Interferogram analysis by a modified sinusoid fitting technique

Abstract

Sinusoid fitting (SF) is a numerically efficient technique for evaluating samples of an unknown phase from samples of an intensity into which the phase has been spatially heterodyned. However, SF assumes the phase is invariant over a fringe of the intensity and that three samples per fringe are taken. In practice both assumptions may be violated. The formula for the resultant error in the SF phase estimates is derived. A modification of SF (MSF) is described which permits the phase to vary linearly over a fringe and is insensitive to the number of samples per fringe used. Finally phase reconstructions by both methods are compared for both the noiseless and noisy cases.