Method of using non-specific target to complete structured light plane calibration

A calibration method for line-structured light (LSL) by using a virtual binocular vision system (VBVS) composed of one camera and a front coating plane mirror is promoted in this work. The front coating plane in the VBVS can generate much less coplanarity error in lithographic feature points and remarkably decline the imaging distortion during back coating. An encoded target is proposed to distinguish between real corners and virtual corners (mirrored corners) and achieve high-precision matching between real and virtual corners when the target is occluded during the VBVS calibration. A parameter optimization method based on 3D constraints is presented in the work to obtain accurate structural parameters and thus guarantee precise reconstruction of the LSL. Moreover, the laser stripe and its mirrored image meet the auto-epipolar constraint. Therefore, the matching between the real and virtual stripes can be realized based on the vanish point. The performance of our method is verified in the experiments.

Section: Related Workmentioning

confidence: 99%

A calibration method for line-structured light using mirror-based virtual binocular vision system

Yang

Zhang

et al. 2023

“…It is essential to explore more suitable light sources to ensure the clarity and purity of each ring light image [26]. Furthermore, owing to significant distortions within the depth of field of the imaging system, traditional camera calibration methods exhibit low efficiency and poor applicability for multiring imaging systems [27,28]. Therefore, the development of novel imaging system calibration methods is required [29].…”

Section: Introductionmentioning

confidence: 99%

Accuracy improvement of a multi-ring beam structured inner surface measurement: via novel calibration methodology and light source optimization

Li,

Deng,

et al. 2024

Parts with a large depth-to-diameter ratio play a critical role in the military, aerospace, and automotive industries. However, accurately measuring their inner surface profile remians challenging owing to the lack of adequate and accurate sensors. We developed a multi-ring structured light system to obtain three-dimensional data of inner contours, such as inner diameters, which are crucial for ensuring component performance and safety. In this study, we proposed three simple yet effective techniques to improve the multi-ring beam structured measurement system. First, we designed a distortion correction method to calibrate the imaging system. Second, a two-step calibration approach was used to calibrate the multi-ring projection. Meanwhile, we benchmarked the effects of different light sources on image speckles. The calibration results demonstrated that the coefficient of determination (R-2) used for line fitting exceeded 0.999. Moreover, the measurement experimental results show that the uncertainty of less than 10 µm and the smallest measurable pipe inner diameter can reach 15 mm, demonstrating that our methods are promising for improving the accuracy of structured light optical sensing systems. This system satisfies the measurement requirements and can be immediately utilized to meet the high demand for inner contour measurements in industrial applications.

“…Laser measurement [2], monocular vision, and binocular vision [3,4] are the most commonly used non-contact measurement technologies. Laser measurement employs a camera and linear structured light to create a three-dimensional point cloud of the measured workpiece, which is then dimensioned using an algorithm [5]. Zhao et al [6] used linear structured light to measure the size of the sodium-cooled rapid reactor's fuel assembly, with a final measurement error of 0.05 mm.…”

Section: Introductionmentioning

confidence: 99%

Binocular visual dimension measurement method for rectangular workpiece with a precise stereoscopic matching algorithm

Chen¹,

Zhong²,

Ze³

et al. 2022

Self Cite

Binocular vision measurement benefits from high prediction robustness and low structural complexity. However, there are still significant flaws in its accuracy. In this paper, binocular vision measurement of a rectangular workpiece is investigated. A new precise measurement method based on binocular vision is designed to achieve precise measurement of rectangular workpiece dimensions. Firstly, an algorithm for workpiece location based on Zernike moments and corner matching is proposed and employed to precisely locate the workpiece and extract the sub-pixel coordinates of discrete points on an image's edge. Then, a novel stereoscopic matching algorithm combined with epipolar-geometry and cross-ratio invariance (CMEC) is proposed to improve the accuracy of binocular vision stereoscopic matching. Finally, a projection plane is introduced after the 3D reconstruction of discrete points in the workpiece contours by fitting the plane with least squares. The projection plane limits the coordinate fluctuations of discrete points. Furthermore, the data screening is used to further improve the accuracy of size calculation. The experimental results of the standard checkerboard and actual workpiece show that CMEC's matching accuracy reached 99%, and the proposed method's measurement accuracy reached 0.018 mm. This work presents a novel algorithm for stereoscopic matching in binocular vision and machine vision measurement.