I have a short story idea, and a question came up about part of the plot. Could you cause serious or permanent damage to someones eye by shining a laser pointer into a peephole while someone was using it? From either the outside or inside of the door. What about one of those high-powered flashlights? Or maybe a camera flash?
Most of the commonly available laser pointers aren’t powerful enough to do damage to an eye before the person would automatically blink. The peephole wouldn’t make the effect any worse, in fact it would probably weaken the effect as the laser is already coherent, the lens would probably diffuse the light.
Likewise, a high powered flashlight or camera flash wouldn’t hurt your eyes any more than it would without the peephole - the surface area of the lens outside the door is not much bigger than the aperture on a dilated pupil, so it wouldn’t be gathering any more light than the naked eye would.
Now, those industrial strength lasers that can burn through styrafoam cups might be able to hurt someones eye before they could blink. If something like that happened to me, I’d be sure to open the door and attack the person immediately, as I have a spare eye.
I actually was shined in the eye through a peep hole with a red laser pointer so i can answer this question with full knowledge.
when i closed my eyes i saw a large green spot, then when i opened my eyes i saw it- a giant red spot. everywhere i turned it turned. it was scary. but it went away after a couple days. now im fine.
i think that the damage depends on the strength of the laser, but this one was the lowest strength/priced ones and it did cause temporary damage.
A laser could probably cause about the same amount of damage through a peephole as without. It certainly wouldn’t be more, and would probably be at least somewhat less, but I don’t think that, in practice, a peephole would be very lossy, so it’d be close to the same (probably at least 90% of the power, as a SWAG).
Now, I don’t know which lasers would cause how much damage to begin with: The warnings are probably a little on the conservative side. Still, kids don’t try this at home.
Does the warnings’ ranking system help at all? (Not snarky; thought maybe you knew of something wrong with them).
It seems like class 1 lasers are generally considered safe, 2’s more dangerous but still safe because it causes you to blink before any permanent damage could be done, and beyond that all bets are off.
There are laser pointers out now that put out an awesome amount of power that could blind someone. The peephole optics, of course, alter the beam, but simply shoving that much amount of output into that small a space guarantees that it’s going to get into the eye.
There is at least one company manufacturing hand held lasers that output up to 1 Watt. If you put that into one side of a peephole and put an eye on the other side it will practically guarantee eye damage.
If someone really wanted to get eye damage, they could bring along a unit to plug into the wall, or something with a big battery to exceed even that 1 watt limit. So the scenario is plausible.
It’s like those stories about people putting firecrackers in peepholes. Or firing bullets through them (as in Saw II). You can come up with nightmare scenarios where you can injure people through peepholes.
According to Wikipedia, these are no longer classifiable as “laser pointers”, but they’re the same size, and they are currently available.
I’m not a laser guy (nor, indeed, any kind of experimentalist). My statement was a general one: The warnings might be a little on the conservative side. That is, I would expect that if the actual evidence showed that X power was enough to cause eye damage, that they’d attach the warning to anything with Y power or more, where Y is somewhat less than X, just to err on the side of safety. But I don’t actually know what the value of X or Y would be.
The handheld lasers I refer to above, by the way, are cordless and the size and shape of laser pointers. They look like laser pointers. As far as I can see they serve no useful function, because you wouldn’t want to use them as laser pointers – the reflected light from your projector screen will be too damned bright.
The product rating does, indeed, help. As i say, these 1 Watt handhelds are really off the top of that chart, though.
And for what it’s worth, you shouldn’t even point the class I lasers into your eye.
Yes!
To give you an idea of how bad a 1 WATT laser is when it comes to eyes consider this. A laser has to be a few MILLIWATTS or less to generally be considered “eye safe” and even then, if you work at it, you could possibly do some eye damage. So, these high powered watt level lasers are hundreds to thousands times more powerful than the safe level.
Its like comparing the dangers of electrocution from a AAA battery to that of a power substation.
Another safety point. You can shine a laser on say your fingers or hand and not feel a thing. That same laser that you can’t even feel CAN damage your retina. And that damage will likely be permanent.
How rapidly would the damage of hand-held 1 watt laser be noticed? Instant searing pain, or later effects? People who have looked at arc welders without protection have told me they didn’t notice anything until a couple of hours later.
Years ago when I studied network engineering, we were warned never to use our eyes to check on a fibre optic cable, because a live one can burn a nice little dot into your retina. IIRC it was fast, painless, and you might not notice till later.
Those lasers aren’t especially powerful, and some of them aren’t visible (which is part of the problem: people keep looking when they can’t see anything, so the exposure is longer).
Based on that I expect a laser through a peephole would could easily cause permanent damage, but it probably wouldn’t stun someone or damage their entire field of vision.
I copped a full power camera flash right in the face recently. That hurt.
Actually, it occurs to me that there is one way in which a laser through a peephole might do more damage than one shined into the eyes directly. If you shine a laser into someone’s eyes directly, then which part of the retina gets damaged will depend on which way they’re looking at the moment, and is likely to be one of the lower-resolution parts towards the edge. But if a person is looking through a peephole, they’ve probably got the high-resolution part near the center pointed at the peephole, and the laser will therefore damage that higher-resolution part. So the amount of area of retina that’s damaged will be the same in either case, but it’ll be more important area that gets damaged through the peephole.