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Profile Determination of Threshold for Bar Code Recognition

IP.com Disclosure Number: IPCOM000040098D
Original Publication Date: 1987-Sep-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 68K

Publishing Venue

IBM

Related People

Ramsey, DA: AUTHOR [+2]

Abstract

A bar code reader is shown in the figure for reading a code 2 which includes marks of two lengths, 1/2 high and 1/6 high, which are located in defined regions of a six-region transverse field 7. The location and size of each mark is determined by counting the image pels in each region. The regions are determined to contain a mark where the count of image pels in the region exceeds one-half the count for an adjacent region. A problem in reading these pels is that if they are slanted or tilted, the reader has difficulty in differentiating between the slant and stray marks. Since 1/2 high bars tend to be more slanted than 1/6 high bars, the reader most often misreads the former bars.

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Profile Determination of Threshold for Bar Code Recognition

A bar code reader is shown in the figure for reading a code 2 which includes marks of two lengths, 1/2 high and 1/6 high, which are located in defined regions of a six-region transverse field 7. The location and size of each mark is determined by counting the image pels in each region. The regions are determined to contain a mark where the count of image pels in the region exceeds one-half the count for an adjacent region. A problem in reading these pels is that if they are slanted or tilted, the reader has difficulty in differentiating between the slant and stray marks. Since 1/2 high bars tend to be more slanted than 1/6 high bars, the reader most often misreads the former bars. The subject invention overcomes this difficulty by selectively ignoring small quantities of the pels that may be stray marks while accurately reading the actual marks. The amount of marks ignored is dependent on the type of bar being scanned. In operation, the code pattern 2 on document 3 is presented to a scanner 4 as the document 3 moves in the direction of arrow 5. Analog signals, representing the image of the marks 2, are digitized and assembled into a formatted and framed pattern in circuitry 6, the output of which provides successive scans of image data to a first-in, first- out memory 7. Starting with region 6, shift register 8 shifts image data bits from the first available scan through bit counter 9 and multiplexer 10 to adder 11 for combination with the contents of a region count register...