Patent ID: 8179386

Claim:
An optical sensor comprising a detection photodetecting element for detecting ambient light and a reference photodetecting element covered with a shielding film so as not to receive the ambient light, the optical sensor further comprising: a differential amplifier, one input terminal of which is connected to a cathode of the detection photodetecting element and the other input terminal is connected to a cathode of the reference photodetecting element; an integration capacitor provided between the cathode of the detection photodetecting element and an output terminal of the differential amplifier; a reset switch for resetting the integration capacitor; and an electric potential control circuit connected to the cathode of the reference photodetecting element, the anode of the reference photodetecting element and the anode of the detection photodetecting element for making an electric potential of the anode of the reference photodetecting element and an electric potential of the anode of the detection photodetecting element larger than an electric potential of the cathode of the reference photodetecting element by an open-circuit voltage of the reference photodetecting element.