Sagittal and meridional radii of curvature for a surface with symmetry of revolution by using a null-screen testing method

An algorithm to compute the sagittal and meridional radii of curvature for a surface of revolution is presented. The sagittal radius is obtained from the surface normal, and the meridional radius is calculated from a function fitted to the derivative of the sagittal curvature by using the surface-normals raw data. A calibration spherical surface is tested by using the null-screen testing method. Experimental results of the spherical surface show that the sagittal and meridional radii of curvature differ by 2.600% and 2.604%, respectively, with respect to the actual radius of the calibration spherical surface.