On the spatial sampling of wave fields with circular ring apertures

This paper investigates the sampling criterion needed to image objects within a circular ring array. The array consists of transducer elements deployed along a circular aperture at regular angular intervals. Each transducer excites waves which propagate towards the center of the array and detects outgoing fields traveling towards it. It is shown that while with conventional linear apertures the sampling criterion is dictated by the wavelength of the probing wave only, in the case of a circular aperture the sampling depends on the size of the object relative to the wavelength and its position with respect to the aperture.