Disk-growing algorithm for phase-map unwrapping: application to speckle interferograms

Interferometric techniques combined with phase shifting allow computation of the phase that is linked to the displacement of the object under study. The phases before and after displacement are computed from three or more interferograms (called specklegrams when speckle is used as the information carrier). Subtraction of these two phase patterns leads to a raw phase map. Phase unwrapping restores the 2π discontinuities and gives a continuous phase map. The disk-growing algorithm presented allows the inner and the outer propagation of the unwrapping from a growing disk and so avoids the main problem of anisotropic error propagation for noisy phase maps. It works successfully in speckle interferometry.