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随着时间延迟积分技术(Time Delayed and Integration,TDI)的不断成熟,具有TDI功能的电荷耦合器件(Charge Coupled Devices,CCD)已经广泛应用到高分辨率对地成像系统。然而,采用TDI功能的成像系统在推扫成像过程中必然会受到像移的影响,导致最终成像模糊。主要分析了TDI成像过程中光学系统畸变引起像移的原因,推导了畸变产生像移的数值计算公式,分析了光学系统畸变对TDI成像相机调制传递函数的影响,研究了畸变和像移导致的TDI成像相机图像退化的关系,针对焦距为9 000 mm、积分级次96级、地面像元分辨率GSD=0.6 m,λF/p=1、信噪比为50:1的TDI成像相机,计算了在畸变产生的像移影响下导致的NIIRS(National Imagery Interpretability Rating Scale,美国国家图像解译度分级标准)的变化值ΔNIIRS,计算结果表明在畸变导数值D′(θ)=6.493时引起的ΔNIIRS达到-0.162 4将影响图像的解译需求,最后分析给出了对于该空间相机不影响解译需求的D′(θ)限制条件。可为光学遥感TDI成像系统的设计提供参考。
With the continuous maturation of Time Delayed Integration (TDI), TDI-enabled Charge Coupled Devices (CCDs) have been widely applied to high-resolution ground-based imaging systems. However, TDI-enabled imaging systems are inevitably affected by image shift during push-to-scan imaging, resulting in blurred final images. This paper mainly analyzes the cause of image shift caused by optical system distortion during TDI imaging and deduces the numerical calculation formula of image distortion caused by distortion. The influence of optical system distortion on modulation transfer function of TDI imaging camera is analyzed. The effects of distortion and image shift TDI imaging camera image degradation for the TDI imaging camera with a focal length of 9 000 mm, 96 integral levels, ground pixel resolution of GSD = 0.6 m, λF / p = 1 and a signal-to-noise ratio of 50: 1 The change ΔNIIRS of the NIIRS (National Imagery Interpretability Scale) resulting from the effect of image shift caused by the distortion shows that when the distortion derivative value D ’(θ) = 6.493 ΔNIIRS of -0.162 4 will affect the interpretation requirements of the image. The final analysis gives the D ’(θ) constraint that the space camera does not affect the interpretation requirements. It provides a reference for the design of optical remote sensing TDI imaging system.