Common-path and synchronous phase shifting of lateral shearing interferometry based on micro-polarizer array

Abstract

Based on birefringence theory and polarization-synchronized phase-shifting lateral shearing interferometry technology, we proposed a compact and simple polarization phase-shifting lateral shearing interferometer using a polarization camera integrated with a phase-shifting array of micro-polarizers. This interferometer is designed to realize a common optical path synchronous phase-shifting lateral shearing interference for aspheric surface testing system. This interferometer is composed of a polarization beam displacer (PBD), a quarter-wave plate (QWP), polarization camera (PCam). With the polarization birefringent crystal used as the PBD to realize the lateral shearing, and the parallel beam is divided into linearly polarized light whose polarization directions are orthogonal to each other. With the QWP changed the shear beam formed by the interference of the measuring beam and the self-copy beam into circularly polarized light with the opposite rotation direction. Next, with the micro-polarizer phase-shifting array on the PCam obtained four shearing interferograms with a phase-shifting difference is π/2, which allows for the implement of aplanatic and common optical path shearing interferometer. Therefore, the system possesses significant advantages of simple structure, compact and strong antiinterference ability. Then, by the four-step phase-shifting algorithm demodulated the measurement light field distribution on the shearing interferograms. Finally, using the Zernike polynomial fitting method realized the surface shape reconstruction of the interferogram wavefront. The effectiveness of the interferometer is demonstrated by simulations and experiments, which research results showed that the optical measurement method can extract interferogram information in real time and directly measure the wavefront phase distribution.