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correcting a NDG7475

Dr_Evil

Dr_Evil

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I've been wanting to build a 1W 520 for a while now. I hate the beam specs though. I finally came up with an idea for a host which I'll try to keep under wraps until the project is finished. The problem is getting a better beam. I've been looking around and came across this.

ldbmcor2.gif


Is it necessary to focus the beam before sending it through the prisms? Is there a better way to make the beam more square/round? I want to do this with the least number of optical pieces possible while being able to make the beam more square/round.
 





DE....Correcting the NDG7475 is easy; You do not need much to get down to approx. 1.0 mRad divergence. Very tight !!

Use a G2 lens for collimation....then a pair of 6X Cylindrical lenses to correct the wide beam of the NDG7475.

I have done this many times. See the attached Optics Layout. Not more than that !! Eazy Sleezy !

Now...How you incorporate this into a HH host....well...PM me for some approaches...The attached pic shows a machined Aluminum round bar.... designed and machined to position the LD holder...and the lenses on a flat platform. Of course...the beam MUST enter the Cylindrical Lens pair on centre and the distance between the first Plano Concave Cylindrical lens and the second Plano Convex Cylindrical lens MUST be +/- .05mm to minimize the Far Field divergence.

This design shows a socket to accept the host on one end and a Beam Expander on the other end. Of course...there are many, many ways to position and secure the components. BUT...if you are dumping the beam into a BE...a stand alone/independent LD holder is demanded...for acceptable pitch and yaw adjustability to enter the beam into the BE at a perfect angle.

This design can be modified to accept many host's...with or without a downbeam BE.

Later...Beam out. :san::san:
 

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CDBeam gave you a better way, but I will say this, I have tried to use an unfocused (meaning, not fully focused to infinity) beam into a pair of cylinder lenses and it didn't work for me. The reason was that the beam expanded too much before it reached the 2nd cylinder lens, over shooting the diameter of the lens.

This was using a pointer with G2 lens just taken out of infinity a rather modest amount. I was hoping I could correct a beam without needing to have the pointer completely set to infinity, but it didn't work out for me, due to that problem, I am sure it would be even worse without any amount of collimation of the diode first.

I imagine one could come very close to infinity focus, just a bit out, and then have a larger beam to make sure you completely filled up the 2nd cylinder pair for a fatter beam and the resulting lower divergence. However this was not the correcting scheme you showed with that drawing.
 
Lildutchboy7 said:
Is there a way to place these in a lens barrel kinda deal? I'm not the best when it comes to optics so I'd love to find a way to get these pre-made into some sort of adapter/lens barrel:)
Click to expand...


You can actually get these (or similar) in a round shape instead of square, that may work. Although alignment may be a bit of a pain, both lenses and the LD need to be aligned (on one side to side axis, and in rotation).
 
diachi said:
You can actually get these (or similar) in a round shape instead of square, that may work. Although alignment may be a bit of a pain, both lenses and the LD need to be aligned (on one side to side axis, and in rotation).
Click to expand...

Know where I could get them? If it's too much of a pain in the butt for one of you then I'd probably get too frustrated to do it:crackup: I don't necessarily have the best brains/hands when it comes to these things.
 
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Lildutchboy7 said:
Know where I could get them? If it's too much of a pain in the butt for one of you then I'd probably get too frustrated to do it:crackup: I don't necessarily have the best brains/hands when it comes to these things.
Click to expand...


Thorlabs has them: https://www.thorlabs.com/navigation.cfm?guide_id=14

Not sure where else you might get them. Someone else here likely knows the best combination to get if you're going for that.

Personally I'd stick with the square/rectangular lenses, has been working well for many here, even for portable builds.
 
Probably most anything we can dream up is made by someone, but I have not seem a ready to install round tubed beam corrector for the diodes we use, not small enough to use with our little pointers. I have seen round cylinder lenses, I have a few myself, but not the matching cylinder expander lens to go with them.
 
Hi Doc,

I have used alu U-profile with 12mm inside width as "rail" to adjust cylindricals from Optlasers (they are all 12x12mm square shape what I like in them and by using 3 instead of 2 you can get any expansion up to 12x if I recall correctly). Anyway I had to add a piece of brass with 2 screws under for adjusting optical rotation because I did not want to glue - just used 2 face adhesion tape.

