Bar code error scanner

• US 5,767,498 A
• Filed: 09/17/1996
• Issued: 06/16/1998
• Est. Priority Date: 09/17/1996
• Status: Expired due to Term

• Current Assignee: NCR Corporation (NCR Voyix Corporation)
• Original Assignee: NCR Corporation (NCR Voyix Corporation)
• Inventors: Mergenthaler, Barry M., Heske, Theodore III, Blanford, Denis M.
• Primary Examiner(s): PITTS, HAROLD I
• Application Number:
  US08/718,620
• Time in Patent Office: 637 Days
• Field of Search: 235/462, 235/463, 235/494
• US Class Current: 235/462.16
• CPC Class Codes: G06K 7/14 using light without selection of wavelength, e.g. sensing reflected white light G06K7/10831 - G06K7/1097 take precedence
• CPC Class Codes: G06K 7/1486 Setting the threshold-width for bar codes to be decoded

Abstract

A method and apparatus are disclosed for scanning for a defective bar code having a plurality of alternating bars and spaces of varying widths. A bar code is scanned for providing a bar code signature which is used for measuring the bar and space width as multiples of a minimum width module. By detecting fractional width of adjoining bars and spaces, error in the bar code is correspondingly detected. The measured bar code signature may be corrected by respectively increasing and decreasing the fractional width of an adjoining bar and space for obtaining substantially integer multiple modules thereof. The corrected signature may then be decoded.

Claims

1. A method of scanning a bar code having a plurality of alternating bars and spaces of varying widths comprising:

scanning said bar code sequentially across said bars and spaces for providing a bar code signature;

measuring said bar and space widths in said signature as multiples of a minimum width module; and

detecting a fractional width in adjoining ones of said bars and spaces for detecting error in said bar code.

2. A method according to claim 1 further comprising detecting said fractional width in one of said spaces.

3. A method according to claim 2 wherein said bars and spaces are arranged in a plurality of groups defining respective characters of equal width, and further comprising detecting one of said groups containing said fractional width space.

4. A method according to claim 3 further comprising detecting said fractional width in said space being greater than or less than a single module.

5. A method according to claim 4 further comprising detecting said fractional width of said space being greater than said single module for indicating a first error type defined by an omitted boundary portion at one side of said adjoining bar.

6. A method according to claim 4 further comprising detecting said fractional width of said space being less than said single module for indicating a second error type defined by an omitted interior portion of one of said bars.

7. A method according to claim 5 further comprising:

correcting said detected fractional width of said adjoining bar and space by respectively increasing and decreasing thereof for obtaining substantially integer multiple modules thereof; and

decoding said corrected bar code signature.

8. A method according to claim 7 further comprising:

accumulating said bar code errors in an error log over a plurality of said scans;

detecting said bar code error in a subsequent scan;

comparing said detected bar code error with said log; and

correcting said bar code error in said subsequent scan.

9. A method according to claim 8 wherein said log comprises a linear sequence of registers corresponding with respective locations along a total width of said bar code, with each register indicating the existence of said bar code error at said location associated therewith.

10. A method according to claim 9 further comprising a plurality of said registers corresponding with each of said modules defining said bar code.

11. A method according to claim 10 further comprising:

a plurality of said error logs;

comparing said detected bar code error with each of said logs; and

correcting said bar code error upon matching thereof with a corresponding one of said logs.

12. A scanner for scanning a bar code having a plurality of alternating bars and spaces of varying widths comprising:

means for scanning said bar code sequentially across said bars and spaces for providing a bar code signature;

means for measuring said bar and space widths in said signature as multiples of a minimum width module; and

means for detecting a fractional width in adjoining ones of said bars and spaces for detecting error in said bar code.

13. A scanner according to claim 12 wherein said detecting means is effective for detecting said fractional width in one of said spaces.

14. A scanner according to claim 13 wherein said bars and spaces are arranged in a plurality of groups defining respective characters of equal width, and said detecting means is further effective for detecting one of said groups containing said fractional width space.

15. A scanner according to claim 14 wherein said detecting means is further effective for detecting said fractional width in said space being greater than or less than a single module.

16. A scanner according to claim 15 wherein said detecting means is further effective for detecting said fractional width of said space being greater than said single module for indicating a first error type defined by an omitted boundary portion at one side of said adjoining bar.

17. A scanner according to claim 16 wherein said detecting means is further effective for detecting said fractional width of said space being less than said single module for indicating a second error type defined by an omitted interior portion of said adjoining bar.

18. A scanner according to claim 16 further comprising:

means for correcting said detected fractional width of said adjoining bar and space by respectively increasing and decreasing width thereof in said signature for obtaining substantially integer multiple modules; and

means for decoding said corrected bar code signature.

19. A scanner according to claim 16 further comprising:

an error log for accumulating said bar code errors over a plurality of said scans;

means for detecting said bar code error in a subsequent scan;

means for comparing said detected bar code error with said log; and

means for correcting said bar code error in said subsequent scan.

20. A scanner according to claim 19 wherein said error log comprises a linear sequence of registers corresponding with respective locations along a total width of said bar code, with each register indicating existence of said bar code error at said location associated therewith.

21. A scanner according to claim 20 further comprising a plurality of said registers corresponding with each of said modules defining said bar code.

22. A scanner according to claim 21 further comprising:

a plurality of said error logs; and

wherein said comparing means is effective for comparing said detected bar code error with each of said logs, and said correcting means is effective for correcting said bar code error upon matching thereof with a corresponding one of said logs.