Reflection from window 200mw red

[juust0_]

So, i was playing with my red 200mw dilda and i pointed it under my desk to see how it lights the floor. Then i pointed it at the wall to see how bright it seems when my eyes were closed. I accidentaly pointed it to window and the beam went directly to my eye, but my eye was closed. So, could this make any serious damage to my eye cos my eye wasnt even open? I didnt use any goggles?

 

[potatorage]

I don't think it's that dangerous to not use goggles with a 200mW dilda, but it's your eyes : If your eye was closed, then no serious damage was done.

 

[Benm]

Good your eye was closed. Window glass will reflect up to about 4% of light at a normal angle (and more at lower angles!), which makes 8 mW from your 200. I doubt it'd easily do permanent damage, but it is over whats generally accepted as safe.

 

[juust0_]

Thanks for your replies. Maybe i just overreacted a bit, next time ill use goggles

 

[treb76]

Good your eye was closed. Window glass will reflect up to about 4% of light at a normal angle (and more at lower angles!), which makes 8 mW from your 200. I doubt it'd easily do permanent damage, but it is over whats generally accepted as safe.

So the amount of light reflected off of a surface depends on the angle you shoot it?..?

 

[kendon]

So the amount of light reflected off of a surface depends on the angle you shoot it?..?

yes it does. take a laser and shine it through a flat piece of glas. first in a 90 degree angle, most will pass the glass. now slowly lower the angle, at a certain point (i'd say at roughly 10 degrees) you have yourself a nice beamsplitter.

question here is, what is a "normal" angle?

 

[Deleted member 8382]

[quote author=Benm link=1233785235/0#2 date=1233792445]Good your eye was closed. Window glass will reflect up to about 4% of light at a normal angle (and more at lower angles!), which makes 8 mW from your 200. I doubt it'd easily do permanent damage, but it is over whats generally accepted as safe.

So the amount of light reflected off of a surface depends on the angle you shoot it?..?[/quote]

Yes. plus the reflected light is polarized I think.

 

[usakicksass]

I was at a party showing some people my 200mw red IgorT laser. I shined it at a bathroom mirror and lined up the beam right back at the aperture of the laser and........COD! Catastrophic Optical Damage. The little mirrors in the diode melted. I had a very weak red LED. Moral is dont worry about your eyes, what about the diode!! Just joking about the eyes. Safety first.

 

[lasersbee]

I was at a party showing some people my 200mw red IgorT laser. I shined it at a bathroom mirror and lined up the beam right back at the aperture of the laser and........COD! Catastrophic Optical Damage. The little mirrors in the diode melted. I had a very weak red LED. Moral is dont worry about your eyes, what about the diode!! Just joking about the eyes. Safety first.

Which little mirrors are you referring to... :-?
How far away from the mirror were you with the laser.... :-?

Jerry

 

[laserwanabe]

you should consider yourself lucky.


And what are you doing shining a burning laser around, you have matches to light and balloons to pop! [smiley=evil.gif] [smiley=evil.gif] [smiley=evil.gif]

 

[rocketparrotlet]

Since your eyes were closed, you did not take any damage.

Reflections from glass can often be up to 10%. Not something you want in your eye, but you're lucky you had it closed.

-Mark

 

[919jack]

question here is, what is a "normal" angle?

In mathematics "normal" means "at a 90 degree angle to the surface". In other words straight at the glass or mirror, like usakicksass described above. It might not be typical, but straight-on is geometrically normal.

 

[Benm]

[quote author=usakicksass link=1233785235/0#7 date=1234057044]I was at a party showing some people my 200mw red IgorT laser. I shined it at a bathroom mirror and lined up the beam right back at the aperture of the laser and........COD! Catastrophic Optical Damage. The little mirrors in the diode melted. I had a very weak red LED. Moral is dont worry about your eyes, what about the diode!! Just joking about the eyes. Safety first.

Which little mirrors are you referring to... :-?
[/quote]

They arent seperate mirrors, but reflective faces of the laser diode chip that make up the ends of the lasting cavity. When you shine the beam right back into a laser, these can easily fail because they have to pass much more light than under normal operation.

As for the reflection from glass: the 4% figure is for a normal angle (as explained, 90 degrees or 'dead on') on ordinary window glass. If the glass has an anti-reflection layer, it goes down to about 1% typically. These percentages stay in the same range if the angle isnt exactly normal, a few tens of degrees off don't matter that much.

When you get to a really shallow angle more light reflects than is transmitted. Total reflection is not possible going from air to glass, but it is possible the other way around (glass fiber optics employ that effect). At shallow angles the amount of reflection also depends on polarization, so you might be able to see a difference rotating the laser around its axis.