eye safety question

[sss]

hello
lets say somebody is using a powerful burning laser , burning stuff at his backyard .
if i'm located 100m away , but using binoculars and look directly at his laser dot burning stuff , should i wear safety goggles?

tnx

 

[Blaster]

No you should be totally fine at that distance. Even with binoculars .unless he points the laser at you. Then you would be in big trouble ,it would be safe but its not a good idea because you don't know if he is accidentally going to point it at you without knowing he is doing so and then through binoculars ... then its a disaster on your eyes ....as the question is worded looking at a spot with binoculars from a distance fine, but the spot must stay same place ,you must be able to guarantee this. cheers

 

[OrionBLF]

hello lets say somebody is using a powerful burning laser, burning stuff at his backyard. if i'm located 100m away, but using binoculars and look directly at his laser dot burning stuff, should i wear safety goggles? tnx

Blaster is right. I'm sure telescopejunkies forums also agree. The risk for retina injury from lasers is even higher with binos. Pls see : HERE "Never view a laser pointer using an optical instrument, such as binocular or a microscope." But the only people likely to persist despite that risk are either just not aware or the popo.

 

[sss]

Blaster is right. I'm sure telescopejunkies forums also agree. The risk for retina injury from lasers is even higher with binos. Pls see : HERE "Never view a laser pointer using an optical instrument, such as binocular or a microscope." But the only people likely to persist despite that risk are either just not aware or the popo.

blaster said i dont need protection .
you say "retina injury is even higher with binos"

so how do you say blaster is right ?

so , can , or cant i look at a powerfull laser dot from a distance , using binoculars/telescope - without safety glasses ? (the beam is not pointed towards me, just looking at the dot)

 

[hakzaw1]

I think whats being said here is that using binocs to look from a distance at a laser spot should not be any more dangerous BUT if you are looking directly at the laser with anything like binocs etc would be something to AVOID. A very general rule-- anytime you see after-images that do not go away fairly quick- you may have looked too long at a spot too bright- This is NOT a highly technical method of judging brightness but is a fairly good guideline.< this is according to ILDA LSO instructor Greg M.

I am kinda wondering why you dont apparently know this neighbor well enough to just ask them what they are doing??? Can you tell if there are using eye protection or not? Burning 'stuff' is one of the times when protection the eyes is a must-do. If you want to 'see the burn' look at your video after...

 

[cheejiayuan512]

Irrelevant question here: Is the pair of goggles on lucklaser.com safe enough to be used?

 

[Blaster]

Hakzaw1 is right as my first post is ....relax ....ie as said don't look at direct beam pointing at you with binoculars that's a really really bad move.suicide on eyes ....from distance non direct to eyes no problem .

 

[OrionBLF]

Thanks to Blaster and Hakzaw1 for the clarification pls. This is actually a dual scenario here. It starts as a bino user viewing a laser user's dot 100m away. But it could also end up with the laser being collimated into the bino user's eyes once the laser user changes direction and points it towards the bino user, whether intentionally or not. The bino user does not have control of where the laser user is pointing at. Small or big risk (depends on perspective) that has permanent consequences. So there is that risk to manage when using a laser or bino. It depends on what is one's personally acceptable standard of safety achieved through risk analysis and mitigation.

 

[sss]

its a bit confusing
as far as i know , its "bad" to look directly at the dot of a powerful laser and it can cause eye damage .
so what would be the difference between me aiming a powerful laser at the wall 1m away from me and looking at the dot , compared to me aiming the same laser at the wall 10m away , and looking at the dot via 10x bino ?

does the dot will be less bright (more safe) when looked through the bino ?
why?

 

[LSRFAQ]

Here is the issue simply put.

This is known as "Optically Aided Viewing" in the laser safety community.
It is one of the most dangerous things you can do. Especially with microscopes and binoculars.

This is a situation where measurements and calculations may need to be done for EVERY object the beam hits. This is strongly dependent on the source laser, and the material it is scattering or reflected off of.

