Bar code reader with enhanced sensitivity
US4882476A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Sep 10, 1986 |
| Grant date | Nov 21, 1989 |
| Priority date | — |
| Expiry date | Sep 10, 2006 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04B2001/3894
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
In laser bar code scanners bright sunlight tends to overpower the reflected laser light, drastically reducing the difference between bar code and background signals. In the present bar code reader, a plurality of light detectors are utilized with different spectral response characteristics at the wavelength of the incident laser beam, such that the differential response of the detectors tends to minimize the effect of background illumination. Narrowband optical filters with offset passbands may be used with conventional light sensors. As another example, filters with long wavelength transmission characteristics and offset cutoff wavelengths may be employed if necessary with a neutral density filter to provide balanced responses under broadband illumination.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.