Abstract
We present a technique to measure the mechanical complex amplitude, i.e. themechanical amplitude and phase of vibration, of an ultrasonic plane wavefield ofnanometric amplitude that propagates on a surface. Our aim is to detect perturbationsof the initially smooth wavefronts that indicate the presence of flaws in thematerial. We use bursts of surface acoustic waves (SAWs) and a double-pulsed TVholography system that records two correlograms with time separations down to1.5 µs.The phases of the correlograms are calculated separately using the spatial Fouriertransform method (SFTM) and operated on to obtain the phase change between exposures.In the resultant optical phase map, the field of instantaneous displacements of the surface(that comprises several periods of the SAW) acts as a modulated spatial carrier, nowrelated to the mechanical phase and amplitude, that are extracted by applying the SFTMagain.
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