Novel 3D-Trajectory Analysis Method in Phase Shifting Interferometry

Measurement accuracy in optical interferometry is a critical requirement. This article demonstrates a method for interferogram analysis with a step-by-step phase shift, which allows measurements in optical interferometry without the influence of an error in phase shifts. This allows to achieve greater measurement accuracy. The second section describes measurements in optical interferometry with step-by-step phase shift. In particular, the problem of the influence of the accuracy of phase shifts on the measurement accuracy is described. The following is a description of the method proposed in the study. The method is based on the transformation of the elliptical trajectory of interference signals to a circular one. The algorithm of the method is also demonstrated. The algorithm is based on the representation of an elliptical trajectory of interference signals by a section of a circular cone, the circular trajectory being the base of the cone. The results of experiments on the use of the method with different noise levels are presented. The noise resistance of the proposed method is compared with the existing method of trajectory transformation based on ellipse stretching. Synthesized interferograms with different values of the phase shift error were used in the experiments.

I. Introduction

Currently, measurements in optical interferometry are used in various fields of science and technology. They allow accurate measurements of the surface of an object without direct contact, which is a necessary requirement for many applications [1]. The most widely used optical interferometry technique is step-by-step phase shift interferometry. Instead of studying a single interference pattern, a set of patterns is formed that differ in the phase of the reference beam. This makes it possible to achieve greater accuracy compared to techniques without using phase shifts [2], [3].