Binary coding circuit for OCR

Claim 1

A binary coding circuit for an optical character reader which identifies characters or symbols using a photoelectric conversion cell, comprising: a delay circuit having one input terminal for receiving an output of said photoelectric conversion cell as an input signal, and at least three separate and distinct output terminals providing respective time-shifted output representations of said input signal, said time-shifted output representations having delays that are different from each other; a threshold determining circuit arranged so that when one of said time-shifted output representations of said input signal is selected to be a binary-coding target signal, said threshold determining circuit receives as its inputs a plurality of said time-shifted output representations including one time-shifted output representation having a larger delay time than that of said binary-coding target signal and one time-shifted output representation having a smaller delay time than that of said binary-coding target signal as threshold determining signals for determining a threshold signal, said threshold signal being determined to be the threshold determining signal of said threshold determining signals, having a maximum absolute value for each point in time; and a comparator circuit, having a first input receiving said binary-coding target signal and a second input receiving said threshold signal, for comparing said binary-coding target signal with said threshold signal to thereby produce a binary signal having a first level if said binary-coding target signal is greater than said threshold signal and a second level if said binary-coding target signal is less than said threshold signal.