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Thread: Earnest Safety Question

  1. #1
    Join Date
    Mar 2011
    Chicago area, IL

    Default Earnest Safety Question

    Hello all,

    This is an earnest question. Something happened last night that quite frankly concerned me to the point that I wonder if perhaps this hobby is best left to the professionals. Safety is #1 and even as a new guy I've respected the lasers and obtained two pair of safety glasses while working on my first RGB projector. Fear is sort of a good thing because it breeds respect but this scared the hell of me...

    I had a static beam shining out of the scanner while it was in home position and was shocked when I noted my black computer chair smoking. This beam was emitted from "only" a '100 mW TEC cooled 532 nm laser' and it even passes through a dicro and still burns a hole through the chair in seconds. Yes - I've been safe so far - the beam was on because I working on setting up the correction amp blanking for the laser.

    WOW. There could be no second chances if that hits your eye; Its one thing to read about it but quite another to see it yourself. I thought that staying in the few 100s of mW power would be relatively safe but now wonder if that is the case....

    Is it possible that the chinese laser emits an incredible amount of IR which could make it more hazardous ? I lack the instruments to measure the power.... It is from o-like.

    The 150mW red 'appears' more safe - meaning it is easier on the eyes to observe a scanned image on the wall than the green laser.

    Now I'm almost afraid of the '1 Watt' 445nm blue that is sitting on the bench .... Been reading that the blue is even more dangerous due to the fact that tissue absorbs that radiation more readily than the reds and greens...

    Maybe I'm just 'shocked' by this observation... Into the projector for almost $ 1K USD so far and now the very thing that has attracted me to pursue building a projector (the beauty of laser light) scares the snot outta me .... Interesting that when I was a teenager I bet I wouldn't even give this a second thought...

    This is serious business!

    Pep talks from the experienced are encouraged! And I might mention thanks to Allthatwhichis for sharing his eye injury with the community. This really makes you think...

    Thanks for reading,
    Stay safe!


  2. #2
    Join Date
    Jul 2006
    Connecticut, USA


    Hi Jason-

    you ask some really good questions.

    1) Yes, *some* Chinese lasers are notorious for emitting more IR (infra red) Laser energy than more "quality" laser manufacturers. and this IR is pure heat. Green Lasers (or DPSS) lasers are the only lasers you need to worry about this with though. As the "pump" diodes usually emit laser energy in the high IR ranges and pretty significant powers. Diode Lasers in the Red wavelength do not emit IR. (They are red as it is).

    The thing with IR, is it is no wheres near as collimated and its coherence lenght is *MUCH* shorter than that of the visible laser beam. The IR "leakage" is just that, leaked IR energy from the pump diode. This will lose energy rather quickly and in rather short distances. Also, yo umention that the beam was shooting through a dichro. If this is the case, than you were seeing the raw power of the beam (NO IR) burning your chair. A dichro will reflect/pass only a given wavelength. And They are designed to block/not relfect the IR wavelengths. Therefore, once your beam passes the dichro or reflects off of the dichro- it is just visible laser energy. Any traces of IR leaked laser energy is gone by now.

    1W of 445 can be VERY nasty! it is MUCH "hotter" than say 1W of 532. It does get down to the wavelength and what is absorbed quicker. 445 is a real nasty wavelength. be careful with it.

    I dont think you need to give the hobby up. Just repsect it. You seem very knowledgeable and safety conscious. Respect its powers and you should be fine. And, like you did here- ASK before you attempt something that may be dangerous.


    ILDA- U.S. Laser Regulatory Committee

    Authorized Dealer for:

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    • X-Laser USA
    • CNI Lasers
    • Cambridge Technology & Eye Magic Professional Scanning Systems

    FDA/CDRH Certified Professional LuminanceRGB Laser Light Show Systems

  3. #3
    Join Date
    Feb 2008
    East Sussex, England


    Don't forget that although its rated at 100mW, it could be significantly different in the real world.
    I had an Aixiz 100mW module from a Chinese projector that I sold to a member on here who measured it between 200 and 300mW.
    Also, your chair is black so this will assist the burning process. If you put a piece of white paper fabric in front of it you won't see the same burning issues.

    I think more people should think about beam termination when testing/setting up lasers. I would like a proper beam dump but I doubt I'd ever use it as it would be a pig to set up each time as I don't use a test bench, it's all in the projector (one of the key things about safety is to also make it convenient enough that you actually use it!)

    I found that the aluminium black foil tape (Blacktak, etc) which I use for beam masking on shows is ideal for temporary work. I simply cover the output aperture and all the beams (bar back reflections of optics) stay within the confines of the projector chassis. That means I can worry less about 'random' things like jumping cats, etc
    Frikkin Lasers

    You are using Bonetti's defense against me, ah?

    I thought it fitting, considering the rocky terrain.

  4. #4
    Join Date
    Oct 2010
    Athens, Greece


    oh i can tell you that the 445 even VERY much out of focus can heat things up quickly.

    but this is no reason to panic. just keep it in mind at all times and exercise caution and above all, common sense. after all, the problem is mainly with static beams and not scanned frames.

    take your time, organise your tests properly and enjoy the outcome
    "its called character briggs..."

  5. #5
    Join Date
    Mar 2011
    Chicago area, IL


    Thanks for the thoughts everyone. I'll take my time and be extra careful ....


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