CNI pen- Improved Divergence!

[RA_pierce]

Everyone knows CNI pens are notorious for divergence around 1.5-2.0mRad, and for most this is... acceptable. However, for me, I can't stand it.

So since my X105's poor lens cracked, I began modifying it.
The original plan was to make it focus adjustable, but I decided I liked fixed focus better and I was lazy.
I filed down a nice Zeiss lens from a digital camera to fit the laser nicely and replaced the lens...
So I repaired my laser and was happy because with this new lens I got an improved divergence from the original ~1.2mRad to ~1.1mRad.

Recently, I decided I wanted to make use of my other Zeiss lens (from the same camera). So I resized the other lens and using the original replacement lens with it, I built a collimator into the internal optic assembly in my laser. The result was amazing!
I now have an adjustable laser set at ~0.7mRad! The focal point can be adjusted from 10cm to 60cm. At it's lowest divergence setting, the beam diameter is slightly more than 2.0mm compared to the original <1.0mm. The burning ability is slightly decreased due to the larger beam diameter @aperture but I don't burn much with it anyway. The optics were good and AR coated so I would estimate that the total power loss would be somewhere around 5mW. That really isn't a lot when its compared to the ~120mW this laser produces consistently.

The Original Optics:
Crystals> Concave lens> IR filter (removed)> Convex Lens (Cracked)=====

New Optics:
Crystals> Concave lens> Plano Concave Lens> Plano Convex Lens=====

Here are some pictures:

And some Internal Reflection :

 

[Switch]

Nice results!! Makes sense too. Why did you completely remove the IR filter?

 

[Bionic-Badger]

Wow, that's great stuff. I'd like to do that with my PGL, as it really does widen up. Does it add any beam specks or other crap to the output?

 

[RA_pierce]

I got rid of the IR filter so I could have more room for adjustment and it isn't really necessary. The IR it emits diverges at a huge angle and is emitted in several blobs (multimode diode) so it can't do much harm. Most of it is blocked by the aperture, too.

There are a few specks and lines in the beam but only because I accidentally scratched one of the lenses while I was filing it down. It's small and not really noticeable unless you're really picky, but if you can keep the lenses clean and scratch free it should turn out really good. Before I filed the lenses they were PERFECT.

The lower divergence really makes a difference. Instead of a big blob, the dot on distant objects looks like a tiny sparkly star. It really makes a difference when pointing outside during daylight too. It's a lot more visible.

 

[IgorT]

Man, you did some good work there!

My CNI >150mW also isn't very good when it comes to divergence.. Do you perhaps know the focal length of the lens you used?

Also, how did it affect the beam diameter at the apperture? Is it thicker now?

 

[Switch]

he beam diameter is slightly more than 2.0mm compared to the original <1.0mm

 

[IgorT]

he beam diameter is slightly more than 2.0mm compared to the original <1.0mm

Thanks! Missed that... I was asking CNI about divergence, and they said they can provide a lower one, but that it affects the beam diameter.
So the same might be possible by adjusting the collimator lens, or maybe it would require adjusting the expander lens?

I wonder how much the Zeiss lens affects the power. But without the IR filter, the power of the green is higher anyway.

 

[Switch]

You should adjust the expander lens to the diameter you want, then match the collimator to the lowest divergence.

 

[RA_pierce]

Yeah the diameter @ aperture is bigger.

I think the focal point for the convex is 2 or 3 cm. Dunno about the concave.

Thanks! Missed that... I was asking CNI about divergence, and they said they can provide a lower one, but that it affects the beam diameter.
So the same might be possible by adjusting the collimator lens, or maybe it would require adjusting the expander lens?

Adjusting the collimator alone won't do much. The expander makes the most difference If it could be adjusted/replaced for one that expands the beam slightly more it should work. I was too afraid to completely disassemble my laser so instead of adjusting the expander I just added another one.

Aligning the lenses was a pain in the ass though. It took me almost an hour to get it right.

 

[IgorT]

Yeah, i know.. I've had big problems when replacing an expander in a DX laser. It's only glued on top of the crystals - four drops of glue hold it up in the air above them..

The tiniest tilt or a fraction of a millimeter off, and the beam would shoot out at an angle.
Adjusting the collimator alone also didn't do much good - it could only be made worse...


So you did all this without taking the module out of the body? Just from the top? was the glue bond of the collimator nut hard to break? I was thinking of unscrewing it, to get to the expander, but i noticed in a broken CNI, that the expander has no threads on the metal piece... Don't even know what holds it there (i got it in pieces).

 

[RA_pierce]

Yep, I didn't take the module out, and I'm not sure how to do it (safely) anyway. The glue was pretty easy to get out of the way. I had to clear some of it from the threads with a needle though.

The IR filter wasn't glued down, but the way it was installed was... backwards (the collimator nut has the two holes you can use to unscrew it but the IR filter nut is placed in so the holes are on the other side). The hardest part was getting that out. I actually got it jammed when it was almost out and it took a couple hours of filing to get it free. :-[ It was scary.
Another reason I removed the IR filter was that It was set on the nut with some kind of brittle rubbery glue that would constantly flake off and get all over the optics. I hated it.

I used the IR filter nut to secure the concave lens. I would have taken pictures during disassembly and modification but it didn't occur to me at the time. And I won't dare take it apart again after all the time it took to align the damned thing

The expander confuses me too... I wanted to remove it but it wasn't installed the same way as all the other optics. ???

Also I found that the threads are pretty loose without glue and if you carry it around it comes loose and the focus gets screwed up. I use a tiny blob of hot glue to secure it, but it's loose enough to allow the collimator to still be adjusted. I cut a piece of the hot glue off the stick and dropped it into one of the little holes on the collimator nut then used a soldering iron to melt it. In the last couple of pictures you can kinda see it (it's the blob at the bottom).

 

[mikeeey]

I never knew the Divergence was that bad!
is it just the way the picture turned out or does DX pens have better Divergence?

 

[RA_pierce]

Well I've heard of a few DX pens with pretty good divergence, but generally DX pens have worse specs. My buddy has a true 30 with 1.0mRad divergence. It varies a lot.