Eikonal Theory of Bragg-Diffraction Imaging

Abstract

Although the initial explanation of Bragg-diffraction imaging was based on an intuitive ray approach, it is generally assumed that, because this process is essentially one of diffraction, it is really only explainable on the basis of a wave theory. At the First Symposium on Acoustical Holography such a (two-dimensional) theory was presented which essentially confirmed the predictions of the intuitive ray approach. Because the latter approach, however, is frequently more useful in quickly providing insight into new situations, it seems worthwhile to base it on a more solid foundation. In the present paper a rigorous ray theory is developed from a modified eikonal equation. It will be seen that, not only does this theory confirm the intuitive approach, but also provides quantitative information about the strength of the interaction.