scholarly journals Calibration Method for Line-Structured Light Three-Dimensional Measurements Based on a Single Circular Target

2022 ◽  
Vol 12 (2) ◽  
pp. 588
Author(s):  
Jun Wang ◽  
Xuexing Li
Keyword(s):  
Structured Light ◽  
Three Dimensional ◽  
Calibration Method ◽  
Optical Center ◽  
3D Measurements ◽  
Light Plane ◽  
Laser Projector ◽  
Dimensional Measurements ◽  
Intersection Points ◽  
Circular Target

Single circular targets are widely used as calibration objects during line-structured light three-dimensional (3D) measurements because they are versatile and easy to manufacture. This paper proposes a new calibration method for line-structured light 3D measurements based on a single circular target. First, the target is placed in several positions and illuminated by a light beam emitted from a laser projector. A camera captures the resulting images and extracts an elliptic fitting profile of the target and the laser stripe. Second, an elliptical cone equation defined by the elliptic fitting profile and optical center of the camera is established based on the projective geometry. By combining the obtained elliptical cone and the known diameter of the circular target, two possible positions and orientations of the circular target are determined and two groups of 3D intersection points between the light plane and the circular target are identified. Finally, the correct group of 3D intersection points is filtered and the light plane is progressively fitted. The accuracy and effectiveness of the proposed method are verified both theoretically and experimentally. The obtained results indicate that a calibration accuracy of 0.05 mm can be achieved for an 80 mm × 80 mm planar target.

scholarly journals Field Geometric Calibration Method for Line Structured Light Sensor Using Single Circular Target

2017 ◽  
Vol 2017 ◽  
pp. 1-8 ◽  
Author(s):  
Tianfei Chen ◽  
Lijun Sun ◽  
Qiuwen Zhang ◽  
Xiang Wu ◽  
Defeng Wu
Keyword(s):  
Structured Light ◽  
Linear Equations ◽  
Calibration Method ◽  
Experimental Result ◽  
Normal Vector ◽  
Geometric Calibration ◽  
Light Plane ◽  
Light Sensor ◽  
Fitting Method ◽  
Circular Target

To achieve fast calibration of line structured light sensor, a geometric calibration approach based on single circular calibration target is proposed. The proposed method uses the circular points to establish linear equations, and according to the angle constraint, the camera intrinsic parameters can be calculated through optimization. Then, the light plane calibration is accomplished in two steps. Firstly, when the vanishing lines of target plane at various postures are obtained, the intersections between vanishing lines and laser stripe can be computed, and the normal vector of light plane can be calibrated via line fitting method using intersection points. After that, the distance from the origin of camera coordinate system to the light plane can be derived based on the model of perspective-three-point. The actual experimental result shows that this calibration method has high accuracy, its average measuring accuracy is 0.0451 mm, and relative error is 0.2314%. In addition, the entire calibration process has no complex operations. It is simple, convenient, and suitable for calibration on sites.

Light Plane Calibration Method Using Line Transformation for Line Structured Light Measurement

2021 ◽  
Vol 58 (2) ◽  
pp. 0212001
Author(s):  
翟鹏 Zhai Peng ◽  
崔海华 Cui Haihua ◽  
胡广露 Hu Guanglu ◽  
张益华 Zhang Yihua ◽  
靳宇婷 Jin Yuting ◽  
...  
Keyword(s):  
Structured Light ◽  
Calibration Method ◽  
Light Plane ◽  
Light Measurement

Welding robotic hand-eye calibration method based on structured light plane

2019 ◽  
Author(s):  
Fangkai Xu ◽  
Shengli Fan ◽  
Qingqing Yang ◽  
Chang Zhang ◽  
Yigang Wang
Keyword(s):  
Structured Light ◽  
Calibration Method ◽  
Robotic Hand ◽  
Light Plane

Telecontrol Engineering of Three-Dimensional Measurements from Two-Dimensional Digital Photogrammetry for Scene Reconstruction

2011 ◽  
Vol 271-273 ◽  
pp. 489-494
Author(s):  
Dai Qin Tao ◽  
Zhi Yong Yin ◽  
Sheng Xiong Liu ◽  
Li Jun Wang
Keyword(s):  
Focal Length ◽  
Three Dimensional ◽  
Accurate Method ◽  
Scene Reconstruction ◽  
Digital Photogrammetry ◽  
Maximal Error ◽  
3D Measurements ◽  
Highly Active ◽  
Before And After ◽  
Dimensional Measurements

