Abstract: In an optical information reader controlled by this controller, a laser beam originating in light emitted by a laser diode is reflected by a scan mirror to scan optical information of a bar code or the like, reflected light therefrom is received by a photodiode to be converted to an electrical signal, and the optical information is read by processing the signal. In the controller, a main amp having a characteristic that a gain changes according to a frequency of an input signal amplifies the electrical signal, a detector detects an analog signal resulting from the amplification, and from a. detection output thereof, a MPU (on/off frequency control circuit) detects level of the analog signal and adjusts the gain of the main amp by changing an on/off frequency of the laser diode caused by an APC circuit (light emission on/off circuit), according to the detected level.

Abstract: In an optical information reader controlled by this controller, a laser beam originating in light emitted by a laser diode is reflected by a scan mirror to scan optical information of a bar code or the like, reflected light therefrom is received by a photodiode to be converted to an electrical signal, and the optical information is read by processing the signal. In the controller, a main amp having a characteristic that a gain changes according to a frequency of an input signal amplifies the electrical signal, a detector detects an analog signal resulting from the amplification, and from a. detection output thereof, a MPU (on/off frequency control circuit) detects level of the analog signal and adjusts the gain of the main amp by changing an on/off frequency of the laser diode caused by an APC circuit (light emission on/off circuit), according to the detected level.