Absolute distance measurement using polarization-based spectral-domain interferometer with dual reference path

Abstract

Absolute distance measurement technique can be a useful tool for solving the challenging issues such as large optics fabrication and alignment. An optical system free from non-measurable range of spectral-domain interferometer was proposed by using dual reference paths with orthogonal polarizations. The problem of non-measurable range caused by sampling limit of an interference spectrum having very small optical path difference has already been overcome by making the dual reference path with a pre-determined offset in the previous study. However, the interference signal between the two reference paths could cause the measurement error when it overlaps with the distance measurement signal. In this study, to remove the interference signal between the two reference paths, polarization-based spectral-domain interferometer was proposed and realized. For feasibility test of the proposed method, the absolute distances to the target mirror were measured within the scan range of 200 μm, and the measurement results were compared with those obtained using the commercial laser interferometer simultaneously. As a result, it was verified that the distance measurement error was significantly reduced through the proposed method.