Diffuser speckle model: application to multiple moving diffusers.

A simple model for the scattering of coherent light through diffusers has been applied to a moving diffuser despeckler in order to estimate the scattering angles, speckle decorrelation length, and interaction between multiple diffusers. A Gaussian model for the diffuser thickness variations has been used to derive a relation between the scattering cone of a diffuser and its decorrelation properties. This model is equivalent to a randomized array of lenslets. The lenslet's thickness and diameter correspond to the characteristic heights and widths of the diffuser roughness. This model predicts that a decrease in the decorrelation distance for two closely spaced counterrotating diffusers is accompanied by an increase in their scattering cone. Simulation and experimental measurements have been used to verify the predictions of this model. Significant speckle decorrelation has been demonstrated for a nanosecondpulsed laser source by using moderate diffuser rotation speeds.