High-speed broad-brush laser photocomposition

Abstract

The machine preferably utilizes a laser whose light output, modulated to produce a plurality of beams which move simultaneously across a photosensitive surface, thus forming a 'broad brush' laser beam. In one embodiment, the photosensitive material is in elongated sheet form and moves longitudinally while the broad brush laser moves continuously back and forth across the moving sheet. In another embodiment, the sheet material is wrapped around the surface of a drum and the drum rotates past the laser beam, while the laser beam moves either continuously or intermittently so that contiguous circumferential bands of composition are formed, filling the whole sheet of material with only one pass of the projection mechanism along the length of the drum. Means are provided for compensating for the simultaneous continuous motion of the broad brush and the photosensitive surface in order to produce straight lines of text composition which are perpendicular to the edges of the photosensitive surface. Each sweep of the laser beam is contiguous with the preceding sweep, and in each sweep each full character, or any part of a character, which falls within the sweep path is projected onto the photosensitive surface, thus further enhancing the speed of photocomposition. Characters and graphic matter preferably are stored in digital form by a raster image processor in order to enable this type of operation.