| 摘要 |
PROBLEM TO BE SOLVED: To provide a code information reader that is made able to effectively remove a frequency information unnecessary for reading a code while attaining the expansion of dynamic range. SOLUTION: This code information reader is composed of a photodetector 1 for converting reflected light to a current, an I/V converting circuit 2 for converting the output current of this photodetector to a voltage, gain control amplifier 3 connecting the output of this I/V converting circuit to one input terminal of a differential amplifier 3-2, with which an amplification factor is controlled by a voltage controlled current source 3-3, and the input terminal of a low-pass filter 3-1, in which a cutoff frequency is set lower than the read frequency of the code, and connecting the output terminal of the low-pass filter to the other input terminal of the differential amplifier, a band pass filter 4 connecting the output terminal of this amplifier to an input terminal for extracting only the component required for reading the code, and amplifier connecting the output terminal of the band pass filter to an input terminal and connecting an output terminal to an analog/digital converting circuit. |
