Two-dimensional code reading apparatus

• US 6,000,614 A
• Filed: 12/22/1997
• Issued: 12/14/1999
• Est. Priority Date: 12/20/1996
• Status: Expired due to Term

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Hara, Masahiro, Yang, Xuhua
• Primary Examiner(s): Lee, Michael G.
• Assistant Examiner(s): Lee, Diane I.
• Application Number:
  US08/996,345
• Time in Patent Office: 722 Days
• Field of Search: 235/460, 235/462.08, 235/462.09, 235/462.1, 235/462.11, 235/494, 235/456
• US Class Current: 235/460
• 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 7/1473 error correction

Abstract

A two-dimensional code reading apparatus uses the image of a reference pattern of a known shape in the two-dimensional code to compute areas, shapes and positions of cells in the image of the two-dimensional code and corrects these computed values using correction values obtained by identifying cells isolated from cells of the same type in at least one direction whenever they appear and extracting their actual boundary coordinates directly from the image data. As a result, even if there is distortion in the image of the two-dimensional a reading scope for each cell to be read is set to a suitable area and the reading position of each cell is determined accurately in correspondence with the distortion and the content of the two-dimensional code is thereby read correctly.

Claims

1. A two-dimensional code reading apparatus for reading a two-dimensional code wherein binary code data is expressed as a pattern of black and white cells in a two-dimensional matrix, comprising:

a two-dimensional image detecting device for detecting a two-dimensional image of said two-dimensional code;

a reference position determining device for determining a reference position where each cell constituting a pattern of a predetermined shape lies in said two-dimensional image detected by said two-dimensional image detecting device on the basis of a pattern of said pattern having said predetermined shape;

a cell size determining device for determining a size of a cell in said two-dimensional code from said pattern of said pattern said predetermined shape;

a cell position calculating device for calculating a position of each of cells from said reference position determined by said reference position determining device on the basis of said cell size determined by said cell size determining device;

a cell reading device for determining a type of a cell at a cell position calculated by said cell position calculating device;

an isolated cell distinguishing device for distinguishing whether or not a cell of which type has been determined is an isolated cell;

an actual position determining device for determining an actual position of the isolated cell on the basis of the two-dimensional image of the isolated cell, when said isolated cell distinguishing device distinguishes that the cell is the isolated cell;

a cell position correction value calculating device for calculating a correction value for correcting a calculated cell position from a difference between said calculated position and said actual position of said isolated cell; and

a cell position correcting device for correcting said cell position calculated by said cell position calculating device by using said correction value calculated by said cell position correction value calculating device.

2. A two-dimensional code reading apparatus according to claim 1, wherein said isolated cell a cell sandwiched in an x-direction or a y-direction between cells of an opposite type.

3. A two-dimensional code reading apparatus according to claim 1, wherein said isolated cell a cell sandwiched in an x-direction and a y-direction between cells of an opposite type.

4. A two-dimensional code reading apparatus according to claim 1, wherein said pattern of said predetermined shape includes a position detection pattern consisting of a pattern from which the same frequency component ratios can be obtained with a scan line crossing a center of said pattern irrespective of an angle of said scan line, said position detection pattern being disposed in each of at least two predetermined positions in said two-dimensional code.

5. A two-dimensional code reading apparatus according to claim 4, wherein said pattern of said predetermined shape includes rows of timing cells running between said position detection patterns, wherein cells of opposite types are disposed alternately.

6. A two-dimensional code reading apparatus according to claim 4, wherein said position detection patterns exist at three of corners of a matrix of said two-dimensional code and said cell position determining device determines cell positions starting from cells around the position detection pattern having other position detection patterns on either side of it.

7. A two-dimensional code reading apparatus according to claim 1, further comprising a storing medium which stores a computer program for realizing functions of a plurality of devices.

