Method and apparatus employing zero order Raman-Nath diffraction information to visualize longitudinal character of an acoustic wave field

摘要

A method and apparatus employing zero order Raman-Nath diffraction information to visualize the longitudinal character of an acoustic field. The method includes the steps of directing a first portion of a beam of coherent light at normal incidence to a reflective mirror, propogating an acoustic field within a medium to interact with the first portion of the beam, detecting signals derived from the acousto- optical interaction from which phase change and amplitude change information in the reflected zero order diffraction component of the laser beam can be derived after its return pass through the acoustic field and then generating a two- dimensional raster scan representation of the acoustic field from the detected light signals. The apparatus correspondingly includes a rigid reflective mirror, a coherent light source, an interferometer for splitting a beam from the light source into a first and a second portion and then for directing the first portion at normal incidence to the reflective mirror and intercepting at least the phase-modulated zero order diffraction component of the reflected first portion after its double pass through the acoustic field, and an optical photodetector, translator and display system for visually displaying signals derived from the phase change information in the reflected zero order diffraction component of the first portion of the beam after its passage through the acoustic field.