Title: Accurate positioning for the centre of circular array target based on vanishing points

Authors: Lijun Sun; Shaokui Ma; Tianfei Chen; Ming Yan; Xiaodong Liu

Addresses: School of Information Science and Engineering, Henan University of Technology, Zhengzhou, 450000, China; Key Laboratory of Grain Information Processing and Control, Ministry of Education, Zhengzhou, 450000, China; Henan Key Laboratory of Grain Photoelectric Detection and Control, Zhengzhou, 450000, China ' School of Electrical Engineering, Henan University of Technology, Zhengzhou, 450000, China; Key Laboratory of Grain Information Processing and Control, Ministry of Education, Zhengzhou, 450000, China; Henan Key Laboratory of Grain Photoelectric Detection and Control, Zhengzhou, 450000, China ' School of Information Science and Engineering, Henan University of Technology, Zhengzhou, 450000, China; Key Laboratory of Grain Information Processing and Control, Ministry of Education, Zhengzhou, 450000, China; Henan Key Laboratory of Grain Photoelectric Detection and Control, Zhengzhou, 450000, China ' School of Electrical Engineering, Henan University of Technology, Zhengzhou, 450000, China; Key Laboratory of Grain Information Processing and Control, Ministry of Education, Zhengzhou, 450000, China; Henan Key Laboratory of Grain Photoelectric Detection and Control, Zhengzhou, 450000, China ' School of Electrical Engineering, Henan University of Technology, Zhengzhou, 450000, China; Key Laboratory of Grain Information Processing and Control, Ministry of Education, Zhengzhou, 450000, China; Henan Key Laboratory of Grain Photoelectric Detection and Control, Zhengzhou, 450000, China

Abstract: Circular array target is widely used in vision measurement systems. The detection of circular targets is usually regarded as ellipse detection after projective transformation. However, the centre of the ellipse is not the actual projection of the centre of the target circle. For this reason, this paper proposes an algorithm for locating the imaging centre of the target circle based on the vanishing points. After completing the extraction and filtering of the ellipse edge, the projective transformation matrix is used to obtain the two vanishing points referring to the coordinate axis direction of the target plane. Then utilising the principle of perspective invariance and the two vanishing points, two pairs of tangent points on the ellipse edge are determined. Finally, the cross point between the lines connecting the two pairs of tangent points is the actual projection point of the target circle. Both simulation experiments and actual experiments demonstrate that the proposed algorithm has the characteristics of simple operation, faster running speed, and higher precision.

Keywords: circular array target; projective transformation; vanishing points; homography matrix.

DOI: 10.1504/IJMIC.2021.123385

International Journal of Modelling, Identification and Control, 2021 Vol.39 No.1, pp.19 - 28

Received: 29 Jan 2021
Accepted: 02 Apr 2021

Published online: 16 May 2022 *

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