Statistics of pinned speckles in direct and coronagraphic high-contrast imaging

Remi Soummer; Claude Aime

doi:10.1117/12.551985

25 October 2004 Statistics of pinned speckles in direct and coronagraphic high-contrast imaging

Remi Soummer, Claude Aime

Proceedings Volume 5490, Advancements in Adaptive Optics; (2004) https://doi.org/10.1117/12.551985
Event: SPIE Astronomical Telescopes + Instrumentation, 2004, Glasgow, United Kingdom

Abstract

In this communication we study the utility and limitations of ground based coronagraphy with adaptive optics (AO). In very high AO correction regimes, residual speckles are pinned on the diffraction rings of the Airy pattern. It can be shown that these speckles are due to small defaults of the wavefront, amplified by the coherent part of the wave. Their statistics can be described by a modified Rice distribution, under reasonable physical assumptions. Using properties of the Moment Generating Function (MGF), simple expressions are obtained for the variances of the noise at high flux and at photon counting levels. We discuss the relative importance of speckle and photon noise and present conclusions on the limits of coronagraphy for the detection of an exoplanet. The total variance can be partitioned into two contributions: one that can be suppressed by a coronagraph and one that cannot, and different regimes can be identified. These results enable analysis of when a coronagraph can defeat the noise variance, and they provide a criterion for effectiveness of such instruments.

Citation Download Citation

Remi Soummer and Claude Aime "Statistics of pinned speckles in direct and coronagraphic high-contrast imaging", Proc. SPIE 5490, Advancements in Adaptive Optics, (25 October 2004); https://doi.org/10.1117/12.551985

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