8. A two-dimensional code reading apparatus according to claim 1, further comprising:

a reading control device for when a content of a cell is to be read from said two-dimensional image adjusting a size of a reading scope from which the content of the cell is to be read with respect to a cell size obtained by said cell size determining device according to a distance of the cell from said pattern;

wherein said cell reading device reads a content of a cell in said reading scope adjusted by said reading control device.

9. A two-dimensional code reading apparatus according to claim 8, wherein said reading scope adjusted by the reading control device is set smaller than said cell size obtained by said cell size determining device.

10. A two-dimensional code reading apparatus according to claim 8, wherein said cell reading device reads for each pixel included in said reading scope whether a type of a pixel is black or white, and a type of pixels constituting a majority of all the pixels included in said reading scope is determined to be a type of a cell.

11. A two-dimensional code reading apparatus according to claim 8, wherein said cell reading device reads for pixels located at predetermined positions in said reading scope whether a type of a pixel is black or white, and determines a type of a cell on the basis of a difference between a number of white pixels and a number of black pixels.

12. A two-dimensional code reading apparatus according to claim 8, wherein said pattern of a predetermined shape includes a plurality of patterns located at different positions, said cell size determining device determines a plurality of cell sizes in said two-dimensional image on the basis of each of said plurality of patterns, and said reading control device adjusts said reading scope on the basis of distances of the cell from each of said plurality of patterns and said plurality of cell sizes determined from each of said plurality of patterns.

13. A two-dimensional code reading apparatus according to claim 1, further comprising:

a cell grouping device for grouping cells of said two-dimensional code in said two-dimensional image with a position of said pattern as a reference; and

a reading control device for when cells are to be read from said two-dimensional image adjusting for each group of cells formed by said cell grouping device a size of a reading scope from which a content of each of the cells in a group is to be read with respect to a cell size determined by said cell size determining device;

wherein said cell reading device reads a content of the cell in said reading scope adjusted group by group by said reading control device.

14. A two-dimensional code reading apparatus according to claim 13, wherein said reading scope adjusted by the reading control device is set smaller than said cell size determined by said cell size determining device.

15. A two-dimensional code reading apparatus according to claim 13, wherein said cell reading device reads for each pixel included in said reading scope whether a type of a pixel is black or white, and a type of pixels constituting a majority of all the pixels included in said reading scope is determined to be a type of a cell.

16. A two-dimensional code reading apparatus according to claim 13, wherein said cell reading device reads for pixels located at predetermined positions in said reading scope whether a type of a pixel is black or white, and determines a type of a cell on the basis of a difference between a number of white pixels and a number of black pixels.

17. A two-dimensional code reading apparatus according to claim 13, wherein said pattern of a predetermined shape includes a plurality of patterns located at different positions, said cell size determining device determines a plurality of cell sizes in said two-dimensional image on the basis of each of said plurality of patterns, and said reading control device adjusts for each group of cells said reading scope so that said reading scope for cells in a group is determined on the basis of said cell size determined from said pattern belonging to said group.

18. A two-dimensional code reading apparatus according to claim 1, further comprising:

a reading control device for when a content of a cell is to be read from said two-dimensional image adjusting a shape of a reading scope from which the content of the cell is to be read with respect to a cell size determined by said cell size determining device according to a distance of the cell from said pattern,

wherein said cell reading device reads the content of the cell from said reading scope adjusted by said reading control device.

19. A two-dimensional code reading apparatus according to claim 18, wherein said reading scope adjusted by the reading control device is set smaller than said cell size determined by said cell size determining device.

20. A two-dimensional code reading apparatus according to claim 18, wherein said cell reading device reads for each pixel included in said reading scope whether a type of a pixel is black or white, and a type of pixels constituting a majority of all the pixels included in said reading scope is determined to be a type of a cell.

21. A two-dimensional code reading apparatus according to claim 18, wherein said cell reading device reads for pixels located at predetermined positions in said reading scope whether a type of a pixel is black or white, and determines a type of a cell on the basis of a difference between a number of white pixels and a number of black pixels.

