. Here, for demonstration purpose, we present the initial test result of a coronagraphic system that is based on two liquid crystal spatial light modulators (SLM). In the system, one SLM is served as active pupil apodizing and amplitude correction to suppress the diffraction light; another SLM is used to correct the speckle noise that is caused by the wave-front distortions. In this way, both amplitude and phase error can be actively and efficiently compensated. In the test, we use the stochastic parallel gradient descent (SPGD) algorithm to control two SLMs, which is based on the point spread function (PSF) sensing and evaluation and optimized for a maximum contrast in the discovery area. Finally, it has demonstrated a contrast of 10-6 at an inner working angular distance of ~6.2 λ/D, which is a promising technique to be used for the direct imaging of young exoplanets on ground-based telescopes.
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Jiangpei Dou, Jiangpei Dou, Deqing Ren, Deqing Ren, Xi Zhang, Xi Zhang, Yongtian Zhu, Yongtian Zhu, Gang Zhao, Gang Zhao, Zhen Wu, Zhen Wu, Rui Chen, Rui Chen, Chengchao Liu, Chengchao Liu, Feng Yang, Feng Yang, Chao Yang, Chao Yang, "A coronagraph based on two spatial light modulators for active amplitude apodizing and phase corrections", Proc. SPIE 9147, Ground-based and Airborne Instrumentation for Astronomy V, 91478O (6 August 2014); doi: 10.1117/12.2055327; https://doi.org/10.1117/12.2055327

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