Patent ID: 6811087
Filing Date: 2004-11-02
Classification: G06K

Abstract:
A barcode scanner comprising:a first oscillator to generate a pulse signal of a predetermined frequency; a laser driving circuit to pulse-drive a laser by the pulse signal generated from the first oscillator; and a signal processing section which detects a reflected light signal from a barcode scanned by an emission output of the laser to generate a binarized signal corresponding to the barcode, wherein the signal processing section includes: a preamplifier to convert, into a voltage signal, a current-converted barcode signal outputted from a photodetector which detects the reflected light signal from the barcode scanned by the emission output of the laser, and to supply an amplified voltage signal; a high-pass filter to remove a direct current component contained in the amplified voltage signal from the preamplifier; a variable gain amplifier which controls an amplification gain of an output signal of the high-pass filter, thereby carrying out automatic gain control so as to set an output level almost constant, a synchronous detector to detect a pulse signal contained in an output signal of the variable gain amplifier in synchronization with the pulse signal generated from the first oscillator, and a binarization circuit to binarize an output signal of the synchronous detector.