无控制点条件下机载光电平台图像的几何校正

	无控制点条件下机载光电平台图像的几何校正
其他题名	Geometric correction of Airborne Optoelectronic Image withoutControl Points
	李铁成
学位类型	硕士
导师	刘晶红
	2015-10
学位授予单位	中国科学院大学
学位专业	机械工程
关键词	航空光电成像几何校正相机标定相机内参数相机外参数
摘要	当前，机载光电平台成像技术在各个领域发挥着举足轻重的作用，尤其在航空侦察方面。机载光电平台在采集图像时，由于其自身的姿态、高度、速度等多种因素造成图像发生几何畸变，其体现在现实世界的物体之间的位置关系映射到影像时产生了变化，像元本身与地表对应物体的现实空间排布相产生了弯曲、挤压、偏移、伸缩等。图像产生的上述畸变称之为几何畸变，对其进行的校正即为几何校正。现有的机载光电平台图像几何校正方法主要依赖于地面控制点，利用足量且均匀的地面控制点，采用多项式拟合算法进行校正。由于机载光电平台图像存在数量多、像幅小、图像倾角大且无规律等特点，这种方法需要有足够数量且分布良好的地面控制点才能获得较好的图像校正效果。然而，获取大量的控制点信息，需要专用的测量仪器和大量的人力物力，尤其在山区、海洋、森林等区域，地形复杂且实地勘测难度较大，人工很难精确测量地面控制点[5]。本文简要介绍了运用控制点的几何校正思想，之后详细阐述了在无控制点的情况下，通过相机内外参数对机载光电平台原始畸变图像几何校正，建立精准的几何模型，运用Matlab的Camara Calibration Toolbox完成标定摄像机获取相机内参数的工作，采用惯性导航系统提取飞行姿态角进而获得相机外参数，再依据提取的内外参数对图像的几何畸变进行校正。本文对机载光电平台图像几何畸变原因作了深入的探讨，在其他外部条件理想的情况下，畸变主要受机载光电平台本身的飞行姿态及其载荷相机的旋转角度影响。论文对传统的基于地面控制点的几何校正方法进行了介绍，分析了传统的几何校正方法的局限性，引出了本文的几何校正方法。本文重点研究了机载光电平台成像系统的相机内外参数及坐标变换等内容，详细阐述了相机标定方法的原理和标定模型，提出了正确的校正矩阵，给出了相机内外参数及畸变系数的求解过程。通过机载光电平台载荷相机结合图像采集盒内的图像编码器进行了图像的采集过程，通过Matlab的相机工具箱对相机内参数和畸变系数进行提取及优化。在实验室搭载光电平台模拟航拍的过程中，将惯性导航系统与摄像机相互固定并在PC上显示其提取的姿态角，结合图像编码器读取的相机相对载荷的旋转角度完成相机外参数的获取。根据获取的相机内外参数经严格的数学推理建立了畸变图像到校正图像的转换矩阵。运用双线性插值算法在Matlab环境下编程改进处理，实现了PC上的畸变图像的几何校正过程，且校正速率较快。本文采用均方根对误差进行分析，经分析，此方法校正效果良好，为将本文算法移植到FPGA硬件上进行工程化应用奠定了坚实的基础。
其他摘要	At present, the airborne electro-optical imaging technology plays an important role in various fields, especially in aviation reconnaissance. Airborne optoelectronic platform in the acquisition of images, due to its own attitude, height, speed and other factors resulting in geometric distortion of the image, reflects the position relationship between the objects in the real world mapping to image changes. Pixel itself and surface corresponding to the object of real space arrangement occurred bending, compression, migration and expansion.The distortion of the image is called the geometric distortion, and the correction to this distortion is the geometric correction. The existing methods of airborne optoelectronic platform image geometric correction mainly depend on the ground control points, and the use of polynomial fitting algorithm is used to correct the ground control points.Because of the large amount of airborne optoelectronic platform, such as a large amount of image, large angle and no regularity, this method needs a large number of ground control points and can obtain good image correction results.However, access to a large number of control points, the need for a dedicated measurement instrument and a large number of human and material resources. Especially in mountainous area, sea, forest and other areas, the terrain is complex and difficult to measure. It is difficult to measure the ground control points precisely. In this paper, the geometric correction of control points is introduced briefly, and then the geometric correction of the original distortion image of the airborne electro-optical platform is described in detail. To establish a precise geometric model, the Matlab Calibration Toolbox is used to obtain the camera parameters, and the inertial navigation system is used to extract the flight attitude angle and then obtain the camera external parameters. In this paper, the geometric distortion of airborne electro-optical platform is discussed, and the distortion is mainly influenced by the flight attitude and the rotating angle of the camera. The traditional method of geometric correction based on ground control points is introduced, and the limitation of the traditional method is analyzed. In this paper, the internal and external parameters of the camera and the coordinate transformation of the airborne electro-optical imaging system are studied in this paper. The principle and calibration model of camera calibration method are described in detail. Correct correction matrix is put forward. The solution of the internal and external parameters and distortion coefficients are given. The image acquisition process is carried out by using the airborne photoelectric platform load camera and image acquisition system. The camera parameters and distortion coefficients are extracted and optimized by the Matlab camera.In the laboratory is equipped with aerial photoelectric platform simulation process, the inertial navigation system and the camera are fixed to each other and on the PC display the extracted pose angle, combined with the rotation angle of the camera image coder read relative load completed the acquisition of the camera's parameters.According to the intrinsic and extrinsic parameters of the camera, the transformation matrix of the distorted image to the corrected image is set up.Application of bilinear interpolation algorithm in Matlab programming, the geometric correction of the distorted image on PC is realized, and the correction rate is faster. In this paper, the root mean square error is analyzed, and the method is effective. The method can be applied to FPGA hardware for engineering application.
语种	中文
文献类型	学位论文
条目标识符	http://ir.ciomp.ac.cn/handle/181722/49313
专题	中科院长春光机所知识产出
推荐引用方式 GB/T 7714	李铁成. 无控制点条件下机载光电平台图像的几何校正[D]. 中国科学院大学,2015.

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