But I think you can also adjust a 6x pair (these are 10 and 6mm wide lenses) into profile with 10mm internal width if you glue them at the right place as CDBEAM design suggests.

Not sure if 6x are really needed, greens divergence is not as bad as that of blue ones, is it?
 

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Oh lord, you are right, green.... not so bad, CDBEAM777, can't he use a 3X? I think that diode really should have a 4X, but close enough? I was still thinking NUBM44 from another active thread which needs more correction, but if CDBEAM says to use 6X, he knows, he has recently built a host with beam correction for that diode.
 
OK....I just use the 6X for everything.....I know it works on all the Multimode LD's we currently use.....so.....That is what I use !! I posted the Ebay link a few posts up....

Now....EVEN if one pays the high price for a set of " Round " Cylindrical lenses...WTF...you still MUST radially position both lenses....in the correct position to the Laser Diode....and....to each other....THIS is not easy to do....without an Optical Kinematic Mount.....like this.....

12.5/12.7mm Diameter Kinematic Mount, 2-Screws

From Edmonds....but....who the hell has room for that ???? hahahaha

SO....really....just stick with the rectangular Cylindrical lenses.......for using round Cylindrical lenses just makes thing more difficult...NOT more easy !!!

NOW.........For mounting the Cylindrical lenses....see here.....

http://laserpointerforums.com/f39/aluminum-unit-mount-cylindrical-lenses-94918.html

This is a way to do it.....and that design can be adapted to other host geometries....different diameters...different lengths....so....we have already solved this problem !!!

SO...at the risk of sounding...dismissive....IMNSHO.....the lenses you should use are 6X cylindricals.....and see the link for how to get'em in front if yer diode...Later...

CDBEAM
 
CDBEAM777 said:
OK....I just use the 6X for everything.....I know it works on all the Multimode LD's we currently use.....so.....That is what I use !! I posted the Ebay link a few posts up....

Now....EVEN if one pays the high price for a set of " Round " Cylindrical lenses...WTF...you still MUST radially position both lenses....in the correct position to the Laser Diode....and....to each other....THIS is not easy to do....without an Optical Kinematic Mount.....like this.....

12.5/12.7mm Diameter Kinematic Mount, 2-Screws

From Edmonds....but....who the hell has room for that ???? hahahaha

SO....really....just stick with the rectangular Cylindrical lenses.......for using round Cylindrical lenses just makes thing more difficult...NOT more easy !!!

NOW.........For mounting the Cylindrical lenses....see here.....

http://laserpointerforums.com/f39/aluminum-unit-mount-cylindrical-lenses-94918.html

This is a way to do it.....and that design can be adapted to other host geometries....different diameters...different lengths....so....we have already solved this problem !!!

SO...at the risk of sounding...dismissive....IMNSHO.....the lenses you should use are 6X cylindricals.....and see the link for how to get'em in front if yer diode...Later...

CDBEAM
Click to expand...

That's a bit more of what I was looking for! I bet this can easily be adapted into a host, especially a custom one. Thanks a ton for this man I am actually really tempted now :D

Thanks:beer:
 
Yea....This is stuff I have been working on for several years now. Things like the Aluminum mount unit...Simple...EZ....All ya wanta do is fix the two Cylindrical lenses in front of the collimation lens...NOW....one can get more sophisticated with a special mount for just the lenses...yea...OK...I have and continue to do that....OR.....use a slow set epoxy....and...on a flat smooth surface...just slide/dance the lenses around...

For myself...I like to use another mount for the Cylindrical lenses....and then bolt THAT to the flat surface....BUT....at the end of the day...IT DOES NOT MATTER !!! There are many ways to do things !! Some simplier...some more complex....both work !!

One MUST get the ( Rectangular) Cylindrical lenses in alignment/centered with the beam....and one must set the proper distance between the lenses.... There ya go...no big secret....no use of many, many lenses....SO....with that...I am at a loss as to why more members do not use Cylindrical lenses...it is just too easy !!! See this build....
http://laserpointerforums.com/f42/sky-blue-ramjet-build-94646.html

Oh...and the source for the Cylindrical lenses....
Cylindrical lens pair to suit Mitsubishi red diodes, 445nm and 520nm diodes | eBay

Anyway....enough of my Blah, Blah !!!!!

CDBEAM
 
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