Transducer surface velocity reconstructions using the angular spectrum method

A technique for analyzing the surface velocity patterns of ultrasonic transmitters based on the angular spectrum method of wave-field analysis is presented. In this approach, acoustic propagation between parallel planar surfaces is modeled using the two-dimensional Fourier transform of the wave field, with each element in the spatial frequency domain multiplied by the appropriate phase factor. The technique was extended from the basic monochromatic model to the wideband pulsed case. An experimental system was built to measure the acoustic fields from various transducers, including the single-element and multi-element phased arrays. Backpropagation results are shown for circular planar, circular focused, and rectangular phase-steered transducers. The results demonstrate the ability of the extended angular spectrum method to reconstruct the surface velocity distribution of complex acoustic radiators