Method and apparatus for reducing bandwidth limited noise in bar code scanner
US5852286A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Mar 20, 1996 |
| Grant date | Dec 22, 1998 |
| Priority date | — |
| Expiry date | Mar 20, 2016 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06K7/10584
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A bar code scanner system includes a laser light source that periodically produces a light beam that is swept across a bar code label. The laser light source is periodically turned "on" and "off" according to a duty cycle. A detector produces a first electric signal representative of received bar code label reflected light and ambient light when the laser light source is on, and produces a second electric signal representative of received ambient light when the light source is "off". A demodulator circuit, coupled to the detector, provides a first gain to the first electric signal and provides a second gain to the second electric signal. The gains applied are selected such that the signal and signal component produced solely as a result of the ambient light will significantly cancel out one another when the signals are combined. A filter, coupled to the demodulator circuit, receives the electric signals from the demodulator circuit and reduces out-of-band signal components such as noise. When the duty cycle of the laser light source is equal to 50%, the first gain is equal to the inverse of the second gain.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.