| 摘要 |
PURPOSE:To make it possible to compensate automatically variation in dark current by detecting the dark current by gating part of a signal in the blanking interval of the output signal of a charge transfer element and by converting it into a linear voltage corresponding to its level. CONSTITUTION:A signal lagging 1H behind the output signal of charge transfer element 23 is supplied to clamping circuit 28. A reference level which does not vary with circumferential conditions such as a temperature included in the 1H delay signal is supplied to gate circuit 29 after clamped by circuit 28 to a reference voltage from reference voltage generating circuit 32 for providing bias charges. Circuit 29 gates a dark current and bias charges included in the 1H delay signal with gate pulses, which are generated only in the blanking interval, and integrating and holding circuit 30 converts the output of circuit 29 into a DC voltage and holds it. As the dark current increases according to temperature, the above-mentioned voltage is applied to the 2nd gate electrode of element 23 and the variation in dark current can be canceled by reducing the output signal so that a difference in potential between the 1st and 2nd gate electrodes will lessen. |
