| 摘要 |
PROBLEM TO BE SOLVED: To prevent an after-image from being generated even when a quantity of incident light is small by setting a drain voltage of a MOS transistor to be lower than a steady-state value for only a predetermined time when a light signal is to be detected, and discharging charges accumulated to a photoelectric conversion element connected to a source side to initialize a circuit. SOLUTION: The optical sensor circuit consists of a photodiode PD, a MOS transistor Q1 for converting a sensor current to a voltage signal with a characteristic for outputting logarithmic characteristic, a MOS transistor Q2 for amplifying the voltage signal Vd, and a MOS transistor Q3 for pixel selection which outputs the amplified voltage signal as a pixel signal Vo. A voltage controller 1 is set for variably adjusting a size of a drain voltage VD of the MOS transistor Q1, thereby setting the drain voltage VD of the transistor Q1 to be a value lower than a steady-state value for only a predetermined time when a light signal is to be detected. Charges accumulated to a coupling capacitor C of the photodiode PD connected to a source side are discharged to initialize the circuit.
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