A Calibration Method of CBCT Geometric Parameters Based on the Visual Imaging Model

2019 ◽  
pp. 753-763
Author(s):  
Yanli Wan ◽  
Quan Chen ◽  
Xingyun Lei ◽  
Yan Wang ◽  
Yongxin Chen ◽  
...  
Keyword(s):  
Calibration Method ◽  
Geometric Parameters ◽  
Imaging Model ◽  
Visual Imaging

scholarly journals Improvement of Heavy Load Robot Positioning Accuracy by Combining a Model-Based Identification for Geometric Parameters and an Optimized Neural Network for the Compensation of Nongeometric Errors

Complexity ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Yuxiang Wang ◽  
Zhangwei Chen ◽  
Hongfei Zu ◽  
Xiang Zhang ◽  
Chentao Mao ◽  
...  
Keyword(s):  
Neural Network ◽  
Manufacturing Systems ◽  
Robot Manipulator ◽  
Joint Stiffness ◽  
Calibration Method ◽  
Geometric Parameters ◽  
Heavy Load ◽  
Positioning Accuracy ◽  
Robot Positioning ◽  
Residual Errors

The positioning accuracy of a robot is of great significance in advanced robotic manufacturing systems. This paper proposes a novel calibration method for improving robot positioning accuracy. First of all, geometric parameters are identified on the basis of the product of exponentials (POE) formula. The errors of the reduction ratio and the coupling ratio are identified at the same time. Then, joint stiffness identification is carried out by adding a load to the end-effector. Finally, residual errors caused by nongeometric parameters are compensated by a multilayer perceptron neural network (MLPNN) based on beetle swarm optimization algorithm. The calibration is implemented on a SIASUN SR210D robot manipulator. Results show that the proposed method possesses better performance in terms of faster convergence and higher precision.

A Bridging Method between 2D and 3D Cephalometry Using Computed Tomography Synthesized Cephalograms

2013 ◽  
Vol 284-287 ◽  
pp. 1589-1595
Author(s):  
Jing Jing Fang ◽  
Jia Kuang Liu ◽  
Chia Wei Chang ◽  
Yu Cheng Lin
Keyword(s):  
Computed Tomography ◽  
Random Order ◽  
Calibration Method ◽  
Interactive System ◽  
Average Error ◽  
Imaging Method ◽  
X Rays ◽  
X Ray ◽  
Imaging Model ◽  
3D Cephalometry

Traditional cephalograms are X-ray films, which provide either frontal or lateral overlapped perspective medical imaging. Although computed tomography imaging provides more information in 3-dimensional anatomy, the landmarks for cephalometry are located in space which does not carry normal standards in 3-D cephalometry. The CT natural imaging method is different from X-ray in that they respectively use orthogonal and perspective projections. Thus, we cannot apply the statistical normal values gathered from traditional 2D cephometry to 3D cephalometry. This study makes use of calibrated synthesized cephalograms from computed tomography to construct a cephalometry bridge between 2-D and 3-D. In this thesis, we first review the imaging model of a specific X-ray machine (Asahi OrthoStage AUTO IIIN) by a camera calibration method. We then construct a reference system for a virtual head, and synthesize calibrated X-ray cephalograms using the volume rendering algorithm. System accuracy for the synthesis X-ray cephalograms is verified through an interactive corresponding landmark system between 2-D and 3-D. An experimental clinician was invited to manually place 17 landmarks on the X-rays and their corresponding, shuffled in random order. The systematic error, average error, and standard deviation of landmark positions are 0.15 mm, 0.97 mm, and 0.45 mm, respectively. The interactive system bridges the transformation from orthogonal 3-D to perspective 2-D cephalometry.

scholarly journals Accurate binocular stereo underwater measurement method

2019 ◽  
Vol 16 (5) ◽  
pp. 172988141986446
Author(s):  
Xiaojun Wu ◽  
XingCan Tang
Keyword(s):  
Measurement Accuracy ◽  
Calibration Method ◽  
Correction Method ◽  
Image Correction ◽  
Underwater Imaging ◽  
Epipolar Constraint ◽  
Imaging Model ◽  
Internal Parameters ◽  
Extrinsic Parameters ◽  
Binocular Stereo

Light changes its direction of propagation before entering a camera enclosed in a waterproof housing owing to refraction, which means that perspective imaging models in the air cannot be directly used underwater. In this article, we propose an accurate binocular stereo measurement system in an underwater environment. First, based on the physical underwater imaging model without approximation and Tsai’s calibration method, the proposed system is calibrated to acquire the extrinsic parameters, as the internal parameters can be pre-calibrated in air. Then, based on the calibrated camera parameters, an image correction method is proposed to convert the underwater images to air images. Thus, the epipolar constraint can be used to search the matching point directly. The experimental results show that the proposed method in this article can effectively eliminate the effect of refraction in the binocular vision and the measurement accuracy can be compared with the measurement result in air.

