White Light Scanning Interferometry Based on Generalized Cross-Correlation Time Delay Estimation

Abstract

Based on generalized cross-correlation time delay estimation (GCTDE), a new white light scanning interferometry (WLSI) method is proposed, in which the profile information usually achieved with the zero optical path difference (ZOPD) position is replaced with the relative displacement of interference signal between different pixels. Because all spectral information of interference signal (envelope and phase) and filter is utilized, the proposed GCTDE-based WLSI method reveals the advantages of higher accuracy and better noise suppression capability. Especially, in the case where the shape of interference signal envelope is irregular, the proposed method can achieve profile measurement with high accuracy while the conventional ZOPD position locating method cannot work. Moreover, by introducing laser interferometry system to calibrate the vertical displacement of a piezoelectric ceramic transducer scanning system, the measuring accuracy of the proposed GCTDE-based WLSI is further improved. Both the simulation and the experimental results demonstrate the significant accuracy advantage of the proposed GCTDE-based WLSI.