November 23, 2018 • 34 mins
What are the two main types of night vision? How can you see heat? Why do some night vision systems only display in monochromatic green? Join Jonathan and Chris as they explore the tech behind night vision.
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Speaker 1 (00:04):
Get in touch with technology with tech Stuff from how
stuff works dot Com. Hei there and welcome to tech Stuff.
I'm your host, Jonathan Strickland. I'm an executive producer and
I love all things tech and it is time for
another classic episode of tech Stuff. This episode originally aired
on November two thousand eleven. And Chris Pallette, my co
(00:29):
host and editor at the time, and I decided we
wanted to take a look at something that's kind of
hard to see, that is when it's actually being used.
I'm talking about night vision. How does the technology work? Well,
Chris and I found out and now you will to
enjoy this classic episode night Vision. The technology dates back
(00:50):
to the late thirties early forties. It was technology that
was developed during World War Two and used mainly by
the American, British, and and Soviet forces during World War Two,
although other nations began to to develop their own version
of night vision technology around the same time. Well, yeah,
(01:11):
the Germans, Uh, A lot of what we had as
far as our technology in the United States was based
on some German research that was done in the late thirties. UM.
And really what it comes down to, UM is the
spectrum of light that that you're trying to see. Yeah,
(01:31):
it's it's two different things. It's trying to accept other
parts of light that human eye is not able to detect,
and also to uh to amplify whatever little light is there.
There are two main ways of achieving a night vision
UH technology. One is called image enhancement, and that's where
(01:54):
you're taking the little amount of light that's out there
and UH and trying to amplify it so that you know,
you're able to see better in that environment. And the
other is thermal imaging, which is also you know, we
think of that as being able to see heat. You know,
the whole idea about like if you've ever seen that
documentary Predator, Yeah, the Predator actually uses both forms of this,
(02:20):
but the thermal imaging would be the one where it
switches and it's that really colorful display where the hotter
things in the field of vision are a brighter color,
usually red, uh, and then the cooler things are are
in the other part of the spectrum of light, so
they'd be you know, if it's cold, it might be black,
but if it's cooler, it might be blue or even
(02:41):
kind of an indigo color. Um. Both of those are
ways of achieving night vision. The I think the one
that most people think of when they think of night
vision is the one where you've got the greenish uh display.
That's the image enhancement approach, and well, you know that
that's I think that's the reason people think about it
(03:02):
is because it's used that way in TV in the movies. Yeah,
probably so as a visual clue to the viewer that hey,
we're doing something that you can't normally do, right, Yeah.
I In fact, I watched a movie just last night
that involved having a night vision the screen tinged night vision,
(03:23):
and it was and I'm not going to call it
the documentary because that's how much of a skeptic I am.
It was paranormal activity too, and uh, you know in
paranormal activity those movies, those are done as found footage movies, which,
in case you're not familiar with the term, that's the
idea where the film is presented as if it were
uh collection of clips taken from various cameras. That it
(03:47):
wasn't meant to be a feature film. It was supposed
to be actual footage shot of something, right. So clover
Field is another example, or Blair Witch Project's another example, Yes,
that's the first time I thought about. Yeah, and that
it's really popular with the horror crowd. Uh and uh
so the paranormal activity too. There's one of the cameras
that is being used in that has a night vision
(04:09):
setting and it's using the image enhancement approach. By the way,
in case you're curious about why green, the the answer
I found through my research was that the reason why
you get green images is not because of any technological limitation.
It's because if you're in an environment where you're using
night vision, you want to be able to switch between
(04:32):
night vision and your normal vision as quickly as possible.
But if you use really intense light and and some
of the brighter lights, your pupils will constrict as you're
looking at it, which means when you take the night
vision glasses off, it's going to take more time for
your eyes to readjust to the darkness around you. But
the green that is used is a more subtle light,
(04:53):
and so your your pupils are remain mostly dilated, so
when you remove the night vision goggles, you don't of
as long a time to adjust. It doesn't take as
long for you to adjust to night regular night vision
like our natural night vision. Uh when you when you
go back and forth, and that kind of makes sense
to me. I mean, if you especially when you consider
(05:13):
that night vision was really originally used as a military technology,
you would want to be able to have as much
versatility and flexibility as possible so that you can adapt
to whatever the situation calls for. Yeah, that makes absolute
sense to me. So yeah, so at least according to that,
we could in theory have night vision where it's any color. Uh.
(05:34):
You know, it probably still probably be monochromatic, but we'll
get into that when we get into the you know
exactly what's happening. So so, all the different kinds of
night vision lie at least somewhat on the infrared, uh,
part of the spectrum of light, right, and that infrared
spectrum of light is outside the range of uh, the
(05:57):
visible light spectrum. UM. In fact, there are three parts
to the infrared spectrum, which is near infrared, and that's
the closest one to the visible spectrum spectrum. Yes, I
can say that word mid infrared um and that has uh.
