Application of white-light phase-shifting in white-light scanning interferometry

A method that combines scanning white-light interferometry with phase-shifting interferometry is proposed. The best-focus scanning position of correlograms is located by calculating the maximum modulation contrast, and the twice averaging four-frame algorithm is utilized to determine the phase difference between the best-focus position and the zero optical path difference point. The surface height is obtained according to the best-focus frame position and the unwrapped phase, which is achieved by a process of removing the phase ambiguity. Both simulated and experimental results demonstrate that the advanced method can achieve the advantages of high precision, large dynamic range, and be insensitive to the phase shifting deviation.