Digital simulation of speckle patterns

Digital simulations of speckle patterns are reported. Wavefront propagation and scattering by a diffusely reflecting surface is represented by a generalized Huygens principle for scalar light waves. The surface roughness is expressed by a set of random numbers that are uniformly distributed within variable range. No approximations for the propagation distances are employed between a point source and a surface point as well as between the surface point and an observation one. The 3-dimensionall intensity distributions in the diffraction field of the object that is illuminated by a spherical wave are calculated by adding many wavelets in complex amplitudes of the scattered waves at the observation point. The intensity distributions on the planes parallel and perpendicular to the object are calculated. For analyzing the speckle patterns illuminated by a multimode laser and multiple wavelength lasers incoherent superposition of the speckle patterns arising from superposition from various wavelengths or various source positions are calculated to investigate the effect of speckle suppression by addition of many speckle patterns.