[Goptical] How to use Lens::add_surface() - beginner question

[Dibyendu Majumdar]

Hi,

Thank you for creating this project.

I am a novice user - I know very little about lens design.

I am mainly interested in taking some lens design patents
(https://cameragossip.github.io/nikon-lens-patents.html) and using
goptical to generate various diagrams. So I am trying to modify the
tessar example.

I see that the add_surface() method takes following parameters:

          @param roc spherical radius of curvature. 0 means flat curve.
          @param ap_radius circular aperture radius.
          @param thickness distance to the next surface or exit plane.
@see get_exit_plane.

I am not sure what the meaning of ap_radius is - and what value to
use. I do not see this specified in the patent literature.

I would very much appreciate any help.

Many thanks

Regards
Dibyendu