星上CCD成像非均匀性的实时校正

Real-time correction of nonuniformity in CCD imaging for remote sensing

研究了时间延时积分(TDICCD)成像产生非均匀性的原因,基于两点校正算法探讨了星上图像非均匀性实时校正的可行性方案。鉴于工程一体化设计的要求,在常用的CCD时序处理器FPGA上实现了硬件实时校正。通过对相机均匀辐射定标,利用FPGA读取前32行TDICCD图像数据进行非均匀性等效灰度值(NUEDN)计算,根据工程经验,设定当NUEDN>2时对数字图像进行非均匀性实时校正。硬件实时校正结果表明,均匀辐照下NUEDN可降至0.29。实验室动态目标滚筒成像试验表明,实时校正后TDICCD推扫成像均匀光滑,满足工程需要。

The reasons for the nonuniformity in CCD imaging were researched,and the feasible schemes to correct the nonuniformity of an image from a satellite were discussed by using a flat field correction method.Then,based on FPGA-based processor,a real-time correction approach was presented to control all of the operations of TDICCD to implement the hardware correction of the nonuniformity.Furthermore,the Nonuniformity Equivalent Digital Number （NUEDN） was calculated by using FPGA to extract the first 32 rows of a raw image in the uniform exposure,and the real time correction for digital images was carried out when the NUEDN was set to be more than 2.The experimental results in the uniform exposure indicate that the NUEDN falls to 0.29.Dynamic push-scanning imaging test was also performed with a standard resolution chart attached on a roller,and the results have proved the validity of the approach in practical projects.