Stochastic parallel gradient descent based adaptive optics used for a high contrast imaging coronagraph
Abstract
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 Hartmann-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 2λ/D after being corrected by SPGD based AO.
- Publication:
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Research in Astronomy and Astrophysics
- Pub Date:
- August 2011
- DOI:
- 10.1088/1674-4527/11/8/011
- arXiv:
- arXiv:1105.0976
- Bibcode:
- 2011RAA....11..997D
- Keywords:
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- Astrophysics - Instrumentation and Methods for Astrophysics
- E-Print:
- doi:10.1088/1674-4527/11/8/011