There are lot, depending on your requirements. Anyway you can try: 60+ zoL'
ukR0E4p
1, Refractive: an achromatic as positive + plano-convex as negative; D^[l~K
OR /I 7V\
2, Reflective: two parabolic mirrors; 6 eSo.@*l
{W,5]-
Both of them affer nice spherical aberration performance. 7h
54j
gQ\.|'%
Reminder: compute the laser beam density, ensure you have enough strong optical coating. (e7!p=D
o,rF 15
Good luck.