Surface figure metrology for reflective membrane mirrors based on phase-measuring deflectometry

TL;DR

This paper introduces an advanced phase-measuring deflectometry system for non-contact, high-precision surface measurement of large, flexible membrane mirrors, crucial for next-generation telescope optics.

Contribution

It develops a tailored PMD system with ray-tracing and iterative reconstruction, enabling accurate surface characterization of large, non-rigid membrane mirrors.

Findings

Successfully measured a 1-meter membrane mirror surface.

Demonstrated stability evaluation of membrane optics.

Validated PMD as effective for large, flexible mirrors.

Abstract

Reflective membrane mirrors provide a lightweight, low-cost alternative to traditional optics for next-generation large-aperture telescopes, but their non-rigid, thin structure poses challenges for surface metrology. We present a phase-measuring deflectometry (PMD) system enhanced with tailored ray-tracing and iterative reconstruction to enable non-contact measurement of large membrane optics. The system successfully characterizes the surface figure and evaluates the dynamic stability of a 1-meter Hencky-type membrane mirror. Our results demonstrate the effectiveness of PMD as a practical metrology tool for future membrane-based telescope systems.