Centering and profiling algorithm for processing Newton’s rings fringe patterns

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 perpen- dicular 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 pro- cessing, the parameters of the initial interferogram can be easily ex- tracted. The statistical nature of the algorithm (achieved by taking into account all pixel intensities) leads to a high accuracy and a good immu- nity to noise.