Planar targets with circular marked points are widely used in camera calibration and visual measurement. To obtain the real circular center in the image of a planar target and improve calibration precision, a circular center extraction method based on dual conic geometric characteristics was proposed. The key to this method was that the dual conic matrix C*A of the marked point A in the image has a generalized eigenvector associated with the dual conic matrix C*B of the marked point B in the image, and this generalized eigenvector passed through the two center projections of both points A and B. As a result, after obtaining the subpixel edge points and fitting the ellipse conic function, a vector linking the two center projections could be computed by using the dual conic matrices of the two marked points, and the standardized interpoint of the eigenvectors would be the center projection. To test the extraction accuracy of center projection with the proposed method, the center projection of a huge marked point with a diameter of 90 mm is extracted when the relative angle between the charge-coupled device and the target plane is 40°, and the errors are found to be within 0.1 to 1 pixel. The camera parameters of a handheld scanner are calibrated with these center projections. A three-dimensional workpiece and a planar target with known marked points are scanned with the handheld scanner, and distance errors are within 0.2 mm. The extraction accuracy of this proposed method is higher than that of the elliptical center method and is superior to the precision of camera calibration.