Olive2

OLIVE is a simple to use optical system layout program. It was designed to be an extremely intuitive graphical tool for quickly and accurately prototyping simple optical systems with off-the-shelf or custon designed single or multi element optical systems.
OLIVE's functionality is centered around the interactive Layout Area.

The idea is to select an optic and place it on the Layout Area. Now you can grab and and move the elements as if they were lenses on an optical table. The lenses move along the optical axis and the chief , marginal, and max field-of-view rays trace in real-time. This gives you an immediate
idea of how different optics will effect your design