So You have no control if the guy far away places a Reflective or Specular Mirror Like object in the beam. In which case you may just have focused a collimated beam into your retina. I realize a lot of things have to be aligned for this to happen, but well... ACCIDENTS HAPPEN.

The only way to know if this is safe is to take power measurements and do minute by minute control procedures and follow careful practices. This is ACTUALLY known as "QUALITY CONTROL PROCEDURES" in the industry.

Since you have NO CONTROL over the laser source, have no communications with the guy at the source, and have no idea if he has changed lasers, is using something different, or will aim directly at you, THEN THIS IS NEVER SAFE.

Since you have no control or prior arrangements with the source operator, the aided viewing is NOT safe, even if the power was low enough for it to be safe.

A recent case involved a observer in a police helicopter viewing a high power pointer beam with binoculars. He was hunting the source of a illumination complaint. The person being hunted turned the pointer onto the chopper. He was injured. Get the idea? This is dangerous.

Can I make this safe? Yes, if I have quality control procedures in place, have a co-operative source, and have measuring equipment. Then I can do the math. Until then, you should stop viewing what the fellow is doing.

You simply don't know if the scattering down range will be Specular, Diffuse, Lambertian, Cosine or Reflective. You have no way of controlling that. So there is no way to calculate what you may view under uncontrolled conditions, even if you knew the power, wavelength, spot size, and the divergence of the scattered or un-scattered light.

I realize the source may or may not be a Class IIIB or Class IV device. But since you do not KNOW what is going to happen down range, and have no control over events, the answer is NO WAY.

The ~50 mm area of the binoculars just increased the possible energy collection by a factor of 50/7 = ~8 times alone, per eye. Your eye has a pupil that averages 7 mm. That is before even the focusing process. Since I don't know what spot size, diameter and divergence is incoming, I can't calculate the increased power density at the retina but it is going to be far, far more then unaided viewing.

Yes, at some distance it may be safe under very carefully controlled conditions.

SO DON'T DO IT. Especially if he does not know your viewing him. It might be safe now, but what about the 1 IN 10,000 or so chance that he turns and aims at you?

Go make friends.

Steve

 

[OrionBLF]

Never View Lasers With Binoculars Or Telescopes.

Spot on! This post should be made into a sticky. I've searched LPF and no exact advice came up here on the potential danger of viewing lasers with optics. But only this optic company 'LASER GENETICS' did :

LASER LIGHT - DO NOT STARE INTO BEAM OR VIEW DIRECTLY WITH OPTICAL INSTRUMENTS (BINOCULARS OR TELESCOPES) CLASS 2M LASER PRODUCT.

"Eye injury is theoretically possible if the laser locator’s source is aimed at people using telescopes, rifle scopes, spotting scopes, binoculars, cameras or any other optical light gathering instruments. Do not view laser directly with optical instruments such as binoculars, telescopes etc. These items collect more light than your bare eye if they look directly into the beam or a bright reflection."

Night Vision, Green Lasers for Law Enforcement | Military | EMT | Laser Genetics

Meanwhile I found other posts on eye safety in LPF dating from 2008 :
02-17-2008 http://laserpointerforums.com/f53/lasers-eyes-38337.html
08-17-2009 http://laserpointerforums.com/f53/looking-laser-dot-42816.html
09-07-2009 http://laserpointerforums.com/f53/laser-dot-danger-43384.html
06-18-2010 http://laserpointerforums.com/f53/general-safety-help-51877.html
06-18-2010 http://laserpointerforums.com/f44/safe-too-view-dot-lasers-51871.html
03-11-2011 http://laserpointerforums.com/f44/clarify-dot-viewing-fear-61527.html
05-24-2011 http://laserpointerforums.com/f53/first-high-power-laser-63742.html
02-01-2012 http://laserpointerforums.com/f44/safe-ways-look-my-beam-71135.html
07-05-2012 http://laserpointerforums.com/f53/get-some-safety-goggles-now-75799.html (*)
05-04-2013 http://laserpointerforums.com/f53/when-when-not-wear-goggles-82129.html
09-02-2013 http://laserpointerforums.com/f45/dot-reflection-dangers-85052.html

