Hot topics in structural acoustics: Optical imaging of surface vibrations—Some new developments and applications

Abstract

Laser Doppler vibrometry is routinely used for a vast range of applications to measure surface vibrations in the nanometer range. Some new developments include the use of laser vibrometers with continuous tracking on moving targets, the detection of the vector displacement of a surface (either with multiple beam interferometry or with a photo-emf probe), and the direct measurement of torsional vibrations on rotating shafts. Electronic speckle pattern interferometry (ESPI) is a full-field optical technique that is also commonly used to image surface vibrations. An interesting development of ESPI is electronic shearography. Some applications of these optical techniques will be discussed. These include calibrations of transducers and MEMS devices, imaging of rotating parts, mapping of structural intensity, characterization of the dynamic response of viscoelastic materials, as well as some more exotic applications such as damage assessment of frescoes and painting, three-dimensional vibration imaging of the ossicular chain in cats, and dynamic characterization of human teeth.