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DTR G8 lens

Joined
Jul 10, 2015
Messages
10,184
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113
Looks like a G8

The G8 is a single element wideband AR coated with an 8mm focal length.
G7 is a single wideband with about 7mm FL although some of the chinese units appear to be longer, not much use now that we have the G8
The G2 is a single element wideband AR coated with a 2.39mm focal length. As it sits the closest to the facet/junction it's the most efficient and the best for power testing.
G3 is a single element wideband AR coated with about a 4-5mm focal length, better suited for low divergence diodes.
The 3 elements are multi element and AR coated for either red, blue or green and have about a 4-5mm effective focal length, however there is additional clipping with higher divergence diodes.


In effect the G2 focuses really tight up close but your beam will be wider when you try to focus far away, the G8 is opposite and makes a much nicer looking beam in the far field.

That said different diodes are different as are applications. So buy some of both.

Also you keep more power with the G2 and G8 where as the 3-element robs up to 30% via. beam clipping......I have stopped using the 3 elements.
 
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Joined
Apr 23, 2011
Messages
177
Points
28
Looks like a G8

The G8 is a single element wideband AR coated with an 8mm focal length.
G7 is a single wideband with about 7mm FL although some of the chinese units appear to be longer, not much use now that we have the G8
The G2 is a single element wideband AR coated with a 2.39mm focal length. As it sits the closest to the facet/junction it's the most efficient and the best for power testing.
G3 is a single element wideband AR coated with about a 4-5mm focal length, better suited for low divergence diodes.
The 3 elements are multi element and AR coated for either red, blue or green and have about a 4-5mm effective focal length, however there is additional clipping with higher divergence diodes.


In effect the G2 focuses really tight up close but your beam will be wider when you try to focus far away, the G8 is opposite and makes a much nicer looking beam in the far field.

That said different diodes are different as are applications. So buy some of both.

Also you keep more power with the G2 and G8 where as the 3-element robs up to 30% via. beam clipping......I have stopped using the 3 elements.

Great, thanks!

That dang DTR, I went back to see if I could add a G2 but he'd shipped it out already! (less than two hours after placing)
 
Joined
Dec 2, 2008
Messages
345
Points
28
hello guys,

everybody compares G2, G7, G8

is there any comparison between standard acrylic lens that come with module itself and G8 for example. ?
 
Joined
Jul 10, 2015
Messages
10,184
Points
113
The acrylic is inefficient and can't take power above something like 50-80mw IINM certainly not for prolonged use, I have only used acrylic lenses on some low power reds for which they worked just fine.
 
Joined
Dec 2, 2008
Messages
345
Points
28
Does g8 lens still have problem with not enough threading in 2022?


Is it problem with just brass housing or all of "aixiz" host. ?

What is the fix?

Is this a problem with focusing close for burning,
Or to infinity for nice tight beam?

I am just interested in beam, no burning.

Can anyone elaborate on the problem ?

Thank you
 
Joined
Jul 10, 2015
Messages
10,184
Points
113
It's not a problem for an infinity focus ( beam ) in most cases, but depending on the laser diode when focusing up close, some will require the lens barrel being near the end of the modules threads, this is mostly only an issue with the multi-mode 9mm size diodes.

There are 2 things that work well to address this.
For infinity focused beams I use a retainer to lock down my focus, I have been using the thumb wheels that come with most modules drilled and tapped all the way through for M9x0.5
Also you can get a module with a couple of extra threads here or here, these can also get a better heat transfer from your diodes backing plate.

Note: The Aixiz modules don't move heat away as well as the solid copper modules like the one posted above, for my diodes I use copper.
 
Joined
Dec 2, 2008
Messages
345
Points
28
Thank you.

I want to use it with cooper diode host, sharp 488nm. Main focus is beam. No close up burning messing. Shoul it be all right?

Also that trick with thumb ring sounds like great solution. Thanx
 
Joined
Jul 10, 2015
Messages
10,184
Points
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Works like a champ and you can use a un-drilled thumb ring on the end for aesthetics.

