Determination of surface profiles of transparent plates by means of laser interferometry with wavelength tuning.

Highlights • The method of Surface profiles of both surfaces of a transparent plate by using a series of fringe patterns obtained at different phase shifting caused by wavelength changing is proposed. • Iterative algorithm and the least square method is applied together to improve the precision of results. • Analyzing the influence of error from phase shifting value. • The experiment set up is simple and save time for measurement. Abstract An interferogram obtained from a transparent plate contains information about the profiles of both surfaces of the plate. This information can be extracted by processing fringe patterns measured at different wavelengths. The conventional Fourier analysis applied to solve such problems for a set of a restricted number of the fringe patterns is quite sensitive to the error of detuning the wavelength shifting and suffers from fringe patterns interference noise. This study proposes a method for finding surface profiles of a transparent plate using a series of fringe patterns obtained at different phase shifts caused by wavelength changes. The data treatment is based on the analytical approach for describing spatial distributions of irradiance in interference patterns. The results show that the proposed method is feasible. The experimental setup used herein was a Fizeau interferometer with tunable wavelength laser. A glass plate approximately 1 cm thick was as the test sample. According to the obtained results, the root mean square (RMS) errors for determining both surface profiles did not exceed 2.3 nm. [ABSTRACT FROM AUTHOR]