Phase detection from two phase-shifting interferograms

Abstract

Phase detection is one of the most important processing steps in optical phase-shifting interferometry. It aims to reconstruct the phase field of wavefront from the interferogram. To solve this problem, many algorithms of phase detection have been proposed these years. Here, A FFT-based two-step phase shifting (TPS) algorithm is described in detail and implemented by use of experimental interferograms. This algorithm has been proposed to solve the TPS problem with random phase shift except π. By comparison with the Visibility-Function-based TPS algorithm, it proves that the FFT-based algorithm has obvious advantages in phase extracting. Meanwhile, we present a π-phase-shift supplement to the TPS algorithm, which combines the two interferograms and demodulates the phase map from a combined interferogram. So combining this quasi-two-step method and FFT-based one, one could really implement the TPS with random phase shift. Thereafter, we design an optical setup of two-channel TPS interferometer with random phase shift, which could capture the two interferograms simultaneously. At the same time, we propose a fringe-variable Jamin interferometer to detect reversed domain of ferroelectric crystal in real time. It could realize the two-step phase shifting with π radian.