Surface asymmetry measurements by single-shot cyclic azimuthal shearing interferometry

A cyclic azimuthal shearing interferometer is devised for optical testing with a single-snapshot detection of surface asymmetry. A dove prism is used for azimuthal shearing of the wavefront, while a polarization-pixelated camera is adopted to capture four phase-shifted interferograms at once to calculate the wavefront gradient. Quantitative analysis is made subsequently using Zernike polynomials so as to identify relevant aberration components. The measurement point density turns out far higher than conventional Shack-Hartmann wavefront sensors, providing the potential of efficient real-time measurements for off-axis reflective optical systems intended for adaptive correction of EUV lithography and space telescopes. (c) 2024 CIRP. Published by Elsevier Ltd. All rights reserved.