Patent ID: 8405019

Claim:
A photon detector, comprising: a sinusoidal wave generator that generates a sinusoidal wave-shaped gate signal; a beam splitter that splits the gate signal from the sinusoidal wave generator; a bias circuit that supplies a signal resulting from superimposing one of the gate signals split by the beam splitter on a predetermined DC voltage to an avalanche photodiode that functions as a photon detection element, in synchronism with an input of a photon; a dummy circuit including a capacitor and a resistor, which inputs another of the gate signals split by the beam splitter, and outputs a response signal simulating the avalanche photodiode; a differential amplifier that amplifies a differential input between a response signal from the avalanche photodiode at a time of detecting the photon and the response signal from the dummy circuit; and a comparator that outputs a photon detection signal when an output from the differential amplifier is equal to or higher than a predetermined threshold voltage.