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Laser goggles: Remaining visible light / How bright are high power lasers through safety goggles?

scide

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Hey guys,

looking for some advice for my new laser goggles...

I am planning to do a 465nm build for some movie replica prop (came here from the RPF :D).
As the color is important to match the movie and some power LEDs involved in the project, it seems like I am "stuck" with >1W laser diodes.
That considered, I settled on "safety first" and started looking for quality laser goggles, resulting in buying used "new" Univet goggles with OD 7 from 315-535nm as I wanted a pair with European CE certification...

After they arrived today, I had to test them with some cheap laser pointers I already had.
Now, I am slightly confused that I was able to see the low powered laser dots quite clearly through the googles.
When pointing the laser directly through the goggles (against the wall obviously :D) they blocked everything.

As both lasers (532nm >10mW and 405nm >5mW) were nowhere near the power output of the 465nm diodes I am after,
I am wondering if it normal that you an see this much light remaining or being converted into different wavelengths.

What can I expect when using a diode with ~2000mW?
Is it still comfortable (and safe) to watch the beam and dot from a near distance? E.g. when burning something?
Considering my laser is around 5mW and does produce a quite visible (yellowish) dot through the goggles,
I picture 1000-3500mW insanely bright even through the goggles...

The main purpose of the build is getting some cool video clips of the prop, though I want to be able to "use / play around" with it safely.

Looking forward to your thoughts.
Thanks, scide!


IMG_7348-privat.JPG IMG_7347-privat.JPG
 
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Well of course you had light passing through them, white light isn't monochromatic and your googles only block from UV (315nm) to Green (535nm) light. The remaining light that is passing through them is >535nm, as it shows on the OD and Transmittance graph.

Also, an introduction would be nice, along with a location. If you want us to help you, you have to do the bare minimum and read the Sticky Threads in the Welcome section.
 

scide

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Thanks for the reply, I was talking about the remaining light of the laser dot through the goggles...
Just edited the post for clarity.
 

Immo1282

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Hi - A reflected dot close up can still appear bright through laser goggles - but please don't be freaked out by diffuse reflections of the beam. They may be uncomfortably bright to look at - but will not damage your eyes. Eye damage from lasers is caused by direct hits, or reflected hits from shiny surfaces, mirrors, glass etc. This is because collimated beams from lasers are focused by the cornea and lens of your eyeball into a tiny focused spot on the retina (as this is what the eye's supposed to do so you can see things clearly and in focus). Diffuse beams are not focused into a tight spot so will be less dangerous overall.

A diffuse reflection is very similar to a bright lightbulb, or an LED etc. There's a lot of light energy - but because it is not collimated (i.e. the light spreads out in all directions), it is far less dangerous.

TL;DR - When you're talking about diffuse reflections, Bright does not mean it will cause eye damage. Most users wear laser goggles to prevent accidental direct exposure from accidental specular reflections. I can quite safely point my 1W lasers at a matte-white painted wall a few feet away and look unprotected into the spot. I dont, because there's a glass window halfway up the wall and if I drop my laser and it hits the glass, I could be blinded.

Edit: A rule of thumb - if it hurts, stop. It will not be comfortable (or particularly safe) to observe a focused dot very close up, so don't. A few feet away and on matte surfaces, and you should be fine. You've got good goggles though so continue to use them and you'll never have any issues!
 

scide

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Hey Nick, thanks for the excellent answer!
That was exactly the kind of clarification I needed to feel confident to move on with the project. :)
 

Immo1282

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I should clarify - looking too long at a really bright reflected spot (diffuse) can still cause temporary discomfort and floating shadows in your vision, same as if you looked at the sun for a second - but you're not going to instantly find a new hole in the back of your retina. Take care - but you need not worry, especially when looking through the goggles you purchased.

Also, you will need different goggles to safely observe any laser outside of their quoted frequency range - so if you decide you want to use a yellow or red laser you will need to get another pair :)
 

diachi

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You shouldn't be able to see much if any light from the beam/dot.

The only light you should really be able to see is light caused by fluorescence from the laser beam. I.e. pointing your green laser at something like an orange/yellow highlighter should make the dot clearly visible as they fluoresce brightly under green laser light.

Can you see any of the original colour? I.e. when looking at the 405nm laser through the goggles does the dot look violet?
 

scide

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You shouldn't be able to see much if any light from the beam/dot.

The only light you should really be able to see is light caused by fluorescence from the laser beam. I.e. pointing your green laser at something like an orange/yellow highlighter should make the dot clearly visible as they fluoresce brightly under green laser light.

Can you see any of the original colour? I.e. when looking at the 405nm laser through the goggles does the dot look violet?
No, non of the original color is visible. I just wasn't exception this much fluorescence from the laser beam.
But as 405nm is pretty near to UV it does make sense, that you see some fluorescence.
 

GSS

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Those glasses also have a VLT of 42% which will see the spot a bit better and still give you OD7 protection compared to the cheap ones which are usually around 30% and only protect to OD2 or OD3..
There are Eagle glasses that offer OD5 and OD6 protection with a VLT of 50%.
 
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diachi

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No, non of the original color is visible. I just wasn't exception this much fluorescence from the laser beam.
But as 405nm is pretty near to UV it does make sense, that you see some fluorescence.
Yeah, there's not much 405nm won't cause to fluoresce. It's especially clear when you have glasses blocking out the 405nm portion.
 




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