To speed up a signal reading operation while obtaining difference between an optical output signal and a dark output signal.

Every three storage capacitors C1-C3 are provided according to the respective vertical signal lines 14. A signal in which dark output signals of two selected pixels 11 are superimposed is accumulated in the capacitor C1, a signal corresponding to a signal in which a dark output signal of one of the two selected pixels 11 and an optical output signal of the other pixel are superimposed is accumulated in the capacitor C2, and a signal corresponding to a signal in which optical output signals of the two selected pixels 11 are superimposed is accumulated in the capacitor C3 via switches TV1-TV3. The respective signals accumulated in the capacitors C1-C3 are supplied to horizontal signal lines 16-1 to 16-3 via switches TH1-TH3, respectively, and output via amplifiers AP1-AP3. An external control part obtains difference between output signals of the amplifiers AP1, AP2 and difference between output signals of the amplifiers AP2, AP3.

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