Focal-plane-assisted pyramid wavefront sensor: Enabling frame-by-frame optical gain tracking

¹ Aix Marseille Univ, CNRS, CNES, LAM, Marseille, France
e-mail: vincent.chambouleyron@lam.fr
² DOTA, ONERA, Université Paris Saclay, 91123 Palaiseau, France
³ IFREMER, Laboratoire Detection, Capteurs et Mesures (LDCM), Centre Bretagne, ZI de la Pointe du Diable, CS 10070, 29280 Plouzane, France

Received: 15 January 2021
Accepted: 1 March 2021

Abstract

Aims. With its high sensitivity, the pyramid wavefront sensor (PyWFS) is becoming an advantageous sensor for astronomical adaptive optics (AO) systems. However, this sensor exhibits significant non-linear behaviours leading to challenging AO control issues.

Methods. In order to mitigate these effects, we propose to use in addition to the classical pyramid sensor a focal plane image combined with a convolutive description of the sensor to fast track the PyWFS non-linearities, the so-called optical gains (OG).

Results. We show that this additional focal plane imaging path only requires a small fraction of the total flux while representing a robust solution to estimating the PyWFS OG. Finally, we demonstrate the gain that our method brings with specific examples of bootstrapping and handling non-common path aberrations.