Results 1 to 4 of 4

Thread: Laser Safety for interactive laser display

  1. #1
    Join Date
    Aug 2007
    Location
    Indianapolis, IN
    Posts
    196

    Default Laser Safety for interactive laser display

    OK....

    I've been approached by the Maker Faire to demo my laser harp in May. I've just been having a conversation with the safety officer about the potential safety plan.

    Quick recap:

    http://www.youtube.com/watch?v=sLVXmsbVwUs

    Class 3b laser.

    What would be the recommendations of the group to make this ILDA/OSHA compliant?

  2. #2
    Join Date
    Apr 2006
    Location
    Orlando, FL - USA
    Posts
    1,719

    Default

    I would think you would have to put a kind of "guard" on the bottom of the mirrors (somewhat away from the mirrors and toward the audience) such that, if any of the mirrors came loose, the beam would be terminated on the metal guard and not the audience. Again we would have to ask -- what if something goes wrong (in this case, with the screw holding the position of the mirror).

    There may be other factors such that, how to protect the "performer" from looking downward, and into the beams. If CDRH really took a close look at this, they might not get a "warm and fuzzy" unless you had some kind of, lets say LED-based detection scheme such that, if you put something wider than a hand into the up-coming beams, it would disable the system.

    Bill

  3. #3
    Join Date
    Aug 2007
    Location
    Indianapolis, IN
    Posts
    196

    Default

    Thanks,

    One other thing they've asked me for are safety goggles for participants. I do have the correct goggles, but the only problem is that they eliminate the beam, so are kind of self defeating.

    People will put them on, but then won't be able to see anything...

    Are there goggles that reduce the laser emission, but do not eliminate it?

  4. #4
    Join Date
    Jan 2007
    Location
    Yorkshire, UK
    Posts
    4,564

    Default

    Quote Originally Posted by shobley View Post
    Are there goggles that reduce the laser emission, but do not eliminate it?
    Short answer... Yes

    You need to look at the Optical Density (OD) of the goggles. The higher the OD the more light is blocked. It can be quite a challenge deciding which OD is correct for each particular application. Too high an OD is just as bad as too little, if the OD is too high and you cannot see any of the emission there's always a temptation to lift the goggles just to have a quick peek to see if it really is working

    Likewise if the OD is not high enough you run the risk of getting eye damage from a stray 'flash'.

    Basically, it's your call

    Laser safety eyewear is usually labeled with both the optical density and the wavelength coverage range.

    The formula for optical density is ...

    Optical Density = -1 (Light Transmission)

    Tl = 10 -OD

    Using the formula above you can see that there is a 10x increase in protection (10x decreases in laser transmission) for each increase in OD.

    Jem


    P.S. Just found this slightly better explanation on Wikipedia...

    In optics, density is a unitless measure of the transmittance of an optical element for a given length and wavelength λ:[1]


    O = the per-unit opacity
    T = the per-unit transmittance
    I0 = the intensity of the incident light beam
    I = the intensity of the transmitted light beam

    The higher the optical density, the lower the transmittance.

    Defined in terms of unit length, and expressed in decibels, the density is termed the transmission loss rate For example, an optical density of 0.3 corresponds to a transmission loss of 3 dB per cm. Defined without regard to the length of the sample, the density is a synonym for absorbance. Neutral density filters are typically quantified this way. Some filters, notably welding glass, are rated by shade number, which is 7/3 times the optical density. A shade number of 14 is regarded as safe for direct observation of the sun.
    Last edited by Jem; 04-24-2008 at 06:47. Reason: Wikipedia information
    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

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •