Sunglasses for 15-50 mW lasers?

As I understand, sunglasses can have an absorptance anywhere between 3:1 and 10:1, so I'm thinking if this is evenly distributed across the spectrum you should be able to get adequate protection with sunglasses while using lasers with powers between 3 x 5mW and 10 x 5mW (depending on the quality of your glasses), right?

And even if there's some IR being emitted, that shouldn't be a problem unless you're looking directly into the laser beam like an idiot, otherwise the IR gets scattered/absorbed enough to be harmless, right?

(Oh and before anyone jumps to the oft-repeated warning about the Evil and Destructive Pupil Dilation and Its Effects of Total Devastation, let me point out that it's still 5mW of power incident on the retina I'm talking about here, dilation or no dilation. If anything, spreading out those 5mW over a wider area of your retina should reduce the damage potential, not increase it.)

You cant use sunglasses.

I don't suppose you care to give any explanations with that.

From: Laser FAQ - Laser Wiki

Can I use sunglasses or Welding Goggles for at least some laser protection?

No. This is a common misconception. All sunglasses/welding masks will do is make your pupils dilate, which makes the potential for damage much greater.

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Laser safety goggles actually stop certain wavelengths of light from passing through. It's pretty incredible the first time you see them work. Sun glasses aren't going to do anything unfortunately.

JohnTheRipper said:

All sunglasses/welding masks will do is make your pupils dilate, which makes the potential for damage much greater.

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In fact I don't think it is all they do. In addition to making your pupils dilate (which I have explained above is not a concern when you're talking about a constant safe level of incoming power), they also absorb 33% to 90% of visible light, which could very well include the radiation of your laser. The above wiki quote is not an explanation, it's just a bare assertion without any arguments and it seems contrary to physical facts.

Sun glasses aren't going to do anything unfortunately.

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See above. WHY do you think they don't do anything? As long as they have some broad-spectrum absorptance for visible light, they should partially absorb the radiation from any laser emitting on a visible frequency. That's what physics says should happen. Why are you saying otherwise?

Well, sunglasses would do something, just not very much. IF they absorb evenly over the entire spectrum at, for example, 80%, in theory this would increase the maximum exposure from 5mW to 25 mW.

There is a big downside to this though: As people explained they make your pupils dilate, allowing more light into they eye. Normally, the maximum pupil diameter of about 7mm is assumed in safety calculations. In real situations your pupils tend to be dilated 2 to 4 mm, adding another margin of safety. This extra margin will be lost completely with sunglasses, which is why most people will advise against using them with lasers.

Another issue is that sunglasses arent rated to sustain any amount of light going through them. The dye could bleach out under the intesity of laser light, leaving you with zero protection but dilated pupils.

Benm said:

As people explained they make your pupils dilate, allowing more light into they eye.

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But then as I explained, there isn't "more light" available to do any extra damage, since (using your example) we're still talking about 25 mW being reduced to 5 mW by an 80% absorptance. Pupil dilation doesn't matter, you're still only getting 5 mW into your eye. You'll blink and you'll be saved.

Another issue is that sunglasses arent rated to sustain any amount of light going through them. The dye could bleach out under the intesity of laser light, leaving you with zero protection but dilated pupils.

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Interesting hypothesis, but I'm not sure that would work in real-world use. I wasn't suggesting anyone should use sunglasses to stare directly into the laser beam for a long time, I was only talking about using them for protection from stray reflections. I don't think the occasional stray reflection can really bleach your sunglasses at the kinds of power levels we're talking about here (unless you've got some really really poorly made sunglasses), but even if that happens, there'll be enough time between those accidental reflections for you to begin to notice that your lenses aren't homogenously absorbant across their whole surface anymore.

donjoe said:

I don't suppose you care to give any explanations with that.

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Well, I once tried if my 5mw red laser passed trough sunglasses. Well it did, pretty well.

But sunglasses may reduce the IR power of the laser, im not sure

You have two eyes anyway-- if you damage one.... N/P.... right??
why waste good money -- just keep your favorite eye closed.

TuhOz said:

Well, I once tried if my 5mw red laser passed trough sunglasses. Well it did, pretty well.

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"Pretty well"? Even with glasses that absorb 80% of incident light, it still means you will see 1mW of your 5mW passing through, which will produce a clearly visible hotspot even in daylight, as many class II laser pointers do. But making the laser completely invisible was never the point for me. The point was that with 80% absorption you could very well make a 25mW laser harmless/tolerable without making a hole in your wallet by getting expensive laser protection eyewear. (You just have to make sure somehow that your glasses actually have the absorptance you need before you rely on them for protection, plus you may also want to watch out for any bleaching they might suffer over time, depending on how aggressively you'll be irradiating them.)

