Camera Calibration Robust to Defocus Using Phase-Shifting Patterns

Sensors

Mengchao Ma¹  Keyi Wang²  Yuwei Wang²  Bolin Cai²  Xiangcheng Chen³ 

[1] Department of Instrument Science and Opto-Electronics Engineering, Hefei University of Technology, Hefei 230088, China;Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, Hefei 230026, China;School of Automation, Wuhan University of Technology, Wuhan 430070, China;

关键词: defocus;    camera calibration;    phase-shifting;    feature points;    concentric circle;   

DOI  :  10.3390/s17102361

来源: DOAJ

【 摘 要 】

Camera parameters can’t be estimated accurately using traditional calibration methods if the camera is substantially defocused. To tackle this problem, an improved approach based on three phase-shifting circular grating (PCG) arrays is proposed in this paper. Rather than encoding the feature points into the intensity, the proposed method encodes the feature points into the phase distribution, which can be recovered precisely using phase-shifting methods. The PCG centers are extracted as feature points, which can be located accurately even if the images are severely blurred. Unlike the previous method which just uses a single circle, the proposed method uses a concentric circle to estimate the PCG center, such that the center can be located precisely. This paper also presents a sorting algorithm for the detected feature points automatically. Experiments with both synthetic and real images were carried out to validate the performance of the method. And the results show that the superiority of PCG arrays compared with the concentric circle array even under severe defocus.

【 授权许可】

Unknown