Abstract: A non-destructive, non-contact testing apparatus and method which generally includes an ultrasonic signal generator for inducing one or more ultrasonic signals in a material and an optical interferometer that includes a laser for illuminating a section of the material and for detecting beat frequencies resulting from reflected light from the material. Deformations in the material as a result of the ultrasonic signal cause the beat frequency to be shifted as a result of the Doppler effect. Such differences in the beat frequency are detected by the system and used as an indication of a characteristic of the material.

Abstract: A method of detecting and measuring separately the components of vector dynamics on the surface of a vibrating object comprises directing three beams of coherent light onto a common spot on the surface. Each of these beams has a known optical frequency. Two are arranged symmetrically about a normal to the surface at the point of incidence and the third is arranged asymmetrically about the normal with respect to both the first and second beams. Superposition of each beam with the others on the surface produces scattered light embodying characteristic beat or carrier signals equal to the difference in frequencies between the beams. Vector dynamics including velocity and displacement of the vibrating surface induces Doppler shifts in the beams, which, in turn results in a modulation of the carrier frequencies resulting from the superposition of the beams.