Determination of surface profiles of transparent plates by means of frequency estimation with wavelength tuning interferometry

The information about the profiles of both surfaces of the transparent plate are contained in an interferogram. This information can be extracted by processing fringe patterns measured at different wavelengths. The conventional Fourier analysis applied to solve such problems with a set of a restricted number of the fringe patterns, otherwise this analysis is quite sensitive to the error of frequency drift and suffers from fringe patterns interference noise. This study proposes a method of frequency estimation to obtain profiles of surfaces of transparent plate. A series of fringe patterns obtained at different phase shift caused by wavelength changing are regarded as a set of overlapped sinusoidal signal. Using Total Least Squares method to find the frequency of different signal to attain the separation of interferogram. The simulation shows that the proposed method has the immunity from noise interference.