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