I didn't mention the wavelengths. The wavelengths for near infrared
(06:17):
are from point seven to one point three microns um.
Mid infrared has wavelengths from one point three to three
microns um, and then thermal infrared, which is the biggest
part of the infrared spectrum, and that's from three to
more than thirty microns. Yeah, and so the the thermal
(06:38):
infrared you're talking at that point about infrared radiation really yeah, heat,
in other words, is what's kind of how we perceive
it usually. But uh, that's something that's actually given off
by an object itself, Whereas when we're talking about visible light,
that's something that's reflected off of an object. Right. So
(07:01):
if if I'm looking at a tree in sunlight, what
I'm seeing is the light being reflected off of that tree,
it's that lights hitting my eyes then going through the
whole focal point getting into my brain and somewhere up
there in yeah, somewhere up there in the gray matter,
my brain says, Hello, there's a tree, possibly a large
(07:22):
a large. Um. I recognize that from very far away. Yes,
that's how to recognize trees from very far away, quite
a long way away. Yeah, So that's how that would
normally work with thermal infrared. If I were to see
an object using thermal infrared. Let's say that somehow I
have that ability. You know, we're not talking about technology here,
(07:43):
but I somehow have the the the natural ability to
see the thermal infrared. It happened when they shot him
into space and he was bombarded by cosmic waves while
we're really just pop culturing this all to heck and back.
So yeah, with the thermal infrared ability, I would be
able to see the energy that is being emitted by
any particular object. Um it's not necessarily light that's reflecting off.
(08:06):
In fact, there doesn't have to be any sort of
light source at all. It just so. And if I
were in a perfectly dark room and there was another
object there that's giving off heat, essentially, I would be
able to see it because I would be seeing in
that range even though there's no other light source coming in.
It would just be that I'm actually seeing that that energy.
(08:29):
Because we'll get into why, it's kind of interesting. Has
to do with excitation, but not good vibrations. Yeah, although
perhaps that lady was able. Never mind, So moving on,
I hope you guys are enjoying this classic episode so far.
We've got more to talk about, but first, let's take
a quick break to thank our sponsor. Before we get
(08:59):
into the whole atoms and thermal infrared, let's let's talk
about the image enhancement approach first, because that's the one
that's the most familiar and uh and it's kind of interesting. Um.
The way that it works currently is that you've got
you've got very basic parts to a particular kind of
night vision. You've got you've got your lens. That's where
(09:21):
the light is going through. The objective lens. Just a
lens that catches it's a lens. Yeah, it catches ambient light,
catches near infrared light. So this is the near infrared spectrum,
the light that's closest to the visible spectrum. Now that
light is sent to a tube, and that tube is
called the image intensive fire tube intense. Yeah, and the
(09:46):
drinking energy drinks all day and yeah. So you can
think of this tube. It's almost like a vacuum tube.
In fact, there it is, There is a vacuum in
side of it. So you think of this sort of
imagine a glass vial all right in the middle of
this glass vial or on one end of the class file,
you've got something called a photo cathode. Now, the photo
cathode takes photons. Those are those individual elements of energy
(10:09):
for light. Yes, and and those come in the entire
spectrum of light um so infrared. They're infrared photons, just
as there are visible light photons. So the photo cathode
converts photons into electrons. It's it's one of those. Uh
So it changes light into electricity essentially. Yeah, And if
(10:30):
you listen to our episode about high speed and low
speed photography, we talked about how there are certain types
of materials that when a photon strikes it, it causes
a reaction. That's the case here a photocathode. It's that's
the and that's how it behaves when a photon hits it.
(10:50):
It gives off an electron. Uh So, You've got the
photo cathode at one end of this tube, and that's
where the light that's being captured by the lens is
directed to the photo cathode. The electrons emitted by the
photo cathode then have to pass through what is called
a micro channel plate or m c P. That's a
little glass disc. Yeah, I see. I thought MCP was
(11:12):
the master control program. End of line. It is. Okay, However,
two different mcps well it was until Tron got hold
of it. That's right. So glass disc Tron m c P.
I'm sensing some convergence here as we Mentionedron again. Ye.
So anyway, you've got this glass little tiny glass disc
called a micro channel plate and has lots and lots
(11:35):
of channels. That's why it's called a micro channel plate.
Lots of channels that go through this plate. Okay, So
think of the plate. Think of it like a dish.
You got a dish, put it up on its side,
and it has a whole bunch of little holes drilled
in it. Now, those holes are what allow electrons to
pass through. But there's also an electrode on either side
(11:55):
of the dish. So electrons coming from the photo cathodes
strike one side of this micro channel plate and start
to go through one of the channels. And they're going
through in the same direction they came from the the
from the photo cathode uh section of this this uh
(12:15):
this image intensive ire tube. So the photon converts to electron.
