White-Light Interferometer-Micro-profile Measurement Based on Higher Steps Phase-Shifting Algorithm

Abstract

White-light scanning interferometer (WLSI) is a powerful method to measure shape of an object in larger range with higher resolution. It has been widely used in the micro-profile measurement of optical elements and micro-electro-mechanical components. With board light source bandwidth, WLSI is able to overcome 2π phase ambiguity problem, which is often occurred in traditional laser inter-ferometer. Typically, phase-shifting method is used to retrieve the corresponding fringe phases and extract the WLSI signal peak position. For the phase-shifting method, vertical scanning is required but thanks to the improvement of hardware performance, the scanning time is shorter than the traditional zero-order interference fringe identification method. Traditionally, locally linearized five- or seven-step phase-shifting algorithms could be used to retrieve the WLSI signal coherence function and determine the position of zero optical path difference (ZOPD).