wow! definitely NOT IIIa
IIRC the measuring distance for power/classification from the CDRH is 20cm! or ~7.8"
/edit: here found this on SAM's
Question: If a laser puts out more than 5 mw, but through the use of a beamsplitter, diffraction grating, filter, or other device the resulting beams that exit the projector are EACH less than 5 mw, is the show still considered "under 5 mw" and thus exempt from a variance?
Answer: Yes. As long as the beams that exit the device (projector, housing, etc) are each less than 5 mw, and the beams are separated far enough apart such that it is not possible for multiple beams to enter the same pupil, then the entire device is exempt. Thus, you can have a 20 mw laser putting out, say, 8 beams from a diffraction grating, and as long as none of the beams are over 5 mw the entire setup is exempt.
As an aside, he went into considerable detail as to how these beams would be measured for intensity. The basic standard is to use the standardized pupil diameter (listed in the CDRH main document - I forgot to write it down) and measure the power at a minimum distance of 20 centimeters (!) from the apparent source of the laser light. (i.e., the window on the projector housing, the aperture of the scan head, or the output coupler of the laser if the other two do not apply.) The pupil size used for the calculation changes if the environment is such that it would be likely that audience members would be using binoculars. Binoculars?!? I asked?: "Yeah, like in a large arena - folks typically bring a set to make it easier to see the stage." He floored me with that one, but it makes sense if you think about it.
Our history with Lumia effects and pass through "filter" lens, allows us to do what we term as "Audience Exposure", and with proven metered readings of less than 4.95mW per mm2, we have never been turned down for a show notification. As most of you know, the way that the Lumia works, is that it changes the focus of the laser and essentialy becomes a really Fat Beam (such as a 20mRad) but always out of shape, so that there is never a truely Coherent beam, it is always going through a shape changing lens.
As long as the lumia wheel is set so it can not fall out of place, it should be legal for use in public, but I still would suggest to anyone, that they not be aimed at the crowd, not only for safety, but the effect would best be used on a wall, scrim or ceiling to be looked at instead of shot with.
Class I is correct. I have never heard it expressed as mm2 either... Where does that come from Slick?
That's because power density is the defining factor for eye safety.
The reason that usually only power, not density, is mentioned, is because the measuring protocol defines a fixed aperture size for metering (IIRC the size of a dark adapted pupil). Usually this will capture the entire beam and therefore the full beam power is exposed to the retina.
With a high divergence source like a lumia or LED, power density becomes important since it defines the exposure on the retina, because the light entering the eye is not collimated (and will not focus into a single spot on the retina), but will image as a larger spot on the retina surface when viewed directly.
Nonetheless, lumia and LED can eventually reach dangerous power levels, but it takes quite a bit of effort to get there. Moving head fixtures with 20-100W LED are reaching the danger zone.
I think he probably meant cm^2
Frikkin Lasers
http://www.frikkinlasers.co.uk
You are using Bonetti's defense against me, ah?
I thought it fitting, considering the rocky terrain.