Method and apparatus for decoding two-dimensional bar code using CCD/CMD camera
AssigneeSymbol Technologies, Inc.
InventorsStephen J. Shellhammer, Ming-Hua Chen, Arman Nikzad
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Abstract
A method and apparatus for decoding a two-dimensional bar code symbol using a charge-coupled device (CCD) camera or a charge-modulation device (CMD) camera. The CCD/CMD camera takes pictures of the symbol and the picture is converted into digital data. The location and orientation of the two-dimensional bar code symbol is determined and verified. Defects and damages on the symbol are detected and corrected. The symbol is scanned to read the codewords of the two-dimensional bar code symbol.
Claims46
A method for decoding a two-dimensional bar code symbol having rows of bar coded information in which data is represented in each row by a plurality of codewords, each row including a predetermined control codeword which is the same for each row, the codewords being formed of a plurality of modules, the method comprising the steps of:
- optically imaging the two-dimensional bar code symbol, converting the image to lines of image data corresponding to a field of view including the bar code symbol, and storing the image data in a memory;
- determining an orientation of the two-dimensional bar code symbol in the field of view by locating the positions of at least two of the control codewords in the image data;
- determining a sequence of lines passing through the rows of the bar code symbol in the image data from the orientation derived from the positions of the control codewords;
- and
- scanning the two-dimensional bar code symbol in the image data along the sequence of lines to read the codewords.
An apparatus for decoding a two-dimensional bar code symbol having rows of bar coded information in which data is represented in each row by a plurality of codewords, each row including a predetermined control codeword, the codewords being formed of a plurality of modules, comprising:
- means for optically imaging the two-dimensional bar code symbol, converting the image to lines of image data corresponding to a field of view including the bar code symbol, and storing the image data in a memory;
- means for determining an orientation of the two-dimensional bar code symbol in the field of view by locating the positions of at least two of the control codewords in the image data;
- and
- means for determining a sequence of lines passing through the rows of the bar code symbol in the image data from the orientation derived from the positions of the control codewords;
- and
- means for scanning the two-dimensional bar code symbol in the image data along the sequence of lines line to read the codewords.
Dependencies are inferred from the claim text.