So I'm playing around ("Experimenting") with IR lasers and halfway through collimation, I suddenly think, "What if my goggles aren't working?"

So I remove my goggles, and place them between my laser and the detector target ( which converts IR lasers to visible green ).

And the green dot reduces in intensity slightly, but otherwise remains brightly lit, and I realise...



Note to self. First test to do with any new laser protection glasses - Check them against a real laser with the laser power meter.... :(

David.

I'm lost.

lasers are no joke. the answer to I think I want to buy a big china laser to play around with is a fat NO.

Up and at them!

Laser eye pro buyer beware

If I remember correctly they only protect against certain wavelengths and powers.

In just the last few/couple of weeks, I have been shopping for my first laser eye pro, thanks to the Perst 3 thread. And when looking at reviews on most of the ones Amazon sells there was a common theme.  A lot of good reviews, then a 0 or 1 star review. Read that one, and it's a guy that tested it and they don't work.... seems there's a lot of "fake" or just China bob may or may not work... laser eye pro out there. A couple guys told me, don't by from Amazon buy from a "reputable source"  so started looking at those, and wow $200 or more for a set of laser glasses, that may not even be rated as safety glasses (think shooting type safety glasses). So I ended up going the mil surplus way and got some NOS Revolution Sawflies. BUT those where only rated for specific Military lasers normally 1064nm. So I didn't know how they would do with my laser. Someone on hear also bought a set and tested them and shared. So I know they should work for me.

But to farther muddy the water. In my reading, some laser safety glass makers say that. A direct laser strike can change the chemical make up of the glasses, and that is part of how the glasses block the laser. And if the glasses have taken a direct hit, or have any discoloration. To discard the glasses. So I was just GREAT... how do I test them without destroying them... But I think my laser isn't enough power to worry about that, but I don't know. And someone was kind enough to already test what I am using so I feel good about it. BUT if he woudn't have done that. I would still be scratching my head and studying this topic. So I would love to learn some more about this topic.

Chinese goggles?

Yup, supplied by the same people who supplied the lasers if I recall correctly.

And yes, I got the correct goggles for the band I was working with, or at least, the goggles were rated for OD5 at the same wavelength and the band was very narrow - within 10nm... There should have been a BIG visible change in the light that got through the goggles to the test card.

You can't see IR lasers, but you can get tester material, which glows when the laser touches it. Important stuff to use when designing and testing lasers.  So I was just firing up a laser, and collimating it for the first time when I started to wonder if the goggles I had purchased really did what they said on the box. They were blurry as all heck, which made me think there wasn't much quality control in them, so I started to question whether they really blocked the laser or not. My first instinct was to trust them, since that was what they were supposed to do, but my doubts were building pretty quickly.

Note, at this point, I wasn't looking into the laser or anything and that's not something anyone should ever try, even with goggles for that wavelength. I was alongside it, working on it... Anyway, I figured that since I could see a visible indication of the laser on the card, then if I blocked the light with my goggles, the light should disappear, or at least drop to about 1/10000th of the intensity, which would be the same as disappearing for me. There was a change in the intensity, but maybe less than OD1 in total. These goggles were NOT blocking the light I thought they should block. Basically, they were fakes.

So since we only use these kind of lasers in NV, and doubtless some of the people on this forum are going to do the same from time to time, and will most likely buy goggles, I would recommend that the first test you do, after setting up, is check the goggles.... Had I had an accident, these goggles would have done absolutely nothing.

David.

There's been at least one documented case of Chinese glasses sold as being safe for viewing a solar eclipse that resulted in retinal damage. Wouldn't surprise me if many thousands of fakes were sold leading up to the 2017 eclipse. Glasses were very dark in the visible range but provided almost no attenuation in the NIR range. The first thing I did with the filter film I got for viewing the eclipse was to test if it actually provided adequate attenuation across the visible and NIR spectrum (it did).  As an FYI, most plastic sunglasses, even from reputable brands, provide negligible NIR attenuation (~90% transmission) even when providing ~90% attenuation in the visible range.

Last year I was in the market for laser safety glasses for one particular wavelength that isn't very common or popular nowadays. Lots of options from China that were promptly ignored. Not worth the risk or the second guessing even if a quick test suggests they're adequate. All my laser safety gear is from decently reputable brands and is tested to verify that it provides attenuation. Once one needs OD5, OD6, or OD7 attenuation, testing becomes a little bit more difficult. There's a leap of faith involved that if the glasses provide considerable attenuation at the wavelength of interest, they're probably legit. As David found out, the fakes provided almost no attenuation. If someone is making a fake, it's doubtful that any effort will be put in to provide any meaningful attenuation.

Just to make a note, some military goggles designed for range use specifically do not block 1064nm and would not have blocked the wavelength I was testing either. I have a list of which wavelengths they block, and I think it was primarily 808nm from memory, and a few others.

Others, which are used in the field, block a wide range of lasers, so it's important to check.

Here's some documentation on the more common laser-blocking filters supplied by the US military for field operations.

http://aunv.blackice.com.au/userfiles/david-Laser_filter_inserts_for_goggles_sun_wind_and_dust.pdf

This mentions some of the chemicals used to block lasers also.

I didn't know about the discoloration, but I think you'd be correct that a lower power laser wouldn't be able to do much. I don't think they are designed to deliberately burn through the blocking chemicals, which are usually soaked into the outer layer of the plastic, but I can imagine that if the heat was enough, it would certainly do so.

Some goggles reflect, much like the LIFs, by using dichroic mirrors that operate on the band to reject the desired wavelengths. Other use chemicals to absorb that band of the laser. Kind of like how a red filter won't ( shouldn't ) pass green light.

There's no reason that goggles should be expensive, and I suspect mine really are laser blocking goggles, but they are probably intended for another band... The problem is unscrupulous sellers who have no idea what their product does, so they lie about the capabilities of the goggles. Usually I test lasers under NODs, even if I use the daylight cover, and I guess I'll have to do the same once again. At least then I can see the beam and the spot clearly. I thought the seller I chose would have been better than I thought... I guessed wrong.

Lasers are like firearms. If treated correctly, they are pretty safe to use. But faulty safety equipment is still a problem.

Chinese safety equipment... *sigh*... I'm working on a validation project at the moment with respect to the stuff being sold in China, so I should have known better and tested my goggles long ago, rather than at the time when I needed to rely on them, and then I could have ordered some new ones and rejected these. Now I got to get some new goggles - :(

David.