Radial image processing for phase extraction in rough-surface interferometry

Abstract

This paper presents a newly developed phase extraction algorithm to determine surface displacements and accurately estimate surface roughness parameters. The algorithm utilises radial image processing to extract the phase from the central region of an interferogram with circular fringes obtained from a self-built Michelson-type interferometer with a single rough surface. A key advantage of the method lies in its ability to leverage the entire image for phase extraction, even when the fringes are fragmented, or the central region is unclear. The linear relationship between the extracted phase and the object’s displacement eliminates ambiguities associated with intensity measurements near maximum or minimum values while reliably indicating the direction of motion. Furthermore, the algorithm effectively addresses speckle interference challenges, common in industrial applications where lasers are the primary light source. The proposed setup, combined with the advanced image processing algorithm, achieves displacement measurements with sub-micrometre precision, offering a robust tool for analysing rough surfaces in industrial environments.