Patent ID: 7989753

Claim:
A photodetector comprising: a photodiode, generating charges of an amount that is in accordance with an incident light amount; an integrating circuit, having a variable capacitor unit that is selectively set to a capacitance value C n among K capacitance values C 1 to C K , accumulating charges, output from the photodiode, into the variable capacitor unit over an accumulating period T k that is in accordance with a capacitance value C k set in the variable capacitor unit, and outputting a voltage according to the amount of the accumulated charges; a first holding circuit, holding the voltage output from the integrating circuit at the end of an accumulating period T k among accumulating periods T 1 to T K and outputting the held voltage; and a comparing circuit, inputting the voltage output from the integrating circuit or the first holding circuit, performing a quantitative comparison of the input voltage with a reference voltage, outputting a compared signal expressing the comparing result, and, when the voltage output from the integrating circuit or the first holding circuit at the end of an accumulating period T k is less than the reference voltage, instructing the first holding circuit to hold the voltage; wherein the value of a ratio, (T k /C k ), differs according to the value of k (where K is an integer no less than 2 and k is an arbitrary integer no less than 1 and no more than K).