The paper is devoted to study theoretically, the effects
of some parameters on the visibility of the speckle patterns. For this propose,
a theoretical model for a periodic rough surface was considered. Using this
theoretical model, the effects of grain height, its density, the band width and
spectral distribution of the line profile (Gaussian and Lorentzian) illuminating
a rough surface on the visibility of speckle pattern are investigated. An
experimental setup was constructed to study the effect of surface roughness and
coherence of the illuminating light beam on the contrast of speckle pattern.
The general behavior of the experimental results, which agree with published
data, is compatible with the new theoretical model.