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I'll have to post pictures of my 80mw green laser that I just picked up. (looks just like Hans' laser, just brighter, & the beam is very visible under normal viewing conditions. I use it to point out stars & planets to friends when we are stargazing. I was surprised how cheap they are (a friend of mine picked one up for me in Hong Kong for about 50$ US
MRC_Hans
Penultimate Amazing
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No, this is a laser.
DVD burners will be around 650nm. CD burners will be around 780nm, which is just out of the visible spectrum.
http://www.cdrinfo.com/Sections/News/Details.aspx?NewsId=6188
The exact wavelength will likely cary a bit depending on the manufacturer. I don't know if recordable and rewriteable use different wavelengths. It would be much cheaper and more convenient if they use the same, but since they use different materials it might not be the case.
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Mr. Skinny
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Cool.No, this is a laser.
I like this one we have at work. 150kW CO2. The picture only show about half of the laser cavity. I think the target is a piece of plexiglas, which is obviously on fire.
MRC_Hans
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I looked at that site. Lovely stuff, but ... rather expensive. A green 5mW is $80. I paid about $15 for mine (and they probably cheated me even then).
Have now taken DVD writer apart. Of course, the laser in it is a different type than in the video, but that will be a small problem. Btw, it has two lasers, one IR and one red, and a lot of nice optics (this is a rather old DVD player/recorder, so, since it is not a X16, the laser power will probably be more modest, still, should be some fun).
Hans
The red one is the DVD one, the IR one is the CD one.
Incidentally, this is one of the problems of the new HD video formats. Fitting two different lasers into a DVD drive isn't all that hard, but to make an HD reader backwards compatible it will need at least 3 lasers, and 4 if you want a reader that can actually read everything. Fairly soon they're going to have to start dropping CDs, otherwise we won't be able to fit all the different lasers in the same device. Either that or make the things look different so people don't get confused and put them in the wrong drive.
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MRC_Hans
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Yeah, there is already quite a bit of optics in this one. BTW, I have now extracted the red laser device. It does in fact look like the one in the video, but it lacks optics, so the laser "beam" fans out (I think this is normal for LED lasers). So, now I need to add a lens system. I have a nice old laser pointer with an adjustable lens, room for two AAA batteries, and a very dim laser. I aim to make a hot-rod out of that 
.
Hans
.Hans
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Commercial pilots have been injured by cockpit illumination from lasers, the most publicized being a Delta flight landing at Salt Lake City:
http://www.laserinstitute.org/news/releases/Lasers_Congress/pwinder.php
The cockpit window was successfully illuminated, the pilot didn't close his eyes, the perpetrator was not (to my knowledge) found.
Bush Goons didn't gin up a story about laser pointers ... pilots, the FAA, and laser safety industry organizations addressed a valid concern about aircraft safety and the surge in the number of incidents of cockpit illumination. While some have chosen to focus on the speculation that terrorists might employ this method of distracting or disabling a pilot, pilots are concerned about the inability to land a plane no matter who is holding the laser -- prankster or terrorist.
Wicked Lasers' marketing techniques are reprehensible. Just read the "We aren't for everybody" section of their homepage to see the kind of appeal to the perceived elite they're using ... "Maybe you are someone special" and " Are you special enough to own a Wicked Laser?"
These are legitimate tools, but just like many tools they are dangerous in uneducated or irresponsible hands. A careless flash from one of the higher power lasers can cause instantaneous permanent eye damage ... and Wicked Lasers is suggesting that you use their products to "Use lasers to signal your intention -- perhaps the perfect application for a blue laser", "Ward off your enemy with lasers", and says "Our high-powered green laser pointers are used by the US military to disorient and intimidate the enemy" implying that it is acceptable for purchasers to do the same.
Most people have an innate feel for what throwing a knife or firing a projectile at a person would do and almost always refrain from doing so. But laser pointers of this power are new and seem innocuous. Yet many idiots have no problem illuminating performers or bystanders with a very dangerous device.
Marketing these as toys to make you cool and elite is appalling. Unfortunately, there are no regulations to prevent this. (Typically only municipal laws restrict sale and ownership of lasers, and then usually only to minor.)
That wasn't a laser pointer though.
As I said, cockpits have been illuminated by lasers, and no one in the administration began lobbying against laser pointers (or at least no one with any reasonable knowledge on the subject).
