Super resolution in synthesized arrays

Virtual point sources of acoustic waves can be synthesized by using spherically defocused sources, for example, a spherically defocused annular array or a convex transducer. The virtual point source lies at the center of radius of curvature of the leading edge of the defocused transmitted wave. Groups of these virtual point sources can then be used to synthesize a virtual array aperture. By this process, `array synthesis´, a virtual aperture can also be synthesized which is wider than the area occupied by the defocused source or sources. This leads to super resolution images