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Time Tunnel Safety and creation

Permanent Waves

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Is viewing a 'time tunnel' effect reflected off fog safe at 150mW-200mW? I was thinking of a Halloween effect. I see laser light show modules are often in this range and are obviously for long-term viewing. What do I need to know to keep everyone safe? I have viewed many of the threads and videos on youtube but I still don't have a very good idea how this effect is created, the principles behind it , or how to best create it. Any advice?
 

Meatball

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First of all, 200mw would be a very bright and solid time tunnel. However, 50mw wouldn't disappoint either... especially with fog. There is a very simple way to make this effect, try taking a look at FML's tutorial. It should give you a few good ideas.

http://laserpointerforums.com/f51/tunnel-gun-tutorial-36955.html

Keep the dot out of anyone's eye, and it can be used safely. If you're doing this effect at night with fog, a much safer 5mw greenie will do the trick nicely for you!

The further away the tunnel source is, away from the viewer, the less the time the dot spends in one place. If you view the tunnel from a good 15 feet away, and the dot accidentally crosses your eye ONCE, then you are better off than it would have been if you had this happen at 10, or 5 feet.

The only other principles behind this, other than the spinning mirrors, are that it needs to be stationary. Controlling exactly where the dot is at all times is a must. I don't know what your setup is, so I can't give you great advice on it. If you use your head, and think about it before doing it, you should be fine.
 

Cyparagon

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The average power at a point is inversely proportional to the diameter of the circle. You could make a formula, or you could just take measurements with a power meter. MPE is around 10mW/cm² If I remember correctly.
 

Permanent Waves

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I really appreciate the replies but I'm afraid to an "average Joe" like me it's not clear if a 200mW "time tunnel" is a potential hazard or not... would it be a sure thing if I used under 50mW or under 5mW for example?
 

qumefox

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In the revised system, the MPE changes depending on the wavelength of the light so it's really hard to find fixed numbers anymore.

Laser safety - Wikipedia, the free encyclopedia

for the time tunnel.. just wear goggles if you think there's a chance you'll catch a beam in the face. If your standing in the middle facing away from the laser, for example, then there is little chance of that happening unless the room is full of shiny objects or something. It boils down to.. just use your head. Keep the goggles on unless your positive it's safe to take them off.. and if you start moving around again.. put them back on.
 

Meatball

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Since this is for (I'm assuming) a public display for halloween, I would definitely suggest you stick with a 5mw at night with some fog. You want a ghostly effect, not a "Plasma tornado of DOOM" effect. So a 5mw will be fine for public use at night with fog, plus the chances for any collateral damage will be minimal, but NOT non- existent.

In all honesty, and in my own opinion, you could jump up to the 50mw module and you ought to be fine. But again, it still does depend on your setup. Don't use the 50mw module if anyone could come within 15 feet of the spinning mirror though..

( Meatball is not a professional. Meatball's opinion was not made based on scientific findings based upon all the possible theoretical outcomes that are dependent upon the display's setup. Meatball is not responsible for any damage done to anyone's peepers. Use Meatball's advice at your own risk.)
 

qumefox

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Oh. Didn't realize it was for public demonstration. Yeah. For this as long as you kept a reasonably fast mirror speed, up to 25mw would work. I wouldn't exceed that though. And with smoke, you'll probably be surprised at the brightness of that in the dark. Another trick would be to defocus the laser a tiny bit. More divergence means the beam is 'safe' at a closer distance.
 

Permanent Waves

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Any suggestions as far as a focusable (or nonfocusable) 50mW or less continuous use module (as in one that could be left on for hours)? Green would probably look the coolest at the best price but I'd be open to suggestions for any module that would work.
 

hakzaw1

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FIRST......................

Its not TIME tunnel-- just tunnel EFX--time tunnel is SCI-FI

here is what I do- my viewers are wearing safety goggles and once they are inside the tunnel they can look over(or under ) them and put them back on to leave the tunnel. that is the safe way IMO

another tip---- turn OFF all things that make the air move-- ACs- fans-etc

dissapaited fog is boring compared to fresh whispy fog.
try it you will clearly see what I mean.

and if your mirror is mounted on a PC fan cut the blades off. The more 'whispy' and thick your fog the better EFX-same deal for Liquid sky EFX----for beam shots is matters less.

I put plastic baggies over my smoke alarms--easier than removing the batts-- and if you fog like I do they WILL go off.( a real buzzkiller btw)

hak--home laser showman
 

Permanent Waves

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Thanks for the links; great tip on the smoke alarms and air moving- I was planning on putting this outside so might have to rethink it now...
 

hakzaw1

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If there was no wind that would be cool, but using my fogger outside is usually a waste. Maybe on a carport or porch. Foggy nights are mostly windless ones tho--- so nice combo--natural fog and a machine.
 




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