Ultrasonic nondestructive testing with time reversal mirrors

In nondestructive testing, it is necessary to detect metallurgical defects, and the incident beam can be strongly distorted with the change of acoustical impedance created at the liquid-solid interfaces. The use of time reversal mirrors (TRMs) represents an original solution to this problem. They realize in real time a focusing process matched to the defect shape, to the propagation medium, and to the geometries of the mirror and of the medium. The TRM technique is a self-adaptive technique which compensates for any geometrical distortions of the mirror structure, as well as for distortions due to the propagation through interfaces between liquid and solid