Phase difference detecting method, circuit and apparatus

Abstract

In phase difference detecting method, circuit, and apparatus of the present invention, a voltage signal having a predetermined frequency is applied to a photoconductive light-receiving device, and an optical signal is received by this photoconductive light-receiving device. A current generated upon reception of light and flowing in the photoconductive light-receiving device reflects a product value of the voltage signal and the optical signal, and contains a DC component according to a phase difference between the voltage signal and the component of the optical signal having the same intensity modulation frequency as that of the voltage signal. A time average value of the current flowing in the photoconductive light-receiving device or a voltage value obtained upon conversion of this current is generated, and only the DC component is extracted, thereby detecting the phase difference between the voltage signal and the component of the optical signal having the same intensity modulation frequency as that of the voltage signal.

Dependencies are inferred from the claim text.