Speckle from rough rotating objects.

Dynamic speckle from rough rotating objects with nonplanar underlying shape is considered in theory and experiment. The theoretical treatment is based on modeling the optical field as a sum of contributions from discrete scatterers on the surface of the object. It follows that computation of the speckle correlation function requires knowledge of the object's average scattering strength as a function of position and the underlying shape of the object. Calculation of the speckle correlation function reduces to tracing a series of rays that coarsely sample the object and for each ray computing the relative phase shift resulting from object rotation. This method is quite simple compared to previous analytic techniques. Theory and experiment are compared for cylinders with a variety of surface coatings. Dynamic speckle from multiple rotating objects and objects with complicated underlying shape is also considered.