At 10:11 AM Friday 2/24/2006, Klaus Stock wrote:
> >And more easily blind people than the class 1 lasers.
> >
> >Want to kill someone? Wait till he drives past on th efreeway, point the
> >laser at his eyes and there he goes. The perfect crime, killing people
with
> >an intuitive "point and click" interface.
>
>
> I have a class 1 green laser rated at 4.99mW that I use for a star
> pointer which would likely be sufficient for that purpose. (Drives
> the cat crazy, too.) The downside of doing what you describe at
> night is that the beam of even a class 1 green laser is visible at
> night (the very reason it is useful for pointing out objects in the
> sky), so any witnesses would be able to describe where the beam came
> from. The laser Rob described is actually bright enough that the
I was temporarily blinded by a red laser while traveling in a train (some
years ago). I suppose one these normal laser pointers. The air was clear and
I could not make out where the beam came from.
About the only way to make the standard red laser pointer beam
visible is to be in a reasonably dark room (e.g., a lecture hall with
the main room lights out and the main illumination being the lights
on the blackboard or the light coming from a movie or video screen at
the front upon which something is projected) and then to have the
room filled with smoke or steam or to take a couple of dirty erasers
off the chalk tray and clap them together to fill the air with chalk
dust, and the beam won't stay visible for long. That's because the
color of the beam is such a deep red (630-680nm, according to the
label on the one I have here) that the human eye isn't very sensitive
to it. The green ones lase at 532nm, which is near the wavelength
(~550nm) where the human eye is most sensitive, so the beam from a
green laser is much more visible than that from a red laser of the
same power, making the beam from a class 1 green laser pointer
visible in a dark room or outside at night (even when there are some
lights not too far away) as it reflects off moisture and dust
particles naturally present in the air.
I ssume that the beam was
turned on before it hit me, that it took the operator a few seconds to "home
in". If I had noticed the beam (or the spot) before, I would have taken
appropiate measures (having worked around industrial lasers of the
cuts-though-concrete-walls variety, I am trained to extreme reactions at the
sight of a laser beam getting close...). I didn't immediately realize what
happened when the beam hit my left eye - it was the first time that I looked
into a laser beam.
The first time I recall that happening was back in the early 70s when
I was in one of the university physics labs and opened the door to
the next lab (that building was designed in a square ring with most
of the classrooms and faculty offices around the outside and the
inside occupied by a series of interconnecting labs with the
equipment room, power supply board, etc., in the middle) and
discovered that someone had a low-power HeNe laser pointed at the
other side of the door. (I think someone had taped a piece of white
paper to the door to use for a screen to demonstrate diffraction
patterns.) As an astronomer, I do keep a pretty close eye on my
vision (:)), and I haven't noticed any damage from that or subsequent
accidental exposures, although I do take care to avoid exposure.
Since then, I have a few black spots flyling before my left eye (such laser
damage was described to me as being like "flies flying in front of your
eye", and now I can confirm that). A normal retinography shows nothings, but
I can see it, close to the center of my field of view. Took me more than a
year to get used to it.
However, even temporary blinding will be a problem when, for example,
entering a curve. Traffic in the opposite direction is very close, and
during the curve entrace, it is not sufficient just to keep the steering
wheel in position.
That's what I was thinking of, and indeed this green laser pointer I
have would be more than sufficient for that purpose. At night,
shining it into another room with light-colored walls or ceiling
illuminates the other room just as well as shining a flashlight in
there would.
Yup, there are people who enjoy throwing rocks from freeway bridges. People
aleady got killed by that.
Including a professor at another university here in Alabama a few
years ago when an iirc 10-lb rock came crashing through her windshield.
Green lasers might be the new "geek way" to have
such "fun"...
I fear that will be so. Particularly now that the prices for class 1
green lasers are significantly less than $100. (They are still
considerably more expensive than common red laser pointers because to
get the green color requires a 2-step process: the first step
generates an infrared laser beam at 1064nm, then the second step
doubles the frequency to get the green wavelength of 532nm. This
also makes them more fragile to shock, like being dropped: yet
another reason I don't let anyone else handle mine.) There are lots
of people I know who keep a small arsenal of firearms and ammunition
in their homes for hunting and target practice, and I have no worries
about them doing so. (One of them lives next door, where he and his
wife have lived for over 40 years.) I would trust them with
ownership of a class 1 green laser or a .95mW green laser that can
cut through plastic. OTOH, there are a lot of people out there who I
would never hand even an unloaded firearm or a red laser pointer to,
because I have seen them handle such in an unsafe manner. ("Always
treat every firearm as if is loaded," and "Don't point it at anything
you don't want to destroy.")
BTW, you can also order yellow and blue laser pointers on-line, but
the prices of them are still close to $1000. (Selfishly, I hope I
can get a few of these that we've been talking about before they pass
restrictions on them. Of course, if I could afford it and had any
place to keep it, I wouldn't mind having a .50-cal machine gun, if
for no other reason than to tick off any liberals who come to visit . . . :P)
--Ronn! :)
"Since I was a small boy, two states have been added to our country
and two words have been added to the pledge of Allegiance... UNDER
GOD. Wouldn't it be a pity if someone said that is a prayer and that
would be eliminated from schools too?"
-- Red Skelton
(Someone asked me to change my .sig quote back, so I did.)
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