There are lot, depending on your requirements. Anyway you can try: ^QV;[ha,o
W?/7PVGv5h
1, Refractive: an achromatic as positive + plano-convex as negative; qx53,^2
OR ScfW;
2, Reflective: two parabolic mirrors; -i @!{ ?
'&T4ryq3"
Both of them affer nice spherical aberration performance. ,)Z^b$H]
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*$wD
Reminder: compute the laser beam density, ensure you have enough strong optical coating. :ZU
<v[,A8Q
Good luck.