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Method and apparatus for decoding unresolved complex multi-width bar code symbology profiles

  • US 5,514,858 A
  • Filed: 02/10/1995
  • Issued: 05/07/1996
  • Est. Priority Date: 02/10/1995
  • Status: Expired due to Term
First Claim
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1. A method of decoding a bar code symbol representing encoded information, the bar code symbol including a plurality of relatively spaced bars having at least first, second and third widths, and spaces between the bars having at least first, second and third widths, the second and third widths being greater than the first width, the method comprising the steps of:

  • receiving light reflected from the bar code symbol and producing an output signal therefrom that represents the reflectance of the bars and spaces comprising the bar code symbol;

    receiving the output signal and producing a wide feature signal resolving the bars and spaces having the second and third widths, but the wide feature signal having unresolved portions that fail to resolve at least some of the bars and spaces having the first width;

    receiving the wide feature signal and determining which of the bars and spaces are resolved by defining a first threshold and identifying a plurality of resolved portions in the wide feature signal that extend beyond the first threshold, each of the plurality of resolved portions corresponding to one of the resolved bars and spaces;

    determining an environment for each of the plurality of resolved portions based on whether a selected resolved portion is between two other of the plurality of resolved portions, between two unresolved portions, or between a resolved and an unresolved portion in the wide feature signal;

    defining at least a second threshold;

    measuring a width for each of the plurality of portions at one of the first and second thresholds depending upon the environment of the selected resolved portion;

    determining a narrow width of the bars and spaces having the first width based on the measured widths;

    determining a number and location of the bars and spaces having the first width based on the determined narrow width and the measured widths; and

    determining the information encoded in the bar code symbol based on the determined number and location of bars and spaces having the first width and the measured width for each of the plurality of portions.

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