Research On The Theory And Key Techniques Of3D Photogrammetry With One Single Hand-held CCD Camera

Three-dimensional (3D) coordinate measurement is prerequisite for reverse engineering,product quality inspection, robot visual navigation, virtual reality etc. The work in this thesisfocuses on improving the robustness and accuracy of digital close range photogrammetrymeasurement system based on a hand-held CCD camera. Several key issues in3D measurementsystem are further studied in this paper, including target extraction from image, multi-cameraposition and orientation locating, outlier removal in3D reconstruction, globally optimal solutionof3D coordinate, system parameter identification and correction etc. The main contents andcontributions of the dissertation are as follows:1. An edge extraction method based on Canny edge detector and polynomial surface fittingwith sub-pixel accuracy is presented. It provides a good foundation for precise location of thecircular coded marker centers. The precision of the image coordinates of the coded markercenters is one of the critical factors for3D photogrammetry. An improved grey centroid methodis put forward in the paper. Compared with the least-squares ellipse fitting, the traditional greycentroid and the dual conic fitting approach presented recently, the proposed method can obtainsignificantly more stable and precise coded marker centers.2. An improved algorithm for robust estimating the camera relative position and orientationof pairs of views is put forward. The multi-solutions problem involved in the essential matrixestimation is resolved. In addition, the parameter estimation formula in the robust model iscorrected. Comparisons with several representative five-point algorithms show that the algorithmcan advance the robustness and precision of the camera relative orientation. The algorithm serveswell as the input for the following3D reconstruction pipeline. By utilizing the rotationalconsistency theory, an approach to estimating the global rotations in multi-view reconstruction isproposed. It achieves the camera relative orientations under the world coordinate system.According to the maximum spanning tree algorithm in graph theory, image group with thehighest reliability of coded markers correspondences between image pairs is built. A globalmatching relationship can be achieved by the reliable image group.3. A fast and stable method for multiple view geometry reconstruction with known rotationsis presented. Using the linearity of re-projection error function, this article puts forward theadaptive outlier removal method usingL1norm and minmax problem during3D reconstruction.By introducing slack variables into the objective function, the outlier removal problem can beanswered by the linear programming problem about slack variables. It improves the stability and efficiency of the algorithm simultaneously. Comparisons with three representative outlierremoval approaches based on slack variables show that the method in this paper can keepgenuine inliers and decrease the re-projection error.4. According to the convex optimization theory, an approach to verifying global solution formultiple view geometry reconstruction problems usingL2is derived. The convexity of there-projection error function is utilized to verify whether the local solution is globally optimal. Abranch and bound algorithm for globally solving the non-convexity sum of ratios problem is putforward. Compared to Lï¿¥-norm-based global optimization, the proposed approach has highercalculation accuracy and computing efficiency.5. A concise implicit image correction approach for accurate reconstruction of multiple viewgeometry is presented. By introducing six implicit distortion coefficients, the image correctionapproach has been integrated into the3D reconstruction optimization model. Experiments haveevidenced that the method can significantly improve the3D positioning accuracy. The methodplays a key role in accurate multiple view geometry reconstruction.6. Based on the established accurate multiple view geometry, the methods for3Dreconstruction of points or line segments are put forward. Point correspondences between imagepairs are generated. Under the global correspondence of the coded markers, the match for twopoint set is obtained using shape context and probabilistic relaxation. Then the matching result isverified by thin plate spline function. The method for line segments feature extraction, globalcorrespondence, and3D reconstruction is proposed. Practical examples include an automobiledoor sheet metal part, the wing of an aircraft, a pipeline model frame, motorcycles and othersample objects.The proposed algorithms and system modules have all been fully experimented, comparedand analyzed. It has been demonstrated that the representative target objects can be obtained bythe prototype system with good measurement stability, high measurement accuracy, andsatisfactory measurement efficiency.