OPTICAL READER USING DISTANCE MAP DECODING

• US 20120048941A1
• Filed: 08/27/2010
• Published: 03/01/2012
• Est. Priority Date: 08/27/2010
• Status: Active Grant

• Current Assignee: Hand Held Products Incorporated (Honeywell International Inc.)
• Original Assignee: Hand Held Products Incorporated (Honeywell International Inc.)
• Inventors: Wang, Ynjiun P.
• Granted Patent: US 8,302,866 B2
• Time in Patent Office: Days
• US Class Current: 235/462.22
• CPC Class Codes: G06K 7/1404 Methods for optical code recognition

Abstract

A method for decoding an encoded candidate character of a symbology is provided that includes the steps of providing a plurality of valid barcode characters of a symbology having n elements, generating a seed codeword comprising n elements, computing a seed distance value from the seed codeword to each character in the symbology, generating a distance map comprising each character in the symbology and the associated computed seed distance value, and arranging the plurality of seed distance values into a plurality of bins. Each bin contains a subset of the characters in the symbology. The method includes the steps of selecting a candidate barcode character for decoding, computing a candidate distance value from the candidate barcode character to the seed codeword, identifying the bin containing the candidate distance value, and comparing the candidate barcode character with the valid barcode characters in the bin having the candidate distance value.

Claims

1. An optical reader for decoding an encoded candidate character of a symbology, the optical reader comprising:

a lens system for focusing an illuminated encoded candidate character at a plane of focus;

an optical sensor having as an input the detected light intensity corresponding to the illumination reflected from the encoded candidate character, and having as an output an electrical signal encoding information representative of the encoded candidate character;

wherein the optical reader accesses a distance map comprising a seed codeword and a plurality of seed distance values, each seed distance value comprising a computed distance from the seed codeword to a character of the symbology;

wherein the optical reader computes a candidate distance value from the seed codeword to the encoded candidate character;

wherein the optical reader compares the encoded candidate character to a subset of the characters of the symbology, the subset comprising characters of the symbology having seed distance values within a specified range of the candidate distance value.

2. The optical reader of claim 1, wherein each subset of the characters of the symbology is a bin.

3. The optical reader of claim 2, wherein each bin comprises a range of seed distance values.

4. The optical reader of claim 1, wherein the character of the symbology and the seed codeword comprise the same number of elements.

5. The optical reader of claim 4, wherein the seed codeword is selected arbitrarily.

6. The optical reader of claim 1, wherein the same seed codeword is utilized to compute the seed distance value for each character of the symbology.

7. The optical reader of claim 1, wherein the candidate distance value is derived from a sequence of element widths.

8. The optical reader of claim 1, wherein the optical reader compares an e-sequence of the candidate character with an e-sequence of the valid character of the symbology.

9. The optical reader of claim 8, wherein the optical reader determines the e-sequence of the candidate character from a step function derived by subjecting the electrical signal to an action of the optical reader.

10. The optical reader of claim 1, wherein the distance from the candidate character to the seed codeword is a diagonal distance.

11. The optical reader of claim 1, wherein the computed seed distance comprises a diagonal distance.

12. The optical reader of claim 1, wherein the optical reader is a hand-held imager.

13. The optical reader of claim 1, further comprising a trigger mechanism in electrical communication with the optical sensor.

14. The optical reader of claim 1, wherein the distance map comprises a first seed codeword and a second seed codeword.

15. The optical reader of claim 14, wherein the first seed codeword is used to compute the subset of the characters of the symbology, and the second seed codeword is used to compute a second subset comprising characters of the symbology within the first subset.

16. The optical reader of claim 14, wherein the first seed codeword and the second seed codeword are used to compute a high dimensional distance.

17. A method for decoding an encoded candidate character of a symbology, the method comprising the steps of:

providing a plurality of valid barcode characters of a symbology, each barcode character having n elements in conformance with the symbology;

generating a seed codeword comprising n elements;

computing a seed distance value from the seed codeword to each character in the symbology;

generating a distance map comprising each character in the symbology and the associated computed seed distance value;

arranging the plurality of seed distance values into a plurality of bins, each bin containing a subset of the characters in the symbology;

selecting a candidate barcode character for decoding, the character comprising n elements;

computing a candidate distance value from the candidate barcode character to the seed codeword;

identifying the bin containing the candidate distance value; and

attempting to decode the candidate barcode character by comparing the candidate barcode character with the valid barcode characters in the bin having the candidate distance value.

18. The method of claim 17, further comprising the step of storing the valid barcode characters of the symbology, the seed codeword, and the seed distance values in a machine-readable storage medium.

19. The method of claim 17, wherein each bin is characterized by a range of seed distance values.

20. The method of claim 17, wherein the steps of computing a seed distance value and computing a candidate distance value comprise diagonal distance computation.

21. The method of claim 17, further comprising the step of providing a trigger mechanism, the action of which initiates the steps of selecting the candidate barcode character for decoding, computing the candidate distance value, identifying the bin containing the candidate distance value, and attempting to decode the candidate barcode character against the valid barcode characters in the bin having the candidate distance value.

22. The method of claim 17, wherein the steps of selecting the candidate barcode character for decoding, computing the candidate distance value, identifying the bin containing the candidate distance value, and attempting to decode the candidate barcode character against the valid barcode characters in the bin having the candidate distance value are performed by a processor having a clock speed, the steps being further characterized by a decoding parameter, the decoding parameter being less than 2,800 processor clock cycles per character comparison.

23. The method of claim 22, wherein the decoding parameter is less than 1,400 processor clock cycles per character comparison.

24. The method of claim 22, wherein the decoding parameter is less than 530 processor clock cycles per character comparison.

25. The method of claim 17, wherein the step of comparing the candidate barcode character with the valid barcode characters in the bin having the candidate distance value comprises calculating a minimum distance between the candidate barcode character and the valid barcode characters.