Browse Prior Art Database

Skew Detection for Linear Scanner

IP.com Disclosure Number: IPCOM000050626D
Original Publication Date: 1982-Nov-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 23K

Publishing Venue

IBM

Related People

Nagda, JM: AUTHOR [+2]

Abstract

The pattern of marks in the figure represents a row of information marks scan window. If marks A and C cannot be detected during the same linear scan by the scanning system, the document is skewed relative to the scanner to an extent that the information marks B cannot be reliably read.

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Skew Detection for Linear Scanner

The pattern of marks in the figure represents a row of information marks scan window. If marks A and C cannot be detected during the same linear scan by the scanning system, the document is skewed relative to the scanner to an extent that the information marks B cannot be reliably read.

In operation, the scanner accumulates a quantity of black for all of the marks A, B and C in the row being scanned. When the A mark is no longer detected, the scanning system determines how much black has been sensed from the C mark. If the quantity detected exceeds a threshold of 80 percent (other thresholds might be used), then the scanner knows the skew is small enough that the scanner will have also sensed the B marks if any. The scanner then checks for the presence of accumulated black in other portions of the row indicative of the presence of a B mark.

In effect, the dimension lines 10 and 12 between the edges of the A and C mark define an acceptable skew window. The size of the skew window is dependent upon the size of the A and C marks and their distance apart. The A and C marks might be placed on each row to be scanned, or they might be placed at the first or topmost row of a document.

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