Geometrical interpretation of image formation in the Raman-Nath acousto-optic interaction regime

Diffraction of light by ultrasonic waves can be used to produce luminous images of acoustical transparencies. A geometrical interpretation of the imaging mechanism is proposed. The interaction phenomenon is first considered in a principal section plane: the optical image of an acoustical point source can be obtained. An object-image relationship is given. The extension that analysis to 3D interaction gives theoretical diffraction results: in space, the acousto-optic transformation is not an orthogonal one. Consequently, visualization of an image similar to the object requires the use of an anamorphote device. An experimental set-up is described and some experimental results are given as examples.