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Thread: Analog RGB projector - color mix ratios?

  1. #1
    Join Date
    Jul 2007
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    Knoxville, TN & Huntsville, AL, USA
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    Default Analog RGB projector - color mix ratios?

    I realize there are a LOT of factors that could affect analog color mixing with DPSS lasers, so I'm just shooting for "ballpark" answers -

    Can anyone recommend the (relative) ratios of laser power to give a good color balance for grahics projectors? (In other words, X amount of red requires Y amount of green and Z amount of blue).

    Thanks!
    RR

    Metrologic HeNe 3.3mw Modulated laser, 2 Radio Shack motors, and a broken mirror.
    1979.
    Sweet.....

  2. #2
    Join Date
    Oct 2006
    Location
    Central Florida
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    7,067

    Lightbulb

    Well, I think you'll want to at least state what red you are going to go with. 670, 650, or 635. There is a big "power" difference between the three. I have a 5:1:2 (r:g:b) set up with 660 for my red and my white is fairly balanced.

    I see you're in TN. I'd say take a ride to SELEM and you can probably see for yourself. I'm sure we'll have a few differently powered set ups.
    Last edited by allthatwhichis; 08-07-2007 at 04:20. Reason: got ratios wrong... DOH!
    Love, peace, and grease,

    allthat... aka: aaron@pangolin

  3. #3
    Join Date
    Apr 2007
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    Toronto Canada
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    Default

    I always use this formula (RGB)
    for 635nm it is 2.1.1 for 650nm 4.1.1 for 671nm 6.1.1
    Same scenario is also for Blue.
    for 473nm (with 635nm red) it is 2.1.1 for
    457nm 2.1.2 for 440nm 2.1.4 for 405nm 2.1.7

    Don't forget about optical loss..give every dichro 5% give galvo 5% and give green 5% because I have to travel a lot

    Something like 500mw@635nm 350mw@532nm and 250mw@473nm would do a nice cool white.

  4. #4
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    Jul 2007
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    Default

    Thanks for the quick replies and great info!

    Unfortunately, I can't make it to SELEM this year - I'm still hanging out in some hotter parts of the world for Uncle Sam for a few more months!

    I'll definitely try for the first available meet after I get home!
    RR

    Metrologic HeNe 3.3mw Modulated laser, 2 Radio Shack motors, and a broken mirror.
    1979.
    Sweet.....

  5. #5
    Join Date
    Jan 2006
    Location
    Charleston, SC
    Posts
    2,147,488,802

    Cool

    If you're looking for info on color balance, start with this thread. It's got links to *lots* of good information.

    The basic rule of thumb is 4.6 red to 2.4 blue to 1 green. Or, to look at it another way, here's a relative power chart from LaserFX.com that shows power levels as a percent of total output to get ideal color balance.

    Either way though the math works out the same. Note that these numbers are based on 647 nm red (Krypton) and 488 nm blue (Argon), using the human eye's sensitivity chart. If you plan to use 660 nm red (or even 635 nm red), then you need to adjust the numbers some. Likewise, 473 nm blue is not as bright as 488 nm blue, so again you'll need to tweak the numbers. (See Sam's laser faq for a table of more wavelengths and their corresponding apparent brightness values for the human eye.)

    Having said all that, color balance isn't really as crucial as you might think. If it looks good, go with it, and don't be afraid to add extra green... It's cheap, and it's great for beamshows. Just be sure it supports analog modulation so you can dial it back when you want perfect color balance.

    Adam

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