<title>Compound speckles and their statistical and dynamical properties</title>

Two issues will be treated in this presentation, both focusing on gaining a deeper understanding of dynamic speckles, aiming at the use for probing dynamical properties of scattering structures. The first issue to be addressed is the dynamics of speckles arising from illuminating a solid surface giving rise to fully developed speckle with two mutually separated beams. It will be shown that usually the speckle pattern will consist of larger speckles with an inherent fine structure, each of which will usually be moving with different velocity. Next, the dynamics of the speckle pattern arising from scattering off a diffuser as seen through a second static diffuser is analyzed. Here, it is shown that the second and static diffuser will act as a pivot point about which the speckles will move. This facilitates a scaling of the speckle displacement facilitating a very minute measurement of the displacement of the first diffuser.