Abstract
The D.O.R.T. method (French acronym for decomposition of the time-reversal operator) is a scattering analysis technique that uses an array of transducers in pulse-echo mode. The method was applied to detection and selective focusing on pointlike scatterers through inhomogeneous media [J. Acoust. Soc. Am. 99, 2067–2076 (1996)]. Here, laboratory measurements in a water waveguide are presented. Taking advantage of the multiple reflections at the interfaces of the guide, high resolution is achieved with the D.O.R.T. method without using any a priori knowledge of the guide. The separation of two scatterers and the selective focusing are obtained with a transverse resolution at least nine times better than the predicted free space limit. The detection of a scatterer placed at less than half a wavelength from the water/air interface is also achieved with good sensitivity. Finally, the impulse response functions of each scatterer to the array is computed as a combination of the eigenvectors of the time-reversal operator obtained at each frequency. Using these impulse Green functions, selective focusing with high temporal and spatial compression is performed.
Published Version
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