We present a new algorithm for processing the particular fringe patterns known as Newton's rings. The first step of the algorithm consists of finding the common center of the circular fringes using a blockwise Fourier transform of the interferogram. The directions perpendicular to the fringes in several zones are thus detected and combined to give the circles' center. As a second step, a specially adapted type of pixel intensity spectrum is calculated, in which the 2-D pattern is reduced to a 1-D profile showing a periodic structure of fringes. By further processing, the parameters of the initial interferogram can be easily extracted. The statistical nature of the algorithm (achieved by taking into account all pixel intensities) leads to a high accuracy and a good immunity to noise.
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