Aperture disc and method of making the same

摘要

An indexing system for selectively orienting one of a series of arcuately oriented different sized and/or shaped apertures formed around an aperture disc used in a photohead for exposing upon a photosensitive surface detailed graphic information using a light beam. The aperture disc has formed thereon, equidistantly spaced indicators in the form of slots allowing radiant energy generated by a light emitter to impede upon and energize a split cell photosensitive detector. A control system rotates an aperture wheel to a next selected position at a first velocity until a selected aperture is within the vicinity of the next selected position and subsequently rotates the aperture disc at a second slower velocity to precisely position the next selected position in registry with the light beam. A method for creating the aperture disc includes inscribing with a light beam upon a film, the pattern of the aperture and the indicators, developing the film as a master and contact printing copies of the images formed on the master.