Electron goes through this channel. As it goes through the channel,
it starts to actually set off a well a reaction. Yeah,
and it basically functions as a multiplier for the electrons.
It's called a cascaded secondary emission. So this is where
(12:38):
when electron collide collides with something inside that that channel,
it starts to set off other electrons, uh, down that
same pathway, And there's a voltage applied to those electrodes
that's channeling the electrons through that pathway, like that's why
they're going in that direction. So you've got more and
more electrons bouncing off of each other through these channels,
(13:00):
which means that you've you've created an amplifier. And uh,
if you guys want to know kind of like a
big picture way of what this might look like, imagine
having a h and you can see play of videos
of this on YouTube, But imagine having a big glass
container filled with mouse traps, and each mouse trap has
(13:20):
a ping pong ball set on it, and then you
drop a ping pong ball into the glass chamber and
that will set off a mouse trap, and as the
ping pong balls bounce around, they set off more and
more mouse traps, so soon the glass case, like within
a fraction of a second ball, the balls are bouncing everywhere. Right,
same sort of idea here with the micro channel plate,
(13:42):
except that we're talking on a sub atomic level, and
we're talking about something that's really channeled, really has a
firm direction. So instead of the electrons bouncing everywhere, they're
going in a very specific direction. Right now, when they
get to the other side of that micro channel plate,
you've got the electrons still traveling in this ame direction
they were when they came in on the front side,
(14:02):
but now there are way more electrons, right, just amplified
the number. The electrons then hit a screen that's coated
with phosphors. Now phosphors pos phosphors do the they're kind
of like the opposite of the photo cathode, right. They
take When the electron strikes the phosphor, they give off light.
(14:23):
So you're changing the electron back to a photo photon. Right.
But now, because there are more electrons coming through hitting
that phosphoor than they were coming in, the light that's
generated is much greater in intensity than the light that
was coming in. So you've amplified the light. Now that
information that light is sent to a viewer of some type.
(14:44):
It could just be a regular lens, which is usually
called the ocular lens, or it could be sent to
a monitor. So if you have a pair of night
vision goggles or a night vision scope. That's what you're seeing.
You're seeing that amplified light hitting the lens or the
Monitor's cool, it's pretty awesome, right, And again, this isn't
(15:06):
just the the visible light, the ambient visible light that's
out there, but also the infrared light. So um, because
those photons, you know it doesn't you know, the photons,
It doesn't matter if it's visible or not. UM. And uh,
the more light that's hitting certain areas, that the brighter
it's going to be for whatever it is you're looking at.
(15:27):
So if you're looking at something that's that's fairly reflective, um,
you're gonna be able to see it in higher definition
than you could with something that is not as reflective. Now,
there are different ways of actually achieving this too. You
can have a various they're various generations of this technology,
(15:48):
all right. So the earliest generation of this technology actually
involved shining infrared light at the objects you're looking at
through the through the night vision goggles, right, So when
that that infrared light was reflected, then you would be
able to see it, right, because these goggles were not
(16:09):
so sensitive as to be able to take just the
ambient light. Right, if you did that, you would probably
get you you might be able to see marginally better
than you would if you had just use your regular vision.
But using this infrared flashlight, essentially you could illuminate the
scene and be able to see it through the night
vision goggles. But if you did not have the goggles,
(16:31):
because infrared light falls outside the visible spectrum, any independent
observer wouldn't be able to tell what you were doing. Yeah, now,
I UM I did some research on the the US
military website about the history of of night vision and apparently,
um they sent about three hundred sniper scopes over to
(16:54):
be used in the Pacific theater during World War Two,
but they didn't get used very much because of the
way that the technology worked. Um they really could see
less than a hundred yards. Yeah, they weren't very effective, right,
because again, since it's dependent upon a reflected ray of
infrared light, if it's you know, the rays starting to
(17:17):
dispersees as it goes out, Right, it's not not a
not a concentrated like a laser beam. Yeah, it's not
a beam. It does disperse and diffuse as it goes out.
So the further away your target the less likely you're
going to be able to see it, and even with
a really really advanced version. That's, by the way, it's
called active infrared because you're actively beaming infrared radiation out
(17:39):
in order to try and see stuff coming back through
the monitors. Um if because because you're relying on that reflection,
if it's too far away, you're not gonna be all
se very well. So obviously a sniper rifle, where at
least in theory, you want to be able to put
your snipers at a good distance away from the targets
(18:00):
to maximize their effectiveness and minimize the chance that they
will be targeted. Um it doesn't. It's not so effective
if you know your your distance is cut down that dramatically. Yeah. Plus,
the first generation wasn't exactly um useful for someone like
a sniper, considering the batteries were huge and the i
R emitters had to be carried on flatbed trucks. It's
(18:23):
hard to put one of those up in a tree. Yeah. Yeah,
it turns out that also all of these are going
to involve having a power supply of some sort. But
for the active infrared it requires either more more energy
because you're not you're not just for your your actual
night vision device, whether it's a scope or goggles or whatever,
but also for the emitter. By the way, that generation
(18:45):
is normally referred to as generation zero for a night vision.
