Method and apparatus for exploring by wave propagation
AssigneeCentre National de la Recherche Scientifique (CNRS)
InventorsMathias Fink, Gabriel Montaldo, Mickael Tanter
Life of this patent
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Abstract
A method of exploring by wave propagation, in which method an incident wave is emitted a plurality of times towards the same target zone (r0) in a diffusing medium, and then the backscattered signals generated by the waves are averaged.
Claims16
A method of exploring by wave propagation, which method comprises:
- (a) a measurement step including a plurality of emissions (a1) during which a set of transducers i are caused to emit incident waves into a diffusing medium, and a plurality of receptions (a2) during which the set of transducers are caused to pick up signals representative of the waves reverberated by the medium from each incident wave;
- and
- (b) a processing step during which the picked-up signals are processed;
- wherein, during the processing step, consideration is given to a plurality of sets k of reverberated signals Bk(i, t), each of which comes substantially from a point rk belonging to the same isoplanatic zone ZI(r0) that is common to said sets k of signals and that itself relatives to a point r0 of the medium, the points rk being either different from one another regardless of the medium, or coinciding with the point r0 when the medium includes diffusers having random motion;
- wherein the reverberated signals Bk(i, t) of the sets k are re-positioned in time if the points rk are different from one another in order to obtain corrected signals B0k(i, t)=Bk(i, t−Gi(rk)), where the values Gi(rk) are delays such that, by causing the transducers i to emit signals ek(i, t)=e0(i, t+Gi(rk)), the incident wave focuses substantially at the point rk, the signals e0(i, t) being reference signals such that, by causing the transducers i to emit said reference signals e0(i, t), the incident wave focuses substantially at the point r0;
- and wherein the signals B0k(i, t)=Bk(i, t−Gi(rk)) are put into phase and averaged so as to obtain average signals
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- where the values ck are delays making it possible to put the signals B0k into phase, and the values Ak are weighting coefficients.
Apparatus for of exploring by wave propagation, said apparatus comprising a set of transducers i suitable for emitting an incident wave into a diffusing medium, and for picking up signals representative of a reflected wave reverberated by the medium from the incident wave, the apparatus further comprising control means suitable for causing said set of transducers to take at least one measurement including a plurality of emissions (a1) during which the set of transducers i are caused to emit incident waves into the medium, and a plurality of receptions (a2) during which the signals representative of the reflected waves reverberated by the medium from each incident wave are picked up;
- and
- the device further comprising processing means adapted to performing a processing step (b) during which consideration is given to a plurality of sets k of reverberated signals Bk(i, t), each of which comes substantially from a point rk belonging to the same isoplanatic zone ZI(r0) that is common to said sets k of signals and that itself relates to a point r0 of the medium, the points rk being either different from one another regardless of the medium, or coinciding with the point r0 when the medium includes diffusers having random motion;
- said processing means being adapted to:
- re-position in time the reverberated signals Bk(i, t) of the sets k if the points rk are different from one another in order to obtain corrected signals B0k(i, t)=Bk(i, t−Gi(rk)), where the values Gi(rk) are delays such that, by causing the transducers i to emit signals ek(i, t)=e0(i, t+Gi(rk)), the incident wave focuses substantially at the point rk, the signals e0(i, t) being reference signals such that, by causing the transducers i to emit said reference signals e0(i, t), the incident wave focuses substantially at the point r0;
- and to
- put into phase and average the signals B0k(i, t)=Bk(i, t−Gi(rk)) so as to obtain average signals
- Bf
-
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- i
- ,
- t
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- =
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- k
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- A
- k
-
- B
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- k
-
- (
- i
- ,
- t
- -
- c
- k
- )
- where the values ck are delays making it possible to put the signals B0k into phase, and the values Ak are weighting coefficients.
Dependencies are inferred from the claim text.