Real time focusing using an ultrasonic ‘‘one channel time‐reversal mirror’’ coupled to a solid structure Free

Focusing and beam steering is achieved using a time‐reversal process and a unique transducer coupled to a solid structure. This low cost technique allows one to focus acoustic energy anywhere on a 3‐D domain with a spatiotemporal resolution comparable to multiple transducer’s array. We first record the signal emitted by the transducer and detected by a hydrophone needle at a reference point. The signal received is then time‐reversed and remitted using the same transducer. At the reference point one can observes a spatiotemporal recompression. Moreover, it is shown how the experimental Green’s functions at the surface of the cavity can be used to control the emitting ultrasonic field. A careful study of this phenomena leads us to better understand the resolution and the signal to noise ratio of the focusing system. Indeed the side‐lobe level as well as the focal width are no more dependent on the transducer aperture but on the dimensions of the solid structure and the multiple paths covered by the acoustic waves in the solid. Those results are supported both by experiments and numerical modeling.