Well, I just spent my entire morning figuring out how thermionic vacuum 
tubes actually work. (You know how it is once you start surfing 
Wikipedia...) In the process, I came across this:

http://en.wikipedia.org/wiki/Vacuum_fluorescent_display

Now, see, to me this looks like an LED display. However,

http://en.wikipedia.org/wiki/LED_display

suggests that there's no such thing. Now I wonder... Are there any 
devices which actually use LEDs for display? Or are all the devices 
which I thought were LEDs actually VFDs?

Also, I somehow ended up reading about lasers. I still have no idea how 
to make one, but I did come across several /ridiculously/ cool images:

http://tinyurl.com/mxe5tn
http://upload.wikimedia.org/wikipedia/commons/4/4b/Laser_DSC09088.JPG

Quite why you'd be wearing combat uniform while working in a lab, I'm 
not sure. Also why you'd be wearing shades in a dark room. (Although 
perhaps a room with lasers in it makes this a reasonable safety precaution.)

Hmm, I wonder if I could somehow make a laser using normal air as the 
optical medium?

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Le 01/08/2012 14:26, Invisible a écrit :
> suggests that there's no such thing. Now I wonder... Are there any
> devices which actually use LEDs for display? Or are all the devices
> which I thought were LEDs actually VFDs?

A Led is a small spot, with a small emitting cone, about 15° to 25°.
If the form was bigger that a point, it was not a Led.


> 
> Also, I somehow ended up reading about lasers. I still have no idea how
> to make one, but I did come across several /ridiculously/ cool images:
> 
> http://tinyurl.com/mxe5tn
> http://upload.wikimedia.org/wikipedia/commons/4/4b/Laser_DSC09088.JPG
> 
> Quite why you'd be wearing combat uniform while working in a lab, I'm
> not sure. Also why you'd be wearing shades in a dark room. (Although
> perhaps a room with lasers in it makes this a reasonable safety
> precaution.)

You missed the main point on the guy: the goggle are not sun glasses,
they are teinted glass to protect against the laser specific color.

About wearing shade/combat... well, uniform is mandatory inside the
facility. This is a summer-uniform.


> 
> Hmm, I wonder if I could somehow make a laser using normal air as the
> optical medium?

normal air... depend if you can breath in neon, then neon would be your
normal air.
Laser need an atom or molecule getting excited and returning to lower
energy with always the same emission of light (frequency)(and a few
noise around).
You push in white light (full of noise) and get back a lot of one
lambda, dismissing the noise within the resonant cavity (the two
mirrors, one of them being less than perfect).
normal air is 20% O2, 79% N2, ... and when you are around, a bit of CO2.
Stressing O2 or N2 with energy would make them group as O3, N3, NO2...
probably not a good ground to have a laser.

It is possible to have laser-led: it works differently (no mirrors),
it's a single lambda, but the parallelism is not the one of laser until
you post process it with a lens. The power is also far smaller.

-- 
Software is like dirt - it costs time and money to change it and move it
around.

Just because you can't see it, it doesn't weigh anything,
and you can't drill a hole in it and stick a rivet into it doesn't mean
it's free.

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Am 01.08.2012 15:23, schrieb Le_Forgeron:
> Le 01/08/2012 14:26, Invisible a écrit :
>> suggests that there's no such thing. Now I wonder... Are there any
>> devices which actually use LEDs for display? Or are all the devices
>> which I thought were LEDs actually VFDs?
>
> A Led is a small spot, with a small emitting cone, about 15° to 25°.
> If the form was bigger that a point, it was not a Led.

Because an LED embedded in some piece of transparent plastic with a 
frosted surface isn't an LED, or what?

For both of you:

http://en.wikipedia.org/wiki/Seven-segment_display

And yes, the LED version /does/ exist in reality. Some mainboards have a 
pair of them to display BIOS POST failure codes or some such, for 
instance. You also see them frequently in pinball machines, dart 
automats or the like (unless they feature an LCD screen) for score 
display. It's pretty common where you want a bright, viewing 
angle-independent numeric display.

It's less common however where you want a low power consumption, such as 
any device that is supposed to display anything in standby mode, or any 
device that is supposed to operate from batteries. LCD and vacuum 
fluorescent tubes are preferred there.

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> For both of you:
>
> http://en.wikipedia.org/wiki/Seven-segment_display
>
> And yes, the LED version /does/ exist in reality.
>
> It's less common however where you want a low power consumption, such as
> any device that is supposed to display anything in standby mode, or any
> device that is supposed to operate from batteries. LCD and vacuum
> fluorescent tubes are preferred there.

And yet, the VFD article shows several 7-segment displays implemented as 
VFDs, and claims that their main strength is very high brightness.

I don't know, man. Some of those blue LEDs seem pretty ****ing bright to 
me...

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On 01/08/2012 01:26 PM, Invisible wrote:

> Also, I somehow ended up reading about lasers. I still have no idea how
> to make one, but I did come across several /ridiculously/ cool images:

Related: Mike just found this...

http://www.youtube.com/watch?v=VSD3K06rndg

I have no idea where the hell he got this from. But it looks dangerous. 
If shining it on something can set fire to it, I'd be very careful 
pointing it at anything remotely shiny...

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On 8/1/2012 5:26, Invisible wrote:
> Quite why you'd be wearing combat uniform while working in a lab, I'm not
> sure.

It's not a combat uniform. It's just a uniform. A combat uniform has hooks 
to carry weapons, bullet-proof vests, helmets, etc.

> Also why you'd be wearing shades in a dark room. (Although perhaps a
> room with lasers in it makes this a reasonable safety precaution.)

You'll notice they're red shades, and he's working with a blue laser. Think 
about it.

> Hmm, I wonder if I could somehow make a laser using normal air as the
> optical medium?

No.

-- 
Darren New, San Diego CA, USA (PST)
   "Oh no! We're out of code juice!"
   "Don't panic. There's beans and filters
    in the cabinet."

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