In the work reported here, a fiber-optic heterodyne dual-probe interferometer has been developed for ultrasonic displacement measurements. This compact interferometer uses two GRIN-lens-terminated fiber probes for beam delivery and collection. No dynamic path stabilization is needed because of the heterodyne scheme. More compactness, lower cost and more flexibility are achieved. Application to rivet crack detection of fuselage panels is performed and results agree well with those obtained in a previous ...
It has been shown that the use of narrow-band signal generation and detection in a laser-based ultrasonic system can improve the sensitivity of the system. In this paper, a tone-burst-like narrow-band signal is generated in the thermoelastic regime by illuminating the surface of the specimen with an array of laser generated line-sources. The laser line-array is formed by a system of lenses and a diffraction grating which provide for flexible ...
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