Slightly crazy 980 nm laser experiment

Well... should you persist against the other members' reasoning, meter it beforehand. My opinion is that you should use LEDs. But i'm really curious as to know what happens so post results. Even if they are "severe damage".

Yeah... I guess he could still type with his remaining good eye...:eg:

Jerry

IMO, you can do this, but only after a signed affidavit that you've been irreversibly sterilized and can't have children, and currently have not had any already.

So, I think you can go ahead and test this for us, but we'd need you cut off from the human gene-pool forever before you get permission to proceed.

lasersbee said:

Yeah... I guess he could still type with his remaining good eye...:eg:

Jerry

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Well, as the old saying goes:

"Do not look into beam with remaining eye"

Okay, okay, here's my motivation. I noticed that I can see the LED from remote controls - which should have a peak at 940 nm or so, but also a considerable bandwidth. I tested this as well on a LED I bought that is certainly a 940 nm LED; it's easily visible in the dark and glows a dim red. This is a much longer wavelength than I thought we had any sensitivity to. I'm curious to see if this extends to IR light that's extremely monochromatic, or if I'm just seeing the extreme short-wavelength tail of the LED light that's being emitted. This is why I'd want to use a laser. If 980 is visible in any capacity, I'd find that an interesting result.

Once the laser arrives (probably next week sometime), I will start doing some tests. Actually looking into the beam directly is something I don't really plan on doing, but I wanted to get everybody's take on what would happen if it did shine into my eye. If I don't see anything from diffuse reflections, I am likely to try things like looking at the beam off of a somewhat reflective surface (e.g. coarse metal), and I also may try direct viewing of the second-order maxima from a diffraction grating, or at the worst, reflections from glass surfaces. Ultimately, I'm interested in seeing the minimum power that produces a visual response. Also, the laser beam is focusable and will stay unfocused through the experiment.

weeba2kv - How did you end up with permanent eye damage from a 5 mW laser? Did it take a very long exposure or some other unusual condition? I suppose why I think I'm safe even if I were to shine it into my eye is that there are millions of cheap 5 mW red laser pointers and no cases in the literature of permanent eye damage - even temporary eye damage seems to happen only if people force their eyes open and stare for half a minute or longer (negating the main difference between red and IR exposure - the blink reflex). Keep in mind that even if I try the dumbest (OP) version of this experiment, it would be unfocused and limited to 1-2 seconds at the absolute worst. So if you have had permanent damage from 5 mW, or if anybody knows of any cases like that, it would be good to know about it.

As for the laser being over spec, I suppose I find it unlikely that it would be, say, 20 mW instead of 5. It's supposed to be class IIIa, so that would run afoul of labeling requirements, and wouldn't it be more expensive for them to produce a higher output anyway? If I don't get my hands on a meter, I'll at least compare it to my 940 nm LED and a 780 nm laser which I know to be dim by viewing the spot against a wall with a digital camera, to get some crude qualitative idea as to the power output.

Anyway, I'm not surprised that proposing that I ignore the #1 rule of laser safety would get me flamed. I would just like to state that I'm not completely ignorant of what lasers do, and thanks to everybody who did post helpful replies. Once I get the laser, I'll do some tests and come back here to post what I saw, so anybody interested can know whether or not 980 nm light is completely invisible. And although I find it unlikely, if I end up hurting myself, I'll post that too, so you can all give me the visual equivalent of a Darwin Award.

I wasn't joking about being interested by the result. My feeling is that it, realistically, probably won't do damage, i just don't think it's a good thing to do it. Like realistically pointing a non-loaded gun at someone isn't likely to do any harm (apparently soldiers are taught to never point a gun at anyone they don't intend to kill whether the gun is loaded or not) but it's bad practice. As is not hollowing out a peice of clay work that's about to go in the kiln, or not putting tape on the end of a thin peice of metal when it's in a vice to increase visibility, or even not washing your hands after handling animals or using the toilet. In all cases, not likely to do any harm, but still not good practice and should be avoided.

You can see the light from LEDs in remote controls? I'm impressed... lol... i want to see that. What's it like? Just a very dim red? And, as i said, post your results. I once saw the radio waves coming off the arial to a remote controlled car, but i've never seen the projection of an infrared LED. Cool stuff.



Edit: ...ok, sorry, i need to just stop making jokes altogether, i'm not a very funny guy... Ignore the bit about the radio waves, i meant the rest.

