连续激光辐照CMOS相机的像素翻转效应及机理

Pixel upset effect and mechanism of CW laser irradiated CMOS camera

为了研究激光对CMOS图像传感器的干扰效果,利用632.8 nm连续激光开展了对CMOS相机的饱和干扰实验。随着入射激光功率的增加,分别观察到未饱和、饱和、全屏饱和等现象,并发现,在全屏饱和前,功率密度达到1.4 W/cm^2后,光斑强区中心区域出现了像素翻转效应。进一步加大光敏面激光功率密度到95.1 W/cm2,激光作用停止后相机仍能正常成像,证明像素翻转效应并非源自硬损伤。基于CMOS相机芯片的结构和数据采集处理过程进行了机理分析,认为强光辐照产生的过量光生载流子使得光电二极管电容上原来充满的电荷被快速释放,使得相关双采样中的两次采样所得信号V_(reset)与V_(signal)逐渐接近,是输出像素翻转的一种可能原因。

To study the jamming effects of laser on CMOS image sensor, jamming experiments with 632.8 nm CW laser were conducted. With the increasing of laser power, the phenomenon of instauration, saturation and full screen saturation were observed. Pixel upset effect in the maximum laser intensity site of the irradiated CMOS sensor was discovered when the intensity was greater than 1.4 W/cm2 and the full screen saturation had not appeared at this time. Even the laser intensity at the photosensitive surface was up to 95,1 W/era2, the camera could still image normally when the laser irradiation was terminated. It indicated that the pixel upset effect was not caused by laser damage. Analysis based on the device structure, signal detection and processing of the sensor chip was then carried out. It shows that one possible reason is that the two measurements of pixel output voltage （Vsignal and Vreset） are gradually approaching to each other for the electric charges of photodiode capacitance will be quickly reduced by excessive photo-carriers, and the Vreset will be subtracted from Vsignal in correlated double sampling.