Radius measurement using a parallel two-step spatial carrier phase-shifting common-path interferometer

Abstract

A curvature radius (CR) measurement method using a parallel two-step spatial carrier phase-shifting common-path interferometer is presented. This interferometer is built on a 4f optical system with two windows in the input plane and a ronchi grating outside the fourier plane. A test lens is placed in front of one of the two windows. The phase of the test lens is retrieved from the two phase shifted interferograms recorded using this interferometer and then the profile can be obtained. The CR of the test lens is thus directly derived from the profile according to their geometrical relations. The theoretical model and experimental setup are established to illustrate this method and the measurement processes. Experiments are constructed to verify the effectiveness of the CR measurement using this interferometer. The results prove that this interferometer is an effective approach for the CR measurement with inherent simplicity, high robustness and accuracy.