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OPT Lasers Cylindric lenses - NUBM44 beam correction tests

Crazlaser

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I just want less divergence. The lens I've been using is a 3 element lens.
 



Bionic-Badger

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The problem with the NUBM44 and other wide-rectangle-beam shaped laser diodes is that one axis (horizontal or vertical) expands at a different rate than the other. So while you can make your lens focus one axis so that it doesn't diverge (much), the other axis will continue to expand.

This is why you need cylindrical lenses. They only focus one axis while not affecting the other. Then you can use a regular lens to focus one axis, and correct the "fast axis" (the other axis) using a cylindrical lens pair.

So unless you want to invest and mount and focus a cylindrical lens (pair), you'll have to live with a beam that can remain roughly the same width in only one axis.
 
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I just want less divergence. The lens I've been using is a 3 element lens.

Hello,

If you like to obtain smallest possible divergence using our optics would be three element lens + cylindrical lens 3x.

We will be changing the names of the lens on website into 2x and 3x. these are actually 3,14 like PI :)
Cylindrical lenses 638 nm - Opt Lasers
Collimator 445 nm - Opt Lasers

Using these two you can obtain ~2 mrad.

I know that one of the users expanded the beam two times, so he used cylindrical lens twice and obtained around 1 mrad beam but also it is wider at the output, so assuming in my opinion this two optics is best choice and will allow you to obtain around 4-5W power depanding on diode you have.
 
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RedCowboy

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Yes my best results are using cylindrical pairs along with an expander, but just using a cylindrical pair to correct the rapidly diverging axis can help a lot and give you a very decent fixed beam. It's the correct first step before an expander for getting the best results, alignment is critical but not that hard to do with just a little practice wearing the proper laser safety glasses.

Usually I use a G2 and 6X pair but a 3 element and 3X pair could work as well, I like the NUBM44 diode but for an even better beam you may want to try a NDB7A75 diode.

Here are a couple old videos when I was testing, never mind my verbal 1/4 by 1/4 statement on the 06 diode that is much like the NDB7A75, what I meant is it was staying under a 1/4 by 1/4, my final solution was setting the pair closer to the primary and hand tuned while running wearing proper laser safety glasses of course, don't try it without wearing the proper safety glasses, I'm sure you know this but I say it for any casual viewers wanting to experiment.

p.s. Beware of lens splash and lens flare, if using an expander that can block a lot of it or you can use spacial filtering, that it a piece of metal with the beam profile cut out so as to block all but the beam that you want. If you are looking for a simple screw in lens like the 3 element that will fix everything perfectly, that does not exist because one axis diverges faster than the other on most MM diodes, but a simple 3 element looks great on a NDB7875 or M-140 because the natural divergence is lower on those diodes, the osram 1.6w is a nice tight one as well.
>>>>> https://sites.google.com/site/dtrlpf/home/diodes/osram-pltb450-1-4w-450nm


 
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Crazlaser

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Thanks guys. Because I didn't really consider this beforehand, there's not much room in my build, however in the future I'll consider those circular lenses. It's not a host build, rather a project box laser, so it's more for close range burning experiments anyways. :)
 
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You can always reflect the beam and then use cylindrical pair. This way you can safe some place and put optics on side, not in front. Maybe this helps ;) Cheers.
 

ElectricPlasma

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Here is my new 9x setup. I found that putting the two 3x lenses back to back ( flat sides up agains each other) creates much cleaner line. Day and night comparing to putting them one in front of the other facing same direction like i posted in photos earlier. So much cleaner for measuring. Specially when projected at longer distances like 30-100ft.

I highly recommend this layout.!!

you can also see double stick scotch tape in the center which holds lens temporarily. I will cement the corners to the steal when all is done.

I'm really considering buying these lenses, and at first I was thinking for the nubm44 I've got but now I'm considering the setup for my 07E. Has anyone tried this setup, any numbers at all? I'm guessing it would work just as well with the 07E?
 
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Can you fill the the slit between the lenses with some kind of glue or water to test what happen? That might help you. You can also use glue used for smartphone screen.
 

ElectricPlasma

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Hi ElectricPlasma,

Yes I used such a set to correct the beam from 2 PBSed NUBM07E.

Do not you remember that old thread in May? You +repped me then:

http://laserpointerforums.com/f65/pbsing-2-nubm07e-compact-set-97376.html

But you have to be very precise about rotational orientation of all lenses - otherwise spot will be not round!

Thank you very much, I had forgotten about that thread. Did you get the change to measure the divergence? I appreciate the help!
 
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Light superglue

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No, I did not mesure divergence.

I understand that mesuring divergence only makes sence for perfectly collimated beams, but I cannot imagine how to do such collimation (I mean beam after cylindricals) at home.

By making that device I knew that the separation of lenses had to be fixed with <0.1mm precision but when doing this I checked the spot at the wall (5m away) what only means that I focused the beam at 5m and further it must diverge.

So one has to find the position of PCX lens which produces the smallest spot at infinity. Maybe 50-100m would be enough but this means to have a workshop 50-100m long with binoculars fixed to the bench to check the spot when moving lenses.

My imagination says that rifle constructors may have such workshops where they check target scopes or laser aiming devices.
Maybe by use of mirrors it can be done in a smaller room but I would keep from directing such a strong beam into mirrors...
 

steve001

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No, I did not mesure divergence.

