CCD区域倍频读出及其对成像的影响

在某空间项目中，需要使用一款指定的CCD传感器研制一套用于空间成像的CCD摄像机系统，并且要求图像的帧频高于CCD传感器的标准帧频。简单的超频读出CCD会使摄像机的信噪比下降。文中首先分析了CCD摄像机在空间条件下影响成像信噪比的多种原因，发现读出噪声对输出图像的信噪比影响是最大的。使用区域倍频读出方法来提高CCD摄像机的输出帧频，即在图像的水平和垂直方向都使用4倍的时钟读出部分像元。最后把区域倍频读出CCD的图像信号和整体超频读出CCD的图像信号进行了信噪比对比检测，测试结果表明区域倍频读出的CCD图像质量较好。

CCD reginal frequency doubling readout and its effect on the imaging

In some space project,a specific CCD sensor has been used to design a set of space imaging CCD camera system,and the image frame rate is higher than the standard frame rate of CCD sensor.Signal to noise ratio should be decreased by simple overclocking readout the CCD.Firstly,a variety of reasons which could affect the imaging signal to noise ratio of CCD camera under the space conditions were analyzed,it had been found that readout noise was the most important reason.So the regional frequency doubling readout methods was introduced and used to improve the output frame rate of CCD camera.Namely,four times the pixel clock was used to readout part of CCD pixels in the horizontal and vertical directions.Finally,the SNR of image signal by regional frequency doubling readout CCD and overclocking readout CCD was compared.Test result shows that the former image has higher SNR.