  Scattering of optical waves by a multi-scale rough mirror surface as a phase
screen is considered. To solve the problem we used the diffusion phase
approximation and numerical model of a phase jump. The scattering intensity was
averaged over the ensemble of realizations. The results of numerical
calculations of the angular dependence of the intensity are presented for a
backscattering demonstrating the effect of the roughness distribution over the
scales and its secondary impact on the indicatrix of scattering for
multiplicative surface modulation.
