scholarly journals Global Measurement Method for Large-Scale Components Based on a Multiple Field of View Combination

2017 ◽  
Vol 2017 ◽  
pp. 1-12 ◽  
Author(s):  
Yang Zhang ◽  
Wei Liu ◽  
Zhiguang Lan ◽  
Zhiyuan Zhang ◽  
Fan Ye ◽  
...  
Keyword(s):  
Measurement System ◽  
Measurement Method ◽  
Large Scale ◽  
Vision System ◽  
Calibration Method ◽  
Field Of View ◽  
Surface Measurement ◽  
Global Calibration ◽  
Multiple Field ◽  
Measurement Efficiency

Considering the limited measurement range of a machine vision method for the three-dimensional (3D) surface measurement of large-scale components, a noncontact and flexible global measurement method combining a multiple field of view (FOV) is proposed in this paper. The measurement system consists of two theodolites and a binocular vision system with a transfer mark. The process of multiple FOV combinations is described, and a new global calibration method is proposed to solve the coordinate system unification issue of different instruments in the measurement system. In addition, a high-precision image acquisition method, which is based on laser stripe scanning and centre line extraction, is discussed to guarantee the measurement efficiency. With the measured 3D data, surface reconstruction of large-scale components is accomplished by data integration. Experiments are also conducted to verify the precision and effectiveness of the global measurement method.

scholarly journals Flexible method for accurate calibration of large-scale vision metrology system based on virtual 3-D targets and laser tracker

2019 ◽  
Vol 16 (6) ◽  
pp. 172988141989351
Author(s):  
Xi Zhang ◽  
Yuanzhi Xu ◽  
Haichao Li ◽  
Lijing Zhu ◽  
Xin Wang ◽  
...  
Keyword(s):  
High Precision ◽  
Stereo Vision ◽  
Large Scale ◽  
Vision System ◽  
Calibration Method ◽  
Field Of View ◽  
Large Field ◽  
Laser Tracker ◽  
Calibration Target ◽  
Pose Tracking

For the purpose of obtaining high-precision in stereo vision calibration, a large-size precise calibration target, which can cover more than half of the field of view is vital. However, large-scale calibration targets are very difficult to fabricate. Based on the idea of error tracing, a high-precision calibration method for vision system with large field of view by constructing a virtual 3-D calibration target with a laser tracker was proposed in this article. A virtual 3-D calibration target that covers the whole measurement space can be established flexibly and the measurement precision of the vision system can be traceable to the laser tracker. First, virtual 3-D targets by calculating rigid body transformation with unit quaternion method were constructed. Then, the high-order distortion camera model was taken into consideration. Besides, the calibration parameters were solved with Levenberg–Marquardt optimization algorithm. In the experiment, a binocular stereo vision system with the field of view of 4 × 3 × 2 m3 was built for verifying the validity and precision of the proposed calibration method. It is measured that the accuracy with the proposed method can be greatly improved comparing with traditional plane calibration method. The method can be widely used in industrial applications, such as in the field of calibrating large-scale vision-based coordinate metrology, and six-degrees of freedom pose tracking system for dimensional measurement of workpiece, as well as robotics geometrical accuracy detection and compensation.

A Laser Tracking-Vision Guiding Measurement System for Large-Scale Parts Assembly

2013 ◽  
Vol 718-720 ◽  
pp. 868-874 ◽  
Author(s):  
Wen Sun
Keyword(s):  
Measurement System ◽  
Large Scale ◽  
Automatic Measurement ◽  
Calibration Method ◽  
Laser Tracking ◽  
Measurement Systems ◽  
Global Calibration ◽  
Real Time Tracking ◽  
Low Efficiency ◽  
High Degree

To address the problems of low efficiency, high cost and low automatic level existing in traditional laser tracking measurement systems, a laser tracking-vision guiding measurement system for large-scale parts assembly is introduced in this paper. The system is composed of mono-camera and a laser tracker, can fulfill real-time tracking and automatic measurement throughout the whole assembly process. A global calibration method based on public planes and a method for finding the 3D positions of the target reflectors based on monocular vision measuring are expounded. Mathematical model is established, measurement system is built, and the experiment is accomplished. The experiment result indicates that the proposed system features relative high degree of automation and high measuring speed, has future in practical application.

Research on global calibration method for multi-camera visual measurement system

2016 ◽  
Author(s):  
Dongzhao Huang ◽  
Qiancheng Zhao ◽  
Yun Ou ◽  
Tianlong Yang
Keyword(s):  
Measurement System ◽  
Calibration Method ◽  
Visual Measurement ◽  
Global Calibration

The Calibration Method of a stereo-Vision-Based Coordinates Measurement System via a Two-Axis Turntable--The Combination of Stereo Vision and Turntable

2021 ◽  
Vol 14 ◽  
Author(s):  
Zimiao Zhang ◽  
Zhiwu Wang ◽  
Shihai Zhang ◽  
Anqi Fu
Keyword(s):  
Stereo Vision ◽  
Measurement System ◽  
Vision System ◽  
Three Dimensional ◽  
Calibration Method ◽  
Measurement Range ◽  
Measurement Technology ◽  
Rotation Axes ◽  
Internal Parameters ◽  
Calibration Methods

