Wavelength-tuning interferometry with suppression of dispersive error

Abstract In measurements of the variations in the thickness and surface profile of optical flats using wavelength-tuning fringe analysis, an interference signal can be detected based on the modulation frequency of the signal. However, the modulation frequency can deviate from the predetermined value through the refractive-index dispersion of the optical flat. In this study, two types of noble 25-frame phase-detection algorithms that can compensate for the effect of refractive-index dispersion were developed using Fourier analysis. The behaviors of the 25-frame algorithms were visualized on both the frequency domain and complex plane. The dispersion-resistance ability and signal-to-noise ration of the 25-frame algorithm were estimated by calculating the PV errors and using the frequency-transfer-function paradigm, respectively. Finally, the variations in the thickness and surface profile of the optical flat were measured using a wavelength-tuning Fizeau interferometer and the proposed 25-frame algorithms. The standard deviations of the thickness and surface measurements were 1.654 nm and 8.368 nm, respectively, which were much smaller than those of the conventional phase-detection algorithms.