Surface figure measurement tool based on a radial shearing interferometer using a geometric phase lens with various spherical wavefronts

Abstract

We describe a compact radial shearing interferometer based on a geometric phase lens as a surface figure measurement tool. Based on the polarization and diffraction characteristics of a geometric phase lens, two radially sheared wavefronts are simply generated, and the surface figure of a specimen can be immediately reconstructed from the radial wavefront slope calculated with four phase-shifted interferograms obtained from a polarization pixelated complementary metal-oxide semiconductor camera. In order to increase the field of view, moreover, the incident wavefront is adjusted according to the shape of the target, which allows the reflected wavefront to become planar. By the combination of the incident wavefront formula and the measurement result by the proposed system, the whole surface figure of the target can be instantaneously reconstructed. As the experimental result, the surface figures of various optical components were reconstructed at the extended measurement area with less than 0.78 µm deviations, and it was confirmed that the radial shearing ratio was fixed independent of the surface figures.