Mr. Yuan Yun Profile

Yuan Yun

at National Univ of Defense Technology

Publications (3)

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Proceedings Article | 18 August 2011 Paper

A new mosaic method for three-dimensional surface

Yun Yuan, Yongjun Ding

Proceedings Volume 8194, 81942T (2011) https://doi.org/10.1117/12.900864

KEYWORDS: Data modeling, Clouds, Statistical modeling, 3D metrology, Statistical analysis, 3D modeling, Precision measurement, Aerospace engineering, Error analysis, Defense technologies

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Three-dimensional (3-D) data mosaic is a indispensable link in surface measurement and digital terrain map generation. With respect to the mosaic problem of the local unorganized cloud points with rude registration and mass mismatched points, a new mosaic method for 3-D surface based on RANSAC is proposed. Every circular of this method is processed sequentially by random sample with additional shape constraint, data normalization of cloud points, absolute orientation, data denormalization of cloud points, inlier number statistic, etc. After N random sample trials the largest consensus set is selected, and at last the model is re-estimated using all the points in the selected subset. The minimal subset is composed of three non-colinear points which form a triangle. The shape of triangle is considered in random sample selection in order to make the sample selection reasonable. A new coordinate system transformation algorithm presented in this paper is used to avoid the singularity. The whole rotation transformation between the two coordinate systems can be solved by twice rotations expressed by Euler angle vector, each rotation has explicit physical means. Both simulation and real data are used to prove the correctness and validity of this mosaic method. This method has better noise immunity due to its robust estimation property, and has high accuracy as the shape constraint is added to random sample and the data normalization added to the absolute orientation. This method is applicable for high precision measurement of three-dimensional surface and also for the 3-D terrain mosaic.

Proceedings Article | 18 August 2011 Paper

Camera calibration method based on circular ring

Yun Yuan, Zhaokun Zhu

Proceedings Volume 8194, 81942S (2011) https://doi.org/10.1117/12.900863

KEYWORDS: Calibration, Cameras, Imaging systems, Data modeling, 3D image processing, Aerospace engineering, Device simulation, 3D modeling, Image resolution, Defense technologies

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A novel camera calibration method based on circular ring is proposed in this paper. It has been proven that the first two columns of calculated point transfer homography mapping from the circular ring plane to the image plane have one isometric ambiguity. But in that case the restriction of homography on the IAC (the image of absolute conic) is still tenable, so the restriction could be applied to the calibration of the internal camera parameters. The ambiguity of the first two columns of homography directly results in the isometric ambiguity of the rotation matrix which can be explained in geometry as the isotropy of circular ring. But the third column of homography has no ambiguity, so the unique of which could not lead to the ambiguity of the translation vector. The external camera parameters can be calibrated using circular ring while there is a discrepancy of isometric transformation of rotation matrix within the model plane, which is most distinguished from the principle of the other plane-based calibration method such as points, lines and multiple conics. The proposed method has two distinctly superiority over the calibration based on coplanar points or lines: Better noise immunity because of the global property of the circular ring feature, and automatic calibration because the image matching of the circular ring feature is much easier compared with the one of points or lines. Both simulation and real data are used to prove the correctness, high accuracy and robustness of our calibration method.

Proceedings Article | 21 June 2011 Paper

Large bulk-yard 3D measurement based on videogrammetry and projected contour aiding

Jianliang Ou, Xiaohu Zhang, Yun Yuan, Xianwei Zhu

Proceedings Volume 8085, 80850X (2011) https://doi.org/10.1117/12.888665

KEYWORDS: 3D metrology, 3D modeling, 3D image processing, Projection systems, Cameras, 3D image reconstruction, Stereoscopic cameras, Calibration, Photogrammetry, Reflectivity

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Fast and accurate 3D measurement of large stack-yard is important job in bulk load-and-unload and logistics management. Stack-yard holds its special characteristics as: complex and irregular shape, single surface texture and low material reflectivity, thus its 3D measurement is quite difficult to be realized by traditional non-contacting methods, such as LiDAR(LIght Detecting And Ranging) and photogrammetry. Light-section is good at the measurement of small bulk-flow but not suitable for large-scale bulk-yard yet. In the paper, an improved method based on stereo cameras and laser-line projector is proposed. The due theoretical model is composed from such three key points: corresponding point of contour edge matching in stereo imagery based on gradient and epipolar-line constraint, 3D point-set calculating for stereo imagery projected-contour edge with least square adjustment and forward intersection, then the projected 3D-contour reconstructed by RANSAC(RANdom SAmpling Consensus) and contour spatial features from 3D point-set of single contour edge. In this way, stack-yard surface can be scanned easily by the laser-line projector, and certain region's 3D shape can be reconstructed automatically by stereo cameras on an observing position. Experiment proved the proposed method is effective for bulk-yard 3D measurement in fast, automatic, reliable and accurate way.

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