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Thread: Is G2 lens good for all visible wavelengths?

  1. #1
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    Default Is G2 lens good for all visible wavelengths?

    I notice people use G2 lens for their reds and greens too, not only blue. But I thought G2 was coated for the blue wavelengths? Am I wrong? Is there some data loss test of the G2 lens with 638nm and 520/532nm?
    If I'm right, what collimating lens *should* I get for 520 and 638nm?

  2. #2
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    http://www.photonlexicon.com/forums/...ght=lens+types

    Here is a good experiment Dkumpula did with some different lenses. I personally prefer the 3 element glass lenses/acrylic for most scenarios. I like seeing the tighter beams. ;D

  3. #3
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    Quote Originally Posted by neskusen View Post
    I notice people use G2 lens for their reds and greens too, not only blue. But I thought G2 was coated for the blue wavelengths? Am I wrong? Is there some data loss test of the G2 lens with 638nm and 520/532nm?
    If I'm right, what collimating lens *should* I get for 520 and 638nm?
    1st, you should consider: what beam specs do I need or want to achieve? beam waist, mrad etc

    "G2" is usually FL 4,02mm, and you are right, AR coated 445-520. However it works pretty well also on reds. Expect +15% or more power increase over 3-elements lens (FL 8mm approx.) due no beam cliping and less losses (just one aspheric lens).

    However, optics laws, you get double divergence then going with 3-elemnts, so needs more expansion, maybe filtering as well...but as I said, depends on..what beam specs you are looking for ?
    Jordi Luque


    AtenLaser.com
    Barcelona

    "Let there be light"

  4. #4
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    I thank both of you for sharing the informative links and knowledge, I learned a lot.
    There are few things which aren't clear yet and it's my fault because I only now realize I should have been more specific.

    I should have mentioned I'm interested in >500mW multimode diodes.

    The tests by Dkumpula are interesting, but I don't know how similar the beam comparisons would be with multimode diodes.
    Looks like G2 is a clear winner when it comes to power, but gives maybe worse beams without beam correction optics (with prisms or cylindrical lenses). But I'll probably need correction optics for multimode diodes with any collimator lens correct? At least that's the impression I've got by watching TechIngredients (planters) on youtube.

    Another interesting and probably important thing was that in Dkumpula's tests G2 was the only collimator lens made from AR coated single-element aspheric glass. Acrylic is a different material and the 3-element glass lens has more losses from more surfaces the beam has to pass through.
    But aren't there other single element glass lenses like the G2, coated for the red spectrum?
    Maybe it wasn't included in the single mode diodes tests because it wouldn't be practical to use expensive glass lenses for cheap diodes, but do we have an alternative to G2 for reds with better power transmission? What is the reflectance of G2 for 638nm? Has anyone tested that?

    I also did not know G2 was also coated for green. Thank you very much for letting me know, I thought it was only coated for the blue and maybe UV spectrum.

    Quote Originally Posted by jors View Post
    1st, you should consider: what beam specs do I need or want to achieve? beam waist, mrad etc
    I don't know, I hope you'll help me understand what I want by learning what options we have.

    I want to build my dream projector. A big case which I can upgrade as much as I'll wish. I'm getting a bit tired of my 1-2 Watt projectors and want to hit the 10W limit one day and enjoy those brighter beams and larger graphics. I'm not a perfectionist like some and don't expect perfectly circular or marching beam profiles, but I wouldn't also want a projector that is unusable for graphics, with thin horizontal lines instead of more symmetrical profile.
    I don't know what else I should mention, please let me know if there's anything else I can specify to help better determine what I need and should use.

  5. #5
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    we used to love the optima 4mm fl lenses for red wavelengths ( http://www.optima-optics.com/molded.htm ) but this was before the 500mw mitsu appeared

    with multimode diodes you will need correction optics.

    10watts with say, 2watts green (2x520nm diodes) 2watts red (a quad mitsu setup) and 6watts blue??
    getting more than 2watts of red is not so easy without complex setups

    for red, there is always dave's trusted solution with the tiny 2mm lens http://lasershowparts.com/store/inde...ewCat&catId=39
    "its called character briggs..."

  6. #6
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    Quote Originally Posted by LaNeK779 View Post
    we used to love the optima 4mm fl lenses for red wavelengths but this was before the 500mw mitsu appeared
    What does that mean? That you haven't tested it with the newer diodes yet? Or that it isn't as good with those?
    The transmission of 96-98% is for 780 nm, do we have any comparative data of transmission for 638nm between this and G2?

    10watts with say, 2watts green (2x520nm diodes) 2watts red (a quad mitsu setup) and 6watts blue??
    Yeah, not the best ratio but looks decent to me with my 200mW red 200mW green 800mW blue projector. Actually I might go crazy and combine as many 6 Watts blues I can, just for fun. I know it will destroy the color balance, will have the extra blues turned off when using all the colors.

    getting more than 2watts of red is not so easy without complex setups
    I've seen some setup pics and it's just very large knife edges. Probably took forever to calibrate but the method seems the same. Is there more to it?

  7. #7
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    Quote Originally Posted by neskusen View Post
    Another interesting and probably important thing was that in Dkumpula's tests G2 was the only collimator lens made from AR coated single-element aspheric glass. Acrylic is a different material and the 3-element glass lens has more losses from more surfaces the beam has to pass through.
    But aren't there other single element glass lenses like the G2, coated for the red spectrum?
    The last lens included in my tests was the 400-700nm Single Element G2 lens sold by Aixiz. This lens performs nearly as well (and sometimes better) than DTR's G2 lens but is 1/3 the price. One downside is that this other G2 lens has slightly larger threads making it too tight to fit into the diode holders that Dave at Lasershowparts sells. It fits fine into DTR's diode holders though. I tend to use acrylic for lower power reds primarily because I can spare the loss with single mode builds (the reds are the brightest among current single mode red/blue/greens) and get a better otherwise uncorrected beam. I use G2s (DTRs or Aixiz depending on which diode holder I am using for that build) with the greens and blues.

    With multimodes the considerations are slightly more complicated, but I think most people here would start with a DTR G2 lens.

    Have fun with your build!

    -David
    "Help, help, I'm being repressed!"

  8. #8
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    Quote Originally Posted by dkumpula View Post
    this other G2 lens has slightly larger threads making it too tight to fit into the diode holders that Dave at Lasershowparts sells
    Could it be metric vs inch-based threads?

    I see. For the convenience of buying all parts from one place I've been thinking of buying from Techood.
    His housings seem similar http://www.ebay.com/itm/Brass-Laser-...item3ce85f1698

  9. #9
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    Is there a way to tell the difference between different types of lens called "G2"? techood says he has G2 lens but I don't know if its the one I need.

  10. #10
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    It is the lens mounts that have slightly different threads (not the lenses that are different).

    Standard size are metric 9mm 0.5mm pitch, but there are many different mounts on the market.

    With multimode mitsu diodes you probably want shortest possible focal length to limit near field beam size.

    Try Dave's 2mm (ready mounted) lenses for smallest near field multimode mitsu beam size.

    He had a GB (group buy) a few weeks ago and might still have some left over.

    Cheers

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