The Asymmetric Pupil Fourier Wavefront Sensor

TL;DR

This paper presents a new wavefront sensing method using Fourier analysis of a single image, capable of improving adaptive optics performance with high sensitivity and potential for on-sky implementation.

Contribution

It introduces the asymmetric pupil Fourier wavefront sensing (APF-WFS) technique, combining Fourier analysis with pupil asymmetry to measure and correct wavefront errors.

Findings

Can improve Strehl ratio from 50% to over 90% in few iterations

Demonstrates high photon noise sensitivity

Suitable for on-sky adaptive optics correction

Abstract

This paper introduces a novel wavefront sensing approach that relies on the Fourier analysis of a single conventional direct image. In the high Strehl ratio regime, the relation between the phase measured in the Fourier plane and the wavefront errors in the pupil can be linearized, as was shown in a previous work that introduced the notion of generalized closure-phase, or kernel-phase. The technique, to be usable as presented requires two conditions to be met: (1) the wavefront errors must be kept small (of the order of one radian or less) and (2) the pupil must include some asymmetry, that can be introduced with a mask, for the problem to become solvable. Simulations show that this asymmetric pupil Fourier wavefront sensing or APF-WFS technique can improve the Strehl ratio from 50 to over 90 % in just a few iterations, with excellent photon noise sensitivity properties, suggesting that on-sky close loop APF-WFS is possible with an extreme adaptive optics system.