Beam Splash from Internal Lens Reflections Correction Idea?

[IsaacT]

Hey everybody. So, like a number of the members here who's wallets are slaves unto their desires, I recently built a laser from the PL520 diode. You can look at it HERE I am loving it but there is one thing that I would really like to be able to fix.

That being the infamous bat wings we get from our diodes as the light reflects off of the internal wall of the lens nut(I believe that is why we get them....if I am wrong let me know). So I want to fix it.

My idea is simple in theory, complicated in practice. Ideally I want to find an absorptive paint to put in there so that the light does not reflect off and make my dot less pretty than my dreams depict it. I have this feeling black paint alone would not be enough so I was wondering if anyone had any feedback on this idea of mine.

Any thoughts would be great, I look forward to moving this idea either forward or back to the drawing board. either way, my beam profile being wonky simply because the inside of my lens nut is reflective is rubbish! I won't have it I tell you!

Thanks,
Isaac

 

[Lazerbeak]

http://laserpointerforums.com/f44/light-absorbing-paint-darkroom-71447.html

Super black - Wikipedia, the free encyclopedia

Light Absorbing Black-Out Material | Edmund Optics

~ LB

 

[Bionic-Badger]

Well, you could use some ultra-flat spray paint to reduce reflections, but make sure it airs out properly so you don't get funk on the lenses.

Another thing you can try is to create an aperture to simply block out parts of the beam. It'll reduce output, but give you a round(ish) dot.

 

[hakzaw1]

***^^^
Thats what I was thinking too.
make a pin hole lens just big enough to allow most to pass.
I have made a few pin hole lens cameras-
Photos can be taken with no glass parts in the camera-- just a thin copper disc with a tiny hole. I was thinking about using one on both a C mount red,a Mitsub red and a 445 either M or 9mm. my guess would be that the copper would need to be painted black with the flat black made for high heat tolerance- like for spray painting an item that will get very hot-

 

[Pman]

Maybe the hi-temp flat black paint for barbecues? It dries quickly and is VERY flat/dull in appearance

 

[hakzaw1]

^^ yes that is the paint - sold at Walmart- home depot-Lowes etc. guess you would want to paint first and make the hole after- maybe start a small as possible then with goggles see how much you are clipping and enlarge for the best size. Take some pics please- this is one method of improving the beam that not much has been posted about. doing divergence measuring may be a good idea too.
I found it easier to trace the spot on paper as opposed to trying to adjust my calipers to the get an accurate measurement.
V/R hak

 

[norbyx]

Ok, but why not try with a acrylic lens? This diode has very low power so an acrylic should work well and usually the lens nut is black.....

 

[IsaacT]

The plastic lens is too short to be useful and I like using glass. I will pick up some of that paint as soon as possible and take pictures of the mod process and comparative photos of the resulting beam.

 

[RA_pierce]

Doesn't the lens nut already have a dark grey coating?
The original Aixiz lenses I remember from when I first started making lasers were coated flat black. The newer versions have this crappy grey coating.

Anyway, the internal reflection probably comes from the lens itself, not the lens nut.

There are several parts in the lens that could contribute to the splashy output.
1. The inside of the lens nut
2. Any of the 3 optical elements
3. The spacer ring
4. The narrow aperture of the lens nut
5. The retaining ring

I think the first step should be to determine the source of the splash.

A long time ago I took apart a digital camera. I noticed that the edges of the optics were blackened. I got an idea and tried to make the output better by carefully applying black permanent marker to the edges of the lenses.
Example:

This is done to eliminate internal reflection in the optics.
I don't remember what the result was but if there was a significant improvement I am sure I wouldn't have forgotten.

Of course permanent marker isn't an ideal solution. It may work with a better coating although if you apply a layer of paint to the circumference of the lens, you may have to drill out the lens nut to get the optics to fit without scraping off the paint you just applied.

I'm thinking some flat black paint could be applied with a fine tipped paintbrush and a steady hand.

Personally, I just don't use the 3 element lenses. They suck.