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grenadier

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Scare story; do what you can to prevent my mistakes.

It took 5 years' worth of laser experiments, but I finally managed to do myself in. Not with a 100W yag, or a 50W laserscope, but rather, with a divergent 445 diode. Here's what not to repeat:

In one of our research labs' basements there is a long (30 meter) hallway, terminated with a glass door. At night the place is abandoned and locked, making it a somewhat-ideal area to focus a laser. That is, unless one forgets about the glass door.

In short, my photons traveled 30 meters, struck the glass and about 10% ricocheted back. This led to about 300 mW of coherent light forming a 6" rectangle right above me, which I did not notice until standing up and taking off my glasses.

I have a nice scotoma in my mid-peripheral vision now, to serve as a lifelong reminder of laser safety. Do your best, as hobbyists, to not become complacent around these machines.
 
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TheDukeAnumber1

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Is that power density truly capable of damaging eyes under such short exposure times? I haven't ran any numbers or anything and I've learned intuition isn't the best thing to go off of but it just seems like the power density would be very low in that situation.
 
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grenadier

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I did not think so at the time either, but while staring out the window of a cessna the other day I noticed the injury.

There wasn't enough 1/r^2 to prevent damage, evidently.
 
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crazyspaz

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Dang, even at that distance....Sorry that happened to you! Hopefully will serve as another reminder to the newbies-heck, even some of the older members- to WEAR SAFETY GOGGLES. As we are always saying You only have 2 eyes.

Did you go see an optometrist at least?
 

Cyparagon

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Assuming this was a ~6"x1" rectangle, that's ~80µW/mm². Since your pupil can't get bigger than 8mm diameter (50mm²), your "dose" wasn't more than 4mW. This kind of depends on the second dimension of that rectangle, though. A narrower one means a higher power density and vice versa. Either way, your injury might go away in a few weeks. Let us know.
 
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grenadier

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Hi folks,

The scotoma has not disappeared as of yet, and I find it unlikely that it will.

It's kind of annoying, too.
 

Atomicrox

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Are you sure this was damage from the laser? Did you see a doctor about it?
Cyp's calculations seem correct and 4mW should be very safe. AFAIK there have been only a handful of cases of damage from 5mW lasers, all of them due to young kids staring into the beams for a long time.

Or maybe far more than 300mW bounced back, who knows.

Good luck, hope you recover completely!
 

BCGanja

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Mar 13, 2012
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I'v got too many complex clustered floaters and a couple black scotoma dots from glancing at the sun(stupid me). You'l learn to ignore it easily, unless there's snow everywhere. The color white uggh.
 

Sigurthr

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Damn, sorry to hear that, Gren. How've you been fairing with it? Is it obtrusive to daily life?
 




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