- Jul 10, 2015
Focal length doesn't explain why the beam's not staying square.
Read my post #97. I explain it there. The rough example at the bottom is for a m140. The diode you have probably has 2 to 3X the emitter width. You can't have a square beam at the lens and at the far field spot with your diode. The FAC can make it better (more square) by what ever ratio the FAC changes the raw divergence. From laser tree spec it looks to be around 4-5 times.Focal length doesn't explain why the beam's not staying square.
My guess would be with a 75mm FL the SA should be around .5mRad and the FA around .1mRad.SO...I tried a 12.5mm dia / 75mm EFL Convex lens from THOR LAB to tame the Blue FAC
NO Luck !!! Sounds like no one else has
achieved a solution....so...I do not feel so bad !!! I will keep experimenting !! CDBeam
Ditch the G8. use just the 75mm FL.LS...OK....I tried various 75mmEFL positions...10mm from the LD output....to 150mm distance...The LD had a G8 Colli lens attached when the test was made.
Up and down the C/L....ALL CRAP!!! Least geometry achieved was about 100mm Square @ 14M Distance To Target.
The beam output from the G8 fit on the lens....for the full range tested. After seeing this was a Dead End....Not anymore time spent on
documentations....as it was NOT going to be viable....Sigh.....
Like allready stated before this is not possible with multi mode diodes. They have a large M^2 for the slow axis:Focal length doesn't explain why the beam's not staying square.
Yeah, this is what I believed would be the case with these blue diodes. I can't understand exactly what the producers of these "FAC" corrected diodes had in mind by doing this, but I was dubious that it would turn out to be something that would give us a better beam quality. Unfortunately, it is what it is.
I know that go back and read my posts. I have been trying for 10 pages to explain how these work.You can't beat the laws of physics. There is no such a thing as the multi mode diodes we know with a round beam staying round over long distances.