Eye protection - laser edition
November 20, 2020 6:26 AM   Subscribe

What should I look for in inexpensive protective goggles/glasses to make sure their lenses actually protect my eyes effectively from an 810nm class 1 diode laser (for home hair removal)?

I recently bought a (Tria brand) home hair removal laser and while the instructions say no eye protection is necessary (it is an automatic system that only fires when pressed against skin), I want to use eye protection anyway. I'm seeing a huge ($10-$200+) variation in prices and don't really understand how the filtering works, so it's hard for me to assess whether the cheap ones will be OK.

I assume things like how well a pair of glasses or goggles covers the side-view, as well as how clearly you can see through the lenses, are factors in the quality, but I'm specifically curious about how to assess whether the lenses themselves will protect my eyes. (I don't need to see especially well while doing my home lasering.)
posted by needs more cowbell to Science & Nature (10 answers total) 1 user marked this as a favorite
also side note for anyone considering home lasering, you can get the lasers used for 1/3 of the price because a lot of people decide it's either too painful or too tedious and give up
posted by needs more cowbell at 6:27 AM on November 20 [2 favorites]

Styropyro is a Youtuber that does crazy things with powerful lasers. He did a test-to-destruction of several types of laser goggles here. The description of the video includes a recommendation for his preferred brand of safety goggles.

The rest of his channel contains some fun ideas for what you can do with your high-powered laser besides hair removal.
posted by Hatashran at 6:40 AM on November 20 [3 favorites]

I have a Tria (which I also bought used), and you really don't need eye protection. You don't see anything at all when it activates, not even a flash.
posted by Faint of Butt at 7:22 AM on November 20

I have been using mine for awhile (and only just started to worry about this), but I do see a bright red flash each time it fires. I'm not entirely sure whether the red that I see is the laser or some additional light in the machine - I'm guessing it's an additional light since 810nm should be outside the range of what's visible to humans - but thinking about that (and that I can see that flash even when it's pressed against my skin) made me want to be more cautious just in case.

I do feel like sometimes my eyes feel weird after I've used it a bunch, but my eyes are kind of temperamental in general.
posted by needs more cowbell at 7:32 AM on November 20

810nm is at the edge of human visibility. Just because you can't see it doesn't mean you shouldn't protect against it. If you are seeing light from the output, doubly so.
posted by JoeZydeco at 7:32 AM on November 20

This is a video of what I see when I use it: https://streamable.com/6j5jt2
(Well, I remember it seeming brighter, but I took the video with my head turned away.)

For my own peace of mind I want to wear eye protection from now on, but I would love to find some that isn't $200. The brand that the youtuber mentioned above likes and tested, Eagle Pair, doesn't have any that are ideal for 810 nm, unfortunately - the glasses they have that include that in their range don't block super well at that part of the spectrum (per the chart here.)
posted by needs more cowbell at 8:03 AM on November 20

Yanuo IPL Laser Protection Goggles Safety Glasses 200nm-2000nm
$16 at Amazon
posted by Grok Lobster at 9:48 AM on November 20

I like that the one you listed has a OD vs wavelength chart... I'm estimating it has an OD of 1.8 @ 810 nm which means 1/(10^1.8)=.0158 => 1.58% of the 810 nm light gets through. Here is an explanation. BTW, OD5 and higher is what I need when working around ~30 W class 4 lasers (1090 & 10600 nm)
posted by tinker at 10:21 AM on November 20 [2 favorites]

Yanuo IPL Laser Protection Goggles Safety Glasses 200nm-2000nm
$16 at Amazon
posted by Grok Lobster

So am I missing something here, or are they opaque black plastic?
posted by Splunge at 11:30 AM on November 20 [1 favorite]

Have degree in optical physics and have been laser safety person for a few labs.

1. Reiterating that just because you can't see it doesn't mean that it can't cause damage. Wavelengths of light that can get through your eye have the lowest damage thresholds because the lens in your eye can focus them to a small spot increasing the amount of light per unit area. 810nm is at the very edge of what the human eye can detect and is particularly dangerous because you don't have a reflex to close because you can't see it well.

2. Lasers are broken in to different classes based on factors that include optical power, wavelength, and whether they are continuous or pulsed (how much energy is packed into the short pulse is what matters). Class 1 lasers are considered the safest class and and safe under all normal operating conditions. To cause damage you would need to use a lens / objective of sorts to focus the light strongly so that it could reach the damage threshold.

3. Not all lasers are classified correctly, particularly cheap / unregulated lasers. Green laser pointers are some of the worst offenders here as they are actually a 1064nm infrared laser diode which is doubled to 532nm. The crystal used to double the wavelength is not efficient and if not properly coated the 1064 leaks through and out into the world.

If the laser is from a trusted manufacturer you are fine to use without protection. If you still have concerns purchase a set of Laser Safety Goggles which has an OD > 2 in the 800nm - 820nm region.
posted by Quack at 6:40 PM on November 21 [1 favorite]

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