How to make beam fatter?

Last year I was working on 7-color-laser that uses red, BR and green module. The problem is that BR and RED beam is much fatter than Green beam.
Red and BR diodes in Aixiz module give beam that is about 5mm in diameter and green module gives 1.5-2 mm beam in diameter.
When all three beams exit from sled only green beam is noticeable and other beams are almost impossible to see. (Because of its diameter)

Another problem of green module is that divergence is much worse than on BR and Red modules.

I was searching forum in order to find solution to make BR and RED beam thinner and concluded that it could be very expensive and I aim for the cheapest build.

If I could make green beam fatter that would solve my problem.
I have two theories that may solve my problem.

-- To use bigger lens with longer FL.

-- Or I can use different diffuser than would make beam fatter at the same distance from the lens.



If I could make beam fatter than would solve another problem, divergence. Right?

What others think about this?
Has anyone done that before?
Are my theories true?

Thanks!
ReNNo

beam sizes is part of the the problem.. .another possible problem could be your power ratios. coul you please list them? also i don't know the size of your build but you could probably get a beam expander? a little searching here in the optics section will net you some pretty good results.

michael

I don't have LPM to measure lasers power.
This build uses 50mW green module, LOC and PHR.
At about 6-7 meter away from sled green beam expands to size of BR and Red beam and there I can easily see white beam. That means that power ratio is fine.

Problem is tight green beam close to aperture. Tight beam is easier to see than fat beam.

Beam expander is expensive and massive for my build and that is reason why I didn't mention beam expander.

That is how it looks like (Yeah I know, it's from scratch and very, very cheap and bad looking.) and size should be as this plexiglas pad.



Uploaded with ImageShack.us

ok now that i see what you are doing.... it is very similar to the white fusion kit..good news is that i'm pretty sure no beam expander is used. with a 50mw greenie you will need much mor power than a phr....it would be good to use a lot less green (like 5-10mw of green) your LOC is good, and use a 6x or 8x... that should solve your problems. also, are you 100% sure that all of your beams are aligned correctly? it is very difficult.

michael

All modules are adjustable by Lm317/Lm1117 regulators and I can achieve any power by turning potentiometer knob. That is why PHR@120mA is enough for "white beam"
It took me 3-4 months to align beams and they were aligned perfectly. That was not problem.

That is build that I was working on long ago. Now I would like to start all over but first I need to solve this problem with green beam diameter.

Hm I think CNI are doing quite small beam expanders
Size is like 25*50mm for a 2x, 3x or 5x or is that already too big for you?

like i said... a phr can be used. but not with 50 mw of green. its just too much. ideally you would want your red and violet to have the same mw (not ma) rating. also it is not the lm317 that regulates the current... that just regulates the voltage.


good luck
michael

Burnsy said:

Hm I think CNI are doing quite small beam expanders
Size is like 25*50mm for a 2x, 3x or 5x or is that already too big for you?

Click to expand...

Yeah, these expanders are too big, and as I mentioned before they are expensive and I aim for cheap build.
If I had money I would definitely buy white fusion kit.

chipdouglas said:

like i said... a phr can be used. but not with 50 mw of green. its just too much. ideally you would want your red and violet to have the same mw (not ma) rating. also it is not the lm317 that regulates the current... that just regulates the voltage.


good luck
michael

Click to expand...

Cmon, someone with 1k posts should know what is DDL driver (that uses lm317 or lm1117) and with these drivers you can adjust current very precisely. Voltage adjusts by itself.
I want to make cheap and not powerful white laser, that is why I like PHR in this build.
I really cannot afford 6x o 8x.


I want to know what others think about these two theories I wrote above.

cmon back to you!!! you never made clear it was the ddl you only said the lm317... sinse your such a smarty pants you should know that the LM317 is a voltage regulator... not a complete driver... sorry for trying to help you.

i know money is an issue, as it is for most of us... that is why is said to turn down the power on your green.. you need about 4x's more violet than you do green...

michael

Yeah, you got me (words game)
If someone on LPF forum says LM317 or LM1117 that means driver that controls current. (That includes resistor for controlling current, capacitor and silicon diode)

I bought green module from DX and you never know what is real output power, that is why I bought 50mW. If I need less green I can easily decrease current.

But that all is off topic.

In theory you should be able to expand the lens using a concave lens followed by a medium focal length convex lens. Getting the expander right shouldn't be too difficult with the right lenses, the only problem I see would be aligning them to get the best divergence. Unfortunately I don't have that much experience with this kind of stuff, but I know that it is possible.

I did some tests and I have promising results.

I tried to find apsherical lens with a longer focal length and I found one in LPC-815 sled. (Aspherical lens that is in front of turning mirror)
This lens has focal length of about 16mm and was great for experiment.
I made lens holder and glued lens on it, just for test.

Some pictures:



I managed to achieve fatter beam, that is about 2.9mm in diameter that is much better than 1-2mm.
One more thing that I tested is divergence and I was amazed.
I achieved divergence of about 0.6mRad. (Yeah, with green DPSS laser)
And dot was just fine, without scatters.

All that means that it's possible to make green laser with 5mm beam (Like BR and RED in aixiz module) and also to achieve amazing divergence.... and to do it for few dollars or for free

I found another aspherical lens but this time in PHR sled.
It has longer focal length, about 30mm.

At 30mm from diffuser beam is about 3.5mm wide.
With that lens I achieved divergence of 0.3mRad that is amazing.
I never thought that green lasers can have that good divergence.

I need lens with a bit longer FL to get 5mm wide beam...
First I need to test what FL lens I need.

It looks like the cheapest solution to make green laser with amazing divergence.
Also, everyone who wants to combine Red or BR beams with green that would be very helpful.

EDIT: And here are some comparisons, Modified 10-20mW module vs 150mW O-Like

I was going to say, I can't believe nobody's said anything about trying a different collimating lens. Looks like you got it, though. Perhaps since you have been playing around with your green more than I can manage to do, would you say that the light coming directly off of the crystal is more collimated than light directly from a laser diode?

I can't believe that no ones is interested in this modification. Divergence is very significant characteristic of laser. I'm really sick of these high power burning laser with tight beam for burning, and divergence of 2-3mRad. These lasers are not for pointing something on long distances, just for burning.

Yes, light that comes out of crystal in TEM00 mode is very tight and with good divergence.
Light that comes from multimode IR diodes is not collimated at all.

All you are probably doing is modifying the beam expander that most green lasers already have.



The first lens, the one that looks like this " )( " is a double concave lens. The next lens (looks like this " ()" ) is a double convex lens. That is a beam expander. There is probably a way to calculate what focal length would work best, however I do not know what that is. As you have already found, a longer focal length makes the beam fatter. I might suggest looking for a double concave lens to swap out with the one in the module already.

There is another way to make a beam expander, and that is using two double convex lenses with different focal lengths. Try putting another lens in front of your focusing lens at different distances. I think (I'm not 100% sure, don't flame me for a wrong suggestion!) that a shorter focal length lens should be used. Just put it in front and move it till you get it where you want it!

I was planning something similar to this, I was also wondering why nobody had thought of doing something like this in the first place. It seems like not as much about optics is known as there should be. Lasers have progressed a lot in the last couple of years, but for the most part the lenses have stayed the same