Coherence of Light from Random Medium

Abstract

Theoretical descriptions are given of the statistics of the speckled diffraction patterns of diffused coherent light. The amplitude of light disturbance in a diffused source surface is expressed by a spatially continuous complex function. The spatial correlation of the phase angle of the amplitude is discussed and the space-averaged coherence area of phase is given. The coherence area of phase depends on the microscopic processes of the diffusion, but is at least of the square of the wavelength of light. The power spectral density of the diffraction pattern in terms of spatial frequency is shown to be proportional to the autocorrelation function of the intensity distribution of the diffused source and also to the coherence area of phase.