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10 July 2018 A modal approach to optical gain compensation for the pyramid wavefront sensor
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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.
Conference Presentation
© (2018) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
V. Deo, É. Gendron, G. Rousset, F. Vidal, and T. Buey "A modal approach to optical gain compensation for the pyramid wavefront sensor", Proc. SPIE 10703, Adaptive Optics Systems VI, 1070320 (10 July 2018); https://doi.org/10.1117/12.2311631
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