Sparse aperture differential piston measurements using the pyramid wave-front sensor

TL;DR

This study demonstrates the laboratory feasibility of using a pyramid wavefront sensor to measure differential piston in sparse aperture telescopes, a key step towards closed-loop phasing of primary mirrors.

Contribution

It provides experimental validation of pyramid WFS capabilities for differential piston measurement in sparse aperture configurations, advancing telescope phasing techniques.

Findings

Successful wavefront flattening with deformable mirror

Effective differential piston signal measurement between two pupils

Characterization of achromatic double pyramids for wavefront sensing

Abstract

In this paper we report on the laboratory experiment we settled in the Shanghai Astronomical Observatory (SHAO) to investigate the pyramid wavefront sensor (WFS) ability to measure the differential piston on a sparse aperture. The ultimate goal is to verify the ability of the pyramid WFS work in closed loop to perform the phasing of the primary mirrors of a sparse Fizeau imaging telescope. In the experiment we installed on the optical bench we performed various test checking the ability to flat the wave-front using a deformable mirror and to measure the signal of the differential piston on a two pupils setup. These steps represent the background from which we start to perform full closed loop operation on multiple apertures. These steps were also useful to characterize the achromatic double pyramids (double prisms) manufactured in the SHAO optical workshop.