Acoustically modified optical Fresnel diffraction by a slit and a periodic object in relation to periodic partial coherence

Optical Fresnel diffraction by a slit and a periodic rectangular wave object, illuminated with accoustically phase-modulated laser light, is investigated in association with partial coherence. The periodic partial coherence, produced by acousto-optic interaction, much deformes the Fresnel diffraction patterns of the respective objects. A nearly flat-top diffraction pattern by the slit is obtained if the acoustic and slit parameters are adjusted. The self-image by the periodic rectangular wave object is reversed in contrast if the acoustic power exceeds a critical value.