22. A two-dimensional code reading apparatus according to claim 18, wherein said pattern of a predetermined shape includes a plurality of patterns located at different positions, said cell size determining device determines a plurality of cell sizes in said two-dimensional image on the basis of each of said plurality of patterns, and said reading control device adjusts said reading scope on the basis of distances of the cell from each of said plurality of patterns and said plurality of cell sizes calculated from each of said plurality of patterns.

23. A two-dimensional code reading apparatus according to claim 18, wherein said cell shape is specified by its width, its height, and angles at four corners of said cell.

24. A two-dimensional code reading apparatus according to claim 1, further comprising:

a cell grouping device for grouping cells of said two-dimensional code in said two-dimensional image with a position of said pattern as a reference; and

a reading control device for when contents of cells are to be read from said two-dimensional image adjusting for each group of cells formed by said cell grouping device a shape of a reading scope from which the content of each of the cells in a group is to be read with respect to a cell size determined by said cell size determining device;

wherein said cell reading device reads the content of the cell from said reading scope adjusted group by group by said reading control device.

25. A two-dimensional code reading apparatus according to claim 24, wherein said reading scope adjusted by the reading control device is set smaller than said cell size determined by said cell size determining device.

26. A two-dimensional code reading apparatus according to claim 24, wherein said cell reading device reads for each pixel included in said reading scope whether a type of a pixel is black or white, and a type of pixels constituting a majority of all the pixels included in said reading scope is determined to be a type of a cell.

27. A two-dimensional code reading apparatus according to claim 24, wherein said cell reading device reads for pixels located at predetermined positions in said reading scope whether a type of a pixel is black or white, and determines a type of a cell on the basis of a difference between a number of white pixels and a number of black pixels.

28. A two-dimensional code reading apparatus according to claim 24, wherein said pattern of a predetermined shape includes a plurality of patterns located at different positions, said cell size determining device determines a plurality of cell sizes in said two-dimensional image on the basis of each of said plurality of patterns, and said reading control device adjusts for each group of cells said reading scope so that said reading scope for cells in a group is determined on the basis of said cell shape calculated from said reference pattern belonging to said group.

29. A two-dimensional code reading apparatus according to claim 24, wherein said cell shape is specified by its width, its height, and angles at four corners of said cell.

30. A two-dimensional code reading apparatus for reading a two-dimensional code wherein binary code data is expressed as a pattern of black and white cells in a two-dimensional matrix, comprising:

a two-dimensional image detecting device for detecting a two-dimensional image of said two-dimensional code;

a reference pattern detecting device for detecting a reference pattern of a predetermined shape existing in said two-dimensional image of said two-dimensional code detected by said two-dimensional image detecting device;

a cell shape calculating device for obtaining an area of a cell of said two-dimensional code in said two-dimensional image on the basis of said reference pattern detected by said reference pattern detecting device;

a reading control device for when a content of a cell is to be read from said two-dimensional image adjusting a size of a reading scope from which the content of the cell is to be read with respect to a cell area obtained by said cell shape calculating device according to a distance of the cell from said reference pattern; and

a cell reading device for reading a content of a cell from said reading scope adjusted by said reading control device at a position of each cell of said two-dimensional image.

31. A two-dimensional code reading apparatus according to claim 30, wherein said reading scope adjusted by the reading control device is set smaller than said cell area obtained by said cell shape calculating device.

32. A two-dimensional code reading apparatus according to claim 30, wherein said cell reading device reads for each pixel included in said reading scope whether a type of a pixel is black or white, and a type of pixels constituting a majority of all the pixels included in said reading scope is determined to be a type of a cell.

33. A two-dimensional code reading apparatus according to claim 30, wherein said cell reading device reads for pixels located at predetermined positions in said reading scope whether a type of a pixel is black or white, and determines a type of a cell on the basis of a difference between a number of white pixels and a number of black pixels.

