How does a laser blind you?

I have been wondering, how does a laser blind you, and is 5MW really the highest it can be to not blind you? For example, if you got a 7-10MW laser flashed in your eye, would it really be that bad? Is one more MW really enough to cause eye damage?

Introduce yourself in the Welcome section and tell us a little about yourself please.

How? Very easily... MW = mega watt, mW = mili watt

We have had a lot of trolling lately on this kind of subject, I'd like to see the gentleman give a proper introduction, in fact, require this of everyone before they can make a single post in any section.

Radim said:

How? Very easily... MW = mega watt, mW = mili watt

Click to expand...

I meant mW. Not MW, also I will make my introduction soon, I have to go for a half hour to do something.

G1BFTW said:

I have been wondering, how does a laser blind you, and is 5MW really the highest it can be to not blind you? For example, if you got a 7-10MW laser flashed in your eye, would it really be that bad? Is one more MW really enough to cause eye damage?

Click to expand...

A laser can blind you by damaging your eyes retinas.

Google the subject or use LPF's search function at bottom of page.

Read this thread: http://laserpointerforums.com/f53/irreversible-vision-damage-don-t-turn-blind-eye-laser-hazards-71299.html

G1BFTW said:

I meant mW. Not MW, also I will make my introduction soon, I have to go for a half hour to do something.

Click to expand...

Of course. MW laser is quite rare... Good to know you are not troll.

To your question - laser is coherent (waves in phase), monochromatic (narrow spectrum) and with very low divergence (little spreading with distance from source). That means the energy is (almost) the same at output as in the distance, it can be focused preceisly and that's what happens in the eye during hit - focuses on retina and extreme energy just burns it. Quick answer, not complete.

Different wavelengths can burn different parts of your eye. Visible wavelengths are able to pass through your pupil and are able to burn the back of your eye and damage your retina. Your pupil acts like a lens focuses it into a spot, giving the laser the power density needed to burn the retina despite the relatively low powers. A 1mW difference is enough to increase the power density to a point of burning your sensitive retinas. Lasers can damage your retinas, your optical nerves, your cornea etc. With extreme cases people have mentioned hearing a popping sound when a high powered laser hit their eye. That is a sound no-one wants to hear. Lasers can cause anything from temporary vision loss to permanent damage to your eyesight.
So if their is any immature kids or ignorant trolls reading this, laser eye damage is incredibly serious and is not a joking matter.

Edit: Was writing my post at the same time Encap. You linked to the exact thread I got my image from.

This pic explains it greatly. Just to add there is also a blue light hazard - long term cumulative effects from difused and glow radiation of blue - violet region.

Yes blue-uv part of the spectrum is increasingly hazardous but for slightly different reasons.

CurtisOliver said:

Different wavelengths can burn different parts of your eye. Visible wavelengths are able to pass through your pupil and are able to burn the back of your eye and damage your retina. Your pupil acts like a lens focuses it into a spot, giving the laser the power density needed to burn the retina despite the relatively low powers. A 1mW difference is enough to increase the power density to a point of burning your sensitive retinas. Lasers can damage your retinas, your optical nerves, your cornea etc. With extreme cases people have mentioned hearing a popping sound when a high powered laser hit their eye. That is a sound no-one wants to hear. Lasers can cause anything from temporary vision loss to permanent damage to your eyesight.
So if their is any immature kids or ignorant trolls reading this, laser eye damage is incredibly serious and is not a joking matter.

Edit: Was writing my post at the same time Encap. You linked to the exact thread I got my image from.

Click to expand...

What would you say is the most dangerous color laser? Also can you see a laser beam when you have laser protective goggles on. Also what is the maxium mW/W(age) you can look at the beam (not coming in contact with your eye) without goggles on and not causing any eye damage? I am trying to be safe here, as I am of course a begginer.

G1BFTW said:

What would you say is the most dangerous color laser? Also can you see a laser beam when you have laser protective goggles on. Also what is the maxium mW/W(age) you can look at the beam (not coming in contact with your eye) without goggles on and not causing any eye damage? I am trying to be safe here, as I am of course a begginer.

Click to expand...

Any laser of high power is dangerous. But I would say invisible lasers (typicaly IR) are the most as you cannot see them. However it is more complicated to say which color/wavelength is most dangerous. In what terms? Green light is very visible, might distract or flashblind pilots more than violet, violet is very dim but "burns more easily due higher energy of photons" (not exact answer - see diachi's reaction with correction below - sorry I'm tired from long day in work and as not being conistent, better to go to bed ), also blue is dangerous as the peak of blue light hazard is there. Red as well as violet is dim, so blink reflex is not that efficient, but it still has enough power and goes far - as not diffused that much as violet. Also different wavelenghts are lilely to use different technology - diodes have higher powers, but also higher divergence than DPSS lasers...
As you can see no simple answer.

