分析了正常工作条件下CCD信号检测电路工作的全过程;指出了在正常工作状态下CCD对检测电路的注入是以低占空比的周期性窄脉冲方式进行的,配合有效的复位机制,使每个像素的复位电平保持为常值。根据CCD过饱和状态的产生条件和CCD信号传输沟道内的电势分布特点,提出了CCD过饱和状态的物理实质,即激光在CCD的受辐照点处提供了一个光生电流源,光生电荷将CCD的传输势阱全部填满之后使得CCD由一个电荷器件转变为一个电流器件。电流通过由CCD时钟的低电平所确定的沟道传输,使CCD对检测电路的注入以近乎连续的周期性长脉冲方式进行,导致了复位电平的改变,造成过饱和的视频图像。

The charge measurement process of CCD in normal work state has been analyzed. It is indicated that the mode of charge injecting to the measurement capacitor is the periodic narrow pulse that has a low fill factor when the CCD is normal. After the charge signal is measured,the feed-through level is restored under the effective resetting action.According to the condition under which the excessive saturation state of CCD happens and potential characteristics in the signal charge transfer channel of CCD,we put forward the physical mechanism of the CCD excessive saturation effect. That is,an optoelectronic current source is formed by laser in the irridiated spot of the CCD. The charge generated by laser crams the potential well of the CCD and then makes the CCD become a current device from a charge device. The current transfers in the channel provided by the low level of the CCD clock,and almost makes the charge signal injecting to measurement capacitor continuous. Thus the feed-through level is altered,and the excessive saturation video comes into being.