Apparatus And Methods For Decoding Images

• US 20090194590A1
• Filed: 01/31/2008
• Published: 08/06/2009
• Est. Priority Date: 01/31/2008
• Status: Active Grant

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Thiyagarajah, Mohanaraj
• Granted Patent: US 8,313,029 B2
• Time in Patent Office: Days
• US Class Current: 235/462.01
• 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 7/1456 determining the orientation of the optical code with respect to the reader and correcting therefore

Abstract

A method and system for determining an orientation of a data-encoding symbol, such as a PDF417 bar-code symbol, and for decoding the encoded data. One example method may include detecting an encoded data sequence at a first location of the symbol and at a second location of the symbol. The symbol orientation may be determined at least partially based on the first and second locations. Strings of data encoded in the symbol may then be decoded by processing the strings to generate indices and accessing a codeword array using the indices to look up codewords corresponding to the strings. A match between a string and a codeword may be verified with data in the codeword array.

Claims

1. A method of determining an orientation of a data-encoding symbol, the method comprising:

detecting an encoded data sequence at a first location of the symbol;

detecting the encoded data sequence at a second location of the symbol; and

determining the symbol orientation at least partially based on the first and second locations.

2. The method of claim 1, further comprising:

scanning the symbol along scan-lines that are unaligned with the symbol orientation,

wherein the first and second locations respectively include first and second ones of the scan-lines.

3. The method of claim 1, further comprising:

identifying a first point corresponding to a beginning of the data sequence encoded at the first location and a second point corresponding to a beginning of the data sequence encoded at the second location,

wherein determining the symbol orientation includes determining a direction perpendicular to a line defined by the identified first and second points.

4. The method of claim 3, wherein determining the symbol orientation includes checking for valid data encoded along the determined direction.

5. The method of claim 1, further comprising:

identifying a first point corresponding to an end of the data sequence encoded at the first location and a second point corresponding to an end of the data sequence encoded at the second location,

wherein determining the symbol orientation includes determining an angle perpendicular to a line defined by the identified first and second points.

6. The method of claim 5, wherein determining the symbol orientation includes checking for valid data encoded along the determined direction.

7. The method of claim 1, wherein the encoded data sequence is associated with a periphery of the symbol and indicates at least one of a start region and a stop region of the symbol.

8. The method of claim 1 wherein the symbol is a PDF417 symbol.

9. The method of claim 1, further comprising:

identifying a first pair of points corresponding, respectively, to a beginning and an end of the data sequence encoded at the first location and a second pair of points corresponding, respectively, to a beginning and an end of the data sequence encoded at the second location,

wherein determining the symbol orientation includes;

determining a plurality of candidate orientations based on the identified first and second pairs of points; and

selecting a candidate orientation as the symbol orientation if valid data is detected using the candidate orientation.

10. A computer-readable medium having computer-executable instructions adapted to carry out the method of claim 1.

11. A device for decoding data encoded in a symbol, the device comprising:

a scanner adapted to read a plurality of symbol regions; and

a processor adapted to;

detect a data sequence encoded in a first one of the plurality of symbol regions;

detect the data sequence encoded in a second one of the plurality of symbol regions;

determine the symbol orientation based on a first point in the first symbol region and a second point in the second symbol region.

12. The device of claim 11, wherein the scanner is adapted to read the plurality of symbol regions by scanning the symbol along scan-lines that are unaligned with the symbol orientation, the first and second locations respectively including first and second ones of the scan-lines.

13. The device of claim 11, wherein the first point corresponds to a beginning of the data sequence encoded at the first location and the second point corresponds to a beginning of the data sequence encoded at the second location, the determined symbol orientation being perpendicular to a line defined by the first and second points.

14. The device of claim 11, wherein the first point corresponds to an end of the data sequence encoded at the first location and the second point corresponds to an end of the data sequence encoded at the second location, the determined symbol orientation being perpendicular to a line defined by the first and second points.

15. The device of claim 11, wherein the encoded data sequence is associated with a periphery of the symbol and indicates at least one of a start region and a stop region of the symbol.

16. The device of claim 11, wherein the symbol is a PDF417 symbol.

17. The device of claim 11, wherein the processor is further configured to determine the symbol orientation based on a third point in the first symbol region and a fourth point in the second symbol region, the first and third points each corresponding to a data sequence starting point and the second and fourth points each corresponding to a data sequence ending point, and wherein the first, second, third, and fourth points define a plurality of candidate orientations from which the symbol orientation is selected.

18. A method for decoding a string of data, the method comprising:

processing the string to generate an index;

accessing a codeword array using the index to look up a codeword corresponding to the string; and

verifying, with data in the codeword array, a match between the string and the codeword.

19. The method of claim 18, further comprising:

if the string and the codeword do not match, accessing the codeword array using a sub-index to look up the codeword corresponding to the string,

wherein the codeword array associates the sub-index with the index.

20. The method of claim 18, the method further comprising:

processing the string to generate a first value,

wherein the string is uniquely related to the first value but not to the index.

21. The method of claim 20, wherein verifying a match includes using the index to look up a second value and comparing the second value with the first value, and wherein the codeword corresponding to the string is associated with the second value in the codeword array.

22. A device for decoding bar code data, the device comprising:

a scanner adapted to read a string of bar code data; and

a processor adapted to;

process the string to generate an index;

access a codeword array using the index to look up a codeword corresponding to the string; and

verify, with data in the codeword array, a match between the string and the codeword.

23. A method for generating a codeword array for use in decoding data, the method comprising:

processing a first string of data to generate a first value;

processing the first value to generate a first index;

storing the first value in a first field of a first record in the codeword array, the first record corresponding to the first index; and

storing codeword information associated with the first string in a second field of the first record.

24. The method of claim 23, wherein the codeword information associated with the first string comprises at least one of a first codeword associated with the first string and an index associated with the first codeword.

25. The method of claim 23, wherein processing the string to generate the first value comprises computing a function of the string.

26. The method of claim 23, further comprising:

processing a second string of data to generate a second value;

processing the second value to generate a second index;

storing the second value in a first field of a second record in the codeword array; and

if the second index matches the first index, storing a sub-index corresponding to the second record in a third field of the first record; and

storing codeword information associated with the second string in a second field of the second record.

27. The method of claim 26, wherein the codeword information associated with the second string comprises at least one of a second codeword associated with the second string and an index associated with the second codeword.