Three-dimensional light beam scanner utilizing tandemly arranged diffraction gratings

Claim 1

A three-dimensional light beam scanner comprising: a first disc having a plurality of diffraction gratings disposed thereon in a circular band, a light source providing a beam of light directed onto a fixed region located in the plane of the circular band on said first disc occupied by only one of said gratings, a second disc having a plurality of diffraction gratings disposed thereon in a circular band and positioned relative to said first disc such that the light diffracted by said first disc is incident on a fixed region in the plane of the circular band occupied by only one of said gratings on said second disc, means for synchronously rotating said first and second discs at different rotational rates about axes passing through the center of said circular bands, the gratings on one of said first and second discs being identical uniform straight line gratings so that the light incident thereon is repetitively scanned in a single direction as the gratings traverse the light, each grating on the other of said first and second discs being portions of different zone plates each having a discrete focal length so as to focus the incident light at individually distinct distances from said other disc and oriented on said other disc relative to the incident light as to be operative in the course of rotating to additionally scan the light in a direction transverse to the scanning direction provided by said one disc, and mask means having an aperture for blocking all the light coming from said second disc except for the desired portion diffracted by the gratings on said second disc.