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20 January 2006 A new sub-pixel detector for grid target points in camera calibration
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Proceedings Volume 6027, ICO20: Optical Information Processing; 60272N (2006)
Event: ICO20:Optical Devices and Instruments, 2005, Changchun, China
Sub-pixel detection of target points is an important task in camera calibration. Grid target points are widely used in camera calibration for their junctions can be easily detected. Traditional method detects the sub-pixel position of grid-point by calculating the intersection of two beelines fitted by centers of grid-lines. Generally, this method yields low precision because of the effect of projective distortion of camera lens. In this paper, we propose a new sub-pixel detector for grid target points. We firstly use a new shape operator based on Hessian matrix to detect the pixel position of grid-point. Then the intensity of sub-pixel points in the neighborhood of grid point is calculated by cubic interpolation. A minimum restriction for searching grid-point is deduced by the fact that the grid-point to be detected is just the extremal point of local intensity profile. According to this restriction, the sub-pixel position of grid-point is finally determined by a graded morphological shrinking operation. Computer simulation results indicate that our new algorithm is more accurate and robust than the traditional algorithm.
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D. Chen, Y. Wang, and G. Zhang "A new sub-pixel detector for grid target points in camera calibration", Proc. SPIE 6027, ICO20: Optical Information Processing, 60272N (20 January 2006);

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