21 September 2012 A dark-hole correction test for the step-transmission filter based coronagraphic system
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We present the initial test of the dark-hole correction for the high-contrast imaging coronagraph that is based on the step-transmission filter. The dark hole is created by a 12x12 actuator deformable mirror (DM) that has been put in the conjugate plane of the pupil image of the coronagraph. In this test, we use the stochastic parallel gradient descent (SPGD) optimization algorithm to directly control the DM to provide an optimal phase to minimize the intensity in target regions, where the dark hole is created and the contrast can be enhanced. For demonstration purpose, the test is carried out in a single wavelength and should be improved in next step for broad-band high-contrast imaging. Finally, it is shown in the test that an extra contrast ~50 times improvement has reached in the dark hole in the coronagraphic image plane. Such a technique could be used for a future space-based high-contrast observation and is promising for the direct imaging of an Earth-like exoplanet.
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Jiangpei Dou, Jiangpei Dou, Deqing Ren, Deqing Ren, Yongtian Zhu, Yongtian Zhu, Xi Zhang, Xi Zhang, Rong Li, Rong Li, } "A dark-hole correction test for the step-transmission filter based coronagraphic system", Proc. SPIE 8442, Space Telescopes and Instrumentation 2012: Optical, Infrared, and Millimeter Wave, 84420D (21 September 2012); doi: 10.1117/12.924248; https://doi.org/10.1117/12.924248

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