Abstract: A method and apparatus involving the generation of a digital screen at different screen angles for reproducing an image in raster form as a series of adjacent picture elements disposed along a plurality of adjacent parallel lines. The digital screen is generated by the repetition of one screen cell in first and second directions, each cell being divided into a series of unique address locations and each location being characterized by a selected optical density value. A memory array is provided for storage of the optical density values at address locations which correspond to address locations in the digital screen. The digital values of the actual picture elements in the image, which are obtained by scanning of the image, are compared to the screen values stored in the memory at corresponding addresses in order to generate output data signals defining the image to be reproduced.

Abstract: A method and apparatus are disclosed for referencing the position of a rotatable drum in a scanner/plotter. The rotatable drum is rotatable held in axial alignment by means of a drum headstock and a spring loader, moving center tailstock. An optical shaft encoder provides a reference pulse for the headstock drum shaft and a plurality of drive shaft position pulses. The rotatable drum has a magnetic pellet mounted thereon. A magnetic transducer is positioned with respect to the predetermined drive shaft position to detect the presence of the drum pellet. As the drum rotates, the transducer detects the pellet and produces an output signal which is used to electronically cross-reference the drum pellet to the predetermined drive shaft position.

Abstract: A method and apparatus are disclosed for producing photographic reproductions of line and continuous tone graphic materials. The invention is useful in the newspaper field for opto-electrically producing plate-ready negatives or plates themselves from line and continuous tone copy. The line and continuous tone graphic materials are scanned incrementally to produce high resolution signals representative of the gray levels of incremental areas of both the line and continuous tone materials. A plurality of the high resolution signals representing the gray levels of the incremental areas of the scanned continuous tone material are combined to produce low resolution signals representing the gray levels of larger, low resolution incremental areas of the scanned continuous tone graphic material. The high and low resolution signals are employed to control an incremental, scan exposure of a photosensitive member.