Parameters
n : refraction index
R1 : radius of curvature of the first surface
R2 : radius of curvature of the second surface
e : center thickness
x : distance from the vertex of the first surface to the object
D : aperture diameter of the lens
l : distance from the vertex of the first surface to the primary principal plane
li : distance from the vertex of the second surface to the secondary principal plane
s : distance from the primary principal plane to the object
si : distance from the secondary principal plane to the image
xi : distance from the vertex of the second surface to the image
m : magnification
NA : numerical aperture in the object space
NAi : numerical aperture in the image space
