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Thread: Lasers for stage use

  1. #1
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    Default Lasers for stage use

    Hi all,

    need some advice off you clever guys and gals on here! I'm a magician, and I'm currently working on a new stage act involving lasers, where I (without going into too much detail ) do all sorts of things, like 'catching' the laser in my hands, making glowing 'bits' of it fly around me, and then finally actually taking the beam and holding it in my hands... Now I don't expect anyone to help me with all that, that's my problem(!), but I do ideally need a thick laser beam. I've got a 50nm green handheld pointer, which is ok, but maybe not a wide enough beam - do I have to get a higher power laser to produce a wider beam, or indeed, am I living in Star Wars/fantasy land?!? lol

    Take a look at this clip off Youtube, it'll give you an idea of where I'm going with it - incidentally, what power laser do you think this guy used to produce the line across the stage? It looks a stronger beam than mine, or is it just good use of a smoke machine to make it more visible? Prepare to be amazed if you haven't seen this before...

    http://www.youtube.com/watch?v=T-XoN1Ts6Wg

    And before anyone asks, I can't tell you how it's all done, sorry!

    Hopefully someone can help, all advice much appreciated!!!!

    Best Regards

    Rich

  2. #2
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    Central Florida
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    Lightbulb

    I don't have time at the moment to watch the video, but for a quick, low tech answer, you can use a optic or two with any laser to make the beam bigger.

    Lense2-----> |
    Lense1--->|/ |-------------
    -----| |
    Beam IN | | Beam OUT
    -----| |
    |\ |-------------
    |

    Not to scale...
    Love, peace, and grease,

    allthat... aka: aaron@pangolin

  3. #3
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    Default

    some green lasers actually have a flat tip screw on the front of the lesnse and you can pretty much out it out of focus some to make a little bigger beam.

    may i ask what kind of laser you have?

    if it was bought off ebay it may not truly be a 50mw laser. and more like a 5mw.

    a beam from a 50mw should be very good especially with little smoke
    -Josh

  4. #4
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    Smile

    Hi Rich! Welcome to PhotonLexicon. Please full out your profile so we know where you're located.

    I've seen that youtube clip before, and yes - it's quite impressive. Hard to tell what power he's using though. There are a number of variables that could make the laser appear brighter or dimmer.

    You are wise to use a larger beam diameter. This will reduce the power per unit area, which will help make it safer for your audience. However, there are specific limits for eye exposure that you need to follow if you want to be safe, both for you and your audience. And meeting this limit will require more than simply buying a lens and attaching it to your laser. You'll need to accurately measure the power after the lens and perform some calculations before you can be sure.

    Unfortunately, if you want to perform your show here in the US, I'm pretty sure you're also going to need a variance from the CDRH before you can perform such a show legally. While a magic act is not a laser show in the classical sense, I believe a magic act that uses lasers will meet the definition of a laser show. (I don't know if the guy in the Youtube video has a variance or not. My guess is, not.)

    Furthermore, unless you can ensure that the beams can never reach the audience, you're going to have to apply for an audience-scanning variance, and that will require even more work on your part. EDIT: (Admittedly, I'm assuming that you are in the US here, in part because the guy in the Youtube video is from LA... However, even if you're in the UK, there are standards in place for Laser eye exposure there as well. They just aren't enforced nearly as vigorously!)

    Without revealing either the substance of your act or the stagecraft behind it, can you describe what you'll be doing with the laser? If you want to "capture" the beam in your hand and re-direct it so it moves around the room (like you see in the Youtube video), that pretty much meets the definition of a laser display device, even if you keep the beam well above the heads of the audience.

    On the other hand, if you plan to keep the laser more-or-less fixed in position (like a stage prop) and merely wish to interact with it on-stage (with *no* chance of the beam leaving the stage), then there may be an exemption for such a prop. Hopefully some of our more experience members can weigh in on this issue.

    And at the very least, you're going to want to contact the CDRH yourself and ask some questions.

    Adam
    Last edited by buffo; 09-26-2008 at 06:50.

  5. #5
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    Default

    Hi guys,

    thanks for your quick replies - allthatwhichis, I'm afraid I'm a toal newbie to all this, not techie at all!! Is there a product that I can buy (lens/optic thing) that would go on the end of my laser and widen the beam?!! Sorry for appearing dim...

    thesk, it's a silver pen pointer, I picked it up from laserpointers.co.uk - although I can't guarantee it really is 50nm, although it does say it on the sticker! lol No screw that I can see on the front though...

    Adam, thanks so much for all that info - my, what a helpful forum! I'm in the UK, so I'll have to check on the laws regarding laser stage use over here - the laser would essentially, and for the most part, be in a fixed position pointing across the stage, where it could be re-directed via mirrors to ensure nothing reaches the audience, but ideally at the end of the act I would like to 'grasp' the beam and 'wield' it (for want of a better word), so I'm guessing this falls into the 'laser display device' category. hmmmm, some more deliberation required I think....

    Rich
    Last edited by richcraft; 09-26-2008 at 06:55.

  6. #6
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    What you're looking for is called a beam expander. It's just two lenses that make the beam wider while decreasing its divergence (you can use it the other way around too).

    Here is a nice tool to help you with it:
    http://www.newport.com/OpticalAssist...mExpander.aspx

  7. #7
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    Default

    Thought that was his vid

  8. #8
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    Default

    thanks very much tocket, that looks like exactly what I'm looking for - frightening prices mind, but nothing good comes cheap these days!!

    It's not my vid on youtube, that was just an example of the kind of thing I'll be doing - obviously not the same as my act though, just using similar principles...

  9. #9
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    the youtube act uses more than 1 laser.. the first main laser head is a standard lab style 532 at a low (prolly <50)mW power. he is using a mister as well as smoke.

    that laser is used in conjunction with some mirrors and hanging wires to create the effects you see.

    the other lasers are tiny specialy made laser pointers that are palm size. they would require special drivers. the drivers would use a stored charge (like in a copacitor) aling with small watch batteries, and would only lase for a short time before going dead.

    im sure you can figure out all the mirror tricks yourself.. but the electronics in place here are custom made (for the hand lasers)


    with the right amount of fog, you could get away with very low power lasers. green lasers are very visable to the human eye even at low power..


    hope that helps..

  10. #10
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    Hi Keeper, thanks for that - I've worked out how to do the small 'handheld' lasers, I'll be using the 'innards' from 2 laser pointers, linked up to a switch and power pack in my pocket, should be easy enough to put together. Ideally though that beam needs to be as thick as the one coming from the main 'stage' laser, which is proving a little tricky, but I guess if I use a mister, I maybe won't have to make my stage laser any brighter/wider, thus reducing the issue about different sized beams.......

    As I say, I won't be doing the same things as Jason Latimer, I've got my own act/style I'll be using, but I will need to employ some of the same principles i.e. making the beam more visible. So you think a mister would make this a lot easier Keeper?

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