tailieunhanh - Advances in Theory and Applications of Stereo Vision Part 12

Tham khảo tài liệu 'advances in theory and applications of stereo vision part 12', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Navigation in a Box Stereovision for Industry Automation 265 vergence due to calibration so that the corresponding feature in the right camera always lies on the left side along the epipolar line with respect to the left feature coordinates this is not the case of stereo cameras with non zero vergence . In Fig. 10 an example of the described technique is shown. The left feature in the image defines the epipolar line in the right image as well as the related search window along the epipolar line. 6. Stereo triangulation and depth error modelling After the corresponding features in the two images are correctly matched the stereo triangulation can be used to project the interest points in the 3D space. Unfortunately the triangulation procedure is affected by an heteroscedastic error Matei Meer 2006 Dubbelman Groen 2009 non homogeneous and non isotropic as shown in . An accurate error analysis has been performed in order to provide an uncertainty modelling of the stereo system to the subsequent mapping algorithms that are based on probabilistic estimations. Both 2D and 3D modelling has been investigated. Knowing the feature projections in the left and right images xL and xR the two dimensional triangulated point P can be found by the well known relations 13 as a function of the baseline b and the focal length f. xL xR b P b f 13 PX 2 xL - xR xL - xR 1 . xL s xR s PX s z X. z b Pz s b C8 14 Xl s - Xr s 2 Xl s - Xr s A noise error s has been added to the features coordinates in both images and the resulting noise in the triangulation is represented by a rhomboid whose shape is analytically described by eight points obtained appropriately adding and subtracting the noise s to the nominal image coordinates through 14 . The diagonals D and d in represent the corresponding uncertainty in the space reconstruction. The vertical and horizontal displacements H and w in show the heteroscedastic nature of the reconstruction noise since they have different .