Three-component recording of ultrasonic transient vibration by optical heterodyne interferometry

The generation and detection of elastic waves by photoelastic methods, called ''laser ultrasonics,'' is now a rather commonly used method in research. The aim of this paper is to adapt an existing method, based on laser speckle interferometry, in order to record the three components of transient vibration induced by an ultrasonic wave at a point on the surface of a solid model. A detailed description of the method is given. The reliability of the method is experimentally demonstrated. As an illustration, maps of the local three-dimensional transient vibration and of the particle trajectories of different points at the surface of a solid are reported. (C) 1996 Acoustical Society of America.