about

For a spherical refracting surface with a known aperture and working for an object at a given position, calculates the image position, the magnification, the numerical aperture in the object space and the numerical aperture in the image space as functions of the refraction indexes, the surface radius, the aperture diameter and the object position.

Note that the aperture is the plane perpendicular to the optical axis which intersection with the surface is a circle of diameter D. Therefore, it is in general not tangent to the vertex of the surface.