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Proceedings Paper

A modal approach to optical gain compensation for the pyramid wavefront sensor
Author(s): V. Deo; É. Gendron; G. Rousset; F. Vidal; T. Buey
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Paper Abstract

Extremely Large Telescopes are making Pyramid Wavefront Sensors (PWFS) the preferred engineering choice for Adaptive Optics designs, such as the MICADO camera SCAO subsystem currently developed at LESIA. A major PWFS issue is the so-called Optical Gain (OG) effect: PWFSs experience a nonlinearity-induced sensitivity reduction – of 60% or worse at the fitting error on standard atmospheric conditions – which degrades as the turbulence residual increases. OG affects system performance, jeopardizes loop stability and prevents efficient non-common path aberration compensation. We investigate a modal approach to OG impact mitigation, and investigate its impact on nonlinearity error depending on the AO control basis. We evidence that scalar gain compensation of the OG is insufficient on high order systems, as the high spatial frequency range spanned covers high OG value discrepancies over the controlled basis. We quantify the performance improvements obtained with OG modal compensation by end-to-end numerical simulations. Finally, we propose a modelization of OG modal compensation coefficients, in order to allow their computation on-the-fly provided telemetry of the immediate turbulence conditions is available.

Paper Details

Date Published: 10 July 2018
PDF: 18 pages
Proc. SPIE 10703, Adaptive Optics Systems VI, 1070320 (10 July 2018); doi: 10.1117/12.2311631
Show Author Affiliations
V. Deo, LESIA, Observatoire de Paris, Univ. PSL, CNRS, Sorbonne Univ., Univ. Paris Diderot (France)
É. Gendron, LESIA, Observatoire de Paris, Univ. PSL, CNRS, Sorbonne Univ., Univ. Paris Diderot (France)
G. Rousset, LESIA, Observatoire de Paris, Univ. PSL, CNRS, Sorbonne Univ., Univ. Paris Diderot (France)
F. Vidal, LESIA, Observatoire de Paris, Univ. PSL, CNRS, Sorbonne Univ., Univ. Paris Diderot (France)
T. Buey, LESIA, Observatoire de Paris, Univ. PSL, CNRS, Sorbonne Univ., Univ. Paris Diderot (France)


Published in SPIE Proceedings Vol. 10703:
Adaptive Optics Systems VI
Laird M. Close; Laura Schreiber; Dirk Schmidt, Editor(s)

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