“高分七号”卫星双线阵相机暗电流特性分析及校正

Analysis and Correction of Dark Current for the Dual Line Array Camera of GF-7 Satellite

暗电流的有效去除能够提高相机动态范围,提高相机在低辐照条件下的成像能力。文章对"高分七号"卫星双线阵相机应用的两款CCD各谱段的暗电流及其噪声特性进行了分析,在此基础上分别选取了不同的暗电流估计方法,给出了校正算法的数学模型,利用FPGA开发工具对校正算法进行了实现,应用中分析了影响校正效果的各种因素。使用标定的暗电流估计系数进行暗电流校正,结果显示两台相机的暗电流均得到去除,选取的估计方法合理有效。

Dark current is an important and elementary part in CCD output signal,which affects imaging characteristics obviously.Removal of dark current raises dynamic range of the camera and improves the imaging capability in lower irradiation conditions.Firstly,a correction algorithm is given after analyzing the characteristic of CCD dark current and its noise of the high resolution stereo mapping camera of GF-7 satellite.Then,the hardware module of the correction algorithm is developed using a FPGA design tool.Finally,the proposed correction algorithm is tested in hardware circuit and the factors affecting the result of correction are described.The experimental result shows that both the dark current noise of two cameras are removed remarkably by dark current estimation coefficients calculated during the relative radiometric calibration,which improves the validity of the estimation methods.