Collimation problem

Hi guys, I'm very new to this forum and very new to Laser building.

I did my first ''laser'' yesterday but I have problem with Collimation.

it is 405nm from PHR-803T sled

Basically, right now I have self-made driver (as per Laser driver - It can be done) which is connected to the diode in Aixiz casing and I tried using 6V and 9V batteries (9V is much brigter) but I get huge divergence of the beam once it goes past 4-5meters. I tried focusing the lens but to no avail... it looks like a nice dot (snowflake) from 1-4 metres away but then just expands enormously.... I pointed it at the wall which is about 20m away and the ''dot'' get so big (1m probaly in diamater) that you can barely see it.

Any Idea what is the problem?

oh yeah the beam is not visible in
the dark unless i smoke directly into it but it's very bright for the eye from 4m away.

Also: the operating current is 110mA +-5 but when i point it at my black leather wallet it doesnt burn or anything like that (wallet is about 5cm away from it).

Have you tried turning the lense around?
It makes a big difference on my 100mW laser.

Otherwise it could be a problem with the distance between diode and lense.
Like how far the diode is into the module and how far the lense is screwed into the focus knob.

No I havent tried to turn the lens the other way, I just assumed that it went only 1 way for proper usage.... Ill try that when i get home...

The lens is not very much into the focusing knob, actually the optimal position for the lens is when there is small gap between the focusing knob and the diodholder..

ALso got my Odicforce kit for 300MW red laser today )) weekends are sorted )

Well try fiddle with it, you will be surprised at the effect of a small change in distance between diode and lens.
(Do you have goggles?)

Your laser is fine- your eyes are causing the issue.

405nm is on the edge of the visible spectrum, and your eyes have trouble focusing on it. That's why the dot appears blurry and highly divergent at a distance.

Leave your laser on, and walk up to there. You'll find that the dot is fine.

Most people forget this- it may not be a lens issue. Go up to the spot with your goggles, and check out the dot- it's not as big as it looks.

But i Also want it top burn stuff but it doesnt

as for the goggles they should be arriving tomorrow...

If you want to burn stuff, loosen the focusing lens so it sticks out from the module.

That will focus it down to a spot. With the goggles on, you can look for that spot.

It will burn best at that point.

Also the diode should be countersunk in the module. A lot of people flush mount the diode, but it makes focusing a little harder.

Toke said:

Have you tried turning the lense around?
It makes a big difference on my 100mW laser.

Otherwise it could be a problem with the distance between diode and lense.
Like how far the diode is into the module and how far the lense is screwed into the focus knob.

Click to expand...

hey it helped, i turned my lense around and was able to focus the dot much better....too bad it is difficult for the eyes to see it in the dstance i thought i get a laser that would be seen for miles....didnt do my research properly i guess....oh well 300MW red laser awaits over the weekends

thanks for your help.

If you want visibility, go for green. 660nm red is only going to be marginally better than the 405nm is for long range visibility. Only upside is it's not as hard to focus on it. Green will be a LOT brighter per mw though.