Browse Prior Art Database

Candidate Tracking System

IP.com Disclosure Number: IPCOM000040132D
Original Publication Date: 1987-Sep-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 4 page(s) / 60K

Publishing Venue

IBM

Related People

Broockman, EC: AUTHOR

Abstract

Means are provided to effectively track a label across an optical bar code scanning system. Scanners are commonly used with processor-controlled point-of-sale systems in retail stores and supermarkets to identify goods being processed. A bar code label on an item provides input data which can be used by the system to retrieve price data, print customer receipts and update inventory records. In a fixed head scanner system, an item 1 (Fig. 1) to be detected is moved across a transparent scan window, normally in the upper surface of a stationary scanner. Optical elements 2 and 3 within the scanner deflect a laser beam to produce scan lines 4 which sweep through a volume above the scan window. Light reflected from an object passing through the volume is detected.

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Candidate Tracking System

Means are provided to effectively track a label across an optical bar code scanning system. Scanners are commonly used with processor-controlled point-of-sale systems in retail stores and supermarkets to identify goods being processed. A bar code label on an item provides input data which can be used by the system to retrieve price data, print customer receipts and update inventory records. In a fixed head scanner system, an item 1 (Fig. 1) to be detected is moved across a transparent scan window, normally in the upper surface of a stationary scanner. Optical elements 2 and 3 within the scanner deflect a laser beam to produce scan lines 4 which sweep through a volume above the scan window. Light reflected from an object passing through the volume is detected. Potential label candidates are selected and decoded by means including microprocessor
6. The optical energy reflected from item 1 is detected by a photodetector 7 and is

(Image Omitted)

applied as an analog signal stream to a decoder system 5 which digitizes the signal stream. The digitized signal stream is entered into storage 8 under control of microprocessor 6. Under the control of programs containing candidate-selection algorithms, the signal stream data is compared with a candidate-selection database stored in 9. When a complete bar code label is detected by one scan line or by several scan lines, each detecting a portion of the bar code from the same label, the bar code data is transferred to the point-of-sale system for effecting the desired functions. If a label on a product is not successfully read, that product must be brought back across the scanner window in one or more additional passes. Factors such as the print quality of the labels being scanned, the electrical characteristics of the signal detecting system and the decoding algorithms which are employed all have an impact on reading performance. To increase the chances that a randomly-oriented bar code label will be scanned completely during a pass over the scanner window, multi-line scan patterns are used in which the lines intersect each other at angles. Such scan patterns are generated by directing a laser beam from source 2 at a rotating mirror wheel or through a rotating holographic disk 3 to cause the laser beam to be deflected in predetermined directions. Fixed arrangements of mirrors are used to change the beam paths before the beams exit from the scan window to form scan lines. Known scan patterns include non-parallel or intersecting lines and/or parallel lines displaced in space from one another. This article proposes to track a label across the scanning volume traced by the scan lines 4. The disk 3 has a constant known speed which is stored and used by microprocessor 6, for example, one hundred revolutions per second. It will be assumed that articles carrying bar code labels are moved across the scanning volume at a constant rate, e.g., thirty inches per second, and in a

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