Ultraviolet LEDs and Eye Safety?

[beezaur]

Hi Guys,

I am sure this has been discussed before, but I'll be darned if I can find it.

I am contemplating sending my niece "secret notes" on the backs of letters using UV-flourescent invisible ink (Noodler's Blue Ghost ink). I will be sending a UV Photon with my lext letter.

Before I do that, I wanted to make sure that it is safe, or can be made safe for her young eyes. I know there are some eye doctors floating around here. . .

Any information is greatly appreciated.

Scott

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[Iguanadon]

Hey,
I'm by no means an eye doctor, but I've played around with UV LEDs a good bit. It's important to keep in mind that unlike a florescent tube, or any light with woods glass (that black coating you see on blacklights) on it UV LEDs produce UV very efficiently and in a very focused beam. I tried to create a UV LED wash light with ~100 LEDs on it (the PCB I created could hold 200 if I remember correctly) but stopped working on it because it was too powerful for my eyes. It could easily make something glow extremely bright 20+ feet away, but if I used it without some sort of eye protection my eyes would hurt afterwards.

Now the pen you mention is nowhere nearly as powerful as a 100 LED UV wash, but its important to keep in mind that an LED has a concentrated beam. From what I can see from the light, there isn't any easy way to stare directly at the beam, and since she'll be reading the reflection of the ink (which i believe doesn't contain any UV, but don't quote me on it) she should be fine. Just make sure she doesn't use for extended periods/stare at the light a lot.

Now that I probably scared you from my experience with high power UV LEDs, remember that there are people working in Nightclubs and such that are exposed to hours of UV a day, and the florecent/HID bulbs they use has a lower wavelength than a cheap LED (if I remember correctly its around ~350nm) while most cheap LEDs are 390-410nm (on the border of the UV spectrum which is <400nm).

To sum up my post in one sentence: I'm sure it'll be fine, as it isn't as powerful as some other products on the market (especially since it seems to be diffused) nor will she be using it for very long periods each day.

Although if you notice your eyes hurt after using the pen (the symptoms of too much UV exposure can take a couple of hours to appear I believe) that probably means it isn't a good idea to use it.

 

[WadeF]

For fun I ordered some of the cheap $6-8 UV LED flash lights. One has like 12 LED's, the other is a smaller keychain type light. I haven't used these for long periods, just breifly, but it did seem to make my eyes sore. I didn't look into the LED's, just shined around the room, etc, to see what would glow. Shoud I be wearing protective UV glasses while doing this?

 

[2xTrinity]

The thing that makes me nervous about UV LEDs is that the emitters themselves are a lot like a point-source, so while the total amount of radiation is small -- trivial compared to the UV you'd get going outside for example, the fact that it is a point source, and that the eyes might be dialated (ie, if you use it in a dark room) means that a lot of UV might get concentrated into a small spot on the retina if the emitter is looked into directly. this is why I personally have stayed away from any UV LEDs more powerful than a cheap fauxtons to check money/IDs.

Near-visible longwave UV isn't particularly dangerous, however, under normal circumstances, it is attenuated or diffused -- for example, fluorescent black lights inherently emit diffused radiation, the same is true of natural sky light (the shorter wavelength blue and UV light from the sun is scattered in the atmosphere). In the case of that pen, it looks like the UV light is quite diffused, in that case, it should be no more dangerous than a regular blacklight. How concentrated or diffused a light source is makes a very big difference -- that's why it's a lot more comfortable to look at a 3000 lumen fluorescent tube than a 3000 lumen clear incandescent or HID lamp.

I haven't used these for long periods, just breifly, but it did seem to make my eyes sore. I didn't look into the LED's, just shined around the room, etc, to see what would glow. Shoud I be wearing protective UV glasses while doing this?

I'm guessing in the case of walking around rooms using cheap UV LEDs the eyestrain in that case has mostly to do with the fact that your eyes are trying to adjust to see by the visible violet component emitted by the LED -- which doesn't focus very clearly on the retina. I notice similar eye irritation using high intensity red light for extended periods of time -- the light is on the very edge of the visible spectrum and thus doesn't focus as well.

 

[beezaur]

There has been discussion here about the alleged dangers of blue light as well. The opinion of the professionals was that, in the doses relevant to flashlights, it is a complete non-issue.

I suspect that a UV Photon is about as safe as you can get with a UV light source. They are shielded, nominally 370 nm, and not exactly high power.

The problem is the parents' reaction when they read the back of the Photon:

CAUTION Intense UV light can cause eye damage if viewed directly. Keep away from children.

Scott

 

[TOOCOOL]

I just had my eyes checked and the Doc put a very bright UV light directly into my eyes so I don't think short term exposure is much of a risk.
I am no expert on this subject do your own research

 

[beezaur]

I just had my eyes checked and the Doc put a very bright UV light directly into my eyes . . .

That's a scam.

It's like when you take your car in for a checkup and a month later you have all these mechanical problems. Problems which require the services of the mechanic.

The doctor was frying your eyes so you'd be back, in need of more services.





Just kidding.

Scott

 

[TORCH_BOY]

I just don't look directly at my u/v lights full stop

 

[DM51]

I really don't think it is a good idea to send something like that to a child. UV light has a special fascination, almost impelling people to look at it even if they know they shouldn't. Children have a poor ability to assess danger and risk, and even if they are warned about something they quite often go ahead and do it anyway. The chances are your niece would not suffer damage if she risked the occasional look at this light, but is that a risk you are happy to take? And what would her parents say to you if they discovered you had given their daughter something which had a specific "Keep away from children" warning on it?

 

[beezaur]

Well, she is 4, i.e., she cannot yet read, and the light will be in a package to them all as part of a housewarming gift. So the whole thing will be guaranteed parental control.

The situation I fear is a little like when people find out their drinking water comes in an asbestos cement pipe: "AHHHHHH!!! You are damaging my child!!!" They "know" asbestos is always bad, never mind the facts of the matter.

But yes, there is some level of health risk with UV light. I wonder if it is measurable, or if it is vanishingly small as I suspect.

Scott

 

[optolite]

The important thing to keep in mind is not to stare directly at the light source. What you should be considering is an LED packaged in TO-18 Glass ball Lens or a 5mm round model. The reason behind this is that the light is collimated in a 10 degree and 15degree angle respectively(the most common specs). So for the uv light coming out of the LED, the only thing that might hurt is if you shine the LED straight into your eye and if you do it over an extended period. Other packages might have bigger viewing angles so the light might be diffused in a larger area and this will thus increase risk of getting direct uv light into the eye from the sides of the LEDs.