Thanks for your help every time.
I designed it as follows.
1. My lens is designed as a rectangular parallelepiped.
2. The point source exists in the lens and the cone angle of the source is 180.
3. There is a reflector at the end of the lens and a detector at the other end.
4. I want to set the reflector's Radius and Conic as variables.
My purpose is to get the most number of hits detected by the detector.
What should I do to proceed with the optimization?