Generation one was the first generation using passive infrared system. Now,
this was the kind of of night vision goggles or
scope that could just use the ambient light in the area,
although it needed a good amount of the ambient light.
(19:06):
So moonlight or starlight. It's funny you should say starlight. Yeah,
that's what it was called. Yea in the U. S.
Army they called it starlight. Uh, the without the moon
or stars, you wouldn't be able to see very much.
So on an overcast night it would not be terribly useful. Yeah,
but on a clear day you could see forever. You
got a clear day, you don't need night vision. Okay,
(19:29):
starlight first star I see tonight. Um, so yeah, it
was better than Generation zero. Still still pretty far acry
from what we have today. Although interestingly, if you were
to go out and buy a pair of night vision goggles,
you know, a consumer brand version would probably be Generation one,
(19:51):
I would guess, you know that's the military tends to
reserve the more the more advanced forms generations. It's they
could be generation two as well. Generation two where they
had better UH image intensive fire tubes, which meant that
they could use them in extreme low light conditions. So
(20:12):
on a moonless night, you could use these and it
would be strong enough to be able to to amplify
that light. So you can see. Generation three is what
you can find in the U. S Military now, UM,
and that is they used a new kind of photo
cathode called gallium arsenide, so it's even more sensitive than
the previous ones, which means that you know, it's it's
(20:33):
not that the UH they've really advanced the technology that much.
They just found a material that that emits electrons much
more readily than others. Yeah. As a matter of fact,
I believe we talked about gallium arsenid when we talked
about transistors. I believe we did some months back. Yeah,
and then we have generation four, which is yet more
(20:54):
improvements UH and it works both in UH in low
and high level light environments, which that's important too, because
some sometimes you're in an environment where you're gonna have
more light than UH than well, let's take two separate
nights Okay, we have one night where let's say there's
a lot of moonlight, Uh, there's starlight. There might even
be some some lights set up in whatever it is
(21:17):
you're looking at, Like let's say it's an enemy encampment.
Let's say you're sniper looking at an enemy encampment. Uh.
If you're using a device that's meant for low light environments,
you might not be able to see anything anyway, because
all of that light just overwhelms the device, and so
you all you see is just a big, you know,
green screen. Uh. So you need to have one that
(21:38):
can work in both kinds of situations. Um. So yeah,
that's your basic that's your basic. Uh. Image enhancement style
night vision. Chris and I are about to wrap up
this discussion about night vision, but before we get to that,
let's take another quick break to thank our sponsor. Now,
(22:06):
I guess we can move on to the the thermal devices,
which again can look at you can look at stuff
and see the energy it's giving off, the light it's
giving off even though light uh, an outside source of
light isn't necessarily present. M And this has to this
(22:26):
involves the whole concept of excitation. Yeah, yeah, Now, you
have to have a special type of lens to use
when you're working with thermal imaging basically to identify the
infrared light. And you've got to what happens is once
the light is focused through the lens, UM I phased
array of infrared detector elements scans it UM basically trying
(22:51):
to create a pattern called a thermogram, which shows you
the different ranges in temperature UM. And this can be
done pretty quickly, about one of a second. Yeah, so
like okay, thirty frames a second essentially, so yeah, and
considering that film is twenty four frames a second, that
is that's Yeah, it's fast enough so that you can
(23:12):
get a good view. So even if something's in motion,
you should be able to get a pretty good view
of it. Yeah. And then and then, very much like
the other style, it creates a thermogram UH and then
translates it into an electric impulse UM just like that,
and then it's sent to a signal processing unit which
(23:33):
is basically UH electronic circuit board UM and UH. Instead
of converting electrons to photons, it actually creates a display
of information UM. So it's more like a computer than
it is an ocular system with the other one. Yeah,
(23:53):
you wouldn't have a lens. You would have a monitor
of some site, some type. Now that motor might be small, Yeah,
so it could be a motor they then probably Yeah,
it could even fit into a headset or or binoculars
or whatever. Um. Yeah, this is the what I was
talking about with the the documentary Predator, where you've got
the different colors representing different temperatures. So if you've ever
(24:15):
watched any ghost hunting shows where they use thermal detectors
to try and see if there are cold or warm spots,
that's what they're using. By the way, just so just
side note, the air can actually retain heat for a
good amount of time. So let's say that you're with
a big crew of people down in a cold basement
(24:37):
and you've set up a bunch of lights and stuff,
and you're filming some things, and then you turn the
lights off and you go and you turn on the
thermal imaging detector and you see this hot spot in
the air that could possibly be generated by someone who
had been standing there for about five or ten minutes,
or even a light that had been turned on. Not
necessarily a paranormal, uh ghostly presence Okay, rant Over, I
(25:01):
was actually going to use blue Thunder as an example.
