Dot reflection dangers

[Joshuan]

Hello guys,

I wanted to know at what power (mW) in green lasers does looking at the dot on a wall can cause permanent damage?

I know that we can't look directly at the dot at powers around 1W, but my doubt is when that starts to be a hazard, of staring at the dot reflected off a matte wall at a relatively close range?

Thanks for the information, I appreciate it.

 

[hwang21]

Dot viewing will cause damage at power levels 500mW and above.

For a 1W 445nm laser aimed at a white wall, any closer than 3 feet will cause damage

 

[Blaster]

The above is true ,of course green being much more visible to the eyes color sensitivity about 4% for blue to 88% for a green ,the green does pose a higher risk ,when in any doubt googles every time

 

[Joshuan]

So a green below 500mW should be safe for matte wall reflections at close range?

 

[Joshuan]

Thank you for the replies by the way, much appreciated.

 

[Blaster]

If by close you mean less than a meter i would use googles over a meter on same non reflect matt wall probably OK bu't never underestimate the power of any laser over 500mW on reflection on a Matt wall maybe 405 nm would be OK

 

[Joshuan]

One of them is only low power at 50mW so I guess that one would be more than safe used responsibly indoors.

 

[Shakenawake]

I personally think even my ~500mW 405nm has a really bright dot. I suppose It may be slightly over 500mW, but these are your eyes. remember, 500mW of 405nm is just as bright as 500mW of 532nm, just not to our eyes. just because we don't percieve a particular wavelength as well, doesn't mean photons are not hitting your retina. a better example is IR lasers.

 

[shokkunlasers]

The above is true ,of course green being much more visible to the eyes color sensitivity about 4% for blue to 88% for a green ,the green does pose a higher risk ,when in any doubt googles every time

I think its not so easy to say :thinking:
When you are speaking of shock blindness and after images you right the brighter its perceived by our eyes the heavier those effects are
BUT
Most permanent retina damage by lasers is caused by heating the retina to temperatures above 44 degrees C and the power causes this temperature change not the frequency the light has. So we could say every frequency(wavelenght) is equaly dangerous at reflection from a white wall?
No because:
( I didnt mentioned the white wall her its more general--->)

1.Not all wavelenghts are absorbed by our retina in the same percentage. Our Retina is red ( caused by blood vessels and no skin ) so we know red objects absorb deep blue really good and a bit better than green

2.You already said that green is better perceived by our eyes so it seems brighter to us and that causes the iris to close more so and less light can enter our eyes or we blink so if you are using a laser that doesnt look so bright but has got the same or more power (extrem cases IR Lasers) your retina will be exposed to more power and the blink reflexx maybe is slower or doesnt work

So I would suppose the green laser to be more dangerous for short term effects and the blue more dangerous for long term/permanent damage

Vinz

 

[Deleted member 17304]

The above is true ,of course green being much more visible to the eyes color sensitivity about 4% for blue to 88% for a green ,the green does pose a higher risk ,when in any doubt googles every time

Brightness has nothing to do with 500mW of power. 500mW is 500mW. 405nm, 445nm, 532nm or 650nm. It's just as bad for any wavelength really...

 

[Antharak]

Basically there is no safe level of viewing a laser of any power without goggles. You have to remember that your retinas are electro/chemical and if you overload them, they will sustain degrading. The blue wavelengths, 445nm, 450nm, are the worst as the cone takes longer to reset after being hit by the photon and will quickly be overloaded. If you see spots after viewing a dot on the wall you are damaging your eyes. Don't risk it, be safe and don't try to put a value on what your eyes can take. And if your young remember your eyes have a long way to go.

 

[Blaster]

Brightness has nothing to do with 500mW of power. 500mW is 500mW. 405nm, 445nm, 532nm or 650nm. It's just as bad for any wavelength really...

I'm talking about flash blindness short term a green will do that faster than any other color well a yellow ish 565nm is about 100% compared to greens 88 %
Eye brightness ,all lasers will cause same damage given a direct hit at same power, its just a blue or a violet will take a bit longer for the eye to close down the iris and blink ,so short term green worse ,long term blue or violet or easy by far an IR laser .will cause more damage as we all know we are talking fractions of a second that can make a big difference ..moral of story if in any doubt googles wear them as i said before in previous post. If your still looking at a green of a matte wall at 500mw close up well you need your head read ,and any other color laser

 

[shokkunlasers]

Mhh I think nobody reads my whole post

 

[hwang21]

Either case, as long as you can guarantee that the laser is diffused and no reflection takes place, you can view the dot relatively close range as long as the laser is under 500mW. (but even at 500mW that is a freakishly bright dot)

 

[Bionic-Badger]

Um, guys, that 500mW is no magic number, even if it is used to designate between Class 3b and Class 4 lasers. The meaningful distinction between a Class 3b and Class 4 laser designation is that the Class 4 is an environmental hazard (e.g. fire), whereas anything Class 3b and above is an eye hazard, but generally not going to burn things without trying hard.

That "trying hard" carries meaning too. You can produce power densities rivaling Class 4 lasers if you use a magnifying glass with Class 3b or possibly Class 3r lasers. Everyone knows that people can burn paper and matches by focusing a weaker laser down. That 500mW is just a ball-park power figure for a laser beam of an average diameter (3mm? I don't know). Likewise, if you spread out a Class 4 laser over a wide area, it may not actually be harmful for your eyes.

To summarize: don't think you're "safe" viewing a dot from a 30mW anymore than 500mW. The latter has greater potential to cause damage, but they're both not eye-safe in different conditions. You should also wear goggles for the incidents you don't plan for; that's what they're really there to protect you against. What if you bump the table and the laser reflects off the shiny surface of your desk or something? Even a reflection off a diffuse surface may hurt your eyes, or at least irritate them. You should enjoy viewing your lasers, not squint and look away because you're uncomfortable.

 

[hwang21]

Good point^ but for the sake of a ballpark estimate, aiming a laser over 500mW at a white wall and then looking at the dot up close will cause damage. Obviously there are many factors at play, but just to keep things simple