Diffraction by a deeply modulated random-phase screen

A study is made of the intensity fluctuations of waves diffracted by a random screen which imposes large phase changes on an incident plane wave. Numerical results are given for the magnitude of the fluctuations as a function of the distance from the screen; the focusing effect previously found by Mercier is further investigated, and its distance from the screen is related to the magnitude of the phase modulation. The way in which the correlation of the signal intensity varies with the distance from the screen is also studied. The scale of the intensity fluctuations is always less than the scale of the phase fluctuations in the screen, but it may increase or decrease with increasing distance according to the depth of the phase modulation.