Lastly, also never look directly into any laser beam because distance alone isn't a guarantee due to some lasers' ability to sustain a tightly focused beam for miles. Apart from the obvious impact of direct viewing, there's the possibility of transient visual effects from indirect viewing. These effects are commonly called glare, flash-blindness and after-image. While there are variations in terminology, they all refer to temporary vision disruption lasting a few seconds or minutes. While reflections from shiny surfaces like glass and metal (specular) can be just as impactful as direct beams, viewing the reflection from a diffused surface like a white wall or paper may be relatively safer but the glare may still be unbearable for higher powered lasers. This is similar to over-exposure by camera flashes, strobe bulbs, welding sparks, vehicle headlights and staring at sun-rises/sets. The long term effects of this cannot be overestimated. That is the whole idea for using safety goggles when viewing bright stuff.
Laser Pointer Safety - LIA

 

[zyxwv99]

If you at the dot with binoculars, the magnification will attenuate the brightness. If the diameter looks twice as big, then the apparent area of the dot would be four times as great, in which case the intensity per square mm of retina would be 1/4 as great.

However, I am still concerned about your inability to control what direction the laser is pointing.

 

[Bionic-Badger]

If you at the dot with binoculars, the magnification will attenuate the brightness. If the diameter looks twice as big, then the apparent area of the dot would be four times as great, in which case the intensity per square mm of retina would be 1/4 as great.

However, I am still concerned about your inability to control what direction the laser is pointing.

Holy shit! Where in hell did you get this idea? This is just plain wrong. Are you looking through your binoculars backwards or something?

Think about it: does a magnifying lens attenuate the power of the sun when it concentrates the output on a single point? That's effectively what your binoculars are doing with your eyes, and why whatever you're looking at looks bigger.

This is also why it is dangerous to use magnification optics when viewing optical radiation sources. What may be "safe" at a distance is now enhanced and magnified. You're effectively collecting far more light than you would just viewing directly -- and this changes all the assumptions you are making about eye safety.

 

[zyxwv99]

I was going to mention that I forgot to take into account light-gathering ability. All other factors being equal, higher magnification means less brightness as I described. However, telescopes and binoculars have pretty big primary lenses / mirrors (compared with the human eye) which produce the opposite effect.

 

[Bionic-Badger]

Your statements are entirely contradictory, and your assertions are wrong. "All other factors being equal" meaning less brightness, only to follow up by stating that telescopes/binoculars with large primary lenses have the opposite effect? So what is it then?

No. You need to read up on how optics work. The point of magnification is to gather more light from a source and concentrate it on a destination. Even with microscopes, the perceived reduction in brightness is only because you're concentrating on a very small source, with very little light to begin with.

Brightness, as a function of power density, is always increased with magnification because now you're reducing the overall area that the same amount of light is being concentrated on. This is why optics are dangerous with lasers/sun/bright lights. You're increasing the power density in your eyes, which can cause damage.

 

[zyxwv99]

I think we have two different issues here. When I first posted to this thread, I mentioned a fundamental principle of optics: higher magnification reduces brightness by the square of the magnification diameter. As soon as I logged off I realized that I had forgotten something, a second principle of optics about light-gathering ability.

The next time I arrived at this thread, I added the second principle which I had forgotten to mention earlier. While cheap telescopes and binoculars merely magnify, making things look dimmer, the more expensive ones have bigger objective lenses, which increase light-gathering ability. In binoculars and small amateur telescopes, this is done to compensate for the reduced brightness due to magnification.

So I apologize for not having mentioned the second principle in the first post along with the first principle. These two principles do in fact produce conflicting results. That's usually how engineering works: you have an invention that does one thing but produces an unwanted side-effect, so you modify the design to compensate for the side-effect.