Co-phase error detection of segmented mirrors based on polarization-multiplexing multi-wavelength dynamic interferometry

Abstract

The performance of large-aperture telescopes of segmented mirrors is primarily determined by the co-phase metrics among segmented mirrors. This paper proposes a novel method, based on polarization-multiplexing multi-wavelength dynamic interferometry, to measure co-phase errors of segmented mirrors. This method merges two light sources into the orthogonally polarized beams serving as test and reference beams. These beams are regrouped before being recorded, allowing two polarization cameras to respectively record the interferograms at different wavelengths. Consequently, this approach enables simultaneous work for two light sources in a single optical path without crosstalk. By integrating spatial phase shifting, two polarization cameras each capture four phase-shifted interferograms in a single shot. The analysis of error amplification due to environmental disturbance demonstrated the superior environmental insensitivity capability of the proposed method. The feasibility of the proposed method was validated using the experimentally constructed interferometer, which adjusted the piston error of the two segmented mirrors from 40.6 μm to 9.73 nm. This approach minimizes errors caused by environmental disturbance and eliminates the need for high-speed response hardware and their mutual synchronization, offering an effective and economical solution for addressing co-phase errors in large-aperture telescopes of segmented mirrors.