Automated Analysis of Interferograms with Arbitrary Phase Shifts

Phase shifting optical interferometry allows non-contact high-precision measurements. One of the problems of phase shift interferometry is the problem of accurately specifying phase shifts. The error in setting of phase shifts leads to a decrease in measurement accuracy. The aim of the study is to improve the accuracy of measurements in optical interferometry. The method proposed in the study allows measurements to be carried out with arbitrarily set phase shifts. This eliminates the effect of phase shift errors on measurement accuracy. The proposed method consists in converting the elliptical trajectory of interference signals in the intensity space into a circular one by projecting an elliptical section of a spatial cone onto its base. A modified gradient descent algorithm is used to automatically search for the vertex of the cone. A comparison of two gradient descent algorithms has been performed. The modified gradient descent method makes it possible to achieve high measurement accuracy in comparison with the classical approach.