초록 ▼

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 co

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.

대표청구항 ▼

[ What is claimed is:] [1.] A bar code scanner system comprising:a laser light source that periodically produces a light beam that is swept across a bar code label, the laser light source being periodically turned "on" and "off" according to a duty cycle;a detector that produces a first electric sig

[ What is claimed is:] [1.] A bar code scanner system comprising:a laser light source that periodically produces a light beam that is swept across a bar code label, the laser light source being periodically turned "on" and "off" according to a duty cycle;a detector that produces a first electric signal representative of received ambient light and light reflected from the bar code label when the 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, that provides a first gain to the first electric signal and provides a second gain to the second electric signal;a filter, coupled to the demodulator circuit, that receives the electric signals from the demodulator circuit and reduces out-of-band signal components; anda laser pulser coupled to the laser light source and the demodulator circuit, that controls the duty cycle of the laser light source.