Passive imaging: From Geophysics to Medicine and MIMO Radar

by Prof. Mathias Fink
Langevin Institute, ESPCI Paris
HKUST IAS Senior Visiting Fellow

 :  06 Dec 2018 (Thu)
 :  3:00pm - 4:00pm
Venue  :  Classroom 2503 (via lifts 25/26)

Passive seismic imaging methods is now widely used in Geophysics. The idea is to observe the seismic noise that exists continuously everywhere in the earth. Turning this noise into useful data is possible through the measurement of this noise with an array of passive sensors (seismometers). From the analogy with time reversal mirror techniques, it can be shown that the correlation of this ambient noise between passive sensors yields the impulse response between these sensors as if one was a source.  Therefore from the measurement of this noise on multiple sensors, one can have access to all the inter-element impulse responses between the sensors providing a tomographic image of the earth. 
This approach also called “interferometric seismology” has many applications in earth science and we will described some of them. Recently, the same approach where extended to the field of medical electrography with ultrasound or with optical waves as “passive elastography” and we will described it. The idea is to use the vibration noise induced by pulsatile motions or by muscle vibrations to extract elasticity map of tissue. 
Why not to use the same concept to build MIMO Passive Radar that use the electromagnetic noise existing in cities ?
Mathias Fink is the George Charpak Professor at the Ecole Superieure de Physique et de Chimie Industrielles de la Ville de Paris (ESPCI Paris) where he founded in 1990 the Laboratory “Ondes et Acoustique” that became in 2009 the Langevin Institute. He is member of the French Academy of Science and of the National Academy of Technologies of France. In 2008, he was elected at the College de France on the Chair of Technological Innovation. He has received several scientific awards as the CNRS Medal of innovation, the Helmholtz-Rayleigh Award of the Acoustical Society of America, the Rayleigh Award of the IEEE Ultrasonics Society and the Edwin H. Land Medal of the Optical Society of America. Mathias Fink’s area of research is concerned with the propagation of waves in complex media and the development of numerous instruments based on this basic research. His current research interests include time-reversal in physics, wave control in complex media, super-resolution, metamaterials, medical ultrasonic imaging, ultrasonic therapy, multiwave imaging, acoustic smart objects, underwater acoustics, geophysics and telecommunications. He has developed different techniques in medical imaging (ultrafast ultrasonic imaging, transient elastography, supersonic shear imaging). He holds more than 70 patents, and he has published more than 400 peer reviewed papers and book chapters. 6 start-up companies with more than 350 employees have been created from his research (Echosens, Sensitive Object, Supersonic Imagine, Time Reversal Communications, CardiaWave and GreenerWave).