Estimation of the degree of asphericity of a glass sphere using a vectorial shearing interferometer

► Sphere is incorporated as a thick lens into the interferometric setup, illuminating it with an expanded beam. ► The Vectorial Shearing Interferometer is used to determine the spherical aberration induced by a glass sphere on a wave front. ► Spherical aberration depends on the local sphere radius, on the refraction index of the glass, and on the cone angle of the source. ► Degree asphericity is estimated by determining the average radius of curvature in different sections, at various points on the surface of the sphere, and the deviation from it. ► Deviations from spherical aberration are due to the errors in the spherical geometry.