CCD数字像元的合并方法及其应用

星载差分吸收光谱仪中的科学级帧转移型电荷耦合器件(CCD)通常使用四行像元合并(4-Binning)方法提升载荷的信噪比,但该方法仅能工作在目标光强较弱的环境。为使载荷适应目标光线较强的环境,设计了数字像元合并方法(4-AVR)来提升载荷的探测能力。考虑相对常规的4-Binning方法,4-AVR方法会产生CCD信号衰减现象,故对这一现象进行了理论分析,得到由于CCD读出速率导致的信号衰减系数为0.699。在实验室搭建了测试装置,验证了上述结果,结果表明,4-AVR方法下获取的CCD像素值相对于4-Binning方法获取的像素值的衰减系数为0.698,从而证实了理论分析的正确性。实验显示,使用这一系数可完成对4-AVR方式下获取的像素值的校正,从而实现两种方法的无差别化。将校正方法作为载荷一级数据处理的一部分,进行了大气痕量气体的反演测试。结果表明数字像元合并方法可保证大气痕量气体的反演精度,进一步验证了数字像元合并方法的可靠性。

Digital binning method for CCD pixels and its applications

Scientific grade frame-transfer Charged Coupled Devices(CCDs) in a space-borne differential optical absorption spectrometer usually use a Pixel Binning (4-Binning)method to improve its Signal-to-Noise Ratios(SNRs).It is only suitable for the quite weak radiation.Toallow the spectrometer to be used for stronger radiation and to expand itsdetection ability, a digital pixel binning method, 4-AVR, was designed.Comparing to the 4-Binning method, this 4-AVR method brings the attenuation of CCD signals.Therefore, the attenuationwas researched theoretically, and a signal attenuationcoefficient0.699 due to the CCD signal readout speed was obtained.Then, testing devices werebuilt in the lab to get the data of pixel values of CCD in both 4-Binning and 4-AVR methods.The result shows that the attenuation coefficient of CCD pixel values is 0.698, which verifies the theoretical result.The experiment demonstrates that the coefficient can be used to correct the pixel values gained in the4-AVR method to implement the consistency of two methods.By taking the correction as a part of 1-B data processing, the tests of atmospheric trace gases were retrieved, and results indicate that the method ensures the quantitatively data of the space-borne spectrometer, which verifies the reliability of the method.