Background: Stereo-vision-based three-dimensional coordinates measurement technology has been widely applied in the military or civil fields. There are two problems that need to be solved. The first problem is that each camera internal parameters and the two cameras external parameters need to be calibrated. To increase the measurement range, usually the turntable is used with the stereo vision system together. The second problem is the calibration of the turntable. Objective: The aim of the study is to construct and calibrate a stereo-vision-based coordinates measurement system via a two-axis turntable. Methods: Considering that the internal parameters of each camera do not change during the measurement process and the complicated optimization process of one-step self-calibration, a two-step stereo vision calibration method is proposed. In the first step, we calibrate the internal parameters of each camera through a specially designed planar target with circular points. In the second step, on the basis of the calibrated results of the internal parameters, the two cameras external parameters are calibrated through a simple target which could be distributed in the measurement volume. For the calibration of the two-axis turntable, we calibrated the rotation axes of the turntable and the coordinates of points in the 3D space could be measured considering the non-orthogonality of the axes. Results: Some experiments are provided to examine the calibration methods we proposed. They are the plane target measurement experiments, the standard ball center coordinates measurement experiments and target pose measurement experiments. Experiment results demonstrate the superiority of the calibration method we proposed. Conclusion: We studied the calibration methods of the stereo-vision-based coordinates measurement system via a two-axis turntable. The experimental results show the measurement accuracy of our system is less than 0.1mm.

scholarly journals A Stereo-Vision System for Measuring the Ram Speed of Steam Hammers in an Environment with a Large Field of View and Strong Vibrations

Sensors ◽  
2019 ◽  
Vol 19 (5) ◽  
pp. 996 ◽  
Author(s):  
Ran Chen ◽  
Zhongwei Li ◽  
Kai Zhong ◽  
Xingjian Liu ◽  
Yonghui Wu ◽  
...  
Keyword(s):  
Stereo Vision ◽  
High Speed ◽  
Vision System ◽  
Calibration Method ◽  
Bundle Adjustment ◽  
Field Of View ◽  
Large Field ◽  
Practical Applications ◽  
Accuracy Of Measurements ◽  
Ram Speed

The ram speed of a steam hammer is an important parameter that directly affects the forming performance of forgers. This parameter must be monitored regularly in practical applications in industry. Because of the complex and dangerous industrial environment of forging equipment, non-contact measurement methods, such as stereo vision, might be optimal. However, in actual application, the field of view (FOV) required to measure the steam hammer is extremely large, with a value of 2–3 m, and heavy steam hammer, at high-speed, usually causes a strong vibration. These two factors combine to sacrifice the accuracy of measurements, and can even cause the failure of measurements. To solve these issues, a bundle-adjustment-principle-based system calibration method is proposed to realize high-accuracy calibration for a large FOV, which can obtain accurate calibration results when the calibration target is not precisely manufactured. To decrease the influence of strong vibration, a stationary world coordinate system was built, and the external parameters were recalibrated during the entire measurement process. The accuracy and effectiveness of the proposed technique were verified by an experiment to measure the ram speed of a counterblow steam hammer in a die forging device.

scholarly journals Automatic Laser Interferometer And Vision Measurement System For Stripe Rod Calibration

2015 ◽  
Vol 22 (4) ◽  
pp. 491-502 ◽  
Author(s):  
Min Zhao ◽  
Qiu-Hong Huang ◽  
Ling-Jian Zhu ◽  
Zong-Ming Qiu
Keyword(s):  
Measurement System ◽  
Measurement Method ◽  
Laser Interferometer ◽  
Image Data ◽  
Ccd Camera ◽  
Calibration Method ◽  
Feedback Signal ◽  
Long Distance ◽  
Loop Control ◽  
Vision Measurement

Abstract In order to calibrate the stripe precision of a leveling rod, an automatic laser interferometer and a vision measurement system were designed by Xi’an University of Technology in China. The rod was driven by a closed-loop control and the data were collected at the stop state to ensure precision. The laser interferometer provided not only the long distance data but also a position feedback signal in the automatic control loop. CCD camera and a vision measurement method were used to inspect the stripe edge position and defect. A pixel-equivalent self-calibration method was designed to improve precision. ROI (regions of interest) method and an outline tracing method were designed to quickly extract multiple stripe edges. A combination of the image data with the interferometer data reduces control difficulty and ensures the measurement accuracy. The vision measurement method reached sub-pixel precision and the defective edges were reported. The system can automatically calibrate a stripe leveling rod with a high degree of efficiency and precision.

In-Situ Calibration Method for Large-Scale Space Angle Optical Measurement System

2012 ◽  
Vol 39 (10) ◽  
pp. 1008006
Author(s):  
胡文川 Hu Wenchuan ◽  
裘祖荣 Qiu Zurong ◽  
张国雄 Zhang Guoxiong
Keyword(s):  
Measurement System ◽  
Large Scale ◽  
Optical Measurement ◽  
Calibration Method ◽  
Scale Space ◽  
Optical Measurement System ◽  
In Situ Calibration ◽  
Space Angle

3D Body Measurement System Based on Structured Light

2012 ◽  
Vol 503-504 ◽  
pp. 1280-1283
Author(s):  
Zhong Yang Li ◽  
Ze Yuan Liu ◽  
Bai Tong Wang ◽  
Xiu Xiang Huang
Keyword(s):  
Measurement System ◽  
Vision System ◽  
Structured Light ◽  
Calibration Method ◽  
Profile Measurement ◽  
Body Measurement ◽  
Standard Data ◽  
Projection Profile ◽  
Cad Cam ◽  
Visual Interface

This paper presents a 3D body measurement system based on structured light. We analyze the principal of projection profile measurement and model binocular system with two cameras which comprise a stereo vision system. The goal of calibration method is to achieve the high accuracy for human body dimensions. The system software based on VS 2008 and OpenGL provides a visual interface with standard data interface for CAD/CAM.

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