Method and apparatus for reducing bandwidth limited noise in bar

Details Method and apparatus for reducing bandwidth limited noise in bar Method and apparatus for reducing bandwidth limited noise in bar

Filed on

1996-03-20

Date issued

1998-12-22

Examiner

Hajec, Donald T.

Patent Class

Registers

SubClass

Coded record sensors

SubSubClass

Particular sensor structure

Other Related Categories

235455, G06K 710

Type

Patent

Status

active

Patent number

058522867

Description

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.

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patent: 5548108 (1996-08-01), Moldskred et al.
patent: 5608200 (1997-03-01), LeGoff et al.
patent: 5612531 (1997-03-01), Barkan

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