stevel@haddock.UUCP (04/03/84)
#R:sbcs:-60900:haddock:9500010:000:735
haddock!stevel Apr 2 14:28:00 1984
It would be MUCH MUCH SAFER to use a decent spotlight than a
laser. You can get the same effect, i.e. a bright narrow beam
thrown about 200 to 300 feet, without endangering people eyes.
This includes law suits to you over damages to peoples eyes. If
just one instrument falls it could be complete loss of sight to
someones eye.
Look into 2" spot light made by people like Klegel, Centry, Altmans.
These are much more versital and less expensive. You can gell them
different colors, put color wheels on them, use a gabezo to
throw a pattern on the wall, and controll them with normal
switches and dimmers. AND THEY ARE SAFER.
MUCH MUCH SAFER.!!!!!!!!!!!!
Steve Ludlum, decvax!yale-co!ima!stevel, {ucbvax|ihnp4}!cbosgd!ima!stevelrpw3@fortune.UUCP (04/05/84)
#R:infopro:-5000:fortune:16500007:000:1435
fortune!rpw3 Apr 5 00:30:00 1984
Yes, be VERY careful with lasers. There are a lot of "gotcha's" that aren't
obvious:
1. The recommended maximum direct viewing power (looking down the beam)
is well under ONE MILLIWATT! (Ref. some Gov't Std. or other)
2. One milliwatt is not very much when scattered around the room by
a set of music-driven mirrors, so people get tempted to use higher-power
rigs so folks can "see it in the smoke". (Isn't there ALWAYS "smoke"
at a concert? ;-} )
3. Should the music stop for JUST AN INSTANT while someone is looking the
wrong way, bye bye eyes.
4. The "wrong way" is not only facing the laser platform, but could be
anywhere in the room that has what is called a "specular reflector"
(translation: mirror, bright metal, or ANYTHING that reflects the light
coherently, such as tinsel on a Christmas tree or jewelry or even clear
glass, at a shallow angle).
Moral: make sure your equipment is rated for it's intended use, and has
been certified safe for that use. (Some systems detect lack of music drive
and switch to a diffuse scan pattern when than happens.)
Homebrew jury-rigs made out of laboratory lasers bought from equipment
supply houses (and speakers with mirrors on them and guitar amps) might
not be exactly safe.
Rob Warnock
UUCP: {ihnp4,ucbvax!amd70,hpda,harpo,sri-unix,allegra}!fortune!rpw3
DDD: (415)595-8444
USPS: Fortune Systems Corp, 101 Twin Dolphin Drive, Redwood City, CA 94065ron@brl-vgr.ARPA (Ron Natalie <ron>) (04/05/84)
Actually the neatest effect is to get a large (12"-15") speaker. Strech a piece of rubber accross the front of it and glue little mirror tiles to it. Point a 6 or 8" ellipsoidal (LEKO TM) spotlight at it. The effect is rather neat. What is net.arch for? I thought it was for computer architectures. If so, why are we discussing DISCO lights? -Ron
dmmartindale@watcgl.UUCP (Dave Martindale) (04/05/84)
From talking to a few people who put on commercial laser shows, it seems that they tend to use krypton lasers with powers ranging from one to several WATTS of beam power. They are VERY careful that the box containing all of the optics is closed whenever the beam is on, and that the apertures through which the beam projects are properly masked so that the beam cannot hit anything except the screen at which it is aimed, which is a diffuse reflector. And these lasers are expensive, apparently somewhat finicky, and require water cooling. There are small lasers available with beam powers under a milliwatt for moderate prices, which would be much safer to play with. But they aren't going to be as bright as you'd like. And you still want to avoid any chance of looking directly at the beam if you can help it.
koksvik@kvvax4.UUCP (Rolf M. Koksvik) (04/10/84)
<> >The recommended maximum direct viewing power (looking >down the beam) is well under ONE MILLIWATT! (Ref. some >Gov't Std. or other) The standard for maximum dose to the eye is 0,2 microjoules/sq.cm in this country. That is the same as 0,2 microwatt-seconds/sq.cm. Note that time is involved. The longer you are exposed, the greater the damage. Lasers are not toys. Rolf M. Koksvik ({decvax,philabs}!mcvax!kvport!kvvax4!koksvik) A/S Kongsberg Vaapenfabrikk, P.O.Box 25, N-3601 Kongsberg
rpw3@fortune.UUCP (04/14/84)
#R:infopro:-5000:fortune:16500009:000:1571 fortune!rpw3 Apr 14 02:53:00 1984 >>The recommended maximum direct viewing power (looking >>down the beam) is well under ONE MILLIWATT! (Ref. some >>Gov't Std. or other) [ Me. ] >The standard for maximum dose to the eye is 0,2 microjoules/sq.cm >in this country. That is the same as 0,2 microwatt-seconds/sq.cm. From playing with very low-power helium/neon lasers in physics lab (these were rated SAFE at about 0.1 milliwatt), I know (the hard way) that those things appear **BRIGHT** and cause quite a blink/flinch reaction. Assuming a slow 150ms. for that blink (eyes are faster than hands), we're talking about a dose of 0.1*0.15 = .015 milliwatt-second = 15 microwatt-second. Assuming the beam is well collimated enough to entirely enter the pupil (diameter about 2 millimeters -- I just measured mine), you could easily get a focussed spot of 1 millimeter or less (though focussing at true infinity is not a normal thing). So the dose could easily be as high as 15 uW-sec/(.1)^2 sq.cm. (forgetting pi aren't square) ~= 1500 uW/cm^2 !!! That's 7500 times the dose you mention. Yet those lab demo lasers were supposedly "safe". Hmmm... I knew some U.S. standards on radiation dosage were looser than other countries, but... (Well, my retinas get looked at once a year whether they need it or not, and that was 20 years ago and Doc hasn't complained...) But that's nit-picking. You're right. Lasers AREN'T toys! Rob Warnock UUCP: {ihnp4,ucbvax!amd70,hpda,harpo,sri-unix,allegra}!fortune!rpw3 DDD: (415)595-8444 USPS: Fortune Systems Corp, 101 Twin Dolphin Drive, Redwood City, CA 94065