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Browse Prior Art Database

Adaptive Thresholding for a Mark Reading System

IP.com Disclosure Number: IPCOM000080115D
Original Publication Date: 1973-Jan-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 51K

Publishing Venue

IBM

Related People

Dorr, RL: AUTHOR [+2]

Abstract

This thresholding system automatically and dynamically alters the thresholding function, based on statistics accumulated from previously-read data. Typically a General Purpose mark reader must handle documents over a wide range of applications. Marks read from these various applications do not have the same density from application-to-application, thus requiring some form of variable thresholding.

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Adaptive Thresholding for a Mark Reading System

This thresholding system automatically and dynamically alters the thresholding function, based on statistics accumulated from previously-read data. Typically a General Purpose mark reader must handle documents over a wide range of applications. Marks read from these various applications do not have the same density from application-to-application, thus requiring some form of variable thresholding.

A scanner, Fig. 1, comprising a plurality of cells reads a mark-read document, producing analog signals dependent on the density and size of the mark. The analog signals are fed into A/D converters which code the amplitude level of the signal. This binary code is then gated by Channel Select into the Selection Logic Program. Channel Select operates under format control.

A count is accumulated for the number of signals of the selected channels, which lie within the ranges defined by the coded levels. This count is accomplished by feeding a bit into a shift register for each signal of the selected channels lying within the respective ranges. The shift register (SR delay) has a length commensurate with the sample interval to be taken. Each shift register is monitored by a counter, which is incremented when a bit enters the shift register and decremented when a bit exits the shift register. The output from the counters are fed into a "greater" than compare unit which selects the proper level L(i) (L(1), L(2),...L(N)). Each cou...