| 摘要 |
An integration circuit(10)is provided with an amplifier and an integration capacitor in parallel between an input terminal and an output terminal and has a capacitance value switching means for switching the capacitance value of the integration capacitor to any of C<sb>f1</sb>−C<sb>fk</sb>,inputs charges output from a photodiode(PD)to accumulate them in the integration capacitor,and outputs an integral voltage with a value corresponding to the amount of these accumulated charges.An A/D conversion circuit(20)has a reference voltage switching means for switching a reference voltage used for A/D conversion to any of V<sb>ref,1</sb>−V<sb>ref,L</sb>,inputs the integral voltage output from the integration circuit(10),A/D converts the integral voltage on the basis of the reference voltage set by switching it through the reference voltage switching means,and outputs a digital value corresponding to this integral voltage.
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