Abstract:

The use of time reversal to obtain retrodirective focusing of a diverging acoustic wave field has precedents in electromagnetic and optical literature. This history will be discussed and possible acoustic applications will be illustrated by simulated examples. Phase conjugation in underwater acoustics is distinguished by the need to obtain true, rather than approximate, time reversal and by the effects of the ocean waveguide. The remarkable invariance of time-reversed focusing with respect to scattering by the propagation medium and deformation of the array will be discussed along with the sensitivity to time variation of these same factors. [Work supported by ONR.]