Passive imaging by noise correlation
For less than 20 years now, passive imaging methods based on the extraction of Green’s functions have grown dramatically. NCIS has unique expertise in this area in a wide range of applications.
Acoustic and vibrations
Defect localization
In acoustics, as part of the ANR PASNI (collabation with the IEMN Valenciennes), this method was implemented to detect defects from the bending vibration noise correlation.
(L. Chehami,; J. De Rosny, C. Prada, E. Moulin, J. Assaad, "Experimental study of passive defect localization in plates using ambient noise", IEEE Trans. on UFFC.62 (8) (2015))
Localization of a fault by vibratory noise correlation.
Plate thickness
An original passive measurement of plate thickness using the noise cross-correlation bewteen a circular transducer has been proposed.
(Ros K. Ing, Nicolas Etaix, Alexandre Leblanc, Mathias Fink, Measurement of thickness or plate velocity using ambient vibrations, The Journal of the Acoustical Society of America 2010 127:6, EL252-EL257).
Concentric transducers to estimate plate thickness from noise correlation.
Passive Calibration
Still in acoustics, it has been shown that associated with network calibration algorithms, the method allows a self-calibration in positions.
(Nowakowski, T., L. Daudet, and J. De Rosny "Localization of acoustic sensors from passive Green’s function estimation", J. Acoust. Soc. Am.138, no. 5 (2015)).
Green function reconstruction by noise correlation for acoustic network calibration.
Sismology
For several years there has been a strong collaboration with the IPGP on estimating the consistency of a seismic field (Seydoux, L., N. M. Shapiro, J. de Rosny, and M. Landes. Geophysical Research Letters 43, no. 18 (2016)).
Study of the coherence of the seismic field according to the period of the year.
Electromagnetism
More recently, the laboratory has focused on transposing this concept to electromagnetic waves.
Microwaves
In microwaves, in collaboration with the IETR of Rennes, we recently understood the effect of absorption in the emergence of Green’s functions .
(Green’s function retrieval and fluctuations of cross density of states in multiple-scattering media, Davy, M., M. Fink, and J. De Rosny, Green’s function retrieval and passive imaging from correlations of wideband thermal radiations, Physical Review Letters 110, no. 20 (2013))
Optic
In optics, the first observation of the emergence of the Green function between two diffusers was obtained using an interferometric device and an incoherent illumination on a multi-scattering medium.
(Amaury Badon, Geoffroy Lerosey, Albert C. Boccara, Mathias Fink, and Alexandre Aubry, Retrieving Time-Dependent Green’s Functions in Optics with Low-Coherence Interferometry, Phys. Rev. Lett. 114, 023901 (2015))
Optical device for estimating noise correlations.
More recently, the method has made it possible to carry out a passive mapping of the diffusion constant.
(Amaury Badon, Dayan Li, Geoffroy Lerosey, A. Claude Boccara, Mathias Fink, and Alexandre Aubry, Spatio-temporal imaging of light transport in highly scattering media under white light illumination, Optica Vol. 3, 11, 1160-66,2016)
Theory
On the theoretical level, a significant advance has been made on the understanding of the emergence of Green’s function in diffuse media based on the diagrammatic approach of multiple diffusion.
(Green’s function retrieval and fluctuations of cross density of states in multiple-scattering media, J. De Rosny, M. Davy, EPL - Europhysics Letters, 2014, 106 (5), pp.54004)
