【作者】 刘勇；

【导师】 吴成柯；

【作者基本信息】 西安电子科技大学 ， 信号与信息处理， 2001， 博士

【摘要】 运动结构问题是计算机视觉领域的中心问题。而非定标图象序列的运动结构问题是近十年的研究热点。在理论方面，从多视角几何关系、射影重建到相机自定标技术都得到长足进展。在应用方面，随着计算机及网络技术的飞速发展，许多应用领域对三维图形数据提出更高的要求，而以往CAD三维图形获取方法有费工、费时和三维图形模型简单化的局限性。如何尽可能自动地获取复杂、逼真的三维图形模型是当前的一个前沿课题。本文针对这一课题进行探讨，在一些非定标运动结构问题的关键算法上提出一些新的改进。其有效性在仿真数据和真实场景图象序列实验中得到了证明。 1．在图象匹配算法中，提出了一个二维平面映射的随机抽样算法。使图象间共面特征基元的匹配效率提高。这种算法特别适用于特征基元共面占优的情况如建筑物序列。在对极几何关系的精确估计方面，提出了一种综合共面点和非共面点两种情况的基础矩阵优化算法。使得建筑物序列中的特征点的不利配置情况下基础矩阵的求解精度得到提高。 2．通过对相机的临界运动进行分析，指出了相机运动的关键性在于绝对二次曲面求解的模糊性这一结论。相对于以前的定义，我们的定义不仅针对相机内参数可变的情况，而且更清楚地指出关键性运动只是由相机的外参数决定的。 3．提出了综合景物约束条件的相机自定标新算法。该算法将景物中出现的直线的平行性和平面的正交性转换为新的求解相机自定标方程的约束条件。该约束条件使得绝对二次曲面的仿射特性和欧式特性与实际结果更为接近，从而所重建的三维景物的平行结构更为精确。也使使所重建的三维景物的正交性得到保证。并且，新约束条件的应用减少了求解绝对二次曲面的模糊性，从而提高了对于相机关键性运动的鲁棒性。 4．提出一种结合景物深度变化情况的三角剖分算法。该算法所生成的三维网格避免了以往算法容易在一些视角形成大空洞的缺陷，所形成的三维模型具有更好摘要的细节特性。5.对单轴旋转的相机运动进行分析，得到其三维重建所存在的模糊性结论并提 出相应算法去除该模糊性。本章提出的三维重建方法所需要的系统配置简单、 易于实现。适用于快速简单的小型物体建模。更多还原

【Abstract】 The Structure from Motion ( SFM ) problem is the central problem in computer vision community. The uncalibrated structure from motion problem ( USFM ) is the hot topic in the recent 10 years. Many theories, including multiple view geometry, protective reconstruction and camera self-calibration etc. have been proposed and well developed. In the applications, as the technologies of computer and internet developing, many applications require 3D graphic data of high quality. While previous CAD methods for 3D graphics are expensive in time and labor consumption, and the obtained 3D graphic models are often too simple for applications. One challenging problem is how to obtain complicated and realistic 3D graphic models as automatically as possible. This thesis is focused on this problem and improve some key algorithms in the USFM problem. The effectiveness of our algorithms are evaluated in the experiments with simulated data and real image sequences.1. In the image matching algorithm, a RANSAC homography method is proposed to improve the efficiency of coplanar feature matching. It is very suitable for the coplanar dominant case such as building image sequences. In the accurate estimation of epipolar geometry, a optimization algorithm for estimating Fundamental Matrix by integrating coplanar and non-coplanar correspondences. It makes the obtained fundamental matrices more accurate in the bad feature configuration in building sequences.2. An analysis on camera critical motion is given and a conclusion is proposed which clarifies that the critical motion is decided by the ambiguities of the absolute quadric. Comparing to the previous definition, our definition not only useful for the case of variable intrinsic parameters, but clearly show that critical motions are mainly caused by extrinsic parameters.3. A new theory and algorithm for camera auto-calibration is proposed by integrating some prior scene knowledge. The algorithm transform the line parallelism and plane orthogonality into some new constraints on auto-calibration equations, which makes the affine and Euclidean characteristics of the absolute quadric close to the practical one. This results the parallel and orthogonal structure of the reconstructed scene more accurate. Furthermore, the new constraints decrease the ambiguities in solving the absolute quadric, which improves the robustness of the previous algorithms to camera critical motions.4. A triangulation algorithm integrating the 3D depth information of the scene isproposed. It makes the detail characteristics of the reconstructed scene better. While the previous algorithms often produce the reconstructed 3D mesh with some large holes.5. By analyzing on the camera single axis rotations, we concluded that there are ambiguities in the 3D reconstruction. A corresponding approach is proposed to remove the ambiguities. This kind of method for 3D reconstruction requires a simple and feasible system, which is suitable for modeling small objects.更多还原