After recalling the pioneers of acousto-optics, the basis of the phase-vector analysis is considered as an introduction to explain the videocassette, which shows, as an animation, some sequences of the graphical integrations of the formula written for an easy calculation of the light-diffraction by more than one beam of progressive ultrasonic waves. The light amplitude of a given diffraction fringe is calculated by integrating the vectorial contributions carried to a given point of the screen by the elementary light blades into which the entering rectangular light beam can be divided. The resulting vector, in addition to the relative light intensity of a fringe gives, by its phase angle, the phase shift of the light amplitude due to the ultrasonic waves, allowing to determine, e.g., the frequency modulation or the frequency shift. Some reported curves show the graphical integrating curves and the animations evidence their evolution in time for some different diffracting arrangements and the eventual amplitude modulation. A symbol is proposed to summarize the physical parameters of the experimental diffracting arrangement when the symbolism of the Bessel functions cannot be applied.