I always recommend to those new in the hobby to get safety glasses first and than something like 100 mW green laser - 532 nm with IR filter - that means of higher quality. Good to start with, not that expensive, nice beam, little bit of burning and baloon popping as well but mainly a lot of fun and after gaining experience you might go for higher powers.

A very important fact with lasers, it is not the brightness that blinds you, it is the power.
As for danger levels of certain laser powers please look at this. http://www.lasersafetyfacts.com/resources/Spreadsheet---laser-classes.pdf
This is what every laserist needs to know when owning lasers IMO.
It is good to see you wanting to learn laser safety :beer:

G1BFTW said:

What would you say is the most dangerous color laser? Also can you see a laser beam when you have laser protective goggles on. Also what is the maxium mW/W(age) you can look at the beam (not coming in contact with your eye) without goggles on and not causing any eye damage? I am trying to be safe here, as I am of course a begginer.

Click to expand...

I'd say the danger from IR is the highest, just because there's no blink reflex to protect you and no way to see the beam with your own eyes until it's too late.

You can't see a beam with safety glasses on, if you could then they wouldn't be working... You may be able to see a significantly dimmed spot, but that's it.

Safe power for looking at just the beam traveling through the air? It'd take incredible amounts of power for that to become unsafe.

Radim said:

Any laser of high power is dangerous. But I would say invisible lasers (typicaly IR) are the most as you cannot see them. However it is more complicated to say which color/wavelength is most dangerous. In what terms? Green light is very visible, might distract or flashblind pilots more than violet, violet is very dim but burns more easily due higher energy of photons, also blue is dangerous as the peak of blue light hazard is there. Red as well as violet is dim, so blink reflex is not that efficient, but it still has enough power and goes far - as not diffused that much as violet. Also different wavelenghts are lilely to use different technology - diodes have higher powers, but also higher divergence than DPSS lasers...
As you can see no simple answer.

I always recommend to those new in the hobby to get safety glasses first and than something like 100 mW green laser - 532 nm with IR filter - that means of higher quality. Good to start with, not that expensive, nice beam, little bit of burning and baloon popping as well but mainly a lot of fun and after gaining experience you might go for higher powers.

Click to expand...

FYI, violet doesn't burn better due to the photons being a higher energy than those of longer wavelengths. It burns better because short wavelengths (i.e. violet) can be focused to a smaller spot. Not to mention the 405nm diodes we have available to us are still single mode at high powers, so the beam specs are considerably better. 405nm is also absorbed better than a lot of other wavelengths, another plus for burning.

A 1W 405nm produces the same energy as a 1W 650nm, it just takes less photons to do so because each photon contains more energy.

I am not a doctor so always get a professional opinion.

However you should be aware that there is a network of blood vessels called the Bruch's membrane behind the retina that is the network of blood vessels that nourish the retina, this can bleed into the viscous humor if the retina is punctured thus obstructing all vision and possibly causing tissue death, it's not just a small dead spot, 1 laser strike can ruin an eye, the fovea where all our detail vision is generated is tiny, also the optic nerve can be damaged resulting in permanent blindness.

A damaged area can seem to be mostly ok but progress into a rupture in time so don't mess around, if you are hit in the eye get an eye exam right away, an eye Dr. with a special laser can seal off those potential leaks and save your sight, but nothing is guaranteed, better to avoid injury to start with, always wear those laser safety glasses designed to attenuate the wavelength you are working with.

diachi said:

I'd say the danger from IR is the highest, just because there's no blink reflex to protect you and no way to see the beam with your own eyes until it's too late.

You can't see a beam with safety glasses on, if you could then they wouldn't be working... You may be able to see a significantly dimmed spot, but that's it.

Safe power for looking at just the beam traveling through the air? It'd take incredible amounts of power for that to become unsafe.








FYI, violet doesn't burn better due to the photons being a higher energy than those of longer wavelengths. It burns better because short wavelengths (i.e. violet) can be focused to a smaller spot. Not to mention the 405nm diodes we have available to us are still single mode at high powers, so the beam specs are considerably better. 405nm is also absorbed better than a lot of other wavelengths, another plus for burning.

A 1W 405nm produces the same energy as a 1W 650nm, it just takes less photons to do so because each photon contains more energy.

Click to expand...

Shorter wavelength = higher energy of single photon, that's what I meaned. Error with my consistency in the comparsion. But you are absolutely right with your explanation - more suitable to OP as answer. Thanks.