Like they used to they would fly outside and hover
outside the window and they could see the shapes where
people were. Which is funny because when you when you
mentioned it like that and the movies and tv uh,
when a person moves across the room, the heat stay,
you know, stays with the person. It's identifiable human shape.
(25:24):
It's very very much defined to that particular shape. It
seems like in the case of since the air can
retain heat, it seems like they would leave a trail
of some Yeah, depending on how where residual pattern as
much as the roadrunner does with a little cloud of dust.
It takes off well if you're if you're moving, if
you're moving steadily through the environment, you're probably not leaving
(25:47):
much of a trail. But if you have been staying
in a position and then start moving, then it wouldn't
be so quick as to you wouldn't see like a
clearly human defined red shape. Um move from h from
a position that had been standing in for like twenty
minutes and then move across the room. It wouldn't you know,
(26:08):
it wouldn't be in an immediate effect you would still
be able to see at least the residual heat that
was left behind. Now, it might be enough so that
you can clearly tell which one is the human and
which one's just the space that the human was in,
but it's not gonna be, you know, just totally clear cut. Um.
So I'm sorry. I was just gonna say. So if
you're if you're looking at a show and they're showing
(26:32):
a colored image of you know, night vision, basically that's
thermal image and if you're looking at the monochromatic green
screen version, that would be the image ence, So you
know now which one is which, right, So let's why
are you able to see the heat? That's the question. Well,
let me let me talk about some atoms here. Now
(26:52):
you've probably heard us talk about how atoms are. Uh,
normally they're moving. Yes, it's really only if you're at
zero kelvin, when you have no molecular movement, when you
have no movement on the atomic scale, absolutely, thank you,
absolute zero. Yes, uh, Because you know, atoms are always moving,
even in in solid material like a block of marble.
(27:17):
The atoms within that block of marble are moving. They're
not moving necessarily at the same speed as say, uh,
oxygen gas is moving, but they are moving, and atoms
have a specific state, an energy state that they are
naturally found in the ground state. No, no, not that
(27:39):
kind of state. The ground state is what we call it.
That's the ground state energy level. That's the amount of
energy and atom has normally if no other outside forces
or energies are acting upon it. Okay, so you've got
the ground state energy level. That's when all the electrons
are at their normal electron shell. This is from the
(28:00):
nucleus of the atom. When you add energy to an atom,
then you excite the electrons until they start to have
so much energy that they'll pop into outer electron shells
further out from the nucleus, and the more energy you
pour in, the further out they get. Okay, So when
(28:21):
you remove that energy, when that energy is when the
electrons get to a point where the energy is as
decreased enough so that the the electrons are going to
go back toward the nucleus. They have to give off
some kind of energy for that to happen. You all right,
So you think of it almost like you have a
a balloon and you over inflate that balloon. When you
(28:45):
let out the uh, the air, than that balloon is
gonna deflate some. Right, it's gonna come back down to
a smaller size, and if you keep it open, it's
gonna go all the way down to flat. Well, the
electrons are gonna start moving back towards the nucleus. They
give off photons when they do this, and depending upon
the material uh that in question, you'll get different different
(29:08):
kinds of photons within the spectrum of light. So some
things are going to give off light that is actually visible,
especially if you pour enough energy into it. That's why
Let's say you've got a toaster oven and you've got
a toaster oven going on full blast, and you look
in and you see the little toaster oven coils have
turned red. That's actually photons being given off by these atoms.
(29:30):
And uh, if you were to pour even more energy
into it, if you were to crank it up a notch,
those coils might start to glow even brighter and different colors.
So if they went from red to orange, that would
mean that you have even more energy that's being given off, right,
that you've you've poured more into it and it's and
it's giving off higher energy photons. So, uh, all materials,
(29:54):
all all things are giving off at least some kind
of photon energy when the because the whole idea of
movement and excitation, and the more it gives off, the
brighter it's going to be. So that's that's what the
thermal night vision goggles are detecting. When when they're going
when the lights being pulled through that lens, when the
(30:14):
lens is directing that light to the the sensors, it's
detecting the the photons that are given off, the thermal
infrared photons that are given off by things just because
of the excitation of atoms. So that's what we're actually
looking at. That's why you can be in a completely
isolated room. You could be in a cave deep below
(30:37):
the Earth's surface where there's there's no ambient light whatsoever,
and still be able to see based upon the what's
around you. Now, the less the less stuff gives off heat,
then the less you're gonna be able to see, the
less the less excitation is there. So if you're in
a cave where there's nothing else living in there, it
(30:57):
may you know, the thermal the thermal gogs may not
do you any good except to let you see where
your feet are in relation to the rest of you.
