Angular resolution in acousto-optic image filtering

Diffraction divergences of acoustic and optical beams are considered as effects determining the minimum angular size of an image element in acousto-optic filtering of object images. Simple formulas for determining this angular size in the diffraction plane and a perpendicular plane have been obtained in relation to the parameters of an acousto-optic filter. The calculated and experimental data are found to be in good agreement. Analysis of the results obtained indicates that the angular resolution can be increased, the quality of spectral images can be improved, and filters with specified asymmetry of the angular resolution can be designed. Analytical conditions for the existence of a group of acousto-optic filters with symmetric angular resolution, which is important for practical applications, are found; these filters are characterized by equal angular resolutions in two mutually perpendicular planes.