MOVEMENT OF SPACE SPECKLE

The diffusing reflective surface illuminated by coherent light generates random speckle in space. The movement of the surface relative to the source causes corresponding movement of the speckle. When a moving speckle is tracked, it implies that the intensity of speckle is constant yet the phase of the speckle is allowed to vary. From the Fresnel-Kirchhoff Integration, three fundamental rules of speckle movement are derived, i.e. Equations (3), (4) and (5) in this paper. The first and second equations are similar to those of grating. The third equation is similar to the lens law. From these rules, a speckle movement formula, relating to the surface movement, is derived as equation (18), in which the coordinate system adopted is fixed in space. It is an equation in matrix form, which denotes six types of surface movements, i. e. three rotations and three translations. The experimental results are in good agreement with this formula. These fundamental rules can be used to analyse general space diffractive patterns.