Freeform surface interferometry with an adaptive ring-cavity compensator

Abstract

In the existing deformable mirror (DM)-based adaptive interferometers for freeform surfaces test, the departure coverage and the DM surface monitoring load are contradictory to each other. We reported an adaptive ring-cavity compensator (ARCC) based freeform surface interferometer. With the multiple cyclic reflections of the beam in the ARRC, the departure coverage is enlarged to four times of the stroke of one DM. With only one DM, the ARCC achieves the coverage comparable to dual-DMs, without any incremental DM monitoring load and decoupling operation. The interferometer coverage is thus doubled at a relatively low cost. The freeform surface measurement and the DM surface monitoring are performed with a rotatable polaroid for gating, without any other auxiliary devices. Validated experiments are presented.