Back in 1986, the LOA started research on Time Reversal (TR). TR is the essential foundation of the ReverSys® SO technology. TR functions in 4 steps, as described below:
How Time Reversal Works?
C. Draeger and M. Fink, One-Channel Time Reversal of Elastic Waves in a Chaotic 2D-Silicon Cavity, Phys. Rev. Lett., vol. 79, pp. 407-410, 1997.
Why Time Reversal Results are Important?
TR experiences within a cavity demonstrate uniqueness of impulse responses between two given points
Received signal in A after TR signal emitted in B is equal to:
• SA(t) = SB(-t) ∗ hBA(t) = e<A(-t) ∗ hAB(-t) ∗ hBA(t)• hBA, hAB are impulse responses between A and B
• eA is the initial signal excitation function in A
Received signal - after TR - is maximized in power at point A (focusing process). Elsewhere, signals are of weaker amplitudes.From Time Reversal To ReverSys®
ReverSys® replaces “active TR” with “software TR” using reciprocity:SA(t) = eA(-t) ∗ hAB(-t) ∗ hBA(t) = eA(-t) ∗ hAB(-t) ∗hAB(t)
ReverSys® builts on cross correlation processing using a library of impulse responses and a device using at least one acoustic sensor. ReverSys® steps are described in FIG. 1 and FIG. 2 below:
R. K. Ing, N. Quieffin, S. Catheline and M. Fink, In solid localization of finger impacts using acoustic time-reversal process, Appl. Phys. Lett. 87, 204104 (2005).
Virtual Demonstrator
Contributions & Publications
Time-Reversed Lamb Waves - Ros K. Ing and Mathias Fink - 1998 IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 45:1032-1043
Ultrasound puts materials to the test - Mathias Fink - The e-Journal of Non destructive Testing, NDTnet 1998 April, Vol.3 No.4 - www.ndt.net
