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题名	CCD错位成像系统与高分辨率图像重构技术
作者	李亚鹏
学位类别	博士
答辩日期	2015-05
授予单位	中国科学院大学
导师	何斌
关键词	CCD错位成像 分辨率 调制传递函数 仿真验证 KAI-1020 二维平移台 图像重构 图像梯度 改进的维纳滤波 棱镜拼接 ICX415AL 实时错位成像系统
其他题名	CCD subpixel imaging system and high-resolution image reconstruction technique
学位专业	光学工程
中文摘要	电荷耦合器件（CCD）被广泛应用于航空和航天遥感成像中，在环境监测、资源普查、地形测绘和军事侦察等领域发挥着重要作用，随着遥感应用技术的发展，人们对遥感相机的分辨率提出越来越高的要求。采用传统方法提高遥感相机分辨率，一是增大光学系统焦距，则会造成遥感相机体积、质量、成本大大增加，且必须重新设计光学系统；二是减小CCD像元尺寸，在光机系统不变的情况下，减小CCD像元尺寸，造成成像系统MTF下降、信噪比降低，影响成像质量。尤其是在红外探测方面，由于红外谱段的特殊性质及红外谱段感光材料的限制，相比于可见光谱段探测器，红外探测器的像元尺寸一般较大，像元间距也较大，在相同的光学系统下，红外谱段图像的分辨率较低，采用传统方法提高红外相机空间分辨率，将造成卫星相机体积、质量成倍增长，光机结构难以实现，对卫星装载平台要求更苛刻。 如何在现有光机系统不变的前提下，提高成像系统分辨率、增强图像质量，成为研究热点问题。近年来，CCD错位成像技术备受国内外关注。CCD错位成像技术能在不改变光学系统焦距和CCD像元尺寸的前提下，提高相机空间分辨率，增强图像质量，在具有相同或接近的空间分辨率的情况下，能减小相机光学系统的焦距，从而使卫星相机的体积、质量、成本降低，随着航空航天相机向着高分辨、轻型化、小型化方向的不断发展，深入研究和探索CCD错位成像技术，对提高卫星相机、尤其是红外相机空间分辨率、实现卫星小型化具有重大意义。 应用CCD错位成像技术的关键在于如何获取具有亚像素位移的低分辨率图像以及如何从多幅低分辨率图像提取冗余信息重构高分辨率图像，基于此，本文对CCD错位成像系统的实现以及高分辨率图像重构技术做了深入的研究，论文主要研究工作以及研究成果如下。 1，从调制传递函数（MTF）的角度定量评估了CCD错位成像模式的图像质量，建立了不同像元填充因子的CCD错位成像的仿真数学模型，并在Matlab上采用ISO12233靶标进行了仿真验证。基于MTF的定量分析和基于Matlab的仿真表明，错位成像能提高成像图像的MTF，增强图像质量，综合考虑光学遥感成像系统的图像质量、数据量、信噪比及系统复杂度等因素，由两排线阵CCD错位1/2像元的错位成像模式和面阵CCD四点错位成像模式性价比最高，确立了最优的CCD错位成像方案，为CCD错位成像系统的设计提供了参考。 2，建立了一种基于高精度二维平移台的CCD错位成像系统，采用自行设计的KAI-1020成像系统，实现了对角错位成像模式和四点错位成像模式，得到相互错位半个像元的多幅低分辨率图像。采用SIFT配准方法对得到的错位图像进行配准，结果表明，平均错位误差为0.015个像元，最大错位误差为0.05个像元。提出的错位成像实现方法对移位精度要求低、易于实现，克服了现有CCD错位成像实现方法结构复杂、实现难度大、成本高、周期长、对移位精度要求苛刻等缺点。 3，提出了一种基于图像梯度的三次B样条高分辨率图像重构算法，对对角错位成像模式中得到的两幅相互错位半个像元的低分辨率图像进行插值重构，得到重构高分辨率图像。与传统插值算法的对比表明，提出的算法在各项图像质量评价指标上均有所提高，图像的边缘细节更丰富，减小了边缘细节失真，视觉效果更好。 4，提出结合CCD错位成像技术和图像复原技术提高图像质量，并提出了一种基于MTF的改进维纳滤波算法，补偿重构高分辨率图像的MTF。采用基于MTF的改进维纳滤波算法进行图像复原，在锐化图像细节的同时，能在一定程度上抑制平坦区域的噪声，提高图像的信噪比。对错位成像得到的相互错位半个像元的低分辨率图像进行重构，并进一步进行图像复原，实验结果表明，错位成像技术能将图像分辨率至少提高1.4倍，降低图像混叠，增强图像质量。采用基于MTF的改进维纳滤波算法进行图像复原，有效补偿了重构高分辨率图像的MTF，在锐化图像细节的同时，抑制了平坦区域的噪声，提高了图像信噪比。结合CCD错位成像技术和图像复原技术，解决了重构图像分辨率提高、MTF下降的问题。 5，提出了一种CCD错位成像的应用实施方案。采用两片相同的面阵CCD，通过半反半透棱镜拼接实现CCD对角错位成像模式，以FPGA为核心，控制两片面阵CCD同时成像，得到同一时刻、同一场景在二维方向上均相互错位半个像元的两幅图像，在FPGA上实时实现后期高分辨率图像重构算法和图像复原，最终可以实时输出分辨率得到提高、MTF也经过补偿的高分辨率图像。采用两片Sony公司ICX415AL为图像传感器，以Altera公司EP4CE30F484为主控制器，搭建完成了基于棱镜拼接的CCD错位成像系统。
英文摘要	Charge-coupled device (CCD) is widely used in aviation and aerospace remote sensing imaging, and plays an important role in various fields, such as environmental monitoring, resource surveys, topographic mapping and military reconnaissance. With development of remote sensing application technology, higher spatial resolution of space camera is continuously requested. There are two traditional methods to improve spatial resolution of remote sensing camera, increasing the focal length of optical system and reducing the CCD pixel size. Improving spatial resolution of remote sensing camera using traditional methods will result in volume, weight, and costs of space camera increasing significantly, and system MTF, SNR, and image quality decreasing. Especially in infrared imaging field, due to the special nature of the infrared spectrum and limitations of the infrared photosensitive material, compared to the visible spectrum detectors, pixel size and pixel pitch of infrared detector are generally much larger, so spatial resolution of infrared imaging system is lower with the same optical system. Therefore, volume and weight of space camera will increase quickly using traditional methods to improve the spatial resolution, and optics and mechanism of space camera is difficult to realized and requirements of the satellite platform is more rigorous. Research on how to improve the spatial resolution and enhance image quality of the imaging system with the existing system has become a hot issue. CCD subpixel imaging technology has been researched broadly in recent years. CCD subpixel imaging technology is effective to enhance the spatial resolution without changing the focal length of optics and the CCD pixel size. In the case of having the same or nearly same spatial resolution, it can reduce the focal length of optics, and volume, weight of space camera decrease consequently. With development of space camera toward high resolution and miniaturization, it is significant to research and explore CCD subpixel imaging technology. For CCD subpixel imaging technology, how to