模拟增益对电荷耦合器件信噪比与动态范围影响的实验研究

Experimental study of the effects on signal noise ratio and dynamic range caused by analog gain for CCD

电荷耦合器件(CCD)是遥感成像系统的核心部件,为了在低照度、低量化位数的情况下获得高信噪比与大动态范围的遥感图像,首先根据CCD的结构与噪声物理性质给出了模拟增益、量化位数与CCD信噪比的关系,接着搭建了CCD的积分球标定系统,依据实验数据建立了散粒噪声、光子响应非均匀性噪声以及基底噪声的数学模型,然后着重分析了低照度情况下模拟增益与信噪比之间的关系,最后搭建了实际成像系统,获取了低照度情况下不同模拟增益系数的遥感图像.结果表明理论分析、实验室积分球标定数据与实际成像图像符合良好,即模拟增益提高1至2倍,可显著提高CCD信噪比,同时获得较大的动态范围.

Charge coupled device （CCD） is a key component in a remote sensing system. In order to obtain high signal-to-noise ratio （SNR） and dynamic range in low illumination and quantization circumstance, first, according to CCD architecture and noise physical characteristics, relationship between analog gain quantization step and CCD SNR is proposed; next, integrating sphere calibration system is established, shot noise, photo response nonuniformity and noise floor model are also built, and the next relationship between analog gain and SNR in low illumination condition is analyzed thoroughly; finally, the practical photographing system is built, and remote images in different gain parameters are acquired. Theoretical analysis, experimental calibration, and practical images all indicate that when analog gain is increased by one to two times, the SNR is improved greatly and dynamic range is acceptable.