Journal ArticleDOI
Time reversal of ultrasonic fields. I. Basic principles
TLDR
Pulsed wave time-reversal focusing is shown using reciprocity valid in inhomogeneous medium to be optimal in the sense that it realizes the spatial-temporal matched filter to the inhomogeneity propagation transfer function between the array and the target.Abstract:
Time reversal of ultrasonic fields represents a way to focus through an inhomogeneous medium. This may be accomplished by a time-reversal mirror (TRM) made from an array of transmit-receive transducers that respond linearly and allow the incident acoustic pressure to be sampled. The pressure field is then time-reversed and re-emitted. This process can be used to focus through inhomogeneous media on a reflective target that behaves as an acoustic source after being insonified. The time-reversal approach is introduced in a discussion of the classical techniques used for focusing pulsed waves through inhomogeneous media (adaptive time-delay techniques). Pulsed wave time-reversal focusing is shown using reciprocity valid in inhomogeneous medium to be optimal in the sense that it realizes the spatial-temporal matched filter to the inhomogeneous propagation transfer function between the array and the target. The research on time-reversed wave fields has also led to the development of new concepts that are described: time-reversal cavity that extends the concept of the TRM, and iterative time-reversal processing for automatic sorting of targets according to their reflectivity and resonating of extended targets. >read more
Citations
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Journal ArticleDOI
Controlling waves in space and time for imaging and focusing in complex media
TL;DR: In this article, the authors used strongly scattering materials to focus, shape and compress waves by controlling the many degrees of freedom in the incident waves in complex media such as white paint and biological tissue.
Journal ArticleDOI
Seismic tomography, adjoint methods, time reversal and banana-doughnut kernels
Jeroen Tromp,Carl Tape,Qinya Liu +2 more
TL;DR: In this article, the authors show that the Frechet derivatives of the objective function can be obtained for tomographic and (finite) source inversions based on just two numerical simulations for each earthquake: one calculation for the current model and a second, "adjoint" calculation that uses time-reversed signals at the receivers as simultaneous, fictitious sources.
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Pitch-catch Active Sensing Methods in Structural Health Monitoring for Aircraft Structures
Jeong-Beom Ihn,Fu-Kuo Chang +1 more
TL;DR: In this article, a pitch-catch method using a pair of piezoelectric actuator and sensor is introduced to generate a damage indeX which can be used to characterize damage at a known location.
Journal ArticleDOI
Time-reversed acoustics
Mathias Fink,Didier Cassereau,Arnaud Derode,Claire Prada,Philippe Roux,Mickael Tanter,Jean-Louis Thomas,F. Wu +7 more
TL;DR: In this paper, the authors show that time reversal invariance can be exploited in acoustics to create a variety of useful instruments as well as elegant experiments in pure physics, and they describe time reversal cavities and mirrors together with a comparison between time reversal and phase conjugation.
Journal ArticleDOI
A synthetic time-reversal imaging method for structural health monitoring
TL;DR: In this article, the applicability of the time-reversal concept to guided waves in plate-like structures, where the stress waves are dispersive and of multi-modes, was investigated.
References
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Journal ArticleDOI
Transient Radiation from Pistons in an Infinite Planar Baffle
TL;DR: In this article, an approach to compute the near and farfield transient radiation resulting from a specified velocity motion of a piston or array of pistons in a rigid infinite baffle is presented.
Journal ArticleDOI
Phase-aberration correction using signals from point reflectors and diffuse scatterers: basic principles
S.W. Flax,Matthew O'Donnell +1 more
TL;DR: The method presented here has no need for a beacon or an ideal point reflector to act as a source for estimating phase errors, and uses signals from random collections of scatterers to determine phase aberrations accurately.
Journal ArticleDOI
Time-reversal of ultrasonic fields. III. Theory of the closed time-reversal cavity
D. Cassereau,Mathias Fink +1 more
TL;DR: The time-reversal focusing process using a closed cavity in a weakly inhomogeneous medium is compared with more classical techniques to compensate wavefront distortions, thus illustrating the focusing improvement due to the time- reversal method.
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