Error correction for PDF417 and other machine-readable symbologies
US5761219A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jul 12, 1996 |
| Grant date | Jun 2, 1998 |
| Priority date | — |
| Expiry date | Jul 12, 2016 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03M13/151
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A method and apparatus is described which provides improved error correction for reading a PDF417 or other machine-readable symbol having a data region with symbol characters representing encoded data. A processor receives the encoded data read from the PDF417 symbol and executes an error correction routine. The error correction routine includes a two dimensional discrete Fourier transform with a reduced number of arithmetic operations. The transform is a variant of the Good-Thomas FFT performed over the Galois field GF(929), and includes a set of first index values i.sub.1 (consisting of all integers from 0 to 28 inclusive) and a second set of index values i.sub.2 (consisting of all integers from 0 to 31 inclusive). For a given first index value, the transform is performed only over a subset of the second index values. The subset of second index values is the first k values of a sequence given by i.sub.1 +29*r, where r=0, 1, 2, . . . , 31, and k is the minimum of values 31 and b/29!+1. The value b is the number of symbol characters in the data region of the PDF417, and b/29! is the least integer function of the quotient b/29. It is particularly advantageous to collect in a single …
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