So that might be more useful to carry, say a flashlight. Yes, yes,
that might be a good idea to carry a flashlight
or a headlamp even better. And um, yeah, so that's
(31:17):
kind of the basics of night vision. It's pretty cool stuff.
I don't know, have you ever had an opportunity to
actually look through any sort of night vision stuff? No,
not really, I just haven't been exposed to it. Um.
But you can use it for all kinds of different things.
Of course, the military applications are obvious, um. But you
can use it for uh, you know, photography, um, for spelunking.
(31:40):
You know, that was an excellent uh suggestion, you know,
all kinds of sports and things where you might be
out on hunting, you know, out in the woods. There
are a lot of cam quarters out there that have it. Now,
there's also cars that have displays that include night vision
uh a night vision elements so that you see better
(32:01):
when you're driving a night and and they're in fact
cars that use different versions of it. There's some that
use the thermal version where they're really detecting the heat
of things, so that you can get an idea if
there's something in the road, like a person or an animal,
but those are only gonna show you things that are
again active. Really Uh. Then there are other kinds that
(32:22):
use the the the image enhancement style. Um. And there
are even some that use the active image enhancement. So
when you turn on your head lights, you're actually beaming
not just visible light, but infrared rays as well, infrared radiation.
So uh, the the system and those cars picks up
the reflection, just like we were talking about in the
(32:44):
generation zero image enhancement. Night vision he uses that same principle.
And now that of course means that the range is limited,
just as we were talking about earlier. And if it's
a foggy night, it doesn't work so well because the
fog will reflect that h that radiation back before it
can hit something more substantial, so you'll just end up
(33:06):
It's just like fog, right, It's just like if you
were to put your high beams on the fog bank there. Yeah,
and and in that case, the night vision might not
help you out unless you have well, if you have
the thermal one it might, but the the the image
enhancement style not so not so useful in that situation.
(33:27):
And that's it for another classic episode of tech Stuff.
I hope you guys enjoyed this. It's always fun to
look back in the stretches of time and revisit some
of these topics that I've talked about in the past.
I occasionally take these and make new episodes out of them,
so you never know when I might revisit this topic
and talk about the advances that have been made since
(33:48):
two thousand eleven. If you have any suggestions for future episodes,
why not go to tech Stuff podcast dot com. That
website has all the different ways to contact us. Remember
to check out our merchandise store over at t public
dot com slash tech stuff for all your tech stuff
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(34:11):
I'll talk to you again really soon for more on
this and thousands of other topics because it how stuff works.
Dot com
Get in touch with technology with tech Stuff from how
stuff works dot Com. Hei there and welcome to tech Stuff.
I'm your host, Jonathan Strickland. I'm an executive producer and
I love all things tech and it is time for
another classic episode of tech Stuff. This episode originally aired
on November two thousand eleven. And Chris Pallette, my co
(00:29):
host and editor at the time, and I decided we
wanted to take a look at something that's kind of
hard to see, that is when it's actually being used.
I'm talking about night vision. How does the technology work? Well,
Chris and I found out and now you will to
enjoy this classic episode night Vision. The technology dates back
(00:50):
to the late thirties early forties. It was technology that
was developed during World War Two and used mainly by
the American, British, and and Soviet forces during World War Two,
although other nations began to to develop their own version
of night vision technology around the same time. Well, yeah,
(01:11):
the Germans, Uh, A lot of what we had as
far as our technology in the United States was based
on some German research that was done in the late thirties. UM.
And really what it comes down to, UM is the
spectrum of light that that you're trying to see. Yeah,
(01:31):
it's it's two different things. It's trying to accept other
parts of light that human eye is not able to detect,
and also to uh to amplify whatever little light is there.
There are two main ways of achieving a night vision
UH technology. One is called image enhancement, and that's where
(01:54):
you're taking the little amount of light that's out there
and UH and trying to amplify it so that you know,
you're able to see better in that environment. And the
other is thermal imaging, which is also you know, we
think of that as being able to see heat. You know,
the whole idea about like if you've ever seen that
documentary Predator, Yeah, the Predator actually uses both forms of this,
(02:20):
but the thermal imaging would be the one where it
switches and it's that really colorful display where the hotter
things in the field of vision are a brighter color,
usually red, uh, and then the cooler things are are
in the other part of the spectrum of light, so
they'd be you know, if it's cold, it might be black,
but if it's cooler, it might be blue or even
(02:41):
kind of an indigo color. Um. Both of those are
ways of achieving night vision. The I think the one
that most people think of when they think of night
vision is the one where you've got the greenish uh display.
