Laser Interferometric Characterization of Acoustic Emission Transducers
The characterization of the exact response of commercially available, piezoelectric and thin film, acoustic emission transducers is of fundamental importance for the nondestructive evaluation of in-service engineering components. An experimental procedure is developed that uses a laser interferometer to make localized, absolute measurements, with very high fidelity without acoustically loading the specimen. The heterodyne interferometer is operated by splitting a single frequency laser light into two components using an acousto-optic modulator. An important feature of the system is that a linear FM discriminator is used to demodulate the carrier; as a result, the interferometer behaves as a doppler shift detector. An ultrasonic transducer is used to create a repeatable source function on an elastic half-space. The interferometer's response is verified with analytical results, and used to characterize the response of commercially available transducers.