According to what I think that I've gotten from this technical paper:
..my calculations are this:
(..or am I way off base? )
For my 9x40 mitsu ML520G51 diodes:
3.5 mm half max beam dia desired:
40 / 2= 20, 20(sin)= .342, NA =.342
Now, for the EFL:
3.5/ 2(.342) =
3.5/.684=5.117 so,
EFL=5.117
So, what is needed is a 633nm AR coated aspheric lens with an NA of .342 and a EFL of 5.117 mm for a decent beam ?
Thanx in advance,
-Steve
PS- the complete article is here: http://www.lightpath.com/literature/...ationNotes.pdf