Evaluation of Fiber-Reinforced Composites Using a Non-Contact Laser/Air-Transducer System
Ultrasonic evaluation of materials using a non-contact system is sometimes desirable, for example when the material is moving too quickly to allow conventional fluid couplants to be used, is contained in a hostile environment, or the material itself is absorbent or toxic. In such situations, a pulsed laser is ideal for generating a variety of ultrasonic transients , as longitudinal, shear, surface (Rayleigh) waves and plate (Lamb) waves are generated simultaneously. Several types of non-contact detector are also available, including various optical devices  such as interferometers and beam deflectors. The disadvantages of an entirely laser based system are cost, and the optical quality of the test material must be reasonably high.