I understand that mesuring divergence only makes sence for perfectly collimated beams, but I cannot imagine how to do such collimation (I mean beam after cylindricals) at home.

By making that device I knew that the separation of lenses had to be fixed with <0.1mm precision but when doing this I checked the spot at the wall (5m away) what only means that I focused the beam at 5m and further it must diverge.

So one has to find the position of PCX lens which produces the smallest spot at infinity. Maybe 50-100m would be enough but this means to have a workshop 50-100m long with binoculars fixed to the bench to check the spot when moving lenses.

My imagination says that rifle constructors may have such workshops where they check target scopes or laser aiming devices.
Maybe by use of mirrors it can be done in a smaller room but I would keep from directing such a strong beam into mirrors...
Start at 15 meters, then to 30 meters to measure divergence. At that 30 meter length your likely pass the Rayleigh Length. If not increase the next measurement by 5 meters.... until the beam starts to expand. Pass the Rayleigh Length a laser beam will expand linearly. Within the Rayleigh Length the beam will expand 1.4 times its initial diameter. Your not looking for high precision measurements so mirrors could be used.
 
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Light superglue

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Hi steve001,

Thank you for the explanation.
I was not aware of this when doing the device, however I should.

Now that device is dismantled for a while. I may try this when my next project will be ready, but this is not soon at all.

But at 30, even 15 meters I did not see the spot size even wearing new glasses. It was too small, bright (after I suppose this was ca. 9x expansion) and far for my weak eyesight.
And at >8W beam I would not like to be that person who stands there to tell me how the spot is (even wearing protective googles).

Has the divergence to be mesured at highest power or one mesured at lower will be the same?
 
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steve001

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Hi steve001,

Thank you for the explanation.
I was not aware of this when doing the device, however I should.

Now that device is dismantled for a while. I may try this when my next project will be ready, but this is not soon at all.

But at 30, even 15 meters I did not see the spot size even wearing new glasses. It was too small, bright (after I suppose this was ca. 9x expansion) and far for my weak eyesight.
And at >8W beam I would not like to be that person who stands there to tell me how the spot is (even wearing protective googles).

Has the divergence to be mesured at highest power or one mesured at lower will be the same?
Since you do not see a noticeable difference at either distance the Rayleigh length may be greater than 30 meters. Take measurements at greater distances. I'd start at 35 meters this time and increase the distance five meters if no change is seen unti a change is seen, then shorten the distance by one meter until the spot stops getting smaller. I am assuming the beam is focused to infinity also known as "infinite conjugate"
Lower power might allow the diode to perform differently, but I do not know, so try it.

I always measure beam divergence during the day in full sunlight. I also use a flat plate of clear glass. On that plate of glass is a crosshair type marking I've drawn. Both axis have markings starting from the middle at 1 millimeter spacings. Shining the beam through the glass eliminates that too bright to look at, however at 8 watts the laser beam might just burn away the crosshair markings.
 
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Crazlaser

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Oct 11, 2016
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Hi steve001,

Thank you for the explanation.
I was not aware of this when doing the device, however I should.

Now that device is dismantled for a while. I may try this when my next project will be ready, but this is not soon at all.

But at 30, even 15 meters I did not see the spot size even wearing new glasses. It was too small, bright (after I suppose this was ca. 9x expansion) and far for my weak eyesight.
And at >8W beam I would not like to be that person who stands there to tell me how the spot is (even wearing protective googles).

Has the divergence to be mesured at highest power or one mesured at lower will be the same?
With OD4 goggles you can stare at the 44 dot on white surfaces from six inches away without it being uncomfortable at all.
 
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Hurry

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Mar 6, 2017
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Yes my best results are using cylindrical pairs along with an expander, but just using a cylindrical pair to correct the rapidly diverging axis can help a lot and give you a very decent fixed beam. It's the correct first step before an expander for getting the best results, alignment is critical but not that hard to do with just a little practice wearing the proper laser safety glasses.

Usually I use a G2 and 6X pair but a 3 element and 3X pair could work as well, I like the NUBM44 diode but for an even better beam you may want to try a NDB7A75 diode.

Here are a couple old videos when I was testing, never mind my verbal 1/4 by 1/4 statement on the 06 diode that is much like the NDB7A75, what I meant is it was staying under a 1/4 by 1/4, my final solution was setting the pair closer to the primary and hand tuned while running wearing proper laser safety glasses of course, don't try it without wearing the proper safety glasses, I'm sure you know this but I say it for any casual viewers wanting to experiment.

p.s. Beware of lens splash and lens flare, if using an expander that can block a lot of it or you can use spacial filtering, that it a piece of metal with the beam profile cut out so as to block all but the beam that you want. If you are looking for a simple screw in lens like the 3 element that will fix everything perfectly, that does not exist because one axis diverges faster than the other on most MM diodes, but a simple 3 element looks great on a NDB7875 or M-140 because the natural divergence is lower on those diodes, the osram 1.6w is a nice tight one as well.
>>>>> https://sites.google.com/site/dtrlpf/home/diodes/osram-pltb450-1-4w-450nm



I using nubm44, driver 4.5A and cylindrical lens 3x purchased by opt laser.

At 2m the beam spot is about 7mm, but it have lost power, without lens the beam bigger but much powerful.

In your video you burn at 16 feet (5m), how?
Where can I wrong?
 




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