(under subclass 69) Subject matter including means to eliminate the keystone effect or other distortion when the projector is above the viewing screen, as in most theaters, or when the projection axis is oblique to the screen or some other purpose.
SEE OR SEARCH CLASS
352, Optics: Motion Pictures,
105+, for an optical rectifier-type motion-picture device.
359, Optics: Systems (Including Communication) and Elements,
668+, for an anamorphoser which may be used to correct for distortion.
