A method of optical data processing, comprising: providing a first data set to be optically transformed using a transform; combining a reference data set with said first data set to generate coherent light, encoding a combined data set; optically and coherently transforming said light that encodes the combined data set, into coherent light that encodes a transformed combined data set; obtaining a transformed reference data set by determining the effect said optical transform has on light encoding said reference data set; and extracting a second data set that represents a transform of said first data set, from an intensity portion of light encoding said transformed combined data set, using said transformed reference data set to extract a phase of at least one element of said second data set.