Character recognition system and its use in an optical document reader

Claim 1

A character recognition system for an optical document reader for recognizing two types of characters in a single line of characters, the system comprising: means for generating and detecting a video signal, said video signal detecting means having a threshold input; means for generating a threshold signal including signal level controlling circuits for generating a plurality of threshold signals in time multiplex at the threshold input of the video signal detecting means; means for comparing signals for video signal detection; means for storing signals including means for generating one time multiplex channel for each threshold signal and having a plurality of logic circuits incorporated in a program logic array (PLA) circuit including a clock circuit and a cycle counter driven by the clock and counting operating cycles during one line scan, the cycle time of one operating cycle covering one time period of each time multiplex channel, said logic circuits operating in time multiplex mode and having inputs connected to the output of the video signal detector and having outputs connected to a direct memory access (DMA) device storing detected video data in time multiplex into a plurality of storage modules, one module for each threshold signal; and means for processing signals for recognizing character data using video data detected with a first threshold signal and stored in a first module until a separating character is detected and subsequently recognizing character data using video data detected with a second threshold signal and stored in a second module.