Surface Assessment of Transparent Glass Plate with Wavelength-Modulated Interferometry and Harmonic Phase-Iterative Method

Abstract

Multiple reflections and nonlinearity of phase modulating need to be compensated to accurately profile the surface of the glass plate using wavelength-modulated interferometry. In this study, to assess the glass plate surface using wavelength-modulated interferometry, a new phase-iterative method insensitive to the harmonic signals and nonlinear errors was developed. We developed the harmonic phase-iterative method by combining the phase-iterative method with irradiance signal considering the harmonic components. Moreover, for suppression of the harmonic-related errors in the iterative calculation, the noble pixel-selection technique and convergence formula were combined with the phase-iterative method. For estimation of the developed iterative method, we conducted the numerical simulation and assessed the glass plate surface with the Fizeau interferometer. The simulation and assessment results demonstrated that the proposed method could perform phase extraction with improved iterative calculation and suppression of the effects of the harmonics and nonlinearity.