Techhood c-lens pair for multi mode greens.

[RedCowboy]

I ordered a pair of the 2X ? c-lens from ebay for 1w 520-525nm, they just arrived today and are the smallest I have seen yet I will post a pic or two when I test them. They look like about 5 x 8mm and 7 x 8mm which will be just fine for use with a G2 primary and good for compact pointers........catching the beam from a ndg7475 w/G2 where it's thin and correcting the fast axis, this should make a much nicer/tighter bright green beam........I see a new host in my future.

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Just a quick preliminary test looks promising.

 

[Philipnzw]

Would be great to find out the specific correction factor on them. However, even at 2X correction ya can't go wrong with it given its super small size. Now some really tiny corrected builds are a possibility.

 

[RedCowboy]

Sure just a regular hand held build with a shelf on the front and a cover tube.
I'm waiting to see what the divergence is like from THIS new Osram diode, if it's better than ndb7875 then I have 4X and a pair like in this post coated for blue ( likely 3X ) I want to use in a compact

 

[Philipnzw]

I just shot an email at techhood, according to them, it's a 4X correction on those little C lenses. Looks rather promising. Might get one for the heck of it.

 

[RedCowboy]

I love the 6X I use on my nubm44's from our GB and the OPT units which cost a bit more make a world of difference, the techhood cyl's I haven't used before but I will post later when I do, if anyone has feel free to share your results, I also have some anamorphic prism pairs to try out as I haven't used any yet.....will share results later after I do.

 

[Alaskan]

How well does 6x square up the beam with the NUBM44 for a distance of 100 feet? Could we go a bit further with the expansion of one side or does 6x make a very square shape? I choose one hundred feet as an arbitrary distance, I realize the further you go, the further the geometry of the sides will depart from one another as there is no way to keep it perfectly square for all distances.

 

[RedCowboy]

No it's actually still a ribbon/rectangle but the divergence is greatly improved......out of the 6X c-lens pair a 44 with G2 makes a beam that's 7mm wide and about 1.5mm thick....the thickness is not effected by the c-lens pair of course.

The difference is at 15 feet a 44 with G2 makes a bar 1.75 inches wide but with the 6X it's just a little over a 1/4 inch wide...about 5/16 or 45mm wide vs. 8mm wide..............at 75 feet without the 6X the beam/spot is 7 inches wide and with the 6X it's a little over 1 inch wide

At 75 feet a 44 with G2 makes a beam 7 inches wide but with a 6X pair and 3X beam expander it's 3/8 inch wide and 1/8 inch thick that burns it's mark on my plywood target.
So as you can see the fast axis is still diverging a little faster even with the 6X pair but not nearly as much, otherwise the factor is 6X

How close you set your c-lens to your G2 will make a small difference and a chinese G2 is not the same as the DTR G2, even the sanwu G2 is a slightly different FL

 

[Alaskan]

Thanks for the update, so to make it square, do you have an estimate of the x factor we would need?

 

[RedCowboy]

It won't work like that, because of the aggressive divergence and the emitter shape is l
The fast axis is the horizontal part, the thin part, the " left to right " of this l
The fast axis starts out as the narrow part but diverges fast and becomes much wider than tall as seen in this explanation and the c-lens concave makes that fast axis diverge even faster then the c-lens convex reigns it in, it's an one axis beam expander.
I don't know how you can reduce the fast axis divergence and make a square beam this way.......I thought about an anamorphic prism pair and I have some ordered but it achieves the same thing so .......unless I could square the c-lens corrected beam but that might cost divergence down range.

If anyone knows how to reduce the aggressive divergence of our multi mode ld's and make the beam square and have it propagate as square I would love to know........I have wanted to employ c-lens pairs to correct the fast axis of 4 nub44's and then knife edge those beams llll

This would make for a near 30W squarish beam with much improved divergence, however we are still dealing with MM diodes with aggressive divergence so I would also use a big beam expander to get a tight spot in the far field.