An Initial Dot Encoding Scheme with Significantly Improved Robustness and Numbers

Deng, Huaxia; Hu, Guoce; Jin, Zhu Ji; Ma, Mengchao; Zhong, Xuefei; Yang, Ze

doi:10.3390/app9224915

Cited by 3 publications

(1 citation statement)

References 19 publications

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“…As shown in Figure 1 a, a dot-dispersing form is that of a unique and identifiable pattern consisting of discrete circular or rectangle targets, or numerals [ 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 ]. Figure 1 b shows the centripetal form, which consists of a center circle or diagonal target and a surrounding pattern similar to concentric rings with different widths [ 35 ], sector blocks with different areas [ 35 ], regularly arranged circles [ 36 , 37 , 38 , 39 ], or concentric ring segments [ 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 ]. Compared with the dot-dispersing form, centripetal form is more versatile and popular.…”

Section: Introductionmentioning

confidence: 99%

A Novel Concentric Circular Coded Target, and Its Positioning and Identifying Method for Vision Measurement under Challenging Conditions

Liu

Guo

et al. 2021

Sensors

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Coded targets have been demarcated as control points in various vision measurement tasks such as camera calibration, 3D reconstruction, pose estimation, etc. By employing coded targets, matching corresponding image points in multi images can be automatically realized which greatly improves the efficiency and accuracy of the measurement. Although the coded targets are well applied, particularly in the industrial vision system, the design of coded targets and its detection algorithms have encountered difficulties, especially under the conditions of poor illumination and flat viewing angle. This paper presents a novel concentric circular coded target (CCCT), and its positioning and identifying algorithms. The eccentricity error has been corrected based on a practical error-compensation model. Adaptive brightness adjustment has been employed to address the problems of poor illumination such as overexposure and underexposure. The robust recognition is realized by perspective correction based on four vertices of the background area in the CCCT local image. The simulation results indicate that the eccentricity errors of the larger and smaller circles at a large viewing angle of 70° are reduced by 95% and 77% after correction by the proposed method. The result of the wing deformation experiment demonstrates that the error of the vision method based on the corrected center is reduced by up to 18.54% compared with the vision method based on only the ellipse center when the wing is loaded with a weight of 6 kg. The proposed design is highly applicable, and its detection algorithms can achieve accurate positioning and robust identification even in challenging environments.

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Section: Introductionmentioning

confidence: 99%

A Novel Concentric Circular Coded Target, and Its Positioning and Identifying Method for Vision Measurement under Challenging Conditions

Liu

Guo

et al. 2021

Sensors

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A novel capacity expansion and recognition acceleration method for dot-dispersing coded targets in photogrammetry

Wang¹,

Guo²,

Wang³

et al. 2022

Meas. Sci. Technol.

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In close-range photogrammetry, some improved designs have been developed to increase the coding capacity of Schneider-like concentric circular coded targets (SCTs). But another typical type, Hattori-like dot-dispersing coded targets (HCTs), is rarely expanded. In this paper, we give our detailed solution to recognize a kind of non-public HCTs used in V-STARS. Then an advanced HCTs (AHCTs) with multiple templates and simplified -Invariant is proposed, which achieved capacity expansion and recognition acceleration. First, the cross-ratio invariant is used in template recognition, then the affine transformation is used in decoding. Among the template recognition procedure, multiple templates are designed to expand the coding capacity and a simplified -Invariant is adopted to accelerate the recognition. Experiments with different shooting angles ranging from 0° to 80°, with smaller coded targets, with mixed coded targets of different sizes and with large outdoor scenes are carried out, and the results show that AHCTs can not only preserve the stability of the HCTs, but also achieves the capacity growth of coded targets at a faster recognition rate by 14.6%. The AHCTs with large capacity can be applied in scenario with large size or complex structure, and the acceleration advantage can be considered in real-time dynamic domains.

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High-accuracy camera calibration method based on coded concentric ring center extraction

Liu

Jiang³

et al. 2022

Opt. Express

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In the field of three-dimensional (3-D) metrology based on fringe projection profilometry (FPP), accurate camera calibration is an essential task and a primary requirement. In order to improve the accuracy of camera calibration, the calibration board or calibration target needs to be manufactured with high accuracy, and the marker points in calibration image require to be positioned with high accuracy. This paper presents an improved camera calibration method by simultaneously optimizing the camera parameters and target geometry. Specifically, a set of regularly distributed target markers with rich coded concentric ring pattern is first displayed on a liquid crystal display (LCD) screen. Then, the sub-pixel edges of all coded bands radial straight lines are automatically located at several positions of the LCD screen. Finally, the sub-pixel edge point set is mapped into parameter space to form a line set, and the intersection of the lines is defined as the center pixel coordinates of each target point to complete the camera calibration. The simulation and experimental results verify that the proposed camera calibration method is feasible and easy to operate, which can essentially eliminate the perspective transformation error to improve the accuracy of camera parameters and target geometry.

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An Initial Dot Encoding Scheme with Significantly Improved Robustness and Numbers

Cited by 3 publications

References 19 publications

A Novel Concentric Circular Coded Target, and Its Positioning and Identifying Method for Vision Measurement under Challenging Conditions

A Novel Concentric Circular Coded Target, and Its Positioning and Identifying Method for Vision Measurement under Challenging Conditions

A novel capacity expansion and recognition acceleration method for dot-dispersing coded targets in photogrammetry

High-accuracy camera calibration method based on coded concentric ring center extraction

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