Background compensating bar code readers
US4983817A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Aug 10, 1989 |
| Grant date | Jan 8, 1991 |
| Priority date | — |
| Expiry date | Aug 10, 2009 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06K19/06056
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
Methods and apparatus for reading a luminescent and substantially transparent bar code 1 on a background surface 2 whose reflectance may vary over the coded area. Light 7 scans (70), and excites luminescence 8 in, the bar code 1. The light 7 also reflects (9) without luminescence from the background surface 2 of the bar code 1. A first electrical or optical signal 11 is provided (4) responsive to the reflected nonluminescent light 9, and a second electrical or optical signal 10 is provided (4) responsive to the luminescent 8. Typically the first signal 11 is processed (5) to provide a third signal 31 that varies with background reflectance substantially as does the second signal 10; and the second and third signals 10, 31 are combined (5) to provide a fourth signal 12 that is substantially independent of background reflectance in the coded area, and which is decoded (6) to provide the desired reading.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.