pencil lead thin 445nm beam-no prisms no cylinderical lens

[kecked]

Ok so the divergence sucks but it works in my situation. here are some photos to show how well the n=beams match up. Once my prisms come I'll try that as well. In the mean time...............

[drlava]

yeah, I'd say those beams match up really well at 120 feet!

[kecked]

No those pictures are at about 15-20 feet.

[mccarrot]

sorry I was away.

The beam is a little smaller than the size of a pencil when it comes out of the telescope. The expander is 2x. I actually did this just for fun. I was suprised that it worked. I also loose a ton of power doing it. I bet some of the beam is clipped in the telescope.

PS: I dropped the 660nm diodes and went 642nm. Much nicer colors and much brighter. Will be interesting to see what my quad does when loaded with 4 150mw 642nm diodes. I might need that blue power back!

I did as suggested try the beam at about 120 feet that is about as far as I can go. Its about 1 inch wide by 5-6 inches long. Still works for beam shows ok. As I said for my use in my house my solution works for me. I'm just sharing. Do what you will with it.

These beamspecs you can also get if you ave a lens wit a Fl of arround 3.

With a FL of 4-5 you would have better beamspecs <3mrad and still a pretty small beam.

So sure you solution will work fine, but it would make your life much easyer if you just picked the right lens

[kecked]

Your right. I'm just not that technical on the optics to know where to look for a specific lens. I'm stuck with what I see offered. No matter prisms will be here soon.

[edison]

I did some testing on different lenses with different FL,s. I learned a few things and i thought i share it it whith you. Today i compared two different lenses. The testsetup was an open can diode LPC-815 mounted in brass holder. The first lens was the lens with an FL of 4.6 and a NA of 0.55 (mccarots) The second was the lens from laser4u FL was 9 mm NA is unknown.

http://store.laserextreme.nl/catalog...products_id/75



http://cgi.ebay.com/Laser-Module-Hou...ht_1486wt_1137


When i did some test it gave me some good ideas of wich way to go with the FL.
The lens from Mccarrot gives a tight beam of 2mm at the aperture of the collimator and the divergence is low at 8meters
But when testing the ones from Laser4U i noticed that you can focus the beam to less then 1mm when hitting the wallpaper at half a meter. But when turning the setup shooting at a distance of 8meters i needed to focus the beam again because the divergence was huge. When i focused it again the beam at the arperture starts with 5mm and the slowly turns into a 1mm spot after 8 meters. So i think the ones from mccarrot with the FL are within range. I will do also some testing with lenses with a shorter FL then 4.6 so when those arrive i know what the effect will be when using lenses with a shorter FL.




So in a nutshell a lens with an FL of 9mm will result in a fat beam at aperture but a very low divergence. A lens with a Fl of 4.6mm will result in a thigh beam but with an acceptable divergence of 0.6 till 0.8mrd. So with a shorter FL as 4.6 this should result in very tin beam but with a high divergence. A very short FL will result probably thin beam but with a higher divergence at greater distance. I will test 15 lenses with different focuslengths soon on both red opencan and blue diodes. That will proof wich way to go with the FL on both blue and red opencan diodes.

Kvant use a FL of 4.6 with 0.53 NA in their modules and they probably tested also diferent lenses to get the best beam. Arctos uses a telescope in their modules so they probably use lenses with a longer FL that will result in a fatter beam with low divergence. The telescope makes the stacked beam smaller but increases the divergence but if you start with 0.2mrd and use a 4:1 telescope you end up with a 2by2 beam with 0.8mrd when entering the telescope with a beam of 8 by 8 mm.

If i have more result of testing lenses i will let you guys know

[drlava]

it's good you're testing, but note that those divergence results are really only applicable with the red diodes you tested with, the 445 diodes divergence will be quite different due to it having a larger emitter.. what was once 'acceptable' with 4.6mm FL may no longer be acceptable with the emitter of the 445. The ebay ad states the lens NA to be 0.3 (10mm FL) so expect clipping losses with 445.

[edison]

I thought sharing the information on testing lenses would give people an idea of how you can find out wich lens to use for different diodes. Buy 3 lenses with a short FL a middle FL and a long FL gives you an idea what you probably need. You can to this on the blue,s too. I forgot to mention that i,m going to test to other 15 lenses also on the blue,s with a prism set to find out what the blue,s need

[kecked]

This will be really handy in a chart(for us optical fools). maybe do the 660nm diodes and the 445nm diodes and put a chart together showing how they will work. I for one would like to have such a chart.

[Zoof]

To come to grips with the relationship between divergence and beam diameter you can play with this applet. It has been aroudn for a while but I like it a lot.
http://www.ee.buffalo.edu/faculty/ca...ts/index.html#

I still remember being puzzled when I first played with lenses on my 1mw Hene a long time ago: "Why will it not focus properly??"

This applet visualizes that you can focus a laser beam to a tiny dot half a meter from the aperture er the laser but not at 10m from the aperture.

Before the critics say it: the 445s do not have a Gaussian beam profile but it is close enough to use this applet to come to a qualitative understanding.