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correcting a NDG7475

steve001

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Okay, I just want to make sure I'm reading things correctly. Using the 6x cylindrical lens set, I only need those two pieces and a G2 lens? No lens goes after the 6x set? I see the Ebay listing says 35mm between the lenses that come in the set. I assume that is between the front of one and the beck of the other. Since you have a set, can you tell me how thick each piece is? I'd also like to know about how much space is needed between the front of the G2 and back of the first cylindrical lens.

Alaskan, since I can't PM or email you, can you please contact me?
Note: the final beam diameter after correction will determine whether or not a g2 lens is usable. You should use a collimation lens that has a larger diameter than the beam. Placement of the collimation lens is determined by it focal length. To keep divergence low, a long focal length lens should be used.
 

Dr_Evil

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Note: the final beam diameter after correction will determine whether or not a g2 lens is usable. You should use a collimation lens that has a larger diameter than the beam. Placement of the collimation lens is determined by it focal length. To keep divergence low, a long focal length lens should be used.
You just kind of confused me. The way you wrote that sounds like the collimation lens should be after the correction optics. CDBEAM shows it before the corrections optics. As for the G2, Idon't think ti will be bad considering DTR even offers it as an optional add on.
 

CDBEAM777

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OK...yes...the Collimation lense corrects the beam...just after the diode...then the Cylindrical lenses are placed after the Collimation lens. I believe the G2 lens works best for using on the NDG7475....but....I have not yet tested the G7 ??? I will test in the next month or so. The G2 works great with 6X.

CDBEAM
 
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CDBEAM777

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OK...I have tested a set of 6X Cylindrical lenses vs. a set of Opt Cylindrical lenses specified for the NDG7475....And...I just added a set of 6X from Lazereer ( Which are no longer available I think )

Interesting !!! The Opt worked better than I rembered...but not quite as good as the 6X.

See here...Tests we made at 1A current to the NDG7475.

6x Cylindricals/Lazereer Cylindricals

@ 0 Meter Beam width = 2.5mm
@ 7 Meter Beam width = 5.8mm

mRad = 0.472


Opt Laser Cylindricals

@ 0 Meter Beam width = 2.5mm
@ 7 Meter Beam width = 7.0mm

mRad = 0.643

SOooo... the 6X are a little better....and the further down beam one travels... from the diode output to the Far Field beam geometry target...the greater the benefit of using a 6X will present with a lesser width ( more a dot ).

I still like the geometry perimeter of the Opt Laser Cylindrical lenses a bit more than the 6X from LSP/AJAI... in that both lenses are the same size. This same size perimeter makes for a more simplified Cylindrical lens mount

So...you choose !! BOTH mRad metrics are very good....but the 6X is superior.

See attached pic of my set ups.

Note: a 7M ( 23')....when using the 6X lenses...the beam presents something very close to a circle (looks like a circle to me). In reality...the geometry is a round cornered rectangle. I tried taking pics...but the spot is just too bright.

CDBEAM
 

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Alaskan

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Thank you very much for the info Robert, that took some work to set up and measure, not just a five minute check of something. I am surprised 6X is better, if expanding the slow axis, I expected it was too much X and would cause the slow axis diameter to be larger than the fast, at distance. Good thing I have four sets of those 6X pairs Glutton had a group buy on, I will use them in time.

You just kind of confused me. The way you wrote that sounds like the collimation lens should be after the correction optics.
I thought I'd chime in here to explain what is happening differently.

The first lens of the cylinder pair expands one side of the beam, the second lens re-collimates it back to infinity focus.

Normally, almost always, the beam must be fully collimated to infinity focus before going through the lens pair. The beam can be out of infinity focus some, but not much. If it is, a small adjustment of the distance between the pair of cylinder lenses can make up for that, but there isn't much room to do so and if too far out, not going to happen.
 
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steve001

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You just kind of confused me. The way you wrote that sounds like the collimation lens should be after the correction optics. CDBEAM shows it before the corrections optics. As for the G2, Idon't think ti will be bad considering DTR even offers it as an optional add on.
Both ways may be doable. Experiment.
I've read another thread where a beam expander is used after beam shaping optics. I think however using a short focal length lens, G lenses are that, before beam shaping optics will limit the final minimum divergence. If shaping the beam is the entire goal then forget what I said.
I found this free download Ebook via Youtube. Laser Beam Shaping Applications (Optical Science and Engineering) Download eBook Laser Beam Shaping Applications (Optical Science and Engineering)
 

CDBEAM777

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Alaskan,

Glad to do these things. Nothing like experimenting to see what actually is good, better or best.

I just happen to have the Opt Laser lenses....and the 6X were from an old group buy...they are large....but are 6X. The Copper holder is from recent testing I have been doing to get a perfect friction fit between the 12mm module OD and a CU Heat sink. SO...sometimes all things just come together....and a quick experiment pops out...besides...Dr. Evil was " Tapping his toe " hahahaha

I am a real Hack Optical " Gueroo "....I know enough to be dangerous...and the rest...I just experiment and wing it !!

Steve,

Thanx for the link to optic info...hahaha..." As though his ape's brain could understand the secret's of the Krell "
!!!

Later...CDBEAM
 

RedCowboy

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Dam, I thought the NDG7475 was about like the NDB7875, but apparently it's much worse, is it slightly better or worse than a NDB7A75?
 




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