parallel beam

Hi
Do you know how to use zemax to design a lens with output beam is parallel ?
Now I was set the thickness of last surface be infinity , but I think there is some problem in this setting. Is there any operand in merit function editor to describe or simulate the parallel beam ?
Thank you very much ! :em25:

在最后一个面的后面再插入一个Paraxial面，再将该面设定一定的焦距即可优化。

Thank you very much , I will try it .