Two-dimensional Phase Locked Loop Demodulation of Interferograms

Abstract A new technique for continuous phase determination of an interferogram based on a digital phase locked loop is presented. The main advantage of this method, with respect to well established techniques such as Fourier or phase stepping demodulation, is that the traditional approach to phase unwrapping processes by removal of discontinuities is not required. The phase is determined continuously as the phase locked loop scans the two-dimensional interferogram. Because of the sequential nature of the algorithm proposed, this can be implemented using a special purpose video processor for phase determination at video rates. The above mentioned properties makes the presented technique a fast algorithm for phase determination of carrier frequency interferograms modulated by a two-dimensional smooth phase function.