Method and apparatus for decoding bar code symbols using subpixel scan lines
First Claim
1. A method for reading a bar code symbol in a pixel image, comprising the steps of:
- (a) selecting a first scan line substantially parallel to the bars and spaces of said symbol;
(b) scanning said symbol along said first scan line to generate a first value based on intensity values of two or more pixels of the pixel image that are crossed by the first scan line;
(c) selecting a second scan line substantially parallel to the bars and spaces of said symbol, wherein the distance between said first and second scan lines is less than the width of a pixel of said image;
(d) scanning said symbol along said second scan line to generate a second value based on intensity values of two or more pixels of the pixel image that are crossed by the second scan line; and
(e) decoding said symbol in accordance with said first and second values.
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Abstract
A bar code reader decodes a bar code symbol in a pixel image by transforming the data corresponding to the symbol along a first scan line, where the transformation comprises rotation and stretching. The reader generates a composite vector and a count vector from the transformed data. The reader then transforms (by rotating and stretching) another set of data corresponding to the symbol along a second scan line. The reader updates the composite and count vectors using the second set of transformed data. The reader then generates a one-dimensional composite signal from the composite and count vectors. The reader decodes the symbol by decoding the composite signal.
118 Citations
8 Claims
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1. A method for reading a bar code symbol in a pixel image, comprising the steps of:
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(a) selecting a first scan line substantially parallel to the bars and spaces of said symbol; (b) scanning said symbol along said first scan line to generate a first value based on intensity values of two or more pixels of the pixel image that are crossed by the first scan line; (c) selecting a second scan line substantially parallel to the bars and spaces of said symbol, wherein the distance between said first and second scan lines is less than the width of a pixel of said image; (d) scanning said symbol along said second scan line to generate a second value based on intensity values of two or more pixels of the pixel image that are crossed by the second scan line; and (e) decoding said symbol in accordance with said first and second values. - View Dependent Claims (2, 3, 4)
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5. An apparatus for reading a bar code symbol in a pixel image, comprising:
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(a) means for selecting a first scan line substantially parallel to the bars and spaces of said symbol; (b) means for scanning said symbol along said first scan line to generate a first value based on intensity values of two or more pixels of the pixel image that are crossed by the first scan line; (c) means for selecting a second scan line substantially parallel to the bars and spaces of said symbol, wherein the distance between said first and second scan lines is less than the width of a pixel of said image; (d) means for scanning said symbol along said second scan line to generate a second value based on intensity values of two or more pixels of the pixel image that are crossed by the second scan line; and (e) means for decoding said symbol in accordance with said first and second values. - View Dependent Claims (6, 7, 8)
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Specification