Spatial coherence of laser light can be modified almost at will through the acousto-optic interaction. If a laser beam is phase-modulated in space and time by a progressive acoustic wave, its mutual intensity is made to vary with a period of one acoustic wavelength. When the double-slit separation is chosen to be half the acoustic wavelength, the double-slit image is more resolved with an increase in the acoustic power, and its resolution becomes better than it is for the incoherent limit if the acoustic power exceeds a critical level. These effects are explained by the spatial frequency analysis of the image spectrum.