Controller for optical information reader

摘要

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.

主权项

1. A controller for an optical information reader in which a laser beam originating in light emitted by a laser diode is reflected by a scan mirror to scan optical information, reflected light from the optical information is received by a photodiode to be converted to an electrical signal, and the optical information is read by processing the electrical signal, the controller comprising:
an on/off light emission circuit which causes the laser diode to turn on and off to emit light on and off; an amp which amplifies the electrical signal; and an on/off frequency control circuit which detects level of an amplitude of an analog signal resulting from the amplification by the amp, and according to the level, changes an on/off frequency of the laser diode caused by the on/off light emission circuit, wherein the amp is an amp having a characteristic that a gain changes according to a frequency of an input signal.