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How I got my laser eye injury

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Re: How I got my laser eye injury

#301

Post by eru »

ponector wrote: post #291
grundrausch3n wrote: post #282

Earlier quoted context omitted.

Technically basically all buildings in Germany (residential and commercial) run on 400V 3 phase power. But access to it via sockets is only common in residential homes via sockets in a garage. It gets more common with car charging although they rather use 3 x 230V as far as I am aware of.

I'm living in apartment block built in 2016 in eastern EU and here every apartment has a separate 3 phase(5 pin) socket for the stove. It is a 7kw beast, it can easily destroy regular aluminum-steel pan if you put it on max heat. Steel part will fall apart.

Same in Eastern Germany, at least up to the 2000s. (Probably still, but I left, so can't vouch.)

Re: How I got my laser eye injury

#302

Post by eru »

ruined wrote: post #257
sebastiennight wrote: post #249

Earlier quoted context omitted.

This seemed like a wild claim (2500 watts for a tea kettle!? As much as a microwave oven in full blast?) so I looked it up. Wow.

british household AC is wild, it's like they've got a full-power american range plug for every outlet

And just like Americans have special access to 'full-power', there's special access to three phase 400 V in many nominally 230V countries, too.

That's eg common for electric stoves in your kitchen.

Re: How I got my laser eye injury

#303

Post by eru »

queuebert wrote: post #216
tlb wrote: post #100

Earlier quoted context omitted.

Why don't welding/cutting lasers add more divergence with built-in optics? Would it hurt performance? It seems like you could add 1 mrad and it would hardly make a difference at the usual working distance, but spread out to a meter over 1 km, so you can't zap people across town.

Whatever refracts the light will have to stand up to the beam for long periods of time. Maybe it's a materials science problem.

As long as it doesn't absorb the light, it's fine.

Just like the electric cables for your water kettle typically don't get hot.

Re: How I got my laser eye injury

#304

Post by throwup238 »

psd1 wrote: post #299
throwup238 wrote: post #281

Earlier quoted context omitted.

They are in the rich people’s glamping camp. They haven’t lifted a finger on the playa, ever.

Google used to indulge employees' interests. They fund, or used to fund, "the generator", a build shop in Reno. I know a Googler who openly worked on a small art project at the office, albeit a small part of the work. I'm not saying that Google has machine shops purely for burning man. But I strongly suggest that when the idea has been floated in various locations, one recurring theme is "yeah let's! And let's get so…

I don’t mean the rank and file but Page and Brin. They’ve only ever gone the glamping sparkle pony route.

> I'm not saying that Google has machine shops purely for burning man. But I strongly suggest that when the idea has been floated in various locations, one recurring theme is "yeah let's! And let's get some lasers and propane burners!", and I also believe that some managers were thinking "great, this is the culture we want."

There was! It was the predecessor to the Garage. I suspect because the machine shop boys wouldn’t let them use the real toys.

Re: How I got my laser eye injury

#305

Post by tlb »

oh_my_goodness wrote: post #224
tlb wrote: post #100

Earlier quoted context omitted.

Why don't welding/cutting lasers add more divergence with built-in optics? Would it hurt performance? It seems like you could add 1 mrad and it would hardly make a difference at the usual working distance, but spread out to a meter over 1 km, so you can't zap people across town.

If it's a 1-micron wavelength laser with a 60 micron radius spot, the divergence can't be much less than about 5.7 mrad half angle. What makes eye safety tricky is just that 2.5 million milliwatts is a lot of power. Even when you spread it out some.

I'm not an expert here. But according to https://en.wikipedia.org/wiki/Diffraction-limited_system (see last paragraph of the intro) the diameter of a laser beam doesn't impose a diffraction limit on the optics it goes through. You still get the angular resolution you'd expect given the entire aperture of the lens even though the beam is only going through a small area of it.

Re: How I got my laser eye injury

#306

Post by [deleted] »

amluto wrote: post #268
oh_my_goodness wrote: post #224

Earlier quoted context omitted.

If it's a 1-micron wavelength laser with a 60 micron radius spot, the divergence can't be much less than about 5.7 mrad half angle. What makes eye safety tricky is just that 2.5 million milliwatts is a lot of power. Even when you spread it out some.

On the other hand, 2.5kW of light is not outrageous. It’s not drastically higher than some of the larger theatrical lights. (Not that being in a spotlight is pleasant , but it does not permanently blind the actors.) A lot of this comes down to wavelength. Some wavelengths get focused by one’s eye and can concentrate their power in a small spot on the retina. Other wavelengths will be absorbed before they get to the r…

[deleted]

Re: How I got my laser eye injury

#307

Post by ChrisMarshallNY »

fragmer wrote: post #259
ChrisMarshallNY wrote: post #246

One of my favorite sites, was the US Navy Safety Picture Of The Day site. It was crazy, how bad we can get. I think the site has long been retired.

You are probably thinking of this -- long gone, but still archived thanks to the Wayback Machine: http://web.archive.org/web/20081019180813/http://safetycente...

Yup. That's it!

Thanks!

Re: How I got my laser eye injury

#308

Post by eaglefield »

hinkley wrote: post #184
convolvatron wrote: post #134

Earlier quoted context omitted.

I tig. wear a helmet and have to buy argon every year. this seems like a huge hassle in comparison. is there that big a difference in quality and or range of processes that make it worth it?

I know one of the reasons we wanted pico-second and shorter pulsed lasers is that they can cut material with little to no damage of the neighboring material. There was a demo that I read about when this was all brand spanking new research, where they claimed that a laser scalpel causes no heat damage to tissue outside of a cell’s breadth from the contact point.

Here's a figure comparing the hole left in a metal surface with normal and femto-second pulses. The difference is quite stark.

https://www.researchgate.net/figure/SEM-image-of-the-substra...

Re: How I got my laser eye injury

#309

Post by gcanyon »

sho wrote: post #287
sebastiennight wrote: post #249

Earlier quoted context omitted.

This seemed like a wild claim (2500 watts for a tea kettle!? As much as a microwave oven in full blast?) so I looked it up. Wow.

It's actually only americans who unaccountably make do with these horribly underpowered kettles. The rest of the world wants their tea and they want it now...

Technology Connections did an excellent video on this: https://www.youtube.com/watch?v=_yMMTVVJI4c

tl;dw -- kettles in the U.S. only take about 4+ minutes to boil a liter of water. So when you say "now" you really mean it.

Re: How I got my laser eye injury

#310

Post by mandibeet »

NathanielBaking wrote: post #61

Safety guys always ruin the fun. I was in the Marine Corps and every time we got to test some new piece of gear the safety officer was like "No, you can't live fire it off the flight deck of the ship" or "No, not here, that village is down wind of the dust you will kick up when it goes off." No, that has a kill distance of 6 miles, you have to fire it into a hill." Blah, blah, blah. So after I got out I joined the Na…

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