Multiple Stereo Vision Research Articles

Highly accurate three-dimensional measurement of large structures using multiple stereo vision with improved two-step calibration algorithm

A multiple stereo-based three-dimensional (3D) measurement method of large-scale structures is presented, which replaces time-consuming and laborious 3D measurement procedure of laser-based conventional equipment. To have 3D reconstruction accuracy with millimeter-precision, two-step calibration algorithms are improved. Specifically, we use 2D epipolar constraint, using fundamental matrix determined by matched points, to new combination of objective function for intrinsic parameter calibration. We additionally propose an onsite structure parameter calibration algorithm using different epipolar constraint of measurement points in images of large ship block as well as reprojection error of checkerboard, to bypass the limitation of the coverage of checkerboard in large-scale measurement. The actual 3D measurement of the three ship blocks is conducted, and the 3D reconstruction accuracy is validated by comparing the 3D coordinates measured by total station. The experimental results showed that the mean 3D reconstruction error ranged from 6 to 14 mm.

A Unified Probabilistic Framework for Real-Time Depth Map Fusion

This paper proposes a unified probabilistic framework for real-time depth map fusion. By modeling the depth imaging process as a random experiment, the depth map fusion is converted into probability density function (pdf) estimation. The depth fusion problem is decoupled into four parts: the fusion space, the influence term, the visibility term and the confidence term. We combine these four terms in a unified probabilistic framework, and apply the framework in two cases to evaluate the performance. In the first case, multiple stereo vision cameras are used to acquire multiple depth map streams from multiple viewpoints simultaneously in real time. In the second case, two cameras and a Kinect are combined to provide two depth map streams. In both cases, strategies for each part of the framework are presented to perform real-time depth fusion. Experimental results show that the proposed framework is promising for real-time depth map fusion.

Research on Measurement Method of Joint Angle for Underwater Manipulator

Measurement method of joint angle for underwater manipulator is studied in this paper. The swing of a manipulator can be described as a circular motion in spatial. Therefore this paper proposes a spatial circle fitting algorithm. The points for spatial circle fitting come from multiple stereo vision system. At first, attach the designed target to the robot arm, then proposes algorithm to track the target in real time. Then three-dimensional coordinates of target’s movement in space at each location can be obtained by using stereo reconstruction techniques. At last, the center and radius of the circle can be calculated by spatial circle fitting. Through the theory of analytic geometry, the manipulator’s joint angle can be calculated. Experiments show that the algorithm proposed in this paper is well used in manipulator’s joint angle measurement.