It set up a quick and high accurate method of 3D measurements from the 2D digital photogrammetry to reconstruct the scene by teleprocessing. Three types of feature marks in the matrix arrayhave been projected. The calibrations of the camera with fixed focal length have been calculated and compared before and after revision. The cross-shaped feature was the most accurate mark. And the cone barrel with sharp apex was also more accurate than the traditional round dot. The real case practices have been engaged in to verify the practicability and efficiency of the projects. In less than 10m with 6 points, the maximal error has been reduced to 0.029%. In around 20m with 20 to 34 ponits, the maximal error has been reduced to 0.046%. And it was far more accurate than the counterpart research (0.44%).The measurements results of the more big areas have been found to be instability. So the lawful choice of the single photogrammetric image scope should be limited to 20m. In the proper image scope (<26m), the telecontrol 3D measurements are very accurate and highly active. It can be positively applied to the remote scene reconstruction as well as other engineering vistas.

scholarly journals A Model of Diameter Measurement Based on the Machine Vision

Symmetry ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 187
Author(s):  
Qingchang Tan ◽  
Ying Kou ◽  
Jianwei Miao ◽  
Siyuan Liu ◽  
Bosen Chai
Keyword(s):  
Rotational Symmetry ◽  
Structured Light ◽  
Measurement Model ◽  
Optical Center ◽  
Machining Accuracy ◽  
Normal Vector ◽  
Shaft Diameter ◽  
Light Plane ◽  
Elliptic Cone

If the shaft diameter can be measured in-situ during the finishing process, the closed-loop control of the shaft diameter processing process can be realized and the machining accuracy can be improved. Present work studies the measurement of shaft diameter with the structured light system composed of a laser linear light source and a camera. The shaft is a kind of part with rotationally symmetric structure. When the linear structured light irradiates the surface of the shaft, a light stripe will be formed, and the light stripe is a part of the ellipse. Therefore, the in-situ measurement of the shaft diameter can be realized by the light stripe and the rotational symmetry of the shaft. The measurement model of shaft diameter is established by the ellipse formed by the intersection of the light plane and the measured shaft surface. Firstly, in the camera coordinate system, normal vector of the light plane and the coordinates of the ellipse center are obtained by the calibration; then, the equation of oblique elliptic cone is established by taking the ellipse as the bottom and the optical center of the camera as the top. Next, the measurement model of shaft diameter is obtained by the established oblique elliptic cone equation and theoretical image plane equation. Finally, the accuracy of the measurement model of shaft diameter is tested by the checkerboard calibration plate and a lathe. The test results show that the measurement model of shaft diameter is correct, and when the shaft diameter is 36.162mm, the speed is 1250r/min, the maximum average measurement error is 0.019mm. The measurement accuracy meets the engineering requirement.

scholarly journals A-Priori Calibration of a Structured Light Underwater 3D Sensor

2020 ◽  
Vol 8 (9) ◽  
pp. 635
Author(s):  
Christian Bräuer-Burchardt ◽  
Christoph Munkelt ◽  
Ingo Gebhart ◽  
Matthias Heinze ◽  
Stefan Heist ◽  
...  
Keyword(s):  
Structured Light ◽  
A Priori ◽  
Three Dimensional ◽  
Radial Distance ◽  
Calibration Method ◽  
Correction Function ◽  
Camera Model ◽  
Accuracy Measurement ◽  
Distortion Functions ◽  
Future Work

In this study, we introduce a new calibration method for underwater optical stereo scanners. It uses air calibration, additional underwater parameters, and extended camera modeling. The new methodology can be applied to both passive photogrammetric and structured light three-dimensional (3D) scanning systems. The novel camera model uses a variable principal distance depending on the radial distance to the principal point instead of two-dimensional distortion functions. This allows for an initial improvement of 3D reconstruction quality. In a second step, certain underwater-specific parameters—such as refraction indices, glass thickness, and view-port distances—are determined. Finally, a correction function for the entire measurement volume can be obtained from a few underwater measurements. Its application further improves the measurement accuracy. Measurement examples show the performance of the new calibration method in comparison to current underwater calibration strategies. A discussion of the possibilities and limits of the new calibration method and an outlook for future work complete this work.

scholarly journals Optical system calibration for 3D measurements in a hydrodynamic tunnel

2021 ◽  
Vol 45 (1) ◽  
pp. 58-65
Author(s):  
V.A. Knyaz ◽  
D.G. Stepanyants ◽  
O.Y. Tsareva
Keyword(s):  
Optical System ◽  
Three Dimensional ◽  
Image Formation ◽  
Working Environment ◽  
Working Fluid ◽  
3D Measurements ◽  
Optical Media ◽  
Dimensional Measurements ◽  
Fluid Boundary ◽  
Glass Working

For non-contact 3D measurements in hydrodynamic tunnels by photogrammetry methods, it is necessary to refine the standard model of image formation in the camera by taking into account an effect of refraction of rays at the boundaries of optical media, namely, at an air-glass boundary and glass-working fluid boundary. The article presents a model of image formation for shooting in a working environment that includes various optical media and methods for calibrating an optical system for 3D measurements of the coordinates of scene objects, while taking into account the real boundaries of the optical media. Experimental results on calibrating the system of three-dimensional measurements when an object image is formed by rays passing through two optical boundaries are discussed.

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