Provide parameter in source for rays that are not on the optical axis

Provide a parameter in the source, or LightData rays definition which allows for a ray bundle which is not on the optical axis but shifted along the (local) x/y plane. This would allow for point to point imaging.

How should we treat angles then?

For a telecentric design, beam would still go parallel (or symmteric) to the optical axis. Otherwise additional angles must be defined since we (so far) do not use entrance pupils or stop surfaces etc...