Scanning device for reconstructing a complete code from scanned segments

• US 5,296,691 A
• Filed: 09/14/1992
• Issued: 03/22/1994
• Est. Priority Date: 09/14/1992
• Status: Expired due to Term

• Current Assignee: SICK Incorporated (Sick)
• Original Assignee: LazerData Corp (Datalogic ADC Incorporated)
• Inventors: Nordstrom, Larry A., Waldron, James R., Kenney, Daniel A.
• Primary Examiner(s): PITTS, HAROLD I
• Application Number:
  US07/944,506
• Time in Patent Office: 554 Days
• Field of Search: 235/462, 235/467, 235/472, 235/463
• US Class Current: 235/462.12
• CPC Class Codes: G06K 7/10861 sensing of data fields affixed to objects or articles, e.g. coded labels postal sorting B07C3/14, conveying articles B65G47/48
• 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 7/1491 the method including a reconstruction step, e.g. stitching two pieces of bar code together to derive the full bar code

Abstract

This invention features a device and method for reading machine readable code, having a plurality of code elements, on an object. The device includes a scanning apparatus, a signal processor and a data processor. The scanning apparatus successively scans the code and outputs a signal representative of at least a portion of the code, for each successive scan of the code. The signal processor processes each of the signals outputted by the scanning apparatus and further provides signal identification data, including a width and position associated with each of the outputted signals, for each successive scan of the code. The data processor reconstructs the code from the signal identification data for each successive scan of the code, provided by the signal processor. The data processor reconstructs the code by both determining the position of a selected code element for a successive scan and by positionally aligning the selected code element with the corresponding element from a prior scan. In a preferred embodiment, the device of the present invention can simultaneously read and decode a plurality of bar codes affixed to an item which approaches the scan line of the device at any orientation.

Claims

1. A device for reading machine readable code, having a plurality of code elements, comprising:

scanning means for successively scanning the code and for outputting a signal representative of at least a portion of the code, for each successive scan of the code;

signal processing means for processing each of said signals outputted by said scanning means, said signal processing means further providing signal identification data, including a width and position associated with each of said signals, for each successive scan of the code; and

data processing means for reconstructing the code from said signal identification data for each successive scan of the code provided by said signal processing means,

said data processing means including position aligning means, said position aligning means comprising means for selecting an element in a previous scan,

calculating the position of that element in a successive scan based upon a calculated offset, said calculated offset determined by an offset calculating means which calculates the difference in position of features in previous scans, and

aligning said successive scan with said previous scan by means of said calculated offset by placing said selected element in said successive scan in alignment with said selected element in said previous scan.

2. The device for reading machine readable code of claim 1, in which said data processing means further comprises means for both combining and accumulating said signal identification data.

3. The device for reading machine readable code of claim 2, in which said offset calculating means further comprises a first offset calculating means for calculating a positional difference between the position of a selected code element in a first scan of a code, from said combining and accumulating means, and the position of the selected code element in a second scan of the code to provide said calculated offset for determining the expected position of the selected code element in the successive scan.

4. The device for reading machine readable code of claim 3, in which said offset calculating means further comprises:

a second offset calculating means for calculating a positional difference between the position of a selected code element from a previous scan from said combining and accumulating means and the position of said selected code element from a successive scan to provide said calculated offset for determining the expected position of the selected code element in the successive scan.

5. The device for reading machine readable code of claim 4, in which said position aligning means further comprises means for locating a code element in a scan which most closely matches the expected position of the selected code element in said scan by means of said calculated offset determined by said first offset calculating means, said second offset calculating means or said offset averaging means.

6. The device for reading machine readable code of claim 5, in which said data processing means further comprises means for determining the number of scans a code element has been seen in.

7. The device for reading machine readable code of claim 6, wherein the code element, from said combining and accumulating means, selected by said position aligning means is a code element which has been seen in at least two scans.