obtain the low-resolution images with sub-pixel displacement and how to reconstruct the high-resolution image are two key problems. Based on that, realization of CCD subpixel imaging system and high-resolution image reconstruction technique has been mainly researched in this paper. In this paper, the main research contents and achievements can be summarized as follows. First, quantitative evaluation of image quality of subpixel imaging based on MTF is performed. A mathematical model for simulating CCD subpixel imaging with different CCD pixel fill factor is established, and simulation experiment using a sub-image of ISO12233 standard resolution card is performed on Matlab. Quantitative evaluation based on MTF and simulation on Matlab indicates that CCD subpixel imaging technology can improve MTF and enhance image quality. Considering image quality, the amount of data, SNR and system complexity of optical remote sensing imaging system in the round, the 1/2 pixel subpixel imaging mode using two linear CCD and four point subpixel imaging mode is most reasonable, the proposed method has some reference value to the design of CCD subpixel imaging system. Second, an area CCD subpixel imaging system based on high precision two-axis translation table is realized using self-designed KAI-1020 imaging system. Multiple low-resolution images which shift half pixel with each other are achieved according diagonal subpixel imaging mode and four point subpixel imaging mode. Registration by using SIFT method is performed to achieved multiple low-resolution images and result show that the average shift error is 0.015 pixels and the maximum shift error is 0.05 pixels. The method proposed to implement subpixel imaging reduce shift precision requirement and is easy to realize, overcoming some disadvantages in existing subpixel imaging realization ways, such as complex structure, difficult to implement, high cost, high subpixel precision and so on. Third, a cubic B-spline high-resolution reconstruction algorithm based on image gradient is proposed. Two low-resolution images shift half pixel with each other that obtained in diagonal subpixel imaging mode are interpolated and reconstructed using proposed algorithm. Compared to traditional reconstruction algorithm, image quality evaluation parameters of reconstructed image are improved using proposed algorithm. The proposed algorithm also reduces the distortion of reconstructed image edge detail and improves the image quality of reconstructed image. Forth, image restoration combined with CCD subpixel imaging to enhance image quality together is proposed. An improved Wiener filtering algorithm based on MTF is proposed and performed to compensate MTF of reconstructed high-resolution image. Experimental results demonstrate that CCD subpixel imaging can improve image resolution to 1.4 times at least, reduce image aliasing and enhance image quality. Image restoration using proposed improved Wiener filtering algorithm not only can enhance image detail, but can suppress noise and improve SNR of reconstructed image. Image restoration can effectively compensate MTF of reconstruction images of subpixel imaging, which solve the problem of resolution enhancement but MTF reduction in subpixel imaging. Fifth, an application and implementation plan using CCD subpixel imaging is proposed. CCD diagonal subpixel imaging system based on prism is implemented by using two same CCD sensors. The two CCD are fixed manually which shift half pixel in two-dimension direction. The CCD imaging system is designed based on FPGA. The two images obtained by two CCDs shift half pixel in two-dimension direction with each other. Reconstruction and image restoration are realized real-time on hardware based on FPGA controller. Final high-resolution image that spatial resolution is improved and MTF is compensated is output and obtained by CCD subpixel imaging system. CCD subpixel imaging system based on prism is implemented on hardware using two CCD ICX415ALs of Sony Corporation as image sensor and Altera's FPGA EP4CE30F484 as controller.
公开日期	2015-12-24
内容类型	学位论文
源URL	[http://ir.ciomp.ac.cn/handle/181722/48866]
专题	长春光学精密机械与物理研究所_中科院长春光机所知识产出
推荐引用方式 GB/T 7714	李亚鹏. CCD错位成像系统与高分辨率图像重构技术[D]. 中国科学院大学. 2015.

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