为了抑制CCD相机视频处理链路中由于工作温度、器件老化等因素引起偏置变化对图像质量的影响，对整个视频处理电路采取实时偏置修正的方法.首先，为了获取每一帧图像经过链路时偏置的变化，分析并修改了CCD相机驱动电路和图像处理电路等模块的工作时序.然后在图像处理模块中计算每帧图像的像元偏置修正值，并对整幅图像的每个像元进行偏置实时修正.最后输出经过修正的图像.实验结果表明：图像经过实时偏置修正后，每帧图像的偏置值基本都在同一水平.在测试模式下，获得图像偏置的均值都在107 DN左右.在CCD两路输出时，左右两路图像偏置的均值的差值由170.9 DN减小到4.8 DN.所以此方法不仅抑制了整个视频处理链路偏置的不稳定性，而且也消除了CCD双路输出时两路数据偏置的不同.

In order to restrain the effect on the images from the variation of the bias caused by factors such as the working temperature and the aging of electronic devices in video processing circuit of CCD camera, the bias of the circuit are modified in real time. Firstly, the time sequence of the modules in the drive circuit of CCD camera and the image processing circuit was analyzed and modified to acquire the bias variation of the every frame image as passing the circuit. Then the modified values of the pixel of every image were calculated by the image processing block. Finally, the modified image was output. Experimental results indicate that the bias of each image is on the same level after being modified. The mean of modified frame is some 107 DN under test mode. The difference of mean between two output port images is reduced from 170.9DN to 4.8DN. The method not only eliminates the changes of video processing circuit’s bias, but also removes the difference of bias between the two output port of CCD.