Registers – Coded record sensors – Particular sensor structure
Patent
1998-12-22
2000-04-04
Frech, Karl D
Registers
Coded record sensors
Particular sensor structure
23546226, 23546206, G06K 710
Patent
active
060450444
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.
REFERENCES:
patent: 5457309 (1995-10-01), Pelton
patent: 5852286 (1998-12-01), Coleman
Frech Karl D
PSC Inc.
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