可见光CCD的光致过饱和现象

Excessive saturation effect of visible light CCD

报道了可见光CCD的过饱和状态——在强光辐照下,CCD输出图像中的白色饱和区域内出现黑色盲区。介绍了相机成像系统的信号处理过程和CCD的4种基本输出波形,给出了这4种波形的信号在经过相关双采样电路处理之后的结果和对应的CCD的4种基本输出图像效果,即无光照的黑区、弱光照的灰区、光照饱和的白区和强光致过饱和的黑色盲区(即过饱和状态)。过饱和状态CCD的输出信号波形中,复位电平发生改变而与处于饱和的数据电平持平,使该信号在经过相关双采样电路处理后变为零输出,造成CCD输出图像中的白色饱和光斑中间出现黑色盲区。

In the output image of the visible light CCD irradiated by high intensity light, black area appears inside the white saturation scope. In this paper, the phenomenon is called excessive saturation effect of visible light CCD. In the experiment during which excessive saturation effect occurs, there are four basic waveforms. The course of signal processing of the CCD camera system is introduced, in which the correlated double sampling is indispensable for reducing some noise of output signal of CCD. Corresponding to the four basic waveforms, the output results of correlated double sampling（CDS） are given, which bring four basic areas （black area, gray area, saturated white area, excessively saturated black area） in output image of CCD. In waveform corresponding to the excessively saturated black area, feed-through level of the pixel period waveform falls sharply and arrives at the same data level of saturation. As a result, this signal has zero output after CDS processing. Consequently, the area corresponding to this signal in the CCD image is black, which is inside the white saturation scope.