That's the image enhancement approach, and well, you know that
that's I think that's the reason people think about it
(03:02):
is because it's used that way in TV in the movies. Yeah,
probably so as a visual clue to the viewer that hey,
we're doing something that you can't normally do, right, Yeah.
I In fact, I watched a movie just last night
that involved having a night vision the screen tinged night vision,
(03:23):
and it was and I'm not going to call it
the documentary because that's how much of a skeptic I am.
It was paranormal activity too, and uh, you know in
paranormal activity those movies, those are done as found footage movies, which,
in case you're not familiar with the term, that's the
idea where the film is presented as if it were
uh collection of clips taken from various cameras. That it
(03:47):
wasn't meant to be a feature film. It was supposed
to be actual footage shot of something, right. So clover
Field is another example, or Blair Witch Project's another example, Yes,
that's the first time I thought about. Yeah, and that
it's really popular with the horror crowd. Uh and uh
so the paranormal activity too. There's one of the cameras
that is being used in that has a night vision
(04:09):
setting and it's using the image enhancement approach. By the way,
in case you're curious about why green, the the answer
I found through my research was that the reason why
you get green images is not because of any technological limitation.
It's because if you're in an environment where you're using
night vision, you want to be able to switch between
(04:32):
night vision and your normal vision as quickly as possible.
But if you use really intense light and and some
of the brighter lights, your pupils will constrict as you're
looking at it, which means when you take the night
vision glasses off, it's going to take more time for
your eyes to readjust to the darkness around you. But
the green that is used is a more subtle light,
(04:53):
and so your your pupils are remain mostly dilated, so
when you remove the night vision goggles, you don't of
as long a time to adjust. It doesn't take as
long for you to adjust to night regular night vision
like our natural night vision. Uh when you when you
go back and forth, and that kind of makes sense
to me. I mean, if you especially when you consider
(05:13):
that night vision was really originally used as a military technology,
you would want to be able to have as much
versatility and flexibility as possible so that you can adapt
to whatever the situation calls for. Yeah, that makes absolute
sense to me. So yeah, so at least according to that,
we could in theory have night vision where it's any color. Uh.
(05:34):
You know, it probably still probably be monochromatic, but we'll
get into that when we get into the you know
exactly what's happening. So so, all the different kinds of
night vision lie at least somewhat on the infrared, uh,
part of the spectrum of light, right, and that infrared
spectrum of light is outside the range of uh, the
(05:57):
visible light spectrum. UM. In fact, there are three parts
to the infrared spectrum, which is near infrared, and that's
the closest one to the visible spectrum spectrum. Yes, I
can say that word mid infrared um and that has uh.
I didn't mention the wavelengths. The wavelengths for near infrared
(06:17):
are from point seven to one point three microns um.
Mid infrared has wavelengths from one point three to three
microns um, and then thermal infrared, which is the biggest
part of the infrared spectrum, and that's from three to
more than thirty microns. Yeah, and so the the thermal
(06:38):
infrared you're talking at that point about infrared radiation really yeah, heat,
in other words, is what's kind of how we perceive
it usually. But uh, that's something that's actually given off
by an object itself, Whereas when we're talking about visible light,
that's something that's reflected off of an object. Right. So
(07:01):
if if I'm looking at a tree in sunlight, what
I'm seeing is the light being reflected off of that tree,
it's that lights hitting my eyes then going through the
whole focal point getting into my brain and somewhere up
there in yeah, somewhere up there in the gray matter,
my brain says, Hello, there's a tree, possibly a large
(07:22):
a large. Um. I recognize that from very far away. Yes,
that's how to recognize trees from very far away, quite
a long way away. Yeah, So that's how that would
normally work with thermal infrared. If I were to see
an object using thermal infrared. Let's say that somehow I
have that ability. You know, we're not talking about technology here,
(07:43):
but I somehow have the the the natural ability to
see the thermal infrared. It happened when they shot him
into space and he was bombarded by cosmic waves while
we're really just pop culturing this all to heck and back.
So yeah, with the thermal infrared ability, I would be
able to see the energy that is being emitted by
any particular object. Um it's not necessarily light that's reflecting off.
(08:06):
In fact, there doesn't have to be any sort of
light source at all. It just so. And if I
were in a perfectly dark room and there was another
object there that's giving off heat, essentially, I would be
able to see it because I would be seeing in
that range even though there's no other light source coming in.
It would just be that I'm actually seeing that that energy.
(08:29):
Because we'll get into why, it's kind of interesting. Has
to do with excitation, but not good vibrations. Yeah, although
perhaps that lady was able. Never mind, So moving on,
I hope you guys are enjoying this classic episode so far.
We've got more to talk about, but first, let's take
a quick break to thank our sponsor. Before we get
(08:59):
into the whole atoms and thermal infrared, let's let's talk
about the image enhancement approach first, because that's the one
that's the most familiar and uh and it's kind of interesting. Um.
