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Thread: Beam divergence is too low

  1. #1
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    Default Beam divergence is too low

    Hi! I'm building a rgb projector, with 150mw@532nm, 450mw@660nm (maxyz's of course!) and 200mw@473nm.

    Now I have a serious problem: this saturday I will use this laser (even if it's not 100% complete) in a big party, with more than a thousand people... But it's really too powerful! Thanks to the great quality of maxyz's modules and the good green laser, the beam diameter is too low... it melt black plastic from meters of distance! It has burned even the CCD of my kodak camera...

    I have to do something to make the beam more divergent. Any advice about how i can do it? What do you use on your laser to make it safe for the audience?

    I was thinking about a divergent lens, but what focal length it need to have? Probably > 1 meter, otherwise the beam will become too divergent...

  2. #2
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    Well, maybe I'm not understanding it correctly, but when you're doing a beamshow or graphicsshow you'll never have the full power in one beam?

  3. #3
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    But the power is still too high. When it burned the ccd of my camera i was taking pictures of a beamshow...

  4. #4
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    Quote Originally Posted by JeroenVDV View Post
    Well, maybe I'm not understanding it correctly, but when you're doing a beamshow or graphicsshow you'll never have the full power in one beam?
    that is essentially true.
    you can even have all the power in one beam as long as you do not allow the beam to sit still long enough to ignite anything.
    otherwise how would our three watt cubr work for a show?
    then too,there are shows with 40watt yags as well.

    i hate to say this,but it sounds like you don't have much experience with laser shows.

    KEEP THE BEAMS WELL ABOVE THE AUDIENCE!
    even though audience scanning is allowed over there,it is my opinion it should only be done by someone confident and experienced with the practice.
    the last thing you want is to damage anyones sight.
    peace,
    wes
    Last edited by wes; 09-04-2007 at 06:00.

  5. #5
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    Quote Originally Posted by denny View Post
    But the power is still too high. When it burned the ccd of my camera i was taking pictures of a beamshow...
    You probably let one of the beams enter the lens of the camera. Some cameras can take it, but most of them can't. CCD's are quite fragile. I've killed a few pixels in my digital camera with just 200 mw! Just don't let the beam enter the lens and you'll be fine.

    Based on the numbers you provided, you should not have any problems setting things on fire so long as you have the beam moving around. If you keep it in one spot for several seconds, then I can see where you might have problems melting thin plastic.

    Though if you are really having problems with the beam melting/burning things, then you're probably leaking some IR from one of the DPSS lasers. That's something you should check on, because IR is very dangerous to human eyes. (We can't see it, so there's no reflex action to blink or turn away.)

    If the show is just too bright, you can always dial back the power. (The Maxyz modules support analog blanking. You didn't say what your other lasers were, but I'm assuming they're analog as well.) Your software should allow you to set the maximum power to a lower level. (Look for a setting for color or blanking output voltage... Should be a zero to 5 volt range. Set it to 4 volts, or even 3, and see how that looks.)

    Wes' post bears repeating: BE SAFE! Keep the beams out of the audience, and keep them moving. The beams should be at least 3 meters above the highest point in the audience to be safe.

    Adam

  6. #6
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    Quote Originally Posted by wes View Post
    that is essentially true.
    you can even have all the power in one beam as long as you do not allow the beam to sit still long enough to ignite anything.
    otherwise how would our three watt cubr work for a show?
    then too,there are shows with 40watt yags as well.

    i hate to say this,but it sounds like you don't have much experience with laser shows.

    KEEP THE BEAMS WELL ABOVE THE AUDIENCE!
    even though audience scanning is allowed over there,it is my opinion it should only be done by someone confident and experienced with the practice.
    the last thing you want is to damage anyones sight.
    peace,
    wes
    The problem is exactly this. I want to do audience scanning, but safely! And 800 mw in a 3mm wide beam is NOT safe, even if the beam is moving.

  7. #7
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    someone here posted an interesting and important factor to consider when computing formulae for audience scanning.
    namely that eyeglasses greatly increase the effective aperture of the human eye and that you HAVE to assume some of the crowd will be wearing glasses.

    best of luck,
    wes

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    Denny how I wish I had your problem with divergence.! Especially with my 500mw 635nm.

    Anyways Buffo is right. You may be leaking IR somewhere. Your lasers are just not powerful enough to cuz the damage you described.
    I say it's your blue......
    Last edited by Dr Laser; 09-04-2007 at 13:31.

  9. #9
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    Default beam divergence not so high

    get two AR coated 1" diameter 50 mm focal length PCV lenses, and vary their spacing, that will get you close to a 1:1 collimator, you might wish to get a 25mm or 30 mm as well

    shop here

    www.surplusshed.com

    use the lens finder to get what you want.

    1:1 focal length = unity to a little less/grater then unit depending on the
    spacing

    1:1/2 should get you about 2:1 up/downcollimation.

    Steve

  10. #10
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    Hi,

    If your getting into audience scanning can I recommend you read the safety articles at the Pangolin website. WWW.Pangolin.com .. There is a very good paper in there that gives the what's and the why's with a very credible and informed approach. I coudn't see Bill allowing it to be on his website of its wasn't a good paper..


    Cheers

    Ray
    NZ

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