Effect reduction of spurious fringes in interferometric measurement system

To accurately profile transparent element with parallel surface, this article presents a new simple and useful method by using a Fourier analysis technique with single three-beam interfere pattern. The test surface’s frequency spectrum from the frequency spectrum of three-beam interfere pattern is extracted by a spatial filter according to the amplitude in the spatial carrier frequency. The test wavefront is obtained by using inverse Fourier transform method. Simulated results demonstrate the validity of the method and the accuracy which is better than l/1 000. In the experiment, by testing the parallel surface element by FFT with single three-beam interfere pattern, Fourier analysis combined with wavelength tuning and traditional phase shifting interferometry with index matching lacquers