An Optimization Method for Ultrasonic Beamforming with a Synthetic Aperture

Ultrasonic beamforming with a synthetic aperture is widely used in underwater and underground visualizations, but often suffers from visualization results with elliptically symmetric artifacts, due to lack of measurement points or transducers. We propose a newly-developed optimization method for ultrasonic beamforming. The aim of this method is to sharpen the distribution of the point spread function with a limited number of transducers. The characteristic of the point spread function is useful for evaluating the beamforming performance. This optimized beamforming method employs a visualization result by the conventional beamforming method as the initial guess. In the recursive calculation of this optimization method, the initial visualization result is modified by reducing and enhancing the weights of the discretized points in the measurement area. To evaluate this method, we tested it using a computer simulation and an actual measurement experiments, with a limited number of transducers. As the results of the experiments, this method successfully derives a sharp distribution of the point spread function.