Phase sensor for solar adaptive-optics

TL;DR

This paper introduces a novel optical wavefront sensing technique for solar adaptive optics that uses interference patterns to directly measure phase, eliminating the need for fast correlation computations.

Contribution

A new interferometric wavefront sensing method for solar adaptive optics that simplifies phase measurement by using a Mach-Zehnder interferometer with extended sources.

Findings

Direct phase estimation without correlation computation

Applicable to extended sources like the Sun

Requires precise initial optical alignment

Abstract

Wavefront sensing in solar adaptive-optics is currently done with correlating Shack-Hartmann sensors, although the spatial- and temporal-resolutions of the phase measurements are then limited by the extremely fast computing required to correlate the sensor signals at the frequencies of daytime atmospheric-fluctuations. To avoid this limitation, a new wavefront-sensing technique is presented, that makes use of the solar brightness and is applicable to extended sources. The wavefront is sent through a modified Mach-Zehnder interferometer. A small, central part of the wavefront is used as reference and is made to interfere with the rest of the wavefront. The contrast of two simultaneously measured interference-patterns provides a direct estimate of the wavefront phase, no additional computation being required. The proposed optical layout shows precise initial alignment to be the critical point in implementing the new wavefront-sensing scheme.