Measurement of rotation and distortion of opaque surfaces by laser light scattering

Presents an experimental method for measuring velocity gradients caused by distortions and rotations of arbitrary light scattering surfaces. The method is sensitive, gauge-free and has a fairly high resolution. It is based on the scattering of a coherent, plane, laser-generated light wave at the surface and evaluation of the speckle pattern of the scattered light by use of a CCD camera. For a known scattering geometry, it is possible to obtain the velocity gradient of the surface motion from the time lag between two recordings and the translation distance of the speckle pattern. Presents the results of measurements on a rotating disc; strain measurements performed on a flat rubber tape; and bending measurements on a flat plastic rod. (Original abstract - amended)