8. The device for reading machine readable code of claim 5, in which said data processing means further comprises:

means for positionally aligning said signal identification data in said combining and accumulating means with the signal identification data of a successive scan by means of said calculated offset by placing said selected element in said successive scan in alignment with said selected element in said previous scan;

means for identifying width mismatches between aligned signal identification data, where said combining and accumulating means cooperates with said mismatch identifying means such that mismatched signal identification data is not combined and accumulated; and

means for retaining said signal identification data, from said signal processing means, identified as having width mismatches.

9. The device for reading machine readable code of claim 8, in which said data processing means further comprises means for resolving identified width mismatches, identified by said mismatch identifying means, by comparing width data from three scans of signal identification data.

10. The device for reading machine readable code of claim 9, wherein said mismatch resolving means compares the width data for corresponding code elements in the first scan with width data from the third scan to determine if the corresponding widths are consistent and compares the width data for corresponding code elements in the second and third scans to determine if the corresponding widths are consistent.

11. The device for reading machine readable code of claim 10, in which said mismatch resolving means further comprises means for indicating that the signal identification data for the scans having consistent widths is to be combined in the combining and accumulating means and that signal identification data for the other scan is to be ignored.

12. The device for reading machine readable code of claim 9, in which said data processing means further comprises:

scan direction means for determining the direction of a scan; and

data reversing means, responsive to said scan direction means, for reversing the signal identification data for each code element in each scan for a bar code such that the signal identification data for all scans of the bar code is maintained in a predetermined direction.

13. The device for reading machine readable code of claim 12, in which said data processing means further comprises:

means for identifying a first area for which signal identification data is to be accumulated; and

means for identifying a second area for which signal identification data is not to be accumulated.

14. The device for reading machine readable code of claim 13, in which said data processing means further comprises a first means for comparing the signal identification data for each scan, from said signal processing means, to determine if the signal identification data overlaps said first area.

15. The device for reading machine readable code of claim 13, in which said data processing means further comprises a second means for comparing the signal identification data for each scan, from said signal processing means, to determine if the data overlaps said second area.

16. The device for reading machine readable code of claim 15, wherein said means for identifying a second area identifies areas containing machine readable code that is not to be decoded.

17. The device for reading machine readable code having a plurality of code elements of claim 16, wherein the code elements comprise a plurality of intervals including bars and spaces of either narrow or wide interval widths and in which said data processing means further comprises:

means for measuring the interval widths of said signal identification data, from said combining and accumulating means, and for normalizing the interval widths to 1,2,3, and 4 wide bars and spaces to provide a reconstructed bar code; and

means for decoding the reconstructed bar code to provide the encoded information.

18. The device for reading machine readable code of claim 1, in which said scanning means further includes at least one light source and sensing means for successively illuminating a bar code with a predetermined pattern of light and successively sensing light reflected from the bar code.

19. The device for reading machine readable code of claim 1, in which said scanning means further includes a plurality of light source and sensing means for successively illuminating a bar code with a predetermined pattern of light and successively sensing light reflected from the bar code.

20. The device for reading machine readable code of claim 18, in which said light source and sensing means further includes a coherent light source.

21. The device for reading machine readable code of claim 20, in which said scanning means further includes a light directing means for directing the light from said coherent light source to create the predetermined pattern of light.

39. The device according to claim 4 in which said position aligning means further comprises an offset averaging means for averaging said calculated offsets for previous scans with the calculated offset determined by said second offset calculating means to provide a refined calculated offset for determining the expected position of the selected code element in the successive scan.

22. A method for reading machine readable code, having a plurality of code elements, comprising the steps of:

successively scanning the code to provide a signal representative of at least a portion of the code, for each successive scan of the code;

successively processing each signal representative of at least a portion of the code to provide signal identification data, including a width and position associated with each of said signals, for each successive scan of the code; and

reconstructing the code from signal identification data for each successive scan of the code, said reconstructing including the steps of;

selecting an element in a previous scan;

calculating the position of said element in a successive scan based upon a calculated offset, said calculated offset determined by the step of;

calculating the difference in position of features in previous scans; and

aligning said successive scan with said previous scan by means of said calculated offset by the step of;

placing said selected element in said successive scan in alignment with said selected element in said previous scan.

23. The method for reading machine readable code of claim 22, further comprising the steps of combining and accumulating said signal identification data.

