If you have some idea where the rays will meet, the most straightforward method would be to use three sources each emitting a single ray representing the fields, and then put a detector roughly where it should go. Ideally, all three will initially hit the detector. Then you can use the optimization wizard to get a minimum spot size with full power using the X, Y, and Z positions as variables. If the system is a regular symmetric imaging system without folding, you may just need to vary the Z. Use a detector with a fine resolution so you can get good accuracy.

If you want to do them one at a time, just do it with two rays first, and then another two rays, perhaps with two configurations that turn off one or the other of the rays.

You might also try hybrid mode NSC and use the Power Pupil Map/Power Field Map features.

HI kevin,

                Thank you for the reply.  That is currently what I am doing as this is an off centered parabola that has astigmatism.  I have three foci due to the three rays I am tracing through the system.  I will implement the optimization operands to more finely determine the ray crossing.

Thank you much for the help.

I only have the parabolic curve from the CAD object unfortunately.  I do not have the parabolic equation parameters they used.  Is there a way to back calculate this from NSC to SEQ, and back to NSC?

Thanks in advance for the help.