| 摘要 |
For sensing the presence of an ultrasonic wave propagated within a workpiece at the surface of such workpiece, the workpiece surface is illuminated with a laser beam and opto-electric means, such as an interferometer, are used to sense the minute workpiece surface deformation caused by the ultrasonic wave front. In order to sense the ultrasonic waves which are incident upon the workpiece surface at an oblique angle, the workpiece surface is illuminated in a pattern of equidistantly spaced strips. The spacing of the strips is determined by the angle of the ultrasonic wave and the wavelength of the ultrasonic wave. The resulting electrical signals are processed simultaneously or in sequence.
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