Depth-focused interior echo imaging

This paper is concerned with an echo imaging system which utilizes focused beams of an aperture along a specific contour, for example, a line or a circular arc, in both the transmit and receive modes for data collection. Such data collection strategies are useful for imaging internal structures of a target which are located at a certain depth relative to the aperture; unfocused echo signature of an interior structure possesses a low signal-to-clutter/noise power ratio, and is not desirable. The conventional methods for depth-focused echo imaging use transmit/receive focusing on a set of prescribed points in the spatial domain (that is, a two-dimensional grid); this is exceedingly time-consuming though it does not require any postprocessing of the measured data. The proposed scheme of depth-focusing along a contour requires a significantly smaller time period for data acquisition, and relies on a relatively fast Fourier-based method for image formation. This Fourier-based method is shown to be applicable in near-field as well as far-field imaging scenarios, and does not put any restrictions on the size of the aperture, the size of the target area, and the frequency of radiation. The approach is applicable in depth-focused imaging with a mechanically rotating focused aperture, or a phased array. Results are provided.