Method and apparatus to scan randomly oriented two-dimensional bar code symbols
US5523552A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Oct 19, 1994 |
| Grant date | Jun 4, 1996 |
| Priority date | — |
| Expiry date | Oct 19, 2014 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06K7/10871
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
Disclosed are methods and apparatus for automatically aligning the field of view of a two dimensional bar code reading device with a randomly oriented two-dimensional bar code symbol wherein the symbol comprises a unique pattern located contiguously on at least one side thereof. One method is implemented in a laser based embodiment by scanning the symbol with a laser scan line extending through the border pattern (which is a PDF417 start codeword), measuring the length of the start codeword detected by the scan line, and rotating the laser scan line by a predetermined amount. This is repeated for a predetermined number of times, and the rotation angle at which the codeword length is smallest is determined by performing a least squares fit of the measured codeword lengths and rotation angles. The raster pattern is then rotated to the determined rotation angle so as to be aligned with the symbol for subsequent scanning and decoding. In the alternative, a sequential least squares fit can be performed after each start codeword measurement is made rather than waiting for all measurements to be made. An alternative embodiment implements a discrete radial CCD array comprised of linear CCD…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.