Method and device for mapping fibrous media

A device for implementing a mapping method, comprising:

• a set of transducers arranged in a two-dimensional transducer array and control and processing means configured for:
• causing the set of transducers to emit, in a field of view of a medium comprising fibers, a plurality of successive unfocused incident ultrasonic waves having different wavefronts, wherein said plurality of successive unfocused incident ultrasonic waves propagate in the field of view without focusing in said field of view, and causing the set of transducers to capture said plurality of successive unfocused incident ultrasonic waves reverberated by the medium to produce sets of captured signals, wherein solely said successive unfocused incident ultrasonic waves are transmitted to the medium,
• determining coherent signals from said sets of captured signals and for a number M of fictitious focal points Pk in the field of view, wherein the coherent signals correspond to signals that would have been received by the set of transducers if a wave focused at a fictitious focal point Pk had been emitted by said set of transducers,
• calculating, at each fictitious focal point Pk, a spatial coherence parameter in a plurality of alignment directions of said set of transducers using a measure of spatial coherence between said coherent signals, and
• determining the presence and orientation of fibers at each fictitious focal point Pk using the spatial coherence parameter,
• wherein the spatial coherence parameter is based on no shear wave imaging.

A method for mapping fibrous media, comprising:

• a measurement step during which a set of transducers emits, in a field of view of a medium comprising fibers, a plurality of successive unfocused incident ultrasonic waves having different wavefronts, wherein the set of transducers is a two-dimensional transducer array, wherein said plurality of unfocused incident ultrasonic waves successively propagate in the field of view without focusing in said field of view, and wherein said plurality of unfocused incident ultrasonic waves are successively reverberated by the medium and captured by said set of transducers to produce sets of captured signals, wherein solely said unfocused incident ultrasonic waves are transmitted to the medium without propagating shear waves in the medium, wherein no share waves are propagated in the medium,
• a step of synthesizing coherent data to determine coherent signals from said sets of captured signals, and for a number M of fictitious focal points Pk in the field of view, wherein the coherent signals correspond to signals that would have been received by the set of transducers if a wave focused at a fictitious focal point Pk had been emitted by said set of transducers, and
• a step of mapping fibers of the medium comprising calculating, at each fictitious focal point Pk, a spatial coherence parameter in a plurality of alignment directions of said set of transducers, using a measure of spatial coherence between said coherent signals, and
• wherein mapping the fibers of the medium is based on determining the presence and orientation of fibers at each fictitious focal point Pk using the spatial coherence parameter.

A device for implementing a mapping method, comprising:

• a set of transducers arranged in a two-dimensional transducer array and control and processing means configured for:
• causing the set of transducers to successively emit, in a field of view of a medium comprising fibers, a plurality of unfocused incident ultrasonic waves having different wavefronts, wherein said plurality of unfocused incident ultrasonic waves propagate in the field of view without focusing in said field of view, and causing the set of transducers to capture said plurality of unfocused incident ultrasonic waves successively reverberated by the medium to produce sets of captured signals,
• wherein solely said unfocused incident ultrasonic waves are transmitted to the medium without propagating shear waves in the medium, wherein no share waves are propagated in the medium,
• determining coherent signals from said sets of captured signals, and for a number M of fictitious focal points Pk in the field of view, wherein the coherent signals correspond to signals that would have been received by the set of transducers if a wave focused at a fictitious focal point Pk had been emitted by said set of transducers, wherein solely said unfocused incident ultrasonic waves are transmitted to the medium, wherein no share waves are propagated in the medium,
• calculating, at each fictitious focal point Pk, a spatial coherence parameter in a plurality of alignment directions of said set of transducers using a measure of spatial coherence between said coherent signals, and
• determining the presence and orientation of fibers at each fictitious focal point Pk using the spatial coherence parameter.