Ba. Bard et al., LASER-MODULATED PHASE-STEPPING DIGITAL SHEAROGRAPHY FOR QUANTITATIVE FULL-FIELD IMAGING OF ULTRASONIC-WAVES, The Journal of the Acoustical Society of America, 103(6), 1998, pp. 3327-3335
Measurement of surface displacements due to ultrasonic wave propagatio
n in elastic solids has traditionally been studied using single-point
measurement techniques such as ultrasonic transducers or interferomete
rs. Full-field methods, excluding scanning techniques, are uncommon; e
xamples include holographic interferometry and Schlieren imaging. In m
any cases, these techniques have been used to yield qualitative result
s due to inherent difficulties in processing the data. Laser-modulated
phase-stepping digital shearography is a full-field, common-path, int
erferometric method which can be used to quickly visualize ultrasonic
wave fields. A shearography system will be described that provides not
only whole-field images of ultrasonic waves, but quantitative displac
ement data within these fields. Images are shown of propagating plate
and bar waves, and mathematics relating the calculated optical phase t
o the ultrasonic wave parameters are presented. (C) 1998 Acoustical So
ciety of America.