EXTENSION OF LIGHT-DIFFRACTION TOMOGRAPHY BEYOND THE WEAK ACOUSTOOPTIC INTERACTION

The technique of light-diffraction temography for the mapping of ultra sound fields used so far was restricted to weak acousto-optic interact ions. Under this restriction a straight line propagation of the light beam within the sound field could be assumed and additional optical ph ase shifts could be omitted. In this paper, a method is described whic h considerably exceeds the validation limits of the former approach. T he criteria for the range of applicability of this extended technique are discussed in detail and verified experimentally. Special attention is devoted to the occurrence of additional optical phase shifts which play a major role in the data acquisition and evaluation. Depending o n the width of the ultrasound beam, the extended measurement technique makes possible sound field investigations in the frequency range up t o about 20 MHz.