A Calibration Method for the Generalized Imaging Model with Uncertain Calibration Target Coordinates

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.

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Computer Hard Disk Planeness Vision Measurement System Calibration Based on Light Plane Constraint

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.475-476.63 ◽

2013 ◽

Vol 475-476 ◽

pp. 63-67

Author(s):

Rui Yin Tang ◽

Zhou Mo Zeng ◽

Peng Fei Li

Keyword(s):

Nonlinear Model ◽

Constraint Equation ◽

Hard Disk ◽

Calibration Method ◽

Calibration Target ◽

System Calibration ◽

Vision Measurement ◽

Light Plane ◽

Fitting Method ◽

Extrinsic Parameters

This paper proposed a calibration method of sheet-of-light vision measurement sensor based on light plane constraint. Through capturing 12 images of different direction from homemade circular calibration target, the center of the circle and the light stripe is extracted based on Halcon platform of Germany. The experimental results obtained the intrinsic parameters, extrinsic parameters and radial distortion coefficient of the nonlinear model. At the same time the light plane constraint equation is got based on PCA plane fitting method. The results show that the calibration method is simple and reliable, and the method does not need any auxiliary adjustment. The work laid the better foundation for hard disk planeness vision measurement.

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

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.284-287.1589 ◽

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.

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Accurate binocular stereo underwater measurement method

International Journal of Advanced Robotic Systems ◽

10.1177/1729881419864468 ◽

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.

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

IEEE Access ◽

10.1109/access.2021.3066098 ◽

2021 ◽

Vol 9 ◽

pp. 43001-43012

Author(s):

Xiaoning Hu ◽

Bingnan Wang ◽

Maosheng Xiang ◽

Zhongbin Wang

Keyword(s):

Calibration Method ◽

Imaging Model

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A physical based underwater imaging model and camera calibration method

2015 IEEE International Conference on Information and Automation ◽

10.1109/icinfa.2015.7279826 ◽

2015 ◽

Author(s):

Xiaojun Wu ◽

Xingcan Tang

Keyword(s):

Camera Calibration ◽

Calibration Method ◽

Underwater Imaging ◽

Imaging Model

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Combining Digital Image Correlation and Thermal Measurements

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.240.81 ◽

2015 ◽

Vol 240 ◽

pp. 81-86

Author(s):

Pawel Rutkowski ◽

Marcin Malesa ◽

Małgorzata Kujawińska

Keyword(s):

Digital Image Correlation ◽

Digital Image ◽

Calibration Method ◽

Image Correlation ◽

Infrared Light ◽

Light Spectrum ◽

Calibration Target ◽

3D Digital Image Correlation ◽

Human Arm ◽

Thermal Measurements

In this paper we present a calibration method, which enables a combining of 3D Digital Image Correlation and termographic systems for simultaneous measurements of displacements, strains and temperature. It concerns a model of a calibration target, that works for visible and infrared light spectrum and calibration method. The working system was applied for three interesting cases: monitoring of a tank filled with liquid, a heated plexi board and a human arm during muscle contraction.

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VIDEOGRAMMETRIC RECONSTRUCTION APPLIED TO VOLCANOLOGY: PERSPECTIVES FOR A NEW MEASUREMENT TECHNIQUE IN VOLCANO MONITORING

Image Analysis & Stereology ◽

10.5566/ias.v21.p31-36 ◽

2011 ◽

Vol 21 (1) ◽

pp. 31 ◽

Cited By ~ 1

Author(s):

Emmanuelle Cecchi ◽

Jean Marc Lavest ◽

Benjamin Van Wyk De Vries

Keyword(s):

Spatial Location ◽

Calibration Method ◽

Reconstruction Method ◽

Reconstruction Accuracy ◽

Calibration Target ◽

Analogue Model ◽

Reconstruction Process ◽

Internal Parameters ◽

Initial Stage ◽

View Reconstruction

This article deals with videogrammetric reconstruction of volcanic structures. As a first step, the method is tested in laboratory. The objective is to reconstruct small sand and plaster cones, analogous to volcanoes, that deform with time. The initial stage consists in modelling the sensor (internal parameters) and calculating its orientation and position in space, using a multi-view calibration method. In practice two sets of views are taken: a first one around a calibration target and a second one around the studied object. Both sets are combined in the calibration software to simultaneously compute the internal parameters modelling the sensor, and the external parameters giving the spatial location of each view around the cone. Following this first stage, a N-view reconstruction process is carried out. The principle is as follows: an initial 3D model of the cone is created and then iteratively deformed to fit the real object. The deformation of the meshed model is based on a texture coherence criterion. At present, this reconstruction method and its precision are being validated at laboratory scale. The objective will be then to follow analogue model deformation with time using successive reconstructions. In the future, the method will be applied to real volcanic structures. Modifications of the initial code will certainly be required, however excellent reconstruction accuracy, valuable simplicity and flexibility of the technique are expected, compared to classic stereophotogrammetric techniques used in volcanology.

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

Acta Optica Sinica ◽

10.3788/aos201636.0912003 ◽

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

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Rapid Calibration Method for 3D Laser Scanner

Recent Patents on Engineering ◽

10.2174/1872212113666191016140122 ◽

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.

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