SANY5897.JPG

The unit on the right is a 488nm with a G8 lens focused at infinity. Makes a beautiful beam, there is however a small box artifact with sharp 488's that can be seen in low light conditions when viewing the beams spot at short-medium distance in low light, it's caused by internal reflection off the facet but it's smaller with a longer FL lens like the G8 and easy to ignore.
I drive mine @ 250ma for about 120mw out of a G8 lens.
As always please remember to lase safely and wear proper laser safety glasses when appropriate.
SANY5908.JPG
SANY6715.JPG
 
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Joined
Dec 2, 2008
Messages
345
Points
28
thank you soo much for plenty of information. the color is just incredible.. i cannot wait to get the diode.. it has been shipped just recently.

anyway..
lets say i wouldnt mind loosing some mW with G3 lense, is the box reflexion better with g3, and what about beam? is it narower, tighter? have you tried it?

thanks
 
Joined
Jul 10, 2015
Messages
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Points
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The shorter the focal length the narrower the beam will be in the near field ( in front of you ) but the wider the beam will be in the far field.

So a G2 will give you a cool looking thin, intense beam up close, but it spreads out faster over distance, a G3 or 2EG ( 2 element green AR coated ) is a compromise and a G8 with it's longer FL will give you a wider beam up close but a much better looking, tighter beam and smaller spot when pointing far away.

I have used them all and in the end I like the G8 the best for the Sharp 488, however you can build more than one and comparing side by side is by far the best way.

Also the output power is the highest with the G2 and G8 which are both single element wide-band anti-reflective coated, so you can use them for all visible wavelengths.
 
Joined
Dec 2, 2008
Messages
345
Points
28
The shorter the focal length the narrower the beam will be in the near field ( in front of you ) but the wider the beam will be in the far field.

So a G2 will give you a cool looking thin, intense beam up close, but it spreads out faster over distance, a G3 or 2EG ( 2 element green AR coated ) is a compromise and a G8 with it's longer FL will give you a wider beam up close but a much better looking, tighter beam and smaller spot when pointing far away.

I have used them all and in the end I like the G8 the best for the Sharp 488, however you can build more than one and comparing side by side is by far the best way.

Also the output power is the highest with the G2 and G8 which are both single element wide-band anti-reflective coated, so you can use them for all visible wavelengths.
Thank you again.

As i was talking about not minding loosing some mW i was trying to talk about 3elements lens. Not g3.

My bad. Sorry for that.

So g8 vs 3element beam vise?

I guess i buy both to have reference.

Just wanted you opininons
 
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Joined
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From memory the 3EB was noticeably dimmer and the far field spot was not as tight, so it was immediately rejected by myself for this diode.

The effective FL of a 3EB is somewhere in the 4-5mm range IINM, G8 is 8mm and G2 is 2.39mm, you can also try a 2 element green AR coated which is 4-5mm FL IINM and also the G3 which is 4-5mm FL IINM but it is a single element with wide-band AR coating.

There really is no reason to use the 3EB, 2EG, 3EG, 3ER anymore when the G2, G3 and G8 are all more efficient single elements and are all wide-band AR coated, that said the 3E is inexpensive and not as prone to clipping loses with lower divergence diodes such as single modes, I just liked the look of the beam and far field spot with a G8 the best. however the shorter FL lenses can be nice for up close, but they fall short when you point at distance.
 
Joined
Dec 2, 2008
Messages
345
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28
hello guys,

i am about to order some lenses from techhood on ebay as it is convenient for me, pricewise, location, so on..

just wonder if 3 element lense i provided url for is the real one, or one i should get.

i know which techhoods g8 is real deal, as he has lots of them, but i am unsure which 3element to pick as there are also many..

thank you

https://www.ebay.co.uk/itm/143083965274
 
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Joined
Jul 10, 2015
Messages
10,184
Points
113
Why would you over pay that much ?
These are the same lenses at a much better price.

Also this is a better way to buy the G8 if you are in USA as long as you buy at least 4 or more they are 11.21 each with Free shipping and they ship fast.

I mostly use these G8 lenses today and never the 3E anymore, these's no good reason to use the 3E
 
Joined
Dec 2, 2008
Messages
345
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thank you so much

i saw that seller also, just wasnt sure which one to take.

reason i want 3element is to compare G8 beam to 3e beam, and see which one i like most, as i have never had any of those lenses before.. just some coated lenses from 12years ago era for phr bluray diode project i made back then.

but i guess i will stick to those G8 as you were advocating them to me also earlier in the conversation.
 
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Joined
Dec 2, 2008
Messages
345
Points
28
hello,
one more question about G8 lens beam diameter.

how thick is the beam of G8 lens?

asking because i wonder how wide sould be front cap hole of a laser pen (aperture)
standard is around 5mm i suspect it might not be enough..... ????

thank you
 




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