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Browse Prior Art Database

Test Template Fixture

IP.com Disclosure Number: IPCOM000087418D
Original Publication Date: 1977-Jan-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 47K

Publishing Venue

IBM

Related People

Miner, LE: AUTHOR [+2]

Abstract

Testing an optical device for reading bar codes, such as the universal product code (UPC), can most effectively be accomplished by testing the reading ability of the device when the bar code is presented at the reading locations that occasion the greatest difficulty for the reader.

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Test Template Fixture

Testing an optical device for reading bar codes, such as the universal product code (UPC), can most effectively be accomplished by testing the reading ability of the device when the bar code is presented at the reading locations that occasion the greatest difficulty for the reader.

The bar code pattern used for test purposes is shown in Fig. 1 and the waveform generated by scanning the pattern is shown in Fig. 2. The pulse widths of the waveform of Fig. 2 are shown above the trace in mils, and the various black and white bars are identified as a sequence of symbols T1 through T15. The pulse widths or time durations of the bars T1 through T15 are used to generate a series of eleven ratios following the scanning of the large black bar at the left side of the coded sequence which stabilizes the output signal.

The ratio established by reading the bar code on the template, using the device under test, is compared with the reference values to determine whether each is within an acceptable deviation from the specification value. The standard for the reference and the acceptable degree of deviation are established to assure that the correct character will be decoded under worst case conditions.

The ratios are formed by measuring the T-times of the digital data signal as generated from the bar patterns on the test template. The first large black bar will stabilize the output signal and actual measurements begin with T1. The first measurement used for...