Electrophotographic imaging apparatus by variably placing pixel elements

Abstract

A digital laser platemaker for imaging an electrophotographic member by electrostatic techniques using information which is derived from a source of binary data. The binary data may be achieved by scanning a pattern or may be synthesized electrically to represent that which it is desired to reproduce on the electrophotographic member. The binary data is applied to a pixel generator which is constructed and arranged to produce an output in the form of signals for driving an acousto-optical deflector that in turn deflects a laser beam to form a composite of rays. The composite of rays represent the columns of a pattern to be applied to each pixel which is generated, the rows of the pixel being represented by the output of a shaft encoder that is synchronized with the rotation of a cylinder carrying the electrophotographic member. The pixel generator produces hexagonal pixels and the pattern in each pixel represents density information derived from the binary data originally received by the pixel generator. The patterns in the pixels are arranged to prevent undesirable moire effects. The electrophotographic member receives the composite rays from a carriage which moves in synchronism with the rotation of the cylinder and the rate at which the composite rays are applied. The resulting latent image is toned and fused on the cylinder. Thereafter it may be used as the printing plate after certain processing.