A Novel Geometric Calibration Method for Active Stereovision System

2021 ◽  
Author(s):  
Jierui Liu ◽  
Xilong Liu ◽  
Zhiqiang Cao ◽  
Zhonghui Li ◽  
Junzhi Yu
Keyword(s):  
Calibration Method ◽  
Geometric Calibration

scholarly journals On-Orbit Geometric Calibration from the Relative Motion of Stars for Geostationary Cameras

Sensors ◽  
2021 ◽  
Vol 21 (19) ◽  
pp. 6668
Author(s):  
Linyi Jiang ◽  
Xiaoyan Li ◽  
Liyuan Li ◽  
Lin Yang ◽  
Lan Yang ◽  
...  
Keyword(s):  
Relative Motion ◽  
Calibration Method ◽  
System Structure ◽  
Calibration Model ◽  
Control Points ◽  
Penetration Process ◽  
Geometric Calibration ◽  
Positioning Errors ◽  
Ground Control Points ◽  
Motion Transformation

Affected by the vibrations and thermal shocks during launch and the orbit penetration process, the geometric positioning model of the remote sensing cameras measured on the ground will generate a displacement, affecting the geometric accuracy of imagery and requiring recalibration. Conventional methods adopt the ground control points (GCPs) or stars as references for on-orbit geometric calibration. However, inescapable cloud coverage and discontented extraction algorithms make it extremely difficult to collect sufficient high-precision GCPs for modifying the misalignment of the camera, especially for geostationary satellites. Additionally, the number of the observed stars is very likely to be inadequate for calibrating the relative installations of the camera. In terms of the problems above, we propose a novel on-orbit geometric calibration method using the relative motion of stars for geostationary cameras. First, a geometric calibration model is constructed based on the optical system structure. Then, we analyze the relative motion transformation of the observed stars. The stellar trajectory and the auxiliary ephemeris are used to obtain the corresponding object vector for correcting the associated calibration parameters iteratively. Experimental results evaluated on the data of a geostationary experiment satellite demonstrate that the positioning errors corrected by this proposed method can be within ±2.35 pixels. This approach is able to effectively calibrate the camera and improve the positioning accuracy, which avoids the influence of cloud cover and overcomes the great dependence on the number of the observed stars.

Geometric Calibration Method of Side-Scatter Lidar Based on Charge-Coupled Device

2015 ◽  
Vol 44 (2) ◽  
pp. 201002
Author(s):  
麻晓敏 MA Xiao-min ◽  
史博 SHI Bo ◽  
单会会 SHAN Hui-hui ◽  
赵素贵 ZHAO Su-gui ◽  
陶宗明 TAO Zong-ming
Keyword(s):  
Calibration Method ◽  
Charge Coupled Device ◽  
Geometric Calibration

Panoramic Display System Geometric Calibration Method Based on Fisheye Camera

2017 ◽  
Vol 54 (2) ◽  
pp. 021501
Author(s):  
肖朝 Xiao Chao ◽  
陈锋 Chen Feng ◽  
钟敏 Zhong Min ◽  
金川 Jin Chuan
Keyword(s):  
Calibration Method ◽  
Display System ◽  
Geometric Calibration ◽  
Fisheye Camera

scholarly journals A Geometric Calibration Method of Hydrophone Array Based on Maximum Likelihood Estimation with Sources in Near Field

2020 ◽  
Vol 8 (9) ◽  
pp. 678
Author(s):  
Nan Zou ◽  
Zhenqi Jia ◽  
Jin Fu ◽  
Jia Feng ◽  
Mengqi Liu
Keyword(s):  
Maximum Likelihood ◽  
Maximum Likelihood Estimation ◽  
Signal To Noise Ratio ◽  
Near Field ◽  
Likelihood Estimation ◽  
Calibration Method ◽  
Optimization Method ◽  
High Signal ◽  
Geometric Calibration ◽  
Environment Experiment

Considering the requirement of the near-field calibration under strong underwater multipath condition, a high-precision geometric calibration method based on maximum likelihood estimation is proposed. It can be used as both auxiliary-calibration and self-calibration. According to the near-field geometry error model, the objective function of nonlinear optimization problem is constructed by using the unconditional maximum likelihood estimator. The influence of multipath on geometric calibration is studied. The strong reflections are considered as the coherent sources, and the compensation strategy for auxiliary-calibration is realized. The optimization method (differential evolution, DE) is used to solve the geometry errors and sources’ position. The method in this paper is compared with the eigenvector method. The simulation results show that the method in this paper is more accurate than the eigenvector method especially under high signal-to-noise ratio (SNR) and multipath environment. Experiment results further verify the effectiveness.

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.

Approach for Zero Defect Manufacturing: Geometric Calibration of Five-Axis Machine Tools for Blisk Manufacturing Process

2018 ◽  
Author(s):  
Tae Hun Lee ◽  
Jan Behrens ◽  
Sascha Gierlings ◽  
Christian Brecher
Keyword(s):  
Manufacturing Process ◽  
Turbine Blades ◽  
Calibration Method ◽  
Test Method ◽  
Machining Process ◽  
Critical Conditions ◽  
Geometric Calibration ◽  
Measurement Devices ◽  
Five Axis ◽  
Five Axes

