Speckle noise suppression in measurement by phase-shifting digital holography

A new algorithm for fringe phase analysis is proposed for shape and deformation measurement of diffusely reflecting surfaces by digital holography. It derives the phase of the averaged conjugate product of complex amplitudes before and after wavelength change or object deformation, corresponding to the complex coherence factor, and is consistent with a theory on fringe formation in holographic interferometry. By experiments and computer simulations, it is demonstrated that the algorithm is much more immune to speckle noise in phase analysis and unwrapping than conventional methods.