Something isnt quite right with my beam

[adamk]

Hey guys I need some advice.
I recently build a 2W M140 and I am having trouble with the beam. I am using a g-2-lens and I am able to focus the beam to a spot where it will burn through corrugated cardboard in milliseconds. However, inches away from the focused spot the divergence is way too high.

Using this calc (pseudonomen137's JScript Diameter Calculator), my divergence was calculated to be 102.006917910112 mRad.

Pics of the beam at 3 inches (~1-2mm diameter) and ~12 inches (~1 inch diameter) are below.

This is my first project and am not sure as to why the beam is not collimated...any ideas guys?

Also, the lens was purchased pre assembled in its housing through through a trusted forum member here off of ebay. So I am not sure if it is maybe in backwards?

The crappy Paint sketch is what the laser is doing. It is converging at a focal point and then diverging rapidly. This focal point can be moved closer and farther by rotating the lens + housing unit (farthest I tested was at 12 inches).

Help please..!:undecided:

PS: Please ignore the horrible wiring and harnesses for components. Very rough first prototype!

 

[VisibleGreen]

Have you tried rotating the lens?

 

[diachi]

Have you tried rotating the lens?

Sounds like he has, seeing as he can move the focal point.

Do you have the lens in the right way? :yh:

Edit: Accidentally a word

 

[adamk]

Thanks for the replies guys!
I rotated the whole lens unit (housing + lens). This allows me to change the location of the focal point. I have not rotated the lens itself. I also do not know if it is in the right way since I bought the unit already with the lens inside the housing.

How can I check if the lens is in correctly and how can I try rotating the lens itself if it is already inside the housing?

 

[BowtieGuy]

The whole lens assembly should be installed with the lens closest to the diode, and IIRC, the actual lens should be in the lens holder with the flat side of the lens toward the diode. Someone please correct me if I'm mistaken.

 

[adamk]

The whole lens assembly should be installed with the lens closest to the diode, and IIRC, the actual lens should be in the lens holder with the flat side of the lens toward the diode. Someone please correct me if I'm mistaken.

When the lens assembly was screwed in all the way into the Axiz module the focal point was just shifted. The beam divergence was not changed.

I will check on the lens when I can get a chance and let you guys know.

 

[APEX1]

The whole lens assembly should be installed with the lens closest to the diode, and IIRC, the actual lens should be in the lens holder with the flat side of the lens toward the diode. Someone please correct me if I'm mistaken.

you are correct, Those S1 lenses are a little different depending on what WL is being used..

 

[ARG]

Check all the basics, lens in the right way round (rounded dome side facing away from the diode), lens nut screwed in all the way, diode pushed all the way into the module (should be slightly recessed), ect.

If you've checked all that and still have problems you may need a different lens barrel to seat the lens closer to the diode, some lens barrels don't allow the lens to get close enough to the diode for infinity focus.

 

[BowtieGuy]

How can I check if the lens is in correctly and how can I try rotating the lens itself if it is already inside the housing?

If the lens is installed in the holder incorrectly, you will need to unscrew the lens retaining ring with a thin bladed screwdriver, or something that will fit in the two slots cut into the retaining ring.
You will need to be extremely careful not to touch, and thus scratch the lens itself.
I use a tool that I made for myself that just fits in the I.D. of the holder, so it can't slip off and scratch the lens. (See pic below).

 

[Pman]

Going to have to make me a tool like that but a bit more ghetto

 

[BowtieGuy]

Pete, I've got an extra one, I'll send it to you.

 

[Pman]

WooHoo. Great to be me Sorry, got carried away for a sec

 

[adamk]

Check all the basics, lens in the right way round (rounded dome side facing away from the diode), lens nut screwed in all the way, diode pushed all the way into the module (should be slightly recessed), ect.

If you've checked all that and still have problems you may need a different lens barrel to seat the lens closer to the diode, some lens barrels don't allow the lens to get close enough to the diode for infinity focus.

Checked lens and the almost flat part is against the diode while the round part is facing out (see pics).

I tested various lens settings; I changed how much the lens housing was screwed into the module. Pics show beam as the lens is screwed in farther and farther. Silver cap was removed to allow the housing to be screwed even farther into the module. As the lens got closer to the diode, the beam kept on diverging more and more. The pic without the silver cap is the lens as far as the lens can go either because the threading ends or the lens is now touching the diode. I am not sure. I do know though nothing gave a collimated beam.

When I was pressing the diode into the module, I made sure it was slightly recessed. However, it was SLIGHTLY recessed. I was not sure if it was far enough but since it was my first time pressing a diode I stopped. I was worried I would crush it

Should I desolder the driver from the diode and press it in farther??

 

[DTR]

Are you sure you are actually having an issue or just don't like the spot you get with these diodes and the higher power lens. Just to make sure you do know these diodes are multimode and have a more elongated output. Check against the info in this thread.
http://laserpointerforums.com/f65/there-something-wrong-my-beam-spot-59400.html


Also if you got the diode in module with lens from me it would not have left untested and can not be in backwards.

EDIT

Actually the best question is does the spot size as you turn the lens in from all the way out decrease in size to a certain point and then get bigger before bottoming out?

 

[adamk]

DTR I think you are right.:worthy:
After messing with the focus I am able to get a ~2 inch 'spot' at about 30 feet while retaining a decent focus up close.
Thanks for all the help guys, you can now make fun of me (please keep in mind this is my first time dealing with lasers like this!)

Hey now I know how to take apart a lens housing!:san:

 

[DTR]

DTR I think you are right.:worthy:
After messing with the focus I am able to get a ~2 inch 'spot' at about 30 feet while retaining a decent focus up close.
Thanks for all the help guys, you can now make fun of me (please keep in mind this is my first time dealing with lasers like this!)

It is all good. A lot of people that have not worked with higher power diodes think they will produce a pinpoint dot but an elongated spot is one of the sacrifices for having such a powerful diode.:beer: