Some challenges in white light phase shifting interferometry

摘要

White light phase shifting interferometric (WLPSI) techniques allow high precision shape measurement thanks to a combination of phase detection of the interference fringes and detection of the position of the fringe envelope. The WLPSI technique gives excellent results as long as ideal scanning and system aberration-free conditions exist. Ideal conditions rarely exist, however, and errors creep into measurements from a number of error sources. Scanner errors affect the measured phase of the object surface, and the finite size of the optical system and its aberrations cause a variation in the offset between the phase and coherence peak across the field of view of the system. This variation in turn causes unwanted 2π jumps in the phase portion of the measurement. This paper shows ways to overcome these challenges. We propose a real-time solution to correcting scanning position influence on measurement in WLPSI algorithm. In addition, we present adaptive phase shifting algorithms that avoid these jumps. Our overall technique is simple, very fast and yields highly precise and accurate results.