Browse Prior Art Database

Contrast Sensitive Gain Setting for Checkout Scanner

IP.com Disclosure Number: IPCOM000045496D
Original Publication Date: 1983-Apr-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 55K

Publishing Venue

IBM

Related People

Broockman, EC: AUTHOR

Abstract

This article describes apparatus and a technique for setting the gain of a photomultiplier tube (PMT) in a checkout scanner as a function of detected peak to peak values of delimiter characters in a label being scanned. The intended application is reading labels.

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Contrast Sensitive Gain Setting for Checkout Scanner

This article describes apparatus and a technique for setting the gain of a photomultiplier tube (PMT) in a checkout scanner as a function of detected peak to peak values of delimiter characters in a label being scanned. The intended application is reading labels.

Referring to Fig. 1, analog scanner signals are applied to a peak to peak detector circuit 10 and to a threshold circuit 12. Circuit 12 converts the analog signals to a square-wave train which is applied to a candidate select circuit 14. Circuit 14 frames label candidates in the stream of data. The data and framing signals are applied to a memory 16. Signals stored in memory 16 are available to a processor 18 which decodes those signals to establish the label values. The processor 18 also controls the gain setting of the PMT (not shown) which generates the video signals.

Gain setting is described below. Circuit 10 establishes the difference between succeeding high and low peaks in the analog signal, which correspond to label contrast in succeeding space and bar regions. The output of the detector 10 is digitized in an analog to digital (A/D) converter 20. The digitized signal is applied to a four-stage shift register 22. The first three stages are connected to an adder/ averager circuit 24. All four stages are connected to another adder/ averager circuit 26. The outputs of circuits 24 and 26 represent the average peak to peak values for the preceding 3 and 4 preceding digital values, respectively. The...