Laser Curtain

[kamakajee]

Hi All,
How safe is it to use laser curtains like the one below, either horizontal or vertical & what should I consider before using it for an event.
Any suggestion will be well appreciated.

Thanks
kama

[norty303]

It has the same level of safety as any other laser display product.
The skill of the operator in assessing how it should be/could be used safely.
If you don't possess the skill and equipment to evaluate that product effectively befor shining it on people, don't shine it on people.

It does look like the perfect product for people putting on a productiopn of Queen's We Will Rock You musical however, which seems to come up weekly as a question on Blueroom forum ("How do I do the laser cage cheaply?")

[kamakajee]

Thanks Norty33, I do comprehend audience safety is paramount & it is challenging & crucial is our field all the more, as we want the audience to experience something different & spectacular all the time & 'No Audience No Laser show!' but with this product, if put at the entrance of a club or an event, where you have people of different height & size passing by every second how do you mange to control the laser. Or else just don't use it at entrance ?
Or is there any other way.. sorry if I sound too novice!
regards,
Kama

[norty303]

How do you want to use it? Shining down on people as in the pictures?
If so, can you guarantee people won't look up into it?
IF they do, do you know the irradiance they will be exposed to and is it within MPE levels?

If the answer to those questions is no, you should not be pointing the laser at people.

[kamakajee]

Thanks Norty 303

[absolom7691]

Looking at the specs on it, there are 16x 50mW lasers in the unit. Given that they are chinese built lasers, I wonder how accurate that is, +/-. 50mW isn't all that dangerous but given the proximity of the "audience" to the lasers and the fact that they are static, unmodulated beams, I certainly wouldn't risk it.

[dsli_jon]

Mr Kama -

... if put at the entrance of a club or an event, where you have people of different height & size passing by every second how do you mange to control the laser. Or else just don't use it at entrance ?

I think you've answered your own question. For example, if you restricted use to performers ('cage-dancers', whatever, etc..) then you could, at least, adjust the 'distance' to-performer, train them of the dangers of working under those power levels of beams / how to pass-thru safely (divert direct-gaze / move quickly, etc, etc..), whereas, what chance do you have of 'educating' the (likely, drunk / stoned..) public?? Not much, I'd say.. So, I think your final-assessment, 'just don't use it at entrance', is likely the best-answer, imho..

...50mW isn't all that dangerous...

Page 6 respectfully-disagrees with you.

...As you say 'given the proximity' (ie: let's get 'real', here - mostly drunk-people looking straight-up into the beams, as they pass-under it.. ya?) probably-best for Mr Kama to pass.. If this were a 'scanned-effect' (ie: cone / 'sheet', etc, with fog-marbling thru it..) that would at-least be 'less-horrible', since you've the factor of scan-speed (albeit, those *are still* 50mW beams, being shot at small, rapid-steps..) to aid with cutting-down on exposure-duration, but..

..imo, just yet another bad-idea, from the makers of other bad-ideas, ie: http://www.photonlexicon.com/forums/...olorful-golves , and the infamous 2+W blue-pointers sold to whomever has the cash, ([x] YES! Of-course I am at least 18 years old and know what the smack I am doing, senditomeeNAOUUU!! (teehehehehe..) etc, etc.. that will sell, at whatever the 'cost' / risk be damned, yada, yada..

..not trying to 'give you grief'...actually, agreeing with you, just 'underlining it with red-marker'...

.02
ciao
j

[White-Light]

I agree with Jon that 50mw could be way over MPE for a static beam.

That said, I notice from the Lanling web site that these appear to be fat beam lasers which does massively reduce irradiance and help safety.

I'd want to get the full beams specs though, diameter, divergence, true power and then get someone with laser safety calculation knowledge to check the irradiance from 12 inches (30 cm) from the aperture if using it as a door curtain before even considering buying one. Even if it came out within MPE, you're still then going to need to recheck this before using with a power meter and ruler and be prepared to bin it as often powers vary from specified amounts with lasers.

If I did find it within MPE, then I'd mount it on the wall at ceiling height over the top of the door rather than in or on the door frame to get it as far out of the way as possible.

50mw static is potentially dangerous though and calculations are needed to check both before and after buying. If over MPE don't risk it especially with static beams.

Interesting doc btw Jon.

[JStewart]

As others have already pointed out, the comment about 50mW not being ‘all that dangerous’ is wrong.

For laser beams in close proximity to people, (e.g. several metres), and with a typical divergence the math(s!) is really quite simple…

1mW passing through a 7mm diameter aperture is the equivalent to an irradiance (power density) of 25W.m^-2, which in turn is considered the applicable accidental exposure safety limit. (actually, in some instances 0.4mW = 10W.m^-2 may be more applicable – but in any event to keep the numbers very simple, we’ll keep to the 1mW value)

So if 1mW is considered the limit anything in excess of this value is exceeding the limit. e.g. 10mW = 10 over the limit, 20mW = 20x, 30mW = 30x and so on…

So unfortunately, unless you do some decent spreading of the beam by the time it hits the punters, the exposure is very likely to be over the safety limits. If anyone felt uncomfortable about being hit in the eye as they looked up, the owner of the venue would be standing on very thin ice.

Unless a good solution to the problems can be found sometimes what seem good laser ideas are best just kept as ideas.

James

[absolom7691]

I think I misrepresented my statement when I said that 50mW was not all that dangerous. What my intention was that this is not in a projector, 30'~40' away, scanned through fog and modulated. 50mW, unmodulated, static beam right above your head at 1'~2' away is a terrible idea. I should have made that more clear. 50mW is, of course, nothing to be scoffed at or dismissed as it is never a good idea to get ANY laser beam in close proximity to the audiences' eyes.

The other bit too is since these are probably cheap chinese lasers, who knows how many 100s of mW of IR may be pouring out of them.