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SPEAKER: I love this one. You know the night vision scopes?
Have you ever used one? How many people here have used a night vision
scope? Isn't it-- it's awesome.
Totally awesome. How does it work?
Well. It works on the basis of the photoelectric
effect, which is what Einstein was referring to with light hitting
a surface and injects electrons.
So in this case, what they have here is a thin piece of gallium arsenide
They have an optic here, so light coming in hits this gallium arsenide.
And the gallium arsenide is chosen so that things with very long wavelengths
will eject an electron. So you get some electrons.
This machine changes electrons to pho-- I mean, photons to electrons.
And the nice thing about electrons is we can amplify them.
How? Well, there's this thing that they have here.
Well, in this device, it's showing right here. It's a plate with some very fine holes in
it. And so the electron that we've accelerated
from our gallium arsenide, we've put a voltage across there you can see.
So here's the gallium arsenide. Photon comes in, we get an electron, we put
a potential here, we accelerate that electron.
It goes into this plate with all these tiny holes, they
are just a few microns. They're straight channels.
And it hits the side and it knocks more electrons out.
So instead of one electron-- So it's enough energy, we've accelerated here
enough energy, that when it hits this material, it knocks more
electrons out. So I get a cascade of electrons.
And then there's a little phosphorus screen here, that glows as a result of
electrons hitting it. You can accelerate them again, too.
That's what they do here, they accelerate. It's actually done inside the plate.
This is all done inside the plate. And then, the thing that's really cool--
I mean, it has nothing to do with what we talked about in lecture today, but
the thing that's coolest to me is that because you got one lens here, the
image is upside down. Not good if you're looking for the enemy or
something like that, right? You have to think upside down, no.
So what they do is-- Well, you could put another lens and switch
it, but this will make this much longer.
So what they do is they take a bundle of optical fiber, and the bundle of
optical fiber is pushed up against the phosphorous screen and then they twist
it 180 degrees. That is so cool.
I mean, the person that thought of that, they deserve an award because
the first reaction from their boss was, that is the craziest thing I've
ever heard and it works. So this thing can fit in a really small package,
and it goes right in here, and then they have to make it rugged
so you can drop it off the back of your Humvee.