POLYNOMIAL FITTING OF INTERFEROGRAMS WITH GAUSSIAN ERRORS ON FRINGE COORDINATES - III - NONLINEAR SOLUTION

Assuming that the measured coordinates of the fringes of an interferog ram have random errors and that they are considered Gaussian, the syst em of normal equations that is obtained on application of the least-sq uares method is converted into a nonlinear set of equations. We presen t an algorithm to estimate the coefficients of the nonlinear system by applying the Newton-Raphson method and starting the iteration from th e standard classic solution. This algorithm is applied to a pattern of straight and equally spaced fringes, obtaining not only the right coe fficients but also the adequate election of the terms to be included i n the model, to show the contrast with the results of the classic meth od. (C) 1998 Optical Society of America.