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Browse Prior Art Database

Hand Scanner for Bar Codes

IP.com Disclosure Number: IPCOM000047184D
Original Publication Date: 1983-Oct-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 28K

Publishing Venue

IBM

Related People

Cook, RL: AUTHOR [+3]

Abstract

A bar code reader 10, having a hand-held scanner, normalizes bar width measurements to account for scanning speed by referencing the largest bar scanned within a group of bars to be detected. Wand 11 scans bar code 12 to produce color transition signals recognized by circuit 13. Counter 14 develops a count that represents the time duration between successive transitions, and thereby is proportional to bar or space width. Memory 15 stores successive counts produced at successive memory locations until counter 14 overflows, indicating an excessively wide bar or space which separates adjacent code words. The overflow condition initiates a decode attempt. A threshold count for discriminating between wide and narrow bars is computed by determining the largest of the stored counts and multiplying that count by a fraction such as .

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Hand Scanner for Bar Codes

A bar code reader 10, having a hand-held scanner, normalizes bar width measurements to account for scanning speed by referencing the largest bar scanned within a group of bars to be detected. Wand 11 scans bar code 12 to produce color transition signals recognized by circuit 13. Counter 14 develops a count that represents the time duration between successive transitions, and thereby is proportional to bar or space width. Memory 15 stores successive counts produced at successive memory locations until counter 14 overflows, indicating an excessively wide bar or space which separates adjacent code words. The overflow condition initiates a decode attempt. A threshold count for discriminating between wide and narrow bars is computed by determining the largest of the stored counts and multiplying that count by a fraction such as .75, and is stored at memory location 16. This threshold is then compared to each of the stored counts. Counts larger than threshold are interpreted as "wide" (binary
1) and those which are less than the threshold are interpreted as "narrow" (binary
0). Groups of wide and narrow bars thus are decodable as binary code words.

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