24. The method for reading machine readable code of claim 23, in which said step of calculating the position further comprises the step of:

calculating a first positional difference between the position of a selected code element in a first scan of a code, from sad step of combining and accumulating, and the position of said selected code element in a second scan of the code to provide said calculated offset for determining the expected position of the selected code element in the successive scan.

25. The method for reading machine readable code of claim 24, in which said step of calculating the position of a selected code element further comprises the step of:

calculating a second positional difference between the position of a selected code element from a previous scan, from said step of combining and accumulating, and the position of said selected code element from a successive scan to provide said calculated offset for determining the expected position of the selected code element in the successive scan.

26. The method for reading machine readable code of claim 25, in which said reconstructing further comprises the step of:

locating a code element in a scan which most closely matched the expected position of the selected code element in said scan by means of said first positional difference, said second positional difference or said refined calculated offset.

27. The method for reading machine readable code of claim 26, in which said reconstructing further comprises the step of determining the number of scans a code element has been seen in.

28. The method for reading machine readable code of claim 27, in which said step of selecting further comprises the step of selecting a code element, from said combining and accumulating means, which has been seen in at least two scans.

29. The method for reading machine readable code of claim 26, in which said reconstructing further comprises the steps of:

positionally aligning said signal identification data in said step of combining and accumulating with the signal identification data of a successive scan by means of said calculated offset by placing said selected element in said successive scan in alignment with said selected element in said previous scan;

identifying mismatches of code element widths between aligned signal identification data, where said step of combining and accumulating cooperates with said identifying mismatches such that mismatched signal identification data is not combined and accumulated; and

retaining said signal identification data which has been identified, from said identifying mismatches, as having width mismatches.

30. The method for reading machine readable code of claim 29, in which said reconstructing further comprises the step of resolving identified width mismatches from said identifying mismatches identifying means, by comparing width data from three scans of signal identification data.

31. The method for reading machine readable code of claim 30, wherein said resolving mismatches further compares the width data for corresponding code elements in the first scan with width data from the third scan to determine if the corresponding widths are consistent and compares the width data for corresponding code elements in the second and third scans to determine if the corresponding widths are consistent.

32. The method for reading machine readable code of claim 31, in which said resolving mismatches further comprises the step of indicating that the signal identification data for the scans having consistent widths is to be combined in the combining and accumulating means and that signal identification data for the other scan is to be ignored.

33. The method for reading machine readable code of claim 30, in which said reconstructing further comprises the steps of:

determining the direction of a scan; and

reversing the signal identification data for each code element in each scan for a bar code in response to said determining the scan direction, such that the signal identification data for all scans of the bar code is maintained in a predetermined direction.

34. The method for reading machine readable code of claim 33, in which said reconstructing further comprises the steps of:

identifying a first area for which signal identification data is to be accumulated; and

identifying a second area for which signal identification data is not to be accumulated.

40. The method according to claim 25 in which said step of selecting and aligning further comprises the step of:

averaging said calculated offsets for previous scans with the calculated offset from said step of calculating a positional difference to provide a refined calculated offset for determining the expected position of the selected code element in the successive scan.

35. The method for reading machine readable code of claim 35, in which said reconstructing further comprises the step of comparing the first area with the signal identification data for each scan, from said signal processing, to determine if the signal identification data overlaps said first area.

36. The method for reading machine readable code of claim 35, in which said reconstructing further comprises the step of comparing the second area with the signal identification data for each scan, from said signal processing, to determine if the data overlaps said second area.

37. The device for reading machine readable code of claim 36, wherein said identifying a second area further identifies areas containing machine readable code that is not to be decoded.

38. The method for reading machine readable code having a plurality of code elements of claim 37, wherein the code elements comprise a plurality of intervals including bars and spaces of either narrow or wide interval widths and in which said reconstructing further comprises the steps of:

measuring the interval widths of said signal identification data, from said combining and accumulating means;

normalizing the interval widths from said measuring to 1,2,3, and 4 wide bars and spaces to provide a reconstructed bar code; and

decoding the reconstructed bar code to provide the encoded information.