scholarly journals A Novel Airborne Dual-Antenna InSAR Calibration Method for Backprojection Imaging Model

IEEE Access ◽  
2021 ◽  
Vol 9 ◽  
pp. 43001-43012
Author(s):  
Xiaoning Hu ◽  
Bingnan Wang ◽  
Maosheng Xiang ◽  
Zhongbin Wang
Keyword(s):  
Calibration Method ◽  
Imaging Model

A vehicle type-dependent visual imaging model for analysing the heterogeneous car-following dynamics

2015 ◽  
Vol 4 (1) ◽  
pp. 68-85 ◽  
Author(s):  
Liang Zheng ◽  
Peter J. Jin ◽  
Helai Huang ◽  
Mingyun Gao ◽  
Bin Ran
Keyword(s):  
Car Following ◽  
Vehicle Type ◽  
Imaging Model ◽  
Visual Imaging

Calibration Method Based on General Imaging Model for Micro-Object Measurement System

2016 ◽  
Vol 36 (9) ◽  
pp. 0912003
Author(s):  
孔玮琦 Kong Weiqi ◽  
刘京南 Liu Jingnan ◽  
达飞鹏 Da Feipeng ◽  
饶立 Rao Li
Keyword(s):  
Measurement System ◽  
Calibration Method ◽  
Imaging Model

Rapid Calibration Method for 3D Laser Scanner

2020 ◽  
Vol 14 (2) ◽  
pp. 234-241
Author(s):  
Bin Liu ◽  
Qian Qiao ◽  
Fangfang Han
Keyword(s):  
Laser Scanner ◽  
Vertical Direction ◽  
Calibration Method ◽  
Intrinsic Parameters ◽  
Average Value ◽  
Light Plane ◽  
Imaging Model ◽  
Reference Target ◽  
Camera Intrinsic Parameters ◽  
Rapid Calibration

Background: The 3D laser scanner is a non-contact active-sensing system, which has a number of applications. Many patents have been filed on the technologies for calibrating 3D laser scanner. A precise calibration method is important for measuring the accuracy of the 3D laser scanner. The system model contains three categories of parameters to be calibrated which include the camera intrinsic parameters, distortion coefficients and the light plane parameters. Typically, the calibration process is completed in two steps. Based on Zhang’s method, the calibration of the camera intrinsic parameters and distortion coefficients can be performed. Then, 3D feature points on the light plane should precisely be formed and extracted. Finally, the points are used to calculate the light plane parameters. Methods: In this paper, a rapid calibration method is presented. Without any high precision auxiliary device, only one coplanar reference target is used. By using a group of captured images of the coplanar reference target placed in the field of view arbitrarily, calibration can be performed in one step. Based on the constraint from the planes formed by the target in different directions and the camera imaging model, a large amount of 3D points on the light plane can easily be obtained. The light plane equation in the camera coordinates system can be gathered by executing plane fitting to the 3D points. Results: During the experimental process, the developed 3D laser scanner was calibrated by the proposed method. Then, the measuring accuracy of the system was verified with known distance in vertical direction of 1mm with sequential shifting motion generated by precision translation stage. The average value of the measured distances was found to be 1.010mm. The standard deviation was 0.008mm. Conclusion: Experimental results prove that the proposed calibration method is simple and reliable.

Measurement of Cam Spacing on Assembled Camshaft Based on Improved Fundamental Matrix Calibration

2013 ◽  
Vol 850-851 ◽  
pp. 241-244
Author(s):  
Guan Nan Li ◽  
Qing Chang Tan ◽  
Si Yuan Liu
Keyword(s):  
Fundamental Matrix ◽  
Ccd Camera ◽  
Calibration Method ◽  
Measurement Model ◽  
Pinhole Camera ◽  
Epipolar Line ◽  
Camera Model ◽  
Distortion Model ◽  
Imaging Model ◽  
Measurement Results

Imaging model of double CCD camera based on pinhole camera model and distortion model is introduced, and the fundamental matrix is presented. Distortion model is led into the fundamental matrix calibration. Based on the imaging model of Z. Zhangs calibration method, fundamental matrix is carried out. Pixel coordinate for calibration is modified by cameras interior parameters and distortion coefficients. Base on the imaging model of double CCD camera, measurement model for cam spacing is established. Cam spacing is measured by the feature of cam edge. In experiments, accurate pixel coordinates of model plane were used in calibration. The distance between a point and its corresponding epipolar line was estimated as the error. The measurement results show that the accuracy of proposed method satisfied the monitoring requirements of the axial positioning error of the cam piece.

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