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Application of a Sagnac interferometer for the characterization of scattered ultrasonic fields

Knowledge of the spatial and temporal parameters of ultrasonic beams, as well as details of interaction of such beams with small defects is necessary for effective application of ultrasonic techniques to nondestructive evaluation (NDE). The work presented here employs a fiber-optic Sagnac interferometer to characterize acoustical fields generated by conventional piezoelectric transducers (PZT) and a laser ultrasonic source, and the scattering of such ultrasonic fields by flaws. The high spatial resolution of this interferometer and its ability to provide absolute ultrasonic displacements make this device very suitable for: (i) profiling and calibration of ultrasonic beams generated by PZT transducers or laser sources, and (ii) precision measurement of ultrasonic fields scattered by flaws.