34. A two-dimensional code reading apparatus according to claim 30, wherein said reference pattern of a predetermined shape includes a plurality of reference patterns located at different positions, said cell shape calculating device calculates a plurality of cell areas in said two-dimensional image on the basis of each of said plurality of reference patterns, and said reading control device adjusts said reading scope on the basis of distances of the cell from each of said plurality of reference patterns and said plurality of cell areas calculated from each of said plurality of reference patterns.

35. A two-dimensional code reading apparatus according to claim 30, further comprising:

a storing medium which stores a computer program for realizing functions of a plurality of devices.

36. A two-dimensional code reading apparatus for reading a two-dimensional code wherein binary code data is expressed as a pattern of black and white cells in a two-dimensional matrix, comprising:

a two-dimensional image detecting device for detecting a two-dimensional image of said two-dimensional code;

a reference pattern detecting device for detecting a reference pattern of a predetermined shape existing in said two-dimensional image detected by said two-dimensional image detecting device;

a cell shape calculating device for obtaining an area of a cell of said two-dimensional code in said two-dimensional image on the basis of said reference pattern detected by said reference pattern detecting device;

a cell grouping device for grouping cells of said two-dimensional code in said two-dimensional image with a position of said reference pattern detected by said reference pattern detecting device as a reference;

a reading control device for when cells are to be read from said two-dimensional image adjusting for each group of cells formed by said cell grouping device a size of a reading scope from which a content of each of the cells in a group is to be read with respect to a cell area obtained by said cell shape calculating device; and

a cell reading device for reading a content of the cell with said reading scope adjusted group by said reading control device at a position of each cell of said two-dimensional image.

37. A two-dimensional code reading apparatus according to claim 36, wherein said reading scope adjusted by the reading control device is set smaller than said cell area obtained by said cell shape calculating device.

38. A two-dimensional code reading apparatus according to claim 36, wherein said cell reading device reads for each pixel included in said reading scope whether a type of a pixel is black or white, and a type of pixels constituting a majority of all the pixels included in said reading scope is determined to be a type of a cell.

39. A two-dimensional code reading apparatus according to claim 36, wherein said cell reading device reads for pixels located at predetermined positions in said reading scope whether a type of a pixel is black or white, and determines a type of a cell on the basis of a difference between a number of white pixels and a number of black pixels.

40. A two-dimensional code reading apparatus according to claim 36, wherein said reference pattern of a predetermined shape includes a plurality of reference patterns located at different positions, said cell shape calculating device calculates a plurality of cell areas in said two-dimensional image on the basis of each of said plurality of reference patterns, and said reading control device adjusts for each group of cells said reading scope so that said reading scope for cells in a group is determined on the basis of said cell area calculated from said reference pattern belonging to said group.

41. A two-dimensional code reading apparatus according to claim 36, further comprising:

a storing medium which stores a computer program for realizing functions of a plurality of devices.

42. A two-dimensional code reading apparatus for reading a two-dimensional code wherein binary code data is expressed as a pattern of black and white cells in a two-dimensional matrix, comprising:

a two-dimensional image detecting device for detecting a two-dimensional image of said two-dimensional code;

a reference pattern detecting device for detecting a reference pattern of a predetermined shape existing in said two-dimensional image detected by said two-dimensional image detecting device;

a cell shape calculating device for obtaining a shape of a cell of said two-dimensional code in said two-dimensional image on the basis of said reference pattern detected by said reference pattern detecting device;

a reading control device for when a content of a cell is to be read from said two-dimensional image adjusting a shape of a reading scope from which the content of the cell is to be read with respect to a cell shape obtained by said cell shape calculating device according to a distance of the cell from said reference pattern; and

a cell reading device for reading the content of the cell from said reading scope adjusted by said reading control device at a position of each cell of said two-dimensional image.

