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Diffuse reflection - can it damage the eyes?

AlesCZ

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Hi folks,
I bought a Chinese laser at the Vietnamese market(for about 7 USD). I wanted him for a double slit experiment. I felt too strong when I turned it on at home. I tried to aim it closely at the thermal paper, but nothing happened. The problem is that I watched it for about ten seconds. Later I read that powerful lasers have dangerous diffuse reflections. I made a second attempt and pointed the laser at my finger. It burned in seconds. So I tried black rubber from the mouse pad. From a distance of about 5cm, a hole was fired into this pad in about ten seconds. That was quite a shock to me.
Is it possible to estimate the power of this laser? And could seeing enlightened white paper damage my eyes?
I do not believe the parameters on the label. I attach photos of the laser.


Thanks!
(sorry for my english)
Ales
 

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paul1598419

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This same question keeps coming up here even though it has been answered too many times. A diffuse reflection acts like a point source of light and, being so, it decreases in intensity as the square of the distance you are away from it. Unlike a specular reflection that remains collimated, diffuse reflections can be seen by anyone in the room from any position. Those AAA pens don't output more than 100 mW, usually much less. Since yours has an adjustable lens on them they can be adjusted down to a very tight spot at short distances. That is why you can get them to burn. But, since the diffuse reflection is decreasing as the square of the distance you are away from it, it will look dimmer to you the further away from the spot that you get. Regardless, diffuse reflections don't cause eye damage.
 

Kyle L

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This same question keeps coming up here even though it has been answered too many times. A diffuse reflection acts like a point source of light and, being so, it decreases in intensity as the square of the distance you are away from it. Unlike a specular reflection that remains collimated, diffuse reflections can be seen by anyone in the room from any position. Those AAA pens don't output more than 100 mW, usually much less. Since yours has an adjustable lens on them they can be adjusted down to a very tight spot at short distances. That is why you can get them to burn. But, since the diffuse reflection is decreasing as the square of the distance you are away from it, it will look dimmer to you the further away from the spot that you get. Regardless, diffuse reflections don't cause eye damage.
Paul nailed it here. I own one of these, and they meter anywhere from 30-80mw. Although I would always practice caution, I'd say it will not cause any harm unless directly pointed at your eye from short distances.
 
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AlesCZ

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I guessed that the label was meaningless. Although this laser makes a very bright green line and its green spot on the wall can illuminate the entire room very clearly.

Thank you very much guys!

Ales
 
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LSRFAQ

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Quote ". Regardless, diffuse reflections don't cause eye damage"

Like hell they do not. You can create eye damage with a diffuse reflection, for example, one of my 10 watt argons at work had a measured minimum safe distance of three meters from the spot on the wall.

Steve
 

LSRFAQ

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Attached is the file from the University of Chicago Radiation Safety Office with the math, see section 3B
Again, and Again, and Again, I must stress that proper laser safety above class 3A requires math and measurements.
Yes, Diffuse laser reflections can be a hazard, and by definition some class IIIB, and all class IV lasers are an automatic diffuse hazard if the beam is not totally enclosed.

Steve
 

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paul1598419

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Sorry, Steve. I should have added a caveat for more powerful lasers like your argon. Of course there are limitations on how one may view many very powerful lasers, but my point was concerning these small DPSS handhelds and direct diode lasers.
 

Kyle L

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Let me apologize,if its burning your finger, unfocused, then its possible it is more. that being said, that powerful of a diode (if it is) in that small of a host, has to get VERY HOT EXTREMELY FAST!! if there is anything over 500mw in that pen, duty cycle would be mere seconds i would presume. im my experience at least.
be careful not to run for long if it has this kinda of power, the heat can damage the diode
 

paul1598419

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None of the lasers you've shown photos of can be over 100 mW and are likely very much less powerful. They can get a power dense focused spot up close, but in the far field they will not be so power dense. That said they will not cause you eye harm from diffused reflections even at close distances
 




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