
Sam's Laser Repair FAQ - newswasboring
https://www.repairfaq.org/sam/lasersam.htm
======
myself248
This FAQ got me the behind the scenes at a concert.

I'd never owned anything fancier than a Radio Shack laser pointer, but I'd
read Sam's FAQ cover-to-cover out of sheer curiosity.

Sometime around 2010, I found myself dropping some things off at a convention,
where I was not involved but knew some of the staff. This landed me in a
conversation with one of the A/V crew for the dance (happening a few hours
hence), specifically the guy who did the laser show equipment. Pretty fancy
stuff, especially for 2010.

We end up talking a LOT about lasers, most of which I know from the FAQ, never
having touched any of the stuff in the flesh. He takes me down to the ballroom
to check out the setup, we play with it a bit, and I'm totally fascinated, not
just with the hardware, but the controls that sequence the various show
routines. Then he says something like "You seem to have a handle on this..
listen... I never get to GO TO the dance because I'm always back here. You
wanna take a shift on the board?", and next thing you know, the lights are
down, the fog is up, and the DJ is giving me hand signals to know when to
change the laser wibbly-wobbly as he switches songs.

Mid-show, a costumed figure walks up to the board, laser-guy peeks out from
behind the mask, "How ya doin? Need a breather?" and I'm like "Nah this is
awesome, have fun out there!", and he disappears back into the crowd.

~~~
v-h-z
More like unpaid onstage than backstage ;) Awesome though

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superkuh
One of the most useful aspects of this is it's longevity. It's longevity is
mediated by the simplicity of the site. It's just HTML and files on a file
system. There's nothing to break (except links, which he covers in the
introduction). I've been using it for 20+ years.

~~~
Exmoor
At this point it's ancient history, but at the point I first came into contact
with various electronic bulletin boards (FidoNet, Usenet) in the mid-90s FAQs
were a ubiquitous thing. For many topics, just reading the official FAQ for
that subject gave you a very good overview of whatever you were dealing with
extremely efficiently. I've honestly never quite figured out why we moved away
from that as the internet grew in popularity, but it's nice to see at least
one relic still exists.

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nabilhat
The links page (remember those?) is a gold mine of high quality ancient
internet archaeology. I definitely remember Sam's site from the altdot days. I
do miss the sheer quantity of irresponsible electronics that was on the
internet 20 years ago. It's been ages since I've seen a furby electrified with
the wrong end of a utility pole transformer.

[https://www.repairfaq.org/sam/sambook.htm](https://www.repairfaq.org/sam/sambook.htm)

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jbay808
Laser professionals in both academia and industry frequently use this site as
an important reference. It's an immensely valuable trove of information, and
not only for hobbyists.

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the-dude
Disappointed to miss "Don't look into laser with remaining eye".

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osamagirl69
Honestly my favorite website on the entire internet.

The laserfaq is what got my hooked into optics, which sent me down the career
path that I am on now.

I owe it all to you Sam

~~~
non-entity
> The laserfaq is what got my hooked into optics, which sent me down the
> career path that I am on now.

What do you do now?

~~~
osamagirl69
Quantum computing

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discordance
Wow. Totally forgot about this. I studied photonics for my bachelors 15 years
ago and this was incredibly useful. Everyone in the department knew about it.

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ganzuul
Thrawled through this site when trying to understand how stimulated photons
knew how to copy the direction of travel of the incident photon as this was
the only source of information at the time which did not require a lifetime of
commitment to studying quantum mechanics.

I still don't understand it.

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PoachedSausage
My favourite from there:

DED - Dark Emitting Diode

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amelius
> So the 1 mW laser has the potential to produce an intensity on the retina
> 167 times that of direct sunlight!

I really don't understand why laser-pointers are even legal.

~~~
sandworm101
Depends on the optics. "1 mW" isn't enough information. Focus that down enough
and it could burn, but so too can sunlight. It also depends on the time of
day. In the dark of night your iris will be open, making a laser much more
dangerous. Sunlight is more powerful but as a general rule your iris isn't
going to be open during sunlight. A billion years of evolution have made our
eyes rather good at handling sunlight. We have no natural defense againse
lasers, especially invisible IR lasers. (Stay away from the cheap green lasers
from china. They often pump out huge amounts of IR.)

FYI, the general legal limit for "pointers" is 5mW.

~~~
amelius
Did you read the section on laser safety?

[https://www.repairfaq.org/sam/lasersaf.htm#saftoc](https://www.repairfaq.org/sam/lasersaf.htm#saftoc)

EDIT: I read it again and the crux of the matter seems to be this:

> The ability of the retina to dissipate heat is not dependent on the area
> covered, but the periphery (circumference) of the exposed area! The blood
> vessels are in the retina and not the sclera (the surface under the retina)
> - it is the blood flow that dissipates the heat and so can only act on the
> _edge_ not the middle of the exposed area. In circumference terms, the ratio
> drops to 7 times. Furthermore because the larger spot is less efficient at
> dissipating heat, the effective power delivered by the laser beam is only
> about 2 times greater than that of the spot formed by the sun.

~~~
sandworm101
Ya. The cited math is very short, missing many environmental variables.

Lasers safety are also a small part of my job (military). I've got a pile of
"pointers" that would blind in an instant, several in the watt-class (ie
>1000mw). Anyone can buy 50,000mW laser "pointers" for a couple hundred bucks.
I had everyone at work bring in their kid's laser "pointers" a few months ago.
Almost every one of them tested above 5mW. 10-20mW was the norm. Assume that
everything on ebay/amazon is above 5mW.

I refuse to stay in the same room as a working laser engraver/cutter. They are
generally in the 2000-4000mW class, enough for even a slight reflection to
instantly create a colour-specific blindspot.

~~~
TheSpiceIsLife
Do you mean 2000 - 4000 watt, rather than milliwatt?

The one I work with is 4000 watt, capable of cutting up to 20mm carbon steel,
20mm stainless, and 12mm aluminium.

It’s fully enclosed with dual electromechanical locks on each door, and an air
extraction system with dust and collector.

~~~
sandworm101
That one isnt handheld. It isnt part of a 200$ machine being sold to
highschools. Danger is always both technical and situational. I did mean mW. A
mW-class laser is more than enough to do instant damage, damage that would put
an end to a person's career as a pilot.

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orangetea
I just love the old school look of this, but at the same time wish he had a
YouTube channel to explain all this.

~~~
NikolaeVarius
It would be completely against the point of the site.

I'm surprised it even bothers with HTTPS.

~~~
StavrosK
Agreed, I hate YouTube videos for instructional content. I can read much
faster than the instructor can speak, I can ctrl+f, and webpages don't tend to
pad their content to fill a 12-minute video for 10 seconds of actual content.

My only gripe is that the page's margins aren't a bit more narrow.

~~~
_Microft
A lot of videos on Youtube have automatically generated transcripts available
via a menu item in the three-dot menu. Once the transcript is opened, you can
use your browser's search function to search it.

~~~
NikolaeVarius
The problem is that (most) Youtube videos are not people reading a technical
document. It is geared toward "speaking" meaning that a lot of information is
not covered due to time constraints.

