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19 August 2009 Laboratory experiment of a high-contrast imaging coronagraph with new step-transmission filters
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We present the latest results of our laboratory experiment of the coronagraph with step-transmission filters. The primary goal of this work is to test the stability of the coronagraph and identify the main factors that limit its performance. At present, a series of step-transmission filters has been designed. These filters were manufactured with Cr film on a glass substrate with a high surface quality. During the process of the experiment of each filter, we have identified several contrast limiting factors, which includes the non-symmetry of the coating film, transmission error, scattered light and the optical aberration caused by the thickness difference of coating film. To eliminate these factors, we developed a procedure for the correct test of the coronagraph and finally it delivered a contrast in the order of 10-6~10-7 at an angular distance of 4λD, which is well consistent with theoretical design. As a follow-up effort, a deformable mirror has been manufactured to correct the wave-front error of the optical system, which should deliver better performance with an extra contrast improvement in the order of 10-2~10-3. It is shown that the step-transmission filter based coronagraph is promising for the high-contrast imaging of earth-like planets.
© (2009) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Jiangpei Dou, Deqing Ren, Yongtian Zhu, and Xi Zhang "Laboratory experiment of a high-contrast imaging coronagraph with new step-transmission filters", Proc. SPIE 7440, Techniques and Instrumentation for Detection of Exoplanets IV, 744019 (19 August 2009);

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