This is a story of what happens when an idiot gets a good idea.
It’s from the website Funranium Labs, created by health physicist Phil Broughton who has had an interesting life, especially as it relates to ionizing radiation and the various ways humans have created it, controlled it, and stored it in horrifyingly unsafe ways.
What happened?
Unlike poor, dumb Bob, I knew a guy in college who actually managed to burn a hole in his retina after asking “hey, is this on?”. Also, as it happens, with a Nd:YAG laser.
Beyond the obvious (even to dumb college kids) safety issues with determining if a laser is powered by looking directly into the emitter, we were all rather confused exactly what he thought he could visually confirm looking into an IR beam.
Ha! I just finished that, linked from another site.
Of course the point is that there wasn’t any “thought” going on. It was habit:
Look towards a generic omni-directional light source to determine if it’s on. And there’s a brightness gradient, like with the sun, where you can start by looking generally nearby and as your eye is tracking towards looking directly at it, it’ll get uncomfortable enough to trigger looking away well before it gets dangerous.
Which we all, even your lab-mate, know doesn’t apply to lasers in general or IR sources in general, and especially not to IR lasers. But knowledge is useless without thought.
In the next revision of humanity we ought to add “Always pays full attention to whatever it’s doing” to the bug-fix list.
In grad school, I worked in a department with a couple dozen other grad students, many of whom (myself included) were working on projects that utilized laser-based diagnostics (e.g. PIV or LDV) for flow measurements and/or particle velocity measurements. We didn’t have any kind of laser safety program at all, in spite of working with some really powerful lasers. I had a copper vapor laser in my own lab, with about 20 watts of output (yes, output; the input was a couple of kilowatts). I managed to start a fire one day because I was using a cardboard box as a beam dump. A friend of mine managed to burn his hand with a Nd:YAG laser. Somehow, I never heard of anyone getting an eye injury.
One day the primary sponsor of our lab came through on a tour, and someone just happened to be operating a laser in their lab - and inadvertently fired the beam right out of the lab door and across the hallway in front of the approaching tour group.
That was the day we were ordered to get a laser safety program up and running.
Hah! Reminds me of a fellow in grad school. He was working on zero G laser welding, and had a fancy laser in his lab. One day, he was running it, and someone asked where the beam terminated?
That’s when they noticed the smoke rising from a wooden table leg on the other side of the room.
My CV laser had a 1-inch beam diameter. One day from somewhere in the lab I found an 8" diameter lens (so minimal spherical aberration in the central area), and used it to focus the beam down to a point. I was able to slice through plain white paper pretty nicely by passing it through the focal point.
I had laser safety goggles from the get-go, but they filtered out virtually all of the visible-wavelength laser light. So they protected my eyes, but made it more likely that I’d get my hands (or something else) in the beam path. It was at least a couple of years before I got goggles that allowed a useful-but-harmless portion of the beam’s wavelengths to be seen.
In defense of the idiots in the story, they had a pretty good idea. Lasers are actually used today to strip surface rust off of steel:
It should be possible to use this technique safely to remove painted stripes on a roadbed with adequate shielding and safety interlocks.
From the story:
Maybe that would just be something to engineer around; maybe that would be a showstopper.
I agree because isn’t it the idea that counts more than the person who had said idea? I mean, isn’t a brilliant person having a bad idea less desirable because the idea itself is bad?
Reflective road striping usually involves laying down some gooey paint, and then spraying tiny spherical glass beads onto it; the beads stick to the paint and each one then serves as a tiny retroreflector. The gaps between beads should absorb the laser light and cook off, freeing the beads. Moreover, reflective striping at the end of its life features beads that are mostly scratched up or broken, so they aren’t retroreflecting very well anymore.
Is it just me, or is it also pretty dumb to build a laser that you can’t tell if it’s on by looking at it? Put a couple LEDs (if the visible spectrum) on it; when the LEDs are on, the laser is on.
Well, of course there was a power indicator light on it and all sorts of safety warnings and signage. Guy was just being dumb. And if there’s any doubt, assume it’s on and cut the power.
I wasn’t part of the lab. I got the story after “he’s at the hospital” was inefficient explanation. He was working in a research lab and had gotten all the safety training (apparently this also included sliding a piece of paper or cardboard into the invisible beam and burning a hole through it to demonstrate “no, you can’t see the beam with your eyes”).
I can’t imagine the liability issues with letting a regular class of undergrads play with one of those. It was one of those “teachable moments” a lot of people don’t need to learn through firsthand experience.
Possible? Sure. But I’ve seen way too many road crews ignore basic safety rules (and enough construction companies try to cut corners) with normal equipment to think it would ever actually be safe.
It’s not just you: it’s what we do with microphones. It’s elementary.
Still there’s plenty of hot-mic stories going around. Imagine how many more there would be without the LEDs.
I just want to point out that supposedly intelligent scientists can be remarkably stupid when it comes to laser safety. This is what puts the teeth in the sign that says
Do Not Look Into Laser With Remaining Eyeball
One lab I worked in had interlocks built into the doors that prevented you from turning on the lasers unless you had the doors closed. This included the little 1/4 milliwatt HeNe lasers that the scientists clearly thought were not even worth considering. They routinely circumvented the safety interlocks by using C-clamps to trigger the interlocks when the doors were open. So they could use their little red alignment lasers even with the doors open. It also didn’t stop them from firing the big mean lasers that could do damage.
As another data point, although I haven’t confirmed the story, I heard that in the very early says some laser scientists used to align lasers by looking down the barrel of the laser while adjusting the tip/tilt mirror mounts on the ends, and trusting their eye reflex to close their eyes before the laser got too strong. These were probably low-power lasers like HeNe lasers, but looking into such a beam is comparable to staring at the sun. Easier and safer to set up a detector and look for the output to spike.
Nothing is 100% reflective. Even something 99.999% reflective will quickly cook if you apply enough power. As xkcd’s Blackhat Dude so often comments: “More power!” 
Hah!!! I will make sure @typo_knig reads this. He worked with lasers in grad school (PhD in Physics) and was always very, very careful, so he sustained no injuries.
He did manage to give himself a bad case of freezer-burned knees one day, when he didn’t notice there was a liquid nitrogen spill heading his way… IIRC, he had to have a talk with the department’s safety coordinator. Luckily, he just wound up with two very large, and oddly-shaped, blisters, one on each knee.
We used to have a collection of humorous buttons, one of which said “Please do not look into laser with remaining eyeball” (I see Cal Meacham posted the same quote!)
I’ve seen machine shop signs that say “NOT ONLY WILL THIS KILL YOU, IT WILL HURT THE WHOLE TIME YOU’RE DYING.”
I thought I had posted this: