OPTOACOUSTIC MEASUREMENT OF MATERIAL PROPERTIES BY A TWO-POINT LASER-INDUCED GENERATION OF ULTRASONIC WAVES

摘要

Ultrasonic waves are generated at a surface of an object (12) using a pulsed laser beam (18). The beam (18) is incident on the surface at two separate locations (14, 15) at a fixed separation (S). This may be achieved using a beam splitter (22) and a reflector (23). Large lenses are not required, so that the locations (14, 15) can be close together, for example 10 mm apart. Such an apparatus for generating ultrasonic waves may be combined with an apparatus for detecting ultrasonic waves, preferably a laser detector (30, 37). Ultrasonic wave velocities can therefore be measured in a non-contact manner.