The way that it works currently is that you've got
you've got very basic parts to a particular kind of
night vision. You've got you've got your lens. That's where
(09:21):
the light is going through. The objective lens. Just a
lens that catches it's a lens. Yeah, it catches ambient light,
catches near infrared light. So this is the near infrared spectrum,
the light that's closest to the visible spectrum. Now that
light is sent to a tube, and that tube is
called the image intensive fire tube intense. Yeah, and the
(09:46):
drinking energy drinks all day and yeah. So you can
think of this tube. It's almost like a vacuum tube.
In fact, there it is, There is a vacuum in
side of it. So you think of this sort of
imagine a glass vial all right in the middle of
this glass vial or on one end of the class file,
you've got something called a photo cathode. Now, the photo
cathode takes photons. Those are those individual elements of energy
(10:09):
for light. Yes, and and those come in the entire
spectrum of light um so infrared. They're infrared photons, just
as there are visible light photons. So the photo cathode
converts photons into electrons. It's it's one of those. Uh
So it changes light into electricity essentially. Yeah, And if
(10:30):
you listen to our episode about high speed and low
speed photography, we talked about how there are certain types
of materials that when a photon strikes it, it causes
a reaction. That's the case here a photocathode. It's that's
the and that's how it behaves when a photon hits it.
(10:50):
It gives off an electron. Uh So, You've got the
photo cathode at one end of this tube, and that's
where the light that's being captured by the lens is
directed to the photo cathode. The electrons emitted by the
photo cathode then have to pass through what is called
a micro channel plate or m c P. That's a
little glass disc. Yeah, I see. I thought MCP was
(11:12):
the master control program. End of line. It is. Okay, However,
two different mcps well it was until Tron got hold
of it. That's right. So glass disc Tron m c P.
I'm sensing some convergence here as we Mentionedron again. Ye.
So anyway, you've got this glass little tiny glass disc
called a micro channel plate and has lots and lots
(11:35):
of channels. That's why it's called a micro channel plate.
Lots of channels that go through this plate. Okay, So
think of the plate. Think of it like a dish.
You got a dish, put it up on its side,
and it has a whole bunch of little holes drilled
in it. Now, those holes are what allow electrons to
pass through. But there's also an electrode on either side
(11:55):
of the dish. So electrons coming from the photo cathodes
strike one side of this micro channel plate and start
to go through one of the channels. And they're going
through in the same direction they came from the the
from the photo cathode uh section of this this uh
(12:15):
this image intensive ire tube. So the photon converts to electron.
Electron goes through this channel. As it goes through the channel,
it starts to actually set off a well a reaction. Yeah,
and it basically functions as a multiplier for the electrons.
It's called a cascaded secondary emission. So this is where
(12:38):
when electron collide collides with something inside that that channel,
it starts to set off other electrons, uh, down that
same pathway, And there's a voltage applied to those electrodes
that's channeling the electrons through that pathway, like that's why
they're going in that direction. So you've got more and
more electrons bouncing off of each other through these channels,
(13:00):
which means that you've you've created an amplifier. And uh,
if you guys want to know kind of like a
big picture way of what this might look like, imagine
having a h and you can see play of videos
of this on YouTube, But imagine having a big glass
container filled with mouse traps, and each mouse trap has
(13:20):
a ping pong ball set on it, and then you
drop a ping pong ball into the glass chamber and
that will set off a mouse trap, and as the
ping pong balls bounce around, they set off more and
more mouse traps, so soon the glass case, like within
a fraction of a second ball, the balls are bouncing everywhere. Right,
same sort of idea here with the micro channel plate,
(13:42):
except that we're talking on a sub atomic level, and
we're talking about something that's really channeled, really has a
firm direction. So instead of the electrons bouncing everywhere, they're
going in a very specific direction. Right now, when they
get to the other side of that micro channel plate,
you've got the electrons still traveling in this ame direction
they were when they came in on the front side,
(14:02):
but now there are way more electrons, right, just amplified
the number. The electrons then hit a screen that's coated
with phosphors. Now phosphors pos phosphors do the they're kind
of like the opposite of the photo cathode, right. They
take When the electron strikes the phosphor, they give off light.
(14:23):
So you're changing the electron back to a photo photon. Right.
But now, because there are more electrons coming through hitting
that phosphoor than they were coming in, the light that's
generated is much greater in intensity than the light that
was coming in. So you've amplified the light. Now that
information that light is sent to a viewer of some type.
(14:44):
It could just be a regular lens, which is usually
called the ocular lens, or it could be sent to
a monitor. So if you have a pair of night
vision goggles or a night vision scope. That's what you're seeing.
You're seeing that amplified light hitting the lens or the
Monitor's cool, it's pretty awesome, right, