Bar code scanning with correction for spot speed variation
First Claim
1. A method for decoding the output of a bar code scanner of the type used for scanning bar code symbols which have a plurality of characters, each of which comprises a plurality of elements, the output of the scanner representing the time variation of light reflected from a spot moving across the elements of the bar code symbol at a varying speed, said method comprising the steps of:
- receiving a signal comprising a series of values each of which represents the time required for the spot to cross an element in the bar code symbol;
processing said series of values to determine a spot-speed profile for at least a portion of said symbol, said profile having non-zero acceleration within at least some of the characters; and
adjusting said series of values to lessen the effect of variation in spot speed.
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Accused Products
Abstract
Bar code scan data is corrected for spot-speed variation by processing the data to determine a spot-speed profile having non-zero acceleration within at least some of the characters of the bar code symbol being scanned, and then using the speed profile to normalize the scan data. Preferably, average spot speeds across individual characters are determined, and a speed profile is fit to these average spot speed data points in such a manner that the curve is not forced to pass through every data point. In this way, a spot-speed profile is derived that does not incorrectly attribute, to speed variation, errors due to other sources, e.g., random edge errors from printing. Preferably, the spot-speed profile consists of a plurality of straight line segments. The segments may be slightly disjoint, and each segment is from two to four characters in length, depending on the density of the bar code symbol.
22 Citations
24 Claims
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1. A method for decoding the output of a bar code scanner of the type used for scanning bar code symbols which have a plurality of characters, each of which comprises a plurality of elements, the output of the scanner representing the time variation of light reflected from a spot moving across the elements of the bar code symbol at a varying speed, said method comprising the steps of:
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receiving a signal comprising a series of values each of which represents the time required for the spot to cross an element in the bar code symbol; processing said series of values to determine a spot-speed profile for at least a portion of said symbol, said profile having non-zero acceleration within at least some of the characters; and adjusting said series of values to lessen the effect of variation in spot speed. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. Apparatus for decoding the output of a bar code scanner of the type used for scanning bar code symbols which have a plurality of characters, each of which comprises a plurality of elements, the output of the scanner representing the time variation of light reflected from a spot moving across the elements of the bar code symbol at a varying speed, said apparatus comprising:
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means for receiving a signal comprising a series of values each of which represents the time required for the spot to cross an element in the bar code symbol; means for processing said series of values to determine a spot-speed profile for at least a portion of said symbol, said profile having non-zero acceleration within at least some of the characters; and means for adjusting said series of values to lessen the effect of variation in spot speed. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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Specification