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We just bought a green laser pointer on Ebay and had a discussion about the safety. The laser is low end chinese one (5 USD, free shipping :-) ) and the seller says this:

Green Laser Pointer Point Pen 532nm Output power: 5mW (Class IIIb)

the most confusion comes from the "Class IIIB" which, according to Wikipedia should be not safe for common use because it can damage eye even with accidential look or reflection.

However, directly on the pointer is this:

Max power output less than 5mW Wavelegnth 532nm Class III laser product This product complies with 21 CFR 1040

so this looks that it should not be Class IIIB, also because the power is less than 5mW while according to Wikipedia the "B" class should be for 5-200 mW.

I also have a couple of small red keychain lasers which all are the same power output and class.

I do not intend to shine anybody in the eyes but my sister was afraid that there could be potential risk to damage someones eyes with accidential quick exposure (reflection from window in a class or directly from the chalkboard to the class). The green pointer seems to have very intensive light compared to the red ones but it could be a subjective impression caused by the different color.

I think there is rather an incorrect information on the selling page and that the pointer should be safe but I am rather asking to be sure.

thanks

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2 Answers

up vote 6 down vote accepted

I have the impression that the legal restrictions on laser pointers are not enforced. Therefore you should not assume the class labelling is correct.

You also should not assume the power rating is correct. It says 5mW probably because that's the most desired power level that consumers want: As bright as possible without being obviously illegal. But really it could be 2mW, or 10mW, or who knows.

If the laser is 10mW instead of 5mW, I would not lose sleep over it. Obviously you shouldn't play games with it, but nevertheless it requires extreme and unusual bad luck to get permanent eye damage with even a 10mW laser of this type (i.e., visible-light, continuous wave). [Not impossible though.]

A much bigger risk is a poor infrared filter. A 5mW green laser pointer will have a ~100mW infrared diode laser inside it (that's part of how it works). A properly constructed laser will have a filter that blocks the IR from the output. But if it's missing or misaligned, you have a much much more dangerous laser than you expect. The infrared is more dangerous because it's invisible (so you don't blink) and because it's powerful. It won't necessarily be in the same place as the visible beam -- probably it will be more spread out. (Do real-world lasers ever have bad IR filters? I have no idea. Maybe it's a hypothetical problem I made up that never occurs in practice.)

If you have access to a light power meter, especially one that can measure infrared (usually ~850nm wavelength if I recall), you can find out for sure. If not, be extra careful not to point the laser towards other people.

Finally, step back and look at the big picture. A lot of people buy green laser pointers from sketchy overseas companies like you did. If it was easy and probable to cause permanent eye injury with those things, I think that many people would have already done so, and we would have heard about it in the news. So it's probably relatively safe all things considered.

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The classification is dependent on wavelength, and the potential for damage. I would heed the classification, it is right on the edge of safe.

If you want a safe green laser buy a lower rated one.

Realistically it is unlikely to cause damage unless the beam is incident directly into the eye, but damaging the eyes with lasers is pretty much irreversible and will result in vision loss (usually just partial loss). Lasers in the visible range damage the retina, which is what makes them so dangerous.

Personally (and I work with lasers often) I would use the one that you purchased for Astronomical pointing (i.e., star gazing) only. If I wanted to do something else I would get a lower power laser, it isn't worth the risk of eye damage...

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Concur. And the thing about green ones is that the human eye is most sensitive to that color so you can afford lower power and still have a highly visible spot. –  dmckee Jan 3 '13 at 18:31
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