METHOD AND APPARATUS FOR USING A TWO-WAVE MIXING ULTRASONIC DETECTION IN RAPID SCANNING APPLICATIONS

摘要

A wave characteristic adjusting device can compensate for distortion caused by the scanning motion of a probe beam of a two-wave mixing interferometer in a rapid scanning laser ultrasound testing device. In such a device, a laser pulse directed at periodic points along a path across the surface of an object initiates an ultrasonic signal. An interferometer measures this ultrasonic signal by scanning a pulsed probe beam along a similar path directed at the object in the vicinity of the initiating laser pulse. However, the probe beam pulse may exhibit a Doppler shift causing a loss in sensitivity of the two-wave mixing interferometer. The wave characteristic adjusting device compensates for this Doppler shift, thereby improving the sensitivity of the two-wave mixing interferometer.