MRC_Hans
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Interesting. Actually, even here in safety-conscious Denmark, there does not seem to be any regulations about laser pointers.
.............
I was wondering, how far away can a beam from a laser pointer be seen?
There are, of course, (at least) three different viewing criteria:
1) The beam hits a target, and the spot is visible by the person holding the laser.
2) The beam hits a target, and the spot is visible by someone next to the target.
3) Somebody looks directly into the beam (presumably at a safe distance) and sees the light.
Obviously, all depend on general visibility, and #1 and #2 depend strongly on the reflextivity of the target. For exemple, my green 5mW can be seen for miles (#1 condition) if it hits a car license plate or a road-sign.
However, I was wondering: If I could point it at the international space station, would astronauts be able to see it? Or if astronauts return some day to the Moon, could they see laser pointers directed at them?
Could I see a reflection from the laser mirror on the Moon?
Hans
.............
I was wondering, how far away can a beam from a laser pointer be seen?
There are, of course, (at least) three different viewing criteria:
1) The beam hits a target, and the spot is visible by the person holding the laser.
2) The beam hits a target, and the spot is visible by someone next to the target.
3) Somebody looks directly into the beam (presumably at a safe distance) and sees the light.
Obviously, all depend on general visibility, and #1 and #2 depend strongly on the reflextivity of the target. For exemple, my green 5mW can be seen for miles (#1 condition) if it hits a car license plate or a road-sign.
However, I was wondering: If I could point it at the international space station, would astronauts be able to see it? Or if astronauts return some day to the Moon, could they see laser pointers directed at them?
Could I see a reflection from the laser mirror on the Moon?
Hans
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1. No.
2. Hell no.
3. **** no.
The limiting phenomenon is diffraction. Laser pointers (unmodified by a large optical system) have a divergence related to the diameter of the beam of approx. 0.5 to 1.0 milliradians. This means that your beam will expand by 0.5 to 1.0 mm per meter, or 0.5 to 1.0 m per km. At the ISS (340 km or so), the beam will be 170 to 340 meters in diameter.
5 mW into that area will be 0.05 - 0.2 microwatts / m^2, or 0.05 - 0.2 picowatts / cm^2. This is *perhaps* visible with highly dark adapted eyes, if the viewer knew exactly where to look, and there weren't any surrounding lights (Hans standing alone in the middle of a large uninhabited area). I haven't done all the calculations, but the answer is for all intents and purposes, no.
For the Moon, the beam expands to 400 km in diameter.
If you want to propagate a laser beam a long distance, you need to *expand* it. Divergence decreases with increased beam size. So, with the aid of a telescope (used in reverse) if one expands the diameter to half a meter, the size by the time it gets to the ISS it will only have doubled in size. (approx)
MRC_Hans
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Yes, I would have expected that. I actually have an older laser pointer with an adjustable lens, so presumably, you could set it to zero divergence (assuming perfect optics, and quite possibly, other supernatural stuff), but most laser pointers are probably intentionally adjusted to some divergence. After all, what use would a 3mm spot be at several hundred ft? So, they are more or less set to make the spot appear of constant size, regardless of distance.
ETA: As for the laser mirror, if I had a beam with sufficiently low divergence, I would have no chance to hit it with a hand-held laser, so it is a loose - loose game.
Hans
ETA: As for the laser mirror, if I had a beam with sufficiently low divergence, I would have no chance to hit it with a hand-held laser, so it is a loose - loose game
.Hans
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No. As I said the limiting phenomenon is diffraction, which is related to beam diameter. Even if you have a perfectly collimated beam (i.e., perfectly flat wavefront) at one point, the fact that the beam has a finite diameter will cause it to diffract and it will acquire a curvature to the wavefront. At sufficient distance this will become a beam with divergence of
2 * (wavelength)/(pi * beam radius)
for a beam with Gaussian distribution. See:
http://www.mellesgriot.com/products/optics/gb_2_1.htm
for details. The lens on your laser pointer can be used to focus your laser in the near field, or move the beam waist around axially, but it can't be used to maintain constant diameter of the beam regardless of distance. That's physically impossible. The only way to reduce the angle of divergence is to increase the diameter of the beam (since divergence is inversely proportional to beam diameter).