Heyo, I recently purchased a S3 Arctic Class IV laser pointer. I bought the 3500mW. (In case that page expires, it's 445nm wavelength, 1.5mRad variant, NOHD is 279m, beam distance at 0.25 Lux 72km.)

I plan to use this laser in an open area use - not when surrounded by unwitting people of course. I've taken precautions via reading a lot of the safety manuals available, including reading through the Wiki article on laser safety, the UK regulations, laws on the topic, etc. The laser comes with some protective eyewear which I will wear diligently.

Is it correct to say there is no damage to the eye from observing the beam, assuming there is no dot or dot reflection being directly looked at? All the references to 'safe distances' such as NOHD seem to imply 'safe distance from observing the dot or reflection of the dot'. In contrast, the higher-watt lasers are reportedly used for concerts/lightshows, the beams of which are publicly observable and can be seen from a distance.

(There is a similar question, but doesn't seem to be answered with regards to scattering light. I want it clarified definitely.)

The fact implied is the beam itself, - that is, the scattering light from impurities in the air - will not be a problem for observing without any protection, provided the actual emission source of the laser and destination dot are not observable from the observer's position.

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    $\begingroup$ IANAL, but if I were, I would basically tell you to stop this nonsense and take your dangerous toy indoors and restrict its use to closed rooms where nobody is present but you (you can't sue yourself). As for the specs... if they come from the typical laser pointer sites, they are completely useless. Most of that looks simply made up. It takes a fool, no offense, to plainly believe what the sellers of these things claim. $\endgroup$ – CuriousOne Mar 2 '16 at 9:27
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    $\begingroup$ Anything beyond 20mW is likely to cause eye damage. Three Watts is an instant eye popper. $\endgroup$ – user56903 Mar 2 '16 at 9:50
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    $\begingroup$ Please tell me you don't live in my town $\endgroup$ – John Rennie Mar 2 '16 at 9:52
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    $\begingroup$ @Phi To quote from the original post: "I bought the 3500mW" That will both burn thermally and photochemically dissociate skin. Eyeballs are not likely to be more resistant. $\endgroup$ – user56903 Mar 2 '16 at 10:23
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    $\begingroup$ I'm voting to close this question as off-topic because it is about physiology, not physics. $\endgroup$ – Norbert Schuch Mar 2 '16 at 13:12

There may very well be a danger because of the short wavelength. High intensity blue light can damage the eyes far more readily that longer wavelengths. It does not have to be coherent. From a laser sales site:

Blue-light Hazard is defined as the potential for a photochemical induced retinal injury resulting from radiation exposure at wavelengths primarily between 400 nm and 500 nm. The mechanisms for photochemical induced retinal injury are caused by the absorption of light by photoreceptors in the eye. Under normal conditions when light hits a photoreceptor, the cell bleaches and becomes useless until it has recovered through a metabolic process called the visual cycle. Absorption of blue light, however, has been shown to cause a reversal of the process where cells become unbleached and responsive again to light before it is ready. This greatly increases the potential for oxidative damage. By this mechanism, some biological tissues such as skin, the lens of the eye, and in particular the retina may show irreversible changes induced by prolonged exposure to moderate levels of UV radiation and short-wavelength light. (source: http://en.wikipedia.org/wiki/Blue-light_hazard)

  • $\begingroup$ "This has not been shown to occur in humans, only inconclusively in some rodent, primate and in vitro studies." is the second sentence in that link... $\endgroup$ – Phi Mar 2 '16 at 10:01
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    $\begingroup$ So we have ample opportunity to test whether the laser operator is lucky when it comes to viewing intense diffuse blue monochromatic light. Would you care to take the risk? $\endgroup$ – user56903 Mar 2 '16 at 10:21
  • $\begingroup$ Sure, why not. But it's not relevant to the question, which assumes a scenario where the laser operator is wearing protective gear due to proximity, and the potential observers could be at any distance without protection. If it is that dangerous I don't see the point in selling a device that's handheld; the odds of a beam being within public view are very high. I'm not questioning the idea of doing something dangerous, but whether it's dangerous at all, because I'm inclined to believe it is. $\endgroup$ – Phi Mar 2 '16 at 10:53
  • $\begingroup$ @Phi There are all kind of dangerous handheld devices being sold. $\endgroup$ – Norbert Schuch Mar 2 '16 at 13:13

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