Reading system a variable pass-band
US6422467B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Feb 2, 1999 |
| Grant date | Jul 23, 2002 |
| Priority date | — |
| Expiry date | Feb 2, 2019 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06K2207/1013
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
The effects of papers/substrate noise are significantly reduced in multi-focal zone laser scanning systems by processing analog scan data signals with a scan data signal processor having a plurality of pass-band filters and amplifiers that are automatically selected for passing only the spectral components of an analog scan data signal produced when a bar code symbol is scanned at a particular focal zone in the laser scanning system. Two or more different pass-band filter structures can be provided for use in the scan data signal processor, wherein each pass-band filter structure is tuned to the spectral band associated with a particular focal zone in the laser scanning system. When a bar code symbol is scanned by a laser beam focussed within the first focal zone or scanning range of the system, the pass-band filter structure associated with this focal zone or scanning range is automatically switched into operation using a control signal produced by determining the focal distance of the laser scanning beam producing the analog scan data signal and noise existing over this pass-band are allowed within the analog signal processor. By virtue of the present invention, first and second …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.