Two-dimensional code and method of optically reading the same

• US 6,267,296 B1
• Filed: 05/12/1999
• Issued: 07/31/2001
• Est. Priority Date: 05/12/1998
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Tachi, Ryosuke, Ooshima, Tadao
• Primary Examiner(s): Lee, Michael G.
• Assistant Examiner(s): St. Cyr, Daniel
• Application Number:
  US09/310,174
• Time in Patent Office: 811 Days
• Field of Search: 235/494, 235/487, 235/462.01, 235/462.08, 235/462.09, 235/462.1, 235/462.11, 235/462.24, 235/454
• US Class Current: 235/487
• CPC Class Codes: G06K 19/06037 multi-dimensional coding

Abstract

A two-dimensional code made up of a matrix of cells formed with dark and light squares arranged in a pattern carrying an optically readable binary-coded data, and a method of reading such a two-dimensional code. The two-dimensional code features a structure in which at least two data regions are defined in a data field of the matrix. One of the data regions retains a code represented by the cells having a larger size, while the other data region retains a code represented by the cells having a smaller size. The use of cells of different sizes in representing the codes allows the codes to be read correctly under different conditions.

Claims

1. A two-dimensional code comprising:

a matrix of cells arranged in an optically readable pattern to carry information;

location symbols arranged at predetermined locations in said matrix, each of said location symbols comprising a predetermined number of cells arranged in a pattern to carry location data, the location data specifying a location of the two-dimensional code; and

a data field defined in said matrix, the data field including a first and a second data region to respectively carry a first and a second information element, the first data region comprising a first number of cells having a size identical to that of the cells of said location symbols and defined between said location symbols, the second data region comprising a second number of cells having a size smaller than that of the cells in the first data region.

2. The two-dimensional code as set forth in claim 1, wherein the second data region includes a plurality of sections which comprise predetermined numbers of cells having different sizes, and which carry information elements.

3. The two-dimensional code as set forth in claim 1, wherein the first information element is represented by a code of a type specified by the location symbols, and the second information element is represented by a code of a type different from that of the first information element.

4. The two-dimensional code as set forth in claim 3, wherein the second data region includes a plurality of sections which comprise predetermined numbers of cells having different sizes, and which carry a plurality of different information elements that are represented by codes different in type from each other and the first information element.

5. The two-dimensional code as set forth in claim 1, further comprising a format code which is arranged in a preselected positional relation to the location symbols and which indicates a format of the two-dimensional code.

6. The two-dimensional code as set forth in claim 5, wherein said format code comprises a predetermined number of cells arranged in a preselected optical pattern.

7. The two-dimensional code as set forth in claim 5, wherein said format code carries data to specify at least one of a location of each of the first and second data regions, a type of code used in each of the first and second data regions, and a size of the cells in each of the first and second data regions.

8. The two-dimensional code as set forth in claim 5, wherein said format code holds classification information and version information, the classification information representing one of preselected combinations of locations of the first and second data regions, types of code used in the first and second data regions, and sizes of the cells in the first and second data regions, the version information specifying a geometrical pattern of the first data region as a function of a difference in cell size between the first and second data regions.

9. The two-dimensional code as set forth in claim 5, wherein said format code is arranged adjacent to one of the location symbols.

10. The two-dimensional code as set forth in claim 1, further comprising an auxiliary symbol to determine locations of the cells in the second data region based on an optical pattern of said auxiliary symbol and locations of the location symbols.

11. A method of reading a two-dimensional code, comprising:

capturing an image of a two-dimensional code, the two-dimensional code including a matrix of cells arranged in an optically readable pattern to carry information, location symbols arranged at predetermined locations in said matrix, each of said location symbols comprising a predetermined number of cells arranged in a pattern to carry location data, the location data specifying a location of the two-dimensional code, and a data field defined in said matrix, the data field including a first and a second data region having data codes to respectively carry a first and a second information element, the first data region comprising a first number of cells having a size identical to that of the cells of said location symbols and defined between said location symbols, the second data region comprising a second number of cells having a size smaller than that of the cells in the first data region, the image capturing determining locations of the location symbols in the image;

determining a location of each of the cells in at least one of the first and second data regions based on the locations of the location symbols and the size of the cells in the one of the first and second data regions; and

decoding a corresponding one of the data codes in the at least one of the first and second data regions to produce a corresponding one of the first and second information elements based on the cells whose locations are determined.

12. The method as set forth in claim 11, wherein the second data region includes a plurality of sections which comprise predetermined numbers of cells having different sizes to represent data codes which carry a plurality of information elements.

13. The method as set forth in claim 11, wherein the data code of the first information element is of a type specified by the location symbols, and the data code of the second information element is of a type different from that of the first information element, and wherein said decoding decodes the one of the data codes using a decoding algorithm corresponding to the type of the one of the data codes.

14. The method as set forth in claim 13, wherein the second data region includes a plurality of sections which comprise predetermined numbers of cells having different sizes, and which carry different information elements that are represented by data codes different in type from each other and the first information element.

15. The method as set forth in claim 13, wherein said two-dimensional code further includes a format code which is arranged in a preselected positional relation to the location symbols and which carries format information on the two-dimensional code representing locations of the first and second data regions, the sizes of the cells in the first and second data regions, and the types of data codes used in the first and second data regions, and further comprising locating the format code based on the locations of the location symbols to analyze the format information on the two-dimensional code, and wherein said location determining determines the location of each of the cells based on the format information, and said decoding decodes the one of the data codes using a decoding algorithm corresponding to the type of the one of the data codes specified by the format information.

16. The method as set forth in claim 11, wherein said two-dimensional code further includes a format code which is arranged in a preselected positional relation to the location symbols and which carries format information on the two-dimensional code representing locations of the first and second data regions and the sizes of the cells in the first and second data regions, and further comprising locating the format code based on the locations of the location symbols to analyze the format information on the two-dimensional code, and wherein said location determining determines the location of each of the cells based on the format information.

17. The method as set forth in claim 11, wherein the two-dimensional code further includes an auxiliary symbol which is disposed at a location away from the location symbols, and further comprising determining the location of the auxiliary symbol in the image based on the locations of the location symbols and an optical pattern of the auxiliary symbol, and wherein said location determining determines the location of each of the cells in the at least one of the first and second data regions based on the locations of the auxiliary symbol and the location symbols and the size of the cells in the one of the first and second data regions.

18. A software product stored on a computer readable medium containing instructions for execution by a processor, the instructions, when executed:

capturing an image of a two-dimensional code, the two-dimensional code including a matrix of cells arranged in an optically readable pattern to carry information, location symbols arranged at predetermined locations in said matrix, each of said location symbols comprising a predetermined number of cells arranged in a pattern to carry location data, the location data specifying a location of the two-dimensional code, and a data field defined in said matrix, the data field including a first and a second data region having data codes to respectively carry a first and a second information element, the first data region comprising a first number of cells having a size identical to that of the cells of said location symbols and defined between said location symbols, the second data region comprising a second number of cells having a size smaller than that of the cells in the first data region, the image capturing determining locations of the location symbols in the image;

determining a location of each of the cells in at least one of the first and second data regions based on the locations of the location symbols and the size of the cells in the one of the first and second data regions; and

decoding a corresponding one of the data codes in the at least one of the first and second data regions to produce a corresponding one of the first and second information elements based on the cells whose locations are determined.