Analysis of Bragg diffraction imaging by means of a three-dimensional computer ray tracing algorithm

Abstract

Bragg diffraction imaging provides a convenient method of visualizing ultrasonic sound fields. The technique images the transverse sound field profile, and may be conveniently analyzed with ray tracing techniques. We first consider the case of a three-dimensional sound field illuminated by a two-dimensional light field, and then examine an alternative scheme, in which the same sound field is illuminated by a three-dimensional light field. In both cases, the diffracted light is three-dimensional in nature, so that the ray tracing must ultimately be rendered as a two-dimensional projection of the original three-dimensional construct. We discuss the development and implementation of an interactive computer program that realizes three-dimensional acousto-optic ray tracings and generates two-dimensional projections from various vantage angles. Using two slightly different vantage angles makes stereoscopic presentations possible. The ray tracings are depicted by color graphics, such that sound and diffracted/undiffracted light rays are easily distinguishable. Results clearly reveal the astigmatic nature of the image as also predicted by previous geometric analyses of the same configurations.