It's a very dim red that blinks at different frequencies depending on what button you press. The blinking patterns are what communicates information to the TV. It's fun to point it at a digital camera while holding a button and then look at it with your eye. Some quirk of the digital camera causes IR light to appear bluish (although this varies by camera), whereas I see dull red. It's probably possible for most people to see this - I asked a number of people and they could all see it from a certain remote control, although some others were too dim (as verified by the camera). It takes ideal conditions - you have to be in a very dark room, holding it at the right distance from your eye. But you can probably see it too - try it out!

Trajork said:

Once I get the laser, I'll do some tests and come back here to post what I saw, so anybody interested can know whether or not 980 nm light is completely invisible. And although I find it unlikely, if I end up hurting myself, I'll post that too, so you can all give me the visual equivalent of a Darwin Award.

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How about you document your experiments with a video camera so we can all see exactly what not to do with an Infrared laser. :san:
By the way. When you say that you can see the light from a remote control's IR LED, what color is it to you?

It's a dim, flickering red light. Seriously, you should try looking into remote control in a really dark room - you very well might see it, under good conditions.

I'm not going to go ahead and emphasize all the flaws in this, as the warnings have been stated already. But I'd just like to let you know that staring at the dot itself, even on a white wall, can be dangerous. The danger with IR is that you don't know relatively how much is actually entering your eye. Would you stare at the dot of a 5mW green laser in a pitch black room with your eyes dilated? The same harm is done by staring at the dot of a 5mW IR laser, except for the fact that you don't know that it is damaging your vision. Do yourself a favor for us, and don't do this "experiment".

Let me just post some observations here:

You notice you can see a remote controls led when you point it into your eye as a dim red light. This is not unusual. It is, however, a very bad idea. If you had a green led that produced the same amount of power as your remote controls IR led, you would be in pain and seeing spots for quite some time if you looked directly into it. I dont suggest you attempt this, just take my word for it (or be a fool and look straight into the brightest 5mm led you can find).

So, now you want to up the ante a bit, and go for a monochromatic 940 laser, instead of a led that has a broad spectrum that bleeds into the near IR. You will likely discover that 940 nm is really invisible, but you might also discover that everything else is invisible after your experiment.

The safe limit would be a laser with an output power of 0.5 mW or less. And you must assert it is not over that specification before attempting to look into it.

If you want a deterrent: get a 0.5 mW, IR filtered, green laser pointer, and see how long you can stare into that beam. The 0.5 mW of 940 nm is about as dangerous, but will not cause you any discomfort before damage is done. Half a miliwatt sounds like nothing at all, but if you shine it directly into your eye, it will seriously hurt if its green light.

The only time I would have a laser shinning into my eye would be for lasik. To look into a laser is just f###ing stupid!

Jimmymcjimthejim said:

Would you stare at the dot of a 5mW green laser in a pitch black room with your eyes dilated?

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??
Yes.

Trajork: Find an IR LED that actually spec's it's output, bandwidth wise, and see how much of it you see. I have a pile of IR equipment, including 1W 850nm illuminators. They appear a "dull red" - until you actually put an 850nm peak filter on them and then... nothing. Don't be surprised that you can see a small percentage of 850nm IR LED output. However, as you get past 900nm don't expect to see much.

Yeah, that would be a good idea. The datasheets for the 940 nm LEDs I've looked up tend to show bandwidths of ~50 nm, but I didn't actually get any of those, just a cheap Radioshack one and of course the ones on remote controls. More than likely the intersection of the luminosity function and the light output from that is 850+ nm, but I don't really have a way to be sure. I do also have an 850 nm IR illuminator, but again, no helpful information on its LEDs. What is interesting about that illuminator though is that it is bright enough for its light to produce a deep red glow that lights up objects 3+ feet away under dark conditions. $5 bills have a couple of strips of ink that disappear under IR light on their reverse side, and I was able to see that with the naked eye when I held a bill right up to the light. Also, the illuminator didn't noticeably dim when I looked at it through a 750 nm filter, so I think most of the light I see is at least in the high 700s. But yeah, 850 is probably a stretch.

And to the folks who seem to see a problem with the intensity of low-power diffuse reflections and LEDs, uh, there's simply no danger there at all. Really, anybody can look at green 5 mW spots on walls and green LEDs with the same output as remote controls without anything resembling pain; we did this in physics lab all the time. I know direct viewing of a laser (even the glass reflections that I actually do plan on looking at) is a very different beast - that is risky, but I think I can learn something interesting from it.

"the illuminator didn't noticeably dim when I looked at it through a 750 nm filter, so I think most of the light I see is at least in the high 700s."

Yeah, exactly - and the low 700's are deep red.

I tried to find a source for IR flourescence cards (charge them up with white light and they re-radiate orange when exposed to IR peaking at ~1400nm) but no luck. They are good to have when mucking with IR devices.