25 October 2004 Wavefront sensing through spatial filters: the case for coronographic, high-contrast AO systems
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For applications like direct imaging detections of Exo-Planets from the ground e.g. in the CHEOPS project, extreme adaptive optics (XAO) systems using DMs with > 1000 actuators and correction frequencies of ~2kHz are proposed to be used in combination with coronographic devices. If the XAO and science channel work at the same wavelength it is a natural idea to combine the coronograph with the XAO's beam splitter (BS) to make use of the light that would otherwise just be lost. However, the location of the BS in the focal plane and the severe field limitation of the AO by a small (~0.3'') aperture in the focal plane imposes a spatial filtering on the wavefront sensor signal. In this paper, we examine the effect of the spatial filter on the "AO control radius" and the Strehl ratio provided by the system in a semi-analytical way, numerical simulations for various wavefront sensor types and a laboratory verification experiment.
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Markus Feldt, Markus Feldt, Joana B. Costa, Joana B. Costa, Micaela Stumpf, Micaela Stumpf, Hans-Martin Schmid, Hans-Martin Schmid, Alessandro Berton, Alessandro Berton, Stefan Hippler, Stefan Hippler, Remko Stuik, Remko Stuik, Jorge Lima, Jorge Lima, } "Wavefront sensing through spatial filters: the case for coronographic, high-contrast AO systems", Proc. SPIE 5490, Advancements in Adaptive Optics, (25 October 2004); doi: 10.1117/12.550883; https://doi.org/10.1117/12.550883

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