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Acousto-optic processing of images is based on the angular selectivity of acousto-optic interaction resulting in spatial filtration of the image spectrum. We present recent theoretical and experimental investigations carried out in this field. Much attention is given to the analysis of the acousto-optic cell transfer function form depending on the crystal cut, the geometry of acousto-optic interaction, and the ultrasound frequency. Computer simulation results of the two-dimensional acousto-optic spatial filtration of some elementary images are presented. A new method of phase object visualization is suggested and examined that makes it possible to separate amplitude and phase information contained in an optical image. The potentialities of the acousto-optic image processing are experimentally demonstrated by examples of edge enhancement and optical wavefront visualization effects.

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Collinear diffraction of a strongly divergent optical beam by a monochromatic acoustic wave is investigated theoretically and experimentally. Three-dimensional patterns of acousto-optic (AO) phase matching are calculated and their transformation with varying acoustic frequency and ultrasound propagation direction is analysed. Two effects are discussed which appear at spectral collinear filtration of optical images, namely distortion of filtered image structure and spectral resolution deterioration. It is shown that the effects result in contradictory requirements on AO cell parameters. However, a compromise is possible which allows filtering of high-spatial-resolution images with an acceptable reduction in spectral resolution. Experimental results on diffraction of a strongly divergent He-Ne laser beam in a CaMoO 4 AO cell are also presented in this paper.