But sunglasses may reduce the IR power of the laser, im not sure

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Oh, I very much doubt that. If they're designed to absorb anything outside the visible spectrum, they'll most likely be designed to absorb UV, not IR, as UV is the biggest long-term destroyer of human retinas , hence the frequency band most people are trying to get protection from by wearing sunglasses.

So why would you rather use sunglasses? Sorry if I missed it.

he just wants to argue OP do me a favor buy some laser safety glasses and buy some sunglasses and buy a 1W laser

now put on the sunglasses and shine the laser in your eye
but what happened now your blind in that eye

now put on laser safety glasses and point the laser in your eye what? no damage was done.

stop arguing and except that you are wrong all the answers that have been given have been valid

PS don't actually try that you will go blind

Sunglasses probably do not block IR. The problem with sunglasses is that they are not real laser safety glasses, certified laser safety eyewear complies to a long list of standards. Sunglasses just like the fake chinese laser safety eyewear is a bet, you never know what you have. You can be sure that sunglasses won't help much, maybe a factor 2 (or not), the rest is unkown (more like everything). If you consider 5mW safe (which I don't) you may push it to 10mW (that's taking the chance that it attenuates a factor 2 under all conditions), but even with sunglasses I still consider that a risk. Don't be cheap on safety.

Ghostchrome said:

So why would you rather use sunglasses? Sorry if I missed it.

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Cheaper, like I said.

bennett326 said:

stop arguing and except that you are wrong all the answers that have been given have been valid

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Typical troll answer. If you don't know what physics is or what math is or don't care about arguing for your assertions (instead of throwing them around like rocks), by all means feel free to ignore this topic.

Bluefan said:

The problem with sunglasses is that they are not real laser safety glasses, certified laser safety eyewear complies to a long list of standards.

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Let's be serious here, that list isn't really that long. The most important aspect of this is that official laser safety requirements are meant to deal with the absolute worst-case scenario, where 1. you're being a total idiot and shining the laser directly into your eye for 10 seconds or more or 2. a criminal has you tied to a chair and just happens to decide to shine the laser directly into your eye for 10 seconds or more. ) Well, as it happens, I never addressed this topic to the idiots out there, nor was I suggesting that sunglasses could offer adequate protection against criminal assault.
As long as you're being at least semi-rational in the use of your laser and in the expectations you have from your eyewear, sunglasses should be fine for certain power levels.

Sunglasses just like the fake chinese laser safety eyewear is a bet, you never know what you have.

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Never said you did. You have to measure the real absorptance of your sunglasses before relying on them for any kind of protection, that much is clear.

You can be sure that sunglasses won't help much, maybe a factor 2 (or not)

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No I don't think I can be sure of this. Quality sunglasses can reach an absorption power of 5:1 (or 80%). A pair of these could enable you to play around with a 25mW laser without worry (and without buying unnecessarily expensive OD2+ safety glasses or whatever).

If you consider 5mW safe (which I don't)

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Too bad for you. Reports of the damage potential of 5mW have been greatly exaggerated. See here: Laser safety - Wikipedia, the free encyclopedia

you may push it to 10mW (that's taking the chance

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Nope, I never plan to take that chance. I'm not the kind of person who thinks the limits of physics are something meant to be "pushed" (i.e. I don't believe in magic).

Don't be cheap on safety.

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As with all types of safety, the single most important contribution you can make is being smart about what you're doing, paying attention to your every move, planning it in advance etc. No protective material or device in the world can save you from human stupidity. If you're not wearing 100% bullet-proof protection but are being smart, you can get away with certain otherwise risky behaviours, but if you're wearing protection and being a total jackass, you have every chance of hurting yourself and/or others despite the protection.

This topic is not meant as a recommendation for anyone to ignore proper safety glasses if they're going to use a laser with a power output higher than 50 mW. This topic is meant to suggest that smart people who know exactly what they're doing with their <50mW laser could get adequate eye protection without buying safety glasses that cost more than the laser itself, if (and only if) they can find quality sunglasses that absorb enough light to prevent anything above 5mW from hitting their eyes. This topic is not meant for stupid people, it's meant for smart people.

If you're always insisting that people rely completely on officially approved passive protection, you're essentially cultivating stupidity and you risk doing more harm than good. The same thing happened when sunscreen manufacturers told the population that sunscreen lotions kept you completely safe from solar radiation: people used sunscreen, relied on it completely, way beyond its capacity to protect, and they ended up getting more skin cancer instead of less: they thought just because they were using adequate and officially approved passive protection they didn't have to be smart anymore.

Typical troll no
Sick of this question being asked yes
People have already explained
it sunglasses have on average od of 1 mabye 2 and that is simply not enough safety glasses on the other hand have anywhere from 5-7 OD
And that's enough to protect

Bye troll