Camera Matrix Calibration Using Circular Control Points and Separate Correction of the Geometric Distortion Field

We achieve a precise camera calibration using circular control points by, first, separation of the lens distortion parameters from other camera parameters and computation of the distortion field in advance by using a calibration harp. Second, in order to compensate for perspective bias, which is prone to occur when using a circled pattern, we incorporate conic affine transformation into the minimization error when estimating the homography, and leave all the other calibration steps as they are used in the literature. Such an error function allows to compensate for the perspective bias. Combined with precise keypoint detection, the approach is shown to be more stable than current state-of-the-art global calibration method.