Abstract: This disclosure provides an optical scanner for transforming an optical image into electrical signals.Through practice of this disclosure an optical image is projected onto a surface of a photosensitive semiconductor body wherein there is established a charge distribution or perturbation or pattern which reflects the variations in optical intensity of the optical image. Through the parametric interaction of simultaneously applied electric field and acoustic wave to each respective portion of the electrical charge pattern on the photosensitive semiconductor surface, there is obtained a backward acoustic wave which is directed toward the source of the initiating acoustic wave. In particular, the acoustic wave in the acoustic medium may be either a surface acoustic wave (SAW) or a bulk acoustic wave. Where the surface acoustic wave is utilized, the acoustic medium may be commensurately thin.