Recovery of spatial-coherence modulus and phase from complex field correlations: fourth-order correlation interferometry

A method is presented for recovering the modulus and phase of the spatial coherence of a circular complex Gaussian random field, e.g., laser speckle, from fourth-order field correlations. A one-dimensional experimental verification of the method is described, and its usefulness for coherence function imaging is demonstrated. The variance of the measured quantity is shown to agree with a calculation for the high-light-level regime.