Synthetic Aperture Approach to Multi-Beam Scanning Acoustical Imaging

Abstract

An acoustical imaging method is described which realizes high resolution imaging with relatively small number of transmitters and receivers on the basis of a synthetic aperture technique, but does not require a severe phase stability. It uses a sparse planar transmitting array for generating narrow transmitting multi-beams and a dense planar receiving array for resolving the transmitted multi-beams into independent pencil beams and scans the transmitting multi-beams electronically to obtain the whole picture elements of an image. It differs from the usual synthetic aperture method only in that the transmitters are used for beamforming instead for sequential scanning. Under ideal circumstances, both methods are almost equivalent. But, under practical circumstances, the present method has many advantages over the usual method as the following: i) unstability of a transmitter/receiver platform and a medium causes less influences on resolution and image dynamic range, ii) no speckle noise occurs, iii) memory capacity and processing time required for signal processing can be saved, and iv) higher acoustic power can be transmitted under the cavitation limited environment.