Focalisation en émission-réception en milieu inhomogène : le concept de filtre adapté

Abstract
Time reversal of ultrasonic fields is a mean to focus through inhomogeneous media on a reflective target. In previous papers, we have shown that in contrast to time delay focusing techniques, that can only correct distortions produced by a thin aberrator located close to the transducer array, TRM focusing is able to compensate for distortion independently of the aberrator position. We have also shown that the TRM focusing is optimal as it realizes the spatial-temporal matched filter to the propagation transfer function through inhomogeneous media. It is a self-adaptive technique that compensates for any geometrical distortions of the array structure as well as for distortions due to the propagation through inhomogeneous media. However, TRM focusing has only been described in the transmit mode. The extension of this matched filter focusing technique in the receive mode is presented in this paper. This new focusing technique can be achieved using adaptive convolution techniques instead of delay line techniques. Theoretical and experimental results will be presented.