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Re: "Laser beam" deterrent
- To: ukha_d@xxxxxxx
- Subject: Re: "Laser beam" deterrent
- From: "mark_harrison_uk2" <mph@xxxxxxx>
- Date: Tue, 14 Oct 2003 20:41:07 -0000
- Mailing-list: list ukha_d@xxxxxxx; contact
ukha_d-owner@xxxxxxx
- Reply-to: ukha_d@xxxxxxx
--- In ukha_d@xxxxxxx, Ian Tresman <ian@k...> wrote:
> Sometimes we see "laser/light beams" protecting valuable
artwork in=20
the=20
> movies. Are these for real, or do they require a smoke machine to=20
(a) make=20
> the beams visible (b) goggle to protect eye sight.
A laser beam is, well, coherent (*), so you can only see it if you=20
are looking directly into the emitter.
The only way to see WHERE it's going is to suspend (*) something in=20
the way and watch light reflected off it. This typically breaks the=20
coherence, so you can see the impact from a wide viewing angle.
A smoke machine is indeed good for this purpose :-)
As to whether you require goggles - depends on the power of the=20
laser. It's a bit chicken and egg - if you want to run it through a=20
smoke machine because you like the "cool look", then you need to
ramp=20
up the power (because that much more of the light doesn't get=20
through), which makes it more dangerous again...
If I'm honest, I'd suggest that eye protection ALWAYS made sense :-)
* - technical term which may not QUITE mean the "plain
English"=20
meaning. Dunno.
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