Method and apparatus for locating and decoding machine-readable symbols
First Claim
1. A method of locating and decoding a machine-readable symbol representing encoded information, the symbol including a plurality of selectively spaced two-dimensional geometric shapes, the shapes and spaces between the shapes having at least a first width in at least one dimension, the symbol having a predetermined orientation pattern of convexly curved shapes and spaces between the convexly curved shapes, the convexly curved shapes at least partially surrounding a predetermined point of the symbol, the method comprising the steps of:
- storing an image of the symbol;
locating all curved shapes within the stored image of the symbol, including the convexly curved shapes of the predetermined orientation pattern;
determining a pair of tangent lines from endpoints of each located curved shape;
defining a line between each pair of tangent lines;
determining at least one point of intersection of the defined lines;
locating the predetermined point of the symbol based on the at least one point of intersection of the defined lines; and
decoding the information encoded in the symbol based on the located predetermined point of the symbol.
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Abstract
A method and apparatus for locating and decoding machine-readable symbols is provided. The present invention stores an image of the symbol and locates all Jordan curves having an angular length less than π within the image of the symbol. The present invention finds and selects all convex Jordan curves from the set of all Jordan curves found within the stored image. The present invention determines equations of a pair of tangent lines from end points of each convex Jordan curve and determines an equation of a center line for each pair of tangent lines. The present invention determines a point of intersection of the center lines, and based on the point of intersection, locates a center point of a finder pattern of the symbol. The present invention confirms that the located center point is indeed the center of the finder pattern, and thereafter decodes the symbol.
187 Citations
23 Claims
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1. A method of locating and decoding a machine-readable symbol representing encoded information, the symbol including a plurality of selectively spaced two-dimensional geometric shapes, the shapes and spaces between the shapes having at least a first width in at least one dimension, the symbol having a predetermined orientation pattern of convexly curved shapes and spaces between the convexly curved shapes, the convexly curved shapes at least partially surrounding a predetermined point of the symbol, the method comprising the steps of:
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storing an image of the symbol; locating all curved shapes within the stored image of the symbol, including the convexly curved shapes of the predetermined orientation pattern; determining a pair of tangent lines from endpoints of each located curved shape; defining a line between each pair of tangent lines; determining at least one point of intersection of the defined lines; locating the predetermined point of the symbol based on the at least one point of intersection of the defined lines; and decoding the information encoded in the symbol based on the located predetermined point of the symbol. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. In a computer system having a processor and a data storage device, a computer implemented method of locating a predetermined pattern of convexly curved shapes and spaces between the convexly curved shapes within an image stored in the data storage device, the convexly curved shapes at least partially surrounding a preselected point, the method comprising the steps of:
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locating all curved shapes within the stored image, including the convexly curved shapes of the predetermined pattern; determining a pair of tangent lines from endpoints of each located curved shape; defining a line between each pair of tangent lines; determining at least one point of intersection of the defined lines; and locating the preselected point based on the at least one point of intersection of the defined lines. - View Dependent Claims (15, 16, 17, 18)
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19. An apparatus for decoding a machine-readable symbol representing encoded information, the machine-readable symbol including a plurality of spaced two-dimensional shapes, the symbol having a predetermined orientation pattern of convexly curved shapes and spaces between the convexly curved shapes, the convexly curved shapes at least partially surrounding a predetermined point of the symbol, the apparatus comprising:
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a sensor that receives light that is reflected from the symbol and produces an output signal therefrom that represents the reflectance of the shapes and spaces comprising the symbol; a receiver that receives the output signal and produces a digital signal representing an image of the shapes and spaces of the symbol; a storage device for storing the digital signal; and a processor for processing the digital signal and producing a signal indicative of the information encoded in the symbol, the processor (a) locating all curved shapes within the stored digital signal, (b) determining a pair of tangent lines from endpoints of each located curved shape, (c) defining a line between each pair of tangent lines, (d) determining at least one point of intersection of the defined lines, (e) locating the predetermined point based on the at least one point of intersection of the defined lines, and (f) decoding the symbol and producing a signal indicative of the information encoded in the symbol based on the located predetermined point of the symbol. - View Dependent Claims (20, 21, 22, 23)
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Specification