Near-field acoustical imaging with boundary arrays

High-resolution acoustical imaging requires the use of short-duration (wideband) pulses for good resolution in range, and two-dimensional (2-D) transducer arrays for good resolution and scanning in both lateral directions. However, 2-D arrays often contain an impractically large number of elements, so it is important to find sparse 2-D arrays which can perform as well as densely populated 2-D arrays. Boundary arrays are a particular class of sparse arrays which have elements located only on the boundary of some planar region. Signal processing techniques have been developed that effectively fill in the missing elements in the interior of the boundary array. These techniques were originally proposed in the context of narrowband imaging of far-field scenes. The techniques are applied to near-field imaging with wideband pulses. Simulations indicate that the methods are effective in this context also, and thus 2-D boundary arrays can produce high-quality images in acoustical imaging applications