Quantitative imaging of transient acoustic fields by optical heterodyne interferometry

Influence of acousto-optic interactions on the determination of the diffracted field by an array obtained from displacement measurements

“…2 shows the variation of H ðk x Þ in water for a fixed x. First, we see that near from k x ¼ 0, H is close to 1, as already observed by Royer and Casula [7]. For normal plane waves it looks as though the piezo-optic effect takes the optical index of water, n 0 ¼ 1:329, back to 1.03.…”

“…The theoretical analysis developed in this first section follows those developed by Bacon et al [6] and Royer and Casula [7] in the case of a single element ultrasonic transducer. Calculations are conducted for a 2D configuration well suited for a 1D linear array.…”

“…The second one is a phased array with a pitch of 280 lm and working frequency of 2.75 MHz. The pulse generator is a standard commercially available apparatus, which delivers voltage pulses with bandwidth higher than 20 MHz and amplitude of 100 V. Displacements measurements have been performed with the SH140 heterodyne probe, marketed by Thales industry (France), based on a Mach-Zender type interferometer [7]. Measurements of the displacement field have been made at the front face of the two devices when one element is excited.…”

Acousto-optic effect compensation for optical determination of the normal velocity distribution associated with acoustic transducer radiation

“…These include non-flatness of the pellicle, 34 frequency-dependent acoustic transmission, 8,31 excitation of Lamb waves, 31 and, generally, motion-following. Royer and Casula 18 concluded that suitably thin membranes made of Mylar, or a polyethylene terephthalate (PET) polyester film, could transmit spatial and temporal details of acoustic waveforms with fidelity. For a 3-lm-thick aluminum-or goldcoated membrane, Royer and Casula found that the filtering effect and spatial broadening were negligible for frequencies up to 30 MHz and half-power beam diameters greater than 0.2 mm.…”

Desenvolvimento de técnicas de caracterização de transdutores piezelétricos.

“…Tambémé mon- tado um sistema interferométrico em quadratura, descrito na seção 5.5.3. No entanto, o que funciona com maior eficiência são os interferômetros heteródinos [1,6].…”