43. A two-dimensional code reading apparatus according to claim 42, wherein said reading scope adjusted by the reading control device is set smaller than said cell shape obtained by said cell shape calculating device.

44. A two-dimensional code reading apparatus according to claim 42, wherein said cell reading device reads for each pixel included in said reading scope whether a type of a pixel is black or white, and a type of pixels constituting a majority of all the pixels included in said reading scope is determined to be a type of a cell.

45. A two-dimensional code reading apparatus according to claim 42, wherein said cell reading device reads for pixels located at predetermined positions in said reading scope whether a type of a pixel is black or white, and determines a type of a cell on the basis of a difference between a number of white pixels and a number of black pixels.

46. A two-dimensional code reading apparatus according to claim 42, wherein said reference pattern of a predetermined shape includes a plurality of reference patterns located at different positions, said cell shape calculating device calculates a plurality of cell shapes in said two-dimensional image on the basis of each of said plurality of reference patterns, and said reading control device adjusts said reading scope on the basis of distances of the cell from each of said plurality of reference patterns and said plurality of cell shapes calculated from each of said plurality of reference patterns.

47. A two-dimensional code reading apparatus according to claim 42, wherein said cell shape is specified by its width, its height, and angles at four corners of said cell.

48. A two-dimensional code reading apparatus according to claim 42, further comprising a storing medium which stores a computer program for realizing functions of a plurality of devices.

49. A two-dimensional code reading apparatus for reading a two-dimensional code wherein binary code data is expressed as a pattern of black and white cells in a two-dimensional matrix, comprising:

a two-dimensional image detecting device for detecting a two-dimensional image of said two-dimensional code;

a reference pattern detecting device for detecting a reference pattern of a predetermined shape existing in said two-dimensional image detected by said two-dimensional image detecting device;

a cell shape calculating device for obtaining a shape of a cell of said two-dimensional code in said two-dimensional image on the basis of said reference pattern detected by said the reference pattern detecting device;

a cell grouping device for grouping cells of said two-dimensional code in said two-dimensional image with a position of said reference pattern detected by said reference pattern detecting device as a reference;

a reading control device for when contents of cells are to be read from said two-dimensional image adjusting for each group of cells formed by said cell grouping device a shape of a reading scope from which the content of each of the cells in a group is to be read with respect to a cell shape obtained by said cell shape calculating device; and

a cell reading device for reading the content of the cell from said reading scope adjusted group by said reading control device at a position of each cell of said two-dimensional image.

50. A two-dimensional code reading apparatus according to claim 49, wherein said reading scope adjusted by the reading control device is set smaller than said cell shape obtained by said cell shape calculating device.

51. A two-dimensional code reading apparatus according to claim 49, wherein said cell reading device reads for each pixel included in said reading scope whether a type of a pixel is black or white, and a type of pixels constituting a majority of all the pixels included in said reading scope is determined to be a type of a cell.

52. A two-dimensional code reading apparatus according to claim 49, wherein said cell reading device reads for pixels located at predetermined positions in said reading scope whether a type of a pixel is black or white, and determines a type of a cell on the basis of a difference between a number of white pixels and a number of black pixels.

53. A two-dimensional code reading apparatus according to claim 49, wherein said reference pattern of a predetermined shape includes a plurality of reference patterns located at different positions, said cell shape calculating device calculates a plurality of cell shapes in said two-dimensional image on the basis of each of said plurality of reference patterns, and said reading control device adjusts for each group of cells said reading scope so that said reading scope for cells in a group is determined on the basis of said cell shape calculated from said reference pattern belonging to said group.

54. A two-dimensional code reading apparatus according to claim 49, wherein said cell shape is specified by its width, its height, and angles at four corners of said cell.

55. A two-dimensional code reading apparatus according to claim 49, further comprising a storing medium which stores a computer program for realizing functions of a plurality of devices.