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Thread: Mixing red wavelengths

  1. #1
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    Default Mixing red wavelengths

    We know that when mixing red with green that the sum of the power appears less than the individual powers of the lasers, but what happens when we mix two wavelengths of red?

    In other words; I am building a multi red combiner, initially with 800mW of 637 and until funds allow, I was going to fill the remaining slots with 2W of 660; will the darker 660 drag down the 'apparent' brightness of the beam?
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  2. #2
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    Sounds like an interesting project, how will you combine the 660s, 2x6 knifeedged combined with cube and telescope?
    Last edited by DjMagnus; 02-04-2011 at 02:47. Reason: dont listen to my nonsense =)

  3. #3
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    It will not drag down the brightness, just shift the color a little, but will be brighter still.

  4. #4
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    I have 400mW of 660nm combined with 350mW of 642. It makes a lovely rich red and although the difference is subtle I can really notice if the 660nm isn't in the mix.

    Cheers

    Jem
    Quote: "There is a theory which states that if ever, for any reason, anyone discovers what exactly the Universe is for and why it is here it will instantly disappear and be replaced by something even more bizarre and inexplicable. There is another that states that this has already happened.... Douglas Adams 1952 - 2001

  5. #5
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    660nm expands the possible colour palette so should add something to your projector and Jem's feedback suggests it works. I still remember Jem's projector at the LEM I attended and thought how nice the pallette was with 660nm red compared to some of the others with 650nm. However, the penalty for 660 alone is of course brightness.

    As for brightness, it depends how you define drag down. What you're going to end up with is a red with an effective wavelength somewhere between 637 and 660nm. Obviously 2 watts of 660 + .8W 637 should be brighter than 637 alone. However, I would expect it will be dimmer than the equivolent perceived wavelength at 2.8 watts.

    I'm not sure of the accuracy of this because whereas I normally have confidence in Chroma I'm less sure about it for mixed single colour predictions. It predicts a visible wavelength equivolent of 640nm (found by working back from the co-ordinates). The big difference is compared to 2.8w of actual 640 the brightness of the mix is 192 vs 334 lumens or nearly half.

    However, .8w 637 nm is 109 lumens on its own so adding the 2 watts of 660 should give a brightness boost of 83 lumens (192 total).

    Ultimately the only thing to do is try it, but you should see an expanded colour pallette plus some additonal brightness.

  6. #6
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    in my last projector i had 350mw of 635nm mixed with 500mw of 660nm.

    worked very well
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  7. #7
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    Thanks for the input gents, I just don't want to spend a lifetime aligning and fannying if I'm pissing into the wind. This thing is to replace 1.8W of 650 and I know the beam will be tighter yadda yadda, but for beams I don't buy into the tighter beam/higher power density = more apparent brightness rule; for graphics yes, for beams no.

    Halve the energy density double the unit area of illuminated fog. This is based on actual first hand experience with beam expanders/diverging lenses for audience scanning.

    Wavelength is the largest exponent in the apparent brightness equation and though a wide gamut is great for somebody into lasers it dosen't mean sh*t to the crowd in a brightly lit club.
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    Doc's website

    The Health and Safety Act 1971

    Recklessly interfering with Darwins natural selection process, thereby extending the life cycle of dim-witted ignorami; thus perpetuating and magnifying the danger to us all, by enabling them to breed and walk amongst us, our children and loved ones.





  8. #8
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    Quote Originally Posted by andy_con View Post
    in my last projector i had 350mw of 635nm mixed with 500mw of 660nm.

    worked very well
    Hey, how have you combined the two red lasers? With a mirror?
    I also plan to use such a mixed red in my new projector.

  9. #9
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    Quote Originally Posted by matratzki View Post
    Hey, how have you combined the two red lasers? With a mirror?
    I also plan to use such a mixed red in my new projector.
    http://www.laser-man.co.uk/2006/content/view/102/6/
    Eat Sleep Lase Repeat

  10. #10
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    Sorry to reopen this thread. In all the situations above, the more powerful wavelength (mW) was the 660. What would be the result of mixing 300mW 660 with 350mW 640?

    Thanks

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