1. A method of processing an optical image from an optical system, the method comprising: (a) providing a measured magnitude of the Fourier transform of a two-dimensional complex transmission function of the optical image; (b) providing an estimated phase term of the Fourier transform of the two-dimensional complex transmission function of the optical image; (c) multiplying the measured magnitude and the estimated phase term to generate an estimated Fourier transform of the two-dimensional complex transmission function of the optical image; (d) calculating an inverse Fourier transform of the estimated Fourier transform, wherein the inverse Fourier transform is a spatial function; and (e) calculating an estimated two-dimensional complex transmission function of the optical image by applying at least one constraint to the inverse Fourier transform.