Five-axis machining is a key technology of blisk manufacturing process. Blisks generally require high accuracy due to their high performance and safety-critical conditions. However, recent research show that the design of the blisks and turbine blades are getting more complex and require even higher accuracy. This leads also to the application of wide and rare area of movement axes of the machine. Thus, the machine accuracy has to be assured within the overall machine volume. The geometric accuracy demonstrates the base accuracy of the machine. This paper presents a geometric calibration method optimized for the axes movement area of blisk machining process. The accurate calibration of the five-axis machine tool is challenging and hardly possible due to limited error measurement of standard measurement devices. Some measurement methods enable complete calibration of the machine but with complex, time-consuming process and expensive measurement devices. Also, due to the rare axes travel, there is no standard calibration method for the blisk machining process. The calibration method in this paper is developed based on so called ‘R-test’ method. The machine and the errors are modelled mathematically for the measurement. An adapter is applied for the measurement of maximum axis positions. Automation units are developed for the full machine integration and automation of calibration procedure. With the developed method, the machine is calibrated from 130 μm to 10 μm in maximum measurement time of 90 minutes. The calibration quality is validated at an independent measurement position with continuous movement of the five axes.

scholarly journals A Novel Calibration Algorithm for Cable-Driven Parallel Robots with Application to Rehabilitation

2019 ◽  
Vol 9 (11) ◽  
pp. 2182 ◽  
Author(s):  
Han Yuan ◽  
Xianghui You ◽  
Yongqing Zhang ◽  
Wenjing Zhang ◽  
Wenfu Xu
Keyword(s):  
Calibration Method ◽  
Parallel Robot ◽  
Parallel Robots ◽  
Human Robot Interaction ◽  
Automatic Calibration ◽  
Unknown Parameters ◽  
Robot Interaction ◽  
Geometric Calibration ◽  
Rehabilitation Robots ◽  
Calibration Algorithm

Cable-driven parallel robots are suitable candidates for rehabilitation due to their intrinsic flexibility and adaptability, especially considering the safety of human–robot interaction. However, there are still some challenges to apply cable-driven parallel robots to rehabilitation, one of which is the geometric calibration. This paper proposes a new automatic calibration method that is applicable for cable-driven parallel rehabilitation robots. The key point of this method is to establish the mapping between the unknown parameters to be calibrated and the parameters that could be measured by the inner sensors and then use least squares algorithm to find the solutions. Specifically, the unknown parameters herein are the coordinates of the attachment points, and the measured parameters are the lengths of the redundant cables. Simulations are performed on a 3-DOF parallel robot driven by four cables for validation. Results show that the proposed calibration method could precisely find the real coordinate values of the attachment points, with errors less than 10 − 12 mm. Trajectory simulations also indicate that the positioning accuracy of the cable-driven parallel robot (CDPR) could be greatly improved after calibration using the proposed method.

scholarly journals LOW FREQUENCY ERROR ANALYSIS AND CALIBRATION FOR HIGH-RESOLUTION OPTICAL SATELLITE’S UNCONTROLLED GEOMETRIC POSITIONING

2016 ◽  
Vol XLI-B1 ◽  
pp. 395-399
Author(s):  
Mi Wang ◽  
Chengcheng Fang ◽  
Bo Yang ◽  
Yufeng Cheng
Keyword(s):  
High Resolution ◽  
Information Fusion ◽  
Optical Axis ◽  
Low Frequency ◽  
Calibration Method ◽  
Error Model ◽  
Model Construction ◽  
Frequency Error ◽  
Star Sensor ◽  
Geometric Calibration

The low frequency error is a key factor which has affected uncontrolled geometry processing accuracy of the high-resolution optical image. To guarantee the geometric quality of imagery, this paper presents an on-orbit calibration method for the low frequency error based on geometric calibration field. Firstly, we introduce the overall flow of low frequency error on-orbit analysis and calibration, which includes optical axis angle variation detection of star sensor, relative calibration among star sensors, multi-star sensor information fusion, low frequency error model construction and verification. Secondly, we use optical axis angle change detection method to analyze the law of low frequency error variation. Thirdly, we respectively use the method of relative calibration and information fusion among star sensors to realize the datum unity and high precision attitude output. Finally, we realize the low frequency error model construction and optimal estimation of model parameters based on DEM/DOM of geometric calibration field. To evaluate the performance of the proposed calibration method, a certain type satellite’s real data is used. Test results demonstrate that the calibration model in this paper can well describe the law of the low frequency error variation. The uncontrolled geometric positioning accuracy of the high-resolution optical image in the WGS-84 Coordinate Systems is obviously improved after the step-wise calibration.

A geometric calibration approach for industrial cone-beam CT system based on low-rank phantom

2021 ◽  
Author(s):  
Jianqiao Yu ◽  
Jian Lu ◽  
Yi Sun ◽  
Jishun Liu ◽  
Kai Cheng
Keyword(s):  
Cone Beam Ct ◽  
Calibration Method ◽  
Low Rank ◽  
Cone Beam ◽  
Ball Bearings ◽  
Geometric Calibration ◽  
System A ◽  
Ct System ◽  
Local Image ◽  
Calibration Approach

Abstract Precise alignment of the system scan geometry is crucial to ensure the reconstructed image quality in the cone-beam CT system. A calibration method that depends on the local feature of ball bearings phantom and point-like markers is probably affected by local image variations. Besides, multiple projections with circular scanning are usually required by this type of method to derive misaligned parameters. In contrast to previous works, this paper proposes a method that depends on the global symmetric low-rank feature of a novel phantom, which can accurately represent the system geometrical misalignment. All the misaligned parameters of the cone-beam CT system can be estimated from a single perspective direction without circular scanning. Meanwhile, since the global low-rank feature of the phantom is utilized, the proposed method is robust to the noise. Extensive simulations and real experiments validate the accuracy and robustness of our method, which achieves better performance compared to an existing phantom-based method.

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