Ultrasonic imaging technique in liquid and solid waveguides using spatio-temporal matched field (stmf) processing

摘要

The ability to get good images when using ultrasonic data is tied to a certain number of suitable conditions generally found in weakly inhomogeneous media. The relative uniformity of the acoustic properties in such media allows to perform an exploration in depth, because the magnitude of the reflection, refraction and scattering phenomena is limited to a reasonable value. One assumes that the propagation medium behaves as a distribution of scatterers embedded in an homogeneous medium. When the medium is illuminated by an ultrasonic pulse, each scatterer acts as a secondary source and the wave emanating from each one (the Green function) is assumed to be not perturbed by the other scatterers (first-order Born approximation). The purpose of ultrasonic imaging is to reconstruct the map of all the scatterers with the best accuracy and it reduces to develop a processing technique mathced to each possible scattered wave. In conventional imaging techniques, each scatterer is assumed to be a source of a spherical wave that propagates with a constant velocity. The processing is then reduced to the recognition of each of these spherical waves.