Real time identification of several targets by iterative time reversal

Abstract

Finding punctual targets inside an aberrating medium is a problem of interest in nondestructive testing and medical research. Previous works have shown that the iteration of the time reversal method allows us to identify the strongest reflector of the medium in real time but the identification of several targets is not possible with this technique. Using the idea that each strong scatterer is associated to an eigenvalue of the time reversal operator, a method has been developed (the DORT method) to identify punctual diffusers in a medium. This technique requires the experimental acquisition of the whole time reversal operator and its numerical decomposition implies many calculations. We propose here a way to identify in real time all the punctual targets by modifying the time reversal iterative method. In a first step, we identify the strongest reflector by time reversal processing. In a second step, we subtract its contribution in order to find the second reflector contribution and so on. This method allows us to build an ‘‘eigen pulse’’ able to focus a pulsed signal on each target. We demonstrate experimentally its real time feasbility by identifying several targets inside a strongly aberrating medium.