 Random phase screen

A random phase screen models a thin random medium by multiplying a wave field by $e^{i\varphi (x)}$, where $\varphi$ is a real random field on the transverse plane. At the screen itself the modulus is unchanged, but later wave propagation converts phase variation into interference and amplitude variation.

If $\varphi$ is a zero-mean Gaussian random field, its phase factor has correlationThis follows from the characteristic function. The approximation neglects the medium's longitudinal thickness; its covariance and propagation model must be specified before predicting scattering or intensity statistics.