ERROR CORRECTION IN MACRO BAR CODE SYMBOLS

• US 20020088865A1
• Filed: 12/21/1999
• Published: 07/11/2002
• Est. Priority Date: 01/28/1998
• Status: Active Grant

• Current Assignee: Symbol Technologies, LLC (Zebra Technologies Corporation)
• Original Assignee: Duanfeng He, Kevin Hunter, Stephen J. Shellhammer, Sundeep Kumar
• Inventors: KUMAR, SUNDEEP, HUNTER, KEVIN, SHELLHAMMER, STEPHEN J., HE, DUANFENG
• Granted Patent: US 6,651,893 B2
• Time in Patent Office: Days
• US Class Current: 235/494
• 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 data encoding/decoding scheme includes a plurality of bar code symbols each carrying a portion of the data in which improved error correction capabilities are incorporated. According to one aspect, once data codewords have been derived to form the symbols, a first set of data correction elements are derived from a first field, then a second set of error correction elements are derived from the data elements and the first set of error correction elements using a second, wider field.

Claims

1. A method of encoding date in a plurality of discrete graphic symbols, each symbol comprising an array of graphic elements bounded by boundary identification elements wherein each graphic symbol comprises one of a data symbol or an error correction symbol.

2. A method as claimed in claim 1 in which the graphic symbols comprise bar code symbols.

3. A method of decoding date from a plurality of discrete graphic symbols as claimed in claim 1 comprising the steps of decoding the data symbols, decoding the error correction symbols and carrying out error correction.

4. A method of encoding a data stream in a plurality of discrete graphic symbols, each symbol comprising an array of data elements bounded by boundary identification elements in which consecutive portions of the data stream are encoded substantially uninterrupted across consecutive symbols.

17. A method as claimed in claim 4 in which the data elements are divided into a number of sections, and a respective security level is selected for each of the sections.

5. A method of encoding data for retrieval in a graphic symbol, the symbol comprising an array of graphic elements representing one of at least retrievable data or error correction data in which the graphic elements at the physical boundaries of the symbol are those representing either retrievable data or error correction data.

6. A data card comprising a substrate;

and

a pattern of indicia on said substrate including at least two rows of codewords, one row adjacent to and beneath another

each said codeword representing at least one information-bearing character and being selected from among a first, second or third set of detectable mark/space patterns,

each said mark/space pattern comprising a pattern of marks and spaces, each said mark and space being representative of one of a plurality of different states,

each said row having codewords selected from one of a plurality of subsets of said mark/space patterns, each said subset comprising mark/space patterns having discriminator function values that are mutually exclusive of discriminator values corresponding to the mark/space patterns comprising any other subset.

7. A method of encoding a set of data into a plurality of code symbols in which the set of data is represented as information codewords in a matrix having first and second orthogonal rows;

first error correction codewords are derived from each of the first orthogonal rows of information codewords and represented in the matrix as an extension of each respective first orthogonal row of information codewords;

check codewords are derived from the second orthogonal rows of information and first error correction codewords and represented in the matrix as an extension of each respective second orthogonal row, and

second error correction codewords are derived from each of the second orthogonal rows of information codewords,

first error correction codewords and check codewords and represented in the matrix as an extension of each respective second orthogonal row,

wherein each code symbol is then encoded from one of the first or second orthogonal rows.

8. A method as claimed in claim 7 in which the check codewords include a unique identification number for a plurality of code symbols, the appropriate first or second orthogonal row number, the total number of first or second orthogonal rows and the number of first or second orthogonal rows including information codewords.

9. A method of encoding a set of data into a plurality of code symbols in which the set of data is represented as information codewords in a multi-dimensional matrix and respective error correction codewords are derived for information codewords extending in each dimension, and added to the matrix as an extension in the respective dimension, the plurality of code symbols being encoded from the information codewords extending in one of the dimensions.

10. A method of decoding a set of data from a plurality of code symbols in which the plurality of code symbols is derived from a multi-dimensional matrix including information codewords and corresponding error correction codewords extending in each direction, in which the matrix is recreated from the information and error correction codewords in each of the plurality of code symbols.

11. A method of encoding data comprising a plurality of data codewords comprising deriving a first set of error correction codewords from the data codewords from a first error correction field and deriving a second set of error correction codewords from the data codewords and first set of error correction codewords from a second error correction field larger than the first.

12. A method as claimed in claim 11 in which the first and second fields comprise Galois fields.

13. A method as claimed in claim 11 comprising the steps of representing the data codewords, the first set of error correction codewords and the second set of error correction codewords in an array, and representing the array as a plurality of code symbols.

15. A method as claimed in claim 14 in which the position of the position flag element is identified by open-loop observer means modelling the scanning pattern.

14. A method of detecting data stored in a graphic indicia including a position flag element in which the indicia is scanned by a scanning beam following a scanning pattern, the position of the position flag element is detected, the center and orientation of the graphic indicia is derived from the position of the position flag element and the scanning pattern is centered and re-oriented accordingly, wherein the data storing the graphic indicia is subsequently detected using said same scanning pattern.

16. A scan engine for a graphic indicia reader comprising a scanning generator, a scanning beam scanner, a scanner driver, a detector and open-loop observer means for modelling the motion of the scanner and identifying the position of the scanning beam on detection of a predetermined element of the graphic indicia.