Impact of DM misregistration for NCPA compensation in HARMONI's SCAO system
Résumé
Non-Common Path Aberration (NCPA) compensation is crucial for good image quality, especially for high contrast operations. In SCAO mode HARMONI will use a calibration deformable mirror (DM) in conjunction with of low-order DM to calibrate and correct the NCPAs between the wavefront sensor path and the science detectors. However, constraints in the optical design requires the low-order DM to be rotated with respect to the calibration DM, and places them several metres apart, leading to misregistrations between the two DMs. In this paper, we present the results of Monte Carlo simulations to determine how residual WaveFront Errors (WFEs) between the DMs vary with these misregistrations. When controlling the first 50 Zernike modes we find residual WFEs to be ≤ 3% for all rotation angles and pupil shifts ≤ 0.5 of a DM pitch (5% of the pupil). Small magnification errors contribute little to the overall error. This result confirms the LowOrder DM can compensate for NCPAs and deliver a flat wavefront to the Pyramid wavefront sensor (PyWFS) even with relatively large misregistrations.
Format | Autre |
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