【作者】 刘侍刚；

【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， 2005， 博士

【摘要】 本论文研究了如何由非定标图像序列恢复三维物体,对其中的若干关键技术,特别是射影重建和自定标进行了深入研究。传统的方法都是针对已定标的图像序列进行的,因而很难推广应用,实用性较差。本文的重点是在理论和实践两方面研究了,在既不知道相机内部参数,又不知道相机外部参数的情况下,如何由图像序列进行三维欧氏重建。本文给出的方法提高了三维物体重建的精度和速度。主要成果如下: 1.提出了1维子空间射影重建方法。该方法利用第1幅图像点构成的3个行向量外加一个行向量就可以组成射影空间中一个基底的特性,将4维子空间转化为1维子空间。理论分析和实验结果表明,该方法具有重建精度高和计算量小的优点。 2.提出了一种利用重投影点代替遮挡点的基于遮挡射影重建方法。该方法首先假设遮挡点都位于图像中心,进行射影重建,然后利用重投影点代替图像中的遮挡点,经过多次迭代,最后求到遮挡点的真实图像位置并完成射影重建。由于该方法利用了所有可见点的信息求解遮挡点的位置,因此具有较高的重建精度。 3.提出了基于几何距离意义和代数距离意义下的线性迭代集束调整方法。由于调整的参数值变化非常小,可利用上一次迭代求到的值代替本次迭代过程中的值,交替地求取投影矩阵和射影空间点。理论和实验结果表明,该方法具有收敛速度快、运算量小等优点。 4.提出了一种利用绝对二次曲面约束方程的线性迭代自定标方法。该方法首先假设相机的畸变因子为0及主点坐标位于原点,利用绝对二次曲面约束方程,得到相机的初始内参数,再通过图像的坐标变换,使图像符合开始假设的相机所获取的图像,经过多次线性迭代,最终实现相机的自定标。实验结果表明,该自定标方法具有运算量小、收敛性好等优点。 5.提出了一种基于图像变换矩阵,将绝对二次曲面像的各个元素变换到同一个数量级上的自定标方法。在已往的自定标方法中,由于二次曲面像的各个元素不在一个数量级上,导致对噪声极其敏感。本文提出的方法在不增加计算复杂度的条件下,能够提高自定标的精度及鲁棒性。 6.提出了一种适用于摄像机相对景深做较小运动情况下的基于单应性矩阵的增更多还原

【Abstract】 Our research is focused on the problems of 3D reconstruction from image sequences and some critical issues related to this subject, such as projective reconstruction and camera self-calibration. Traditional approaches are based on a preliminary calibration of the camera setup. This, however, is not always possible or practical. The goal of this work is to investigate the theoretical and practical feasibility in Euclidean reconstruction from image sequences without any prior knowledge either about the parameters of the cameras, or about their motions. Meanwhile, several methods, such as how to improve the accuracy and the speed of reconstructed 3D object, are considered in this thesis. Main contributions are as follows:1. An iterative factorization method based on 1D subspace for projective structure and motion is presented. It relies on the fact that the basis of projective subspace can consist of the three rows in the matrix comprising the first image points and one row vector that is orthogonal the former. The experiments with both simulate and real data show that the method is efficient for the recovery of projective structure and motion.2. A method for projective reconstruction from uncalibrated image sequence with occlusions is proposed. The re-projection points replace all the occlusions and projective reconstruction is obtained from all the points alternately, and the real positions of occlusions and the accurate projective reconstruction are finally obtained. Because the occlusions are obtained from all the image points, the method is precise for the recovery of projective structure and motion.3. To minimize the mean-squared algebraic distance and the geometric distance, we propose a linear resection-intersection bundle adjustment method for photogrammetric bundle adjustment. We adjust the parameters in so small range that the values of projection matrices and the space points can be substituted by their values in the last iteration. The theory and experiments show the convergence speed of the method is fast.4. A camera self-calibration method based on the linear iteration is presented. Based on the constraint equations of the absolute quadric and the hypotheses that the skew factor is zero and principle point locates the origin, the initially camera intrinsic parameters are attained. By the coordinate transformation, the image sequence accords with the one that the assumed camera captures. After several iterations, thereal intrinsic parameters are obtained. The experiments show that the self-calibration method is efficient, robust and has good property of convergence.5. The elements of the dual absolute quadric have so large differences in magnitude that solutions are extremely sensitive to noise. To solve the problem, we proposed the method that all the elements of the dual absolute quadric are transformed into the same magnitude based on an evaluative intrinsic parameter. The self-calibration method can lead to an enormous improvement on the stability and robustness of the results without increasing computation.6. We address an augmented reality system that operates in the environment that the translation of the camera is very small compared with the distant to the 3-D scene. This is a special case of the general problem, which significantly simplifies merging the real and the virtual, because a homography can describe the image motion between two frames of a video sequence. The theory and experiments with real video sequence show that the proposed AR system is very simple and efficient.更多还原