As a kid, I'd watch cartoons and shows that would depict lasers
which could burn stuff. I always thought it'd be cool to have a laser
that could actually burn stuff, but alas even laser pointers were out of
reach in those days.
Then in the late nineties I was able to get a red laser pointer for my
birthday. The thing cost $100, but damn, it was a laser! Of course, being
a laser pointer, the laser itself was not very powerful. The
sticker itself said that the light output was < 5mW.
Well times have changed, and now red laser pointers are about $5 at most
places. The cool ones now are green laser pointers, which are
substantially brighter because the eye is more sensitive to green light.
At stores like ThinkGeek.com, they can run about $100 each, but I was able
to buy one off of eBay for about $30 shipped.
Now about this time I ran across some site that had a bunch of people
participating in a "group buy" for a set of Class IIIb green
lasers. Group buys are where a group of people approach a manufacturer and
guarantee them a large purchase of a certain product in exchange for
wholesale prices, or at least a discount. Now a word on lasers and their
class designations:
- Class I lasers are safe enough that they can't do any damage to the
human body (usually eyes). They're the lasers found in CD players and
junk like that.
- Class II lasers are up to 1mW in power, but are weak enough that they
generally don't pose any hazard to eyes (unless you're an idiot
and look into them for half an hour).
- Class IIIa lasers are the typical laser-pointer laser. They can cause
eye damage if directly shown into the eye for multiple seconds, but are
generally safe, and eye reflexes are usually good enough to blink before
anything really bad happens. Such lasers are less than 5mW output
power.
Now we come to Class IIIb lasers:
- Class IIIb lasers are from 5 to 500mW lasers. They're the kind that
can burn stuff, but not very quickly. The army uses such lasers to point
out enemy position for rockets or other air weaponry, but only uses these
more powerful ones because they have greater distance penetration. Lasers
in the 500mW range can be a fire hazard for most ignitable material, but
those lower, like 80-150mW will sting the skin, but only burn materials
which absorb the light well (like electrical tape, or balloons). Class
IIIb lasers can cause blindness very quickly, and therefore have safety
measures in the form of a 5-second delay, aperture cover, operational
lights, a keylock, and a remote-operations plug.
So I got myself a PGA-III-A 80mW Class IIIb green laser, seen below next to
the green laser pointer I bought earlier. It cost me $205 shipped, not bad
for a laser of this power and quality, but definitely a frivolous purchase.
Other laser dealers charge an
arm and leg for lasers like these, and some are known to burn out from lack
of proper laser cooling. Oh well.
Note the plug on the right side. The laser will not turn on without it
plugged in. The laser measures about 8"x1" (~20cm x 2.5cm):
The beam is very visible at night, light a light saber, though not
quite that bright. The dot appears white, but is actually
super-bright green, and the blooming around the dot is caused by the optics
(your eyes will produce that too).
Here's the warning label. The laser was manufactured in China, but it
meets FDA regulations:
A comparison in brightness between my green laser pointer and the 80mW
laser. The 80mW laser is at least 16x more powerful.
Finally, I went outside and shined this, taking care to avoid any planes
that might be flying around (don't want to be brought up on terrorist
charges). You can clearly see the beam at night and it is really quite
cool to wave it around towards the sky. This photo here is a 15-second
exposure shot using a digital camera. You can see the clouds moving.
To prevent my eyes from being fried by this laser, I bought some $13
Laser-enhancement goggles. These goggles are for making red-laser level
dots more visible to the eyes, but they do a fine job of blocking
out green light. The bright laser dot looks like a mere yellow dot on the
wall, about as bright as shining a dim flashlight through a piece of paper.
It almost works too well.
posted by Bionic-Badger on Tuesday 15th August 2006, 02:48:19
Those ones are quite
expensive. You're talking thousands of dollars. The blue
ones are really expensive too, with a good deal being $1000 or so.
Too rich for my blood.
You can actually modify existing green laser pointers to output more
than 5mW. Some go as high as 25mW, which is quite bright and enough
to pop balloons and stuff. Since the laser pointers don't
dissipate heat too well, you can only have the laser on for short
bursts. Even that $30 one I have gets kind of warm after prolonged
use.
Well, you can get a green laser pointer at
ThinkGeek.com and pay their hefty price, or buy a
better--if only less expensive--one at http://www.atlasnova.co
m/ . They're pointers not
modules (Class IIIb lasers), so it won't
kill your eyes--immediately that is. You can also get
one of those Class IIIb-powered ones from that website
too, but you have to call him first to make sure
you're not just some kid or a member of al Qaeda,
or at the very least know what responsibilities it
entails.
Yeah, I've been asked that a bit, and really, I don't know.
I guess it's just to have it and play around with. There really
isn't a good justifiable reason to have or buy one, other than
it's cool.
No moon yet, though there are some accounts that it is possible off
the set of mirrors that were left there in the 70s. I don't
think it'll make it through the smog of the city though, so
I'd need to try it during a new moon while camping or
something.
Yeah, it is harder to achieve and requires more power from the diode.
Whereas in a red laser, the diode can output the light directly, the
green laser has to use a relatively powerful infrared laser and send
that beam through a series of crystals to achieve the correct
frequency. Even then there is a lot of invisible IR that comes out
and that requires a filter too.
It starts to sting my hand after a few seconds, but the problem with
the lasers is that they diverge over distances, and so it may not be
as effective over longer distances. It'd probably sill be good
enough to sting though at around 30ft (~10m).
It'd be hard for them not to notice the light too. Everything
lights up around the point where it hits. If you were to remove the
crystals and recalibrate the lens, you could make an infrared laser
though, which would be very dangerous (especially to eyes, etc.) but
invisible and quite powerful. There are a lot of regulations on those
though.
They should include a scene where "Mitch" goes permanently
blind after a beam bounces off the reflective surface of a button and
into his eyes. Comedy gold!
Laser
