Automatic sensitivity-adjustment for a curvature sensor

TL;DR

This paper proposes two methods for automatically adjusting the sensitivity of curvature sensors in adaptive optics systems, improving image quality by maintaining optimal sensitivity amid changing atmospheric turbulence.

Contribution

It introduces novel techniques for real-time and pre-emptive sensitivity adjustment of curvature sensors in adaptive optics, enhancing their performance under variable atmospheric conditions.

Findings

Performance, measured by Strehl ratio, significantly improves with the proposed methods.

Automatic adjustment methods adapt to turbulence variations, maintaining optimal sensor sensitivity.

Both methods show potential for real-time application in adaptive optics systems.

Abstract

There are different techniques to sense the wavefront phase-distortions due to atmospheric turbulence. Curvature sensors are practical in their sensitivity being adjustable to the prevailing atmospheric conditions. Even at the best sites, the turbulence intensity has been found to vary at times over only a few minutes and regularly over longer periods. Two methods to automatically adjust the sensitivity of a curvature sensor are proposed: First, the defocus distance can be adjusted prior to the adaptive-optics (AO) loop through the acquisition of a long exposure image and can then be kept constant. Secondly, the defocus distance can be changed during the AO loop, based on the voltage values sent to the deformable mirror. We demonstrate that the performance increase - assessed in terms of the image Strehl-ratio - can be significant.