SPECKLE DYNAMICS FROM INPLANE ROTATING DIFFUSE OBJECTS IN COMPLEX ABCD OPTICAL-SYSTEMS

The characteristics of a fully developed speckle pattern that results from in-plane rotation of a diffuse object observed in an arbitrary ob servation plane, as described by the spatiotemporal cross-correlation function of the optical intensity in complex ABCD optical systems, are derived and discussed. Here we consider off-axis illumination, which is in contrast to previous work in which the illuminating beam was ass umed to be parallel to the axis of rotation. The spatiotemporal charac teristics of the observed pattern are interpreted in terms of speckle boiling, rotation, and translation. For off-axis illumination it is sh own theoretically and experimentally that, for Fourier transform optic al systems, in-plane rotation causes the speckles to translate in a di rection perpendicular to the direction of surface motion, whereas for an imaging system, the translation is parallel to the direction of sur face motion. On this basis, we discuss a novel method, which is indepe ndent of both the optical wavelength and the position of the laser spo t on the object, for determining either the angular velocity or the co rresponding in-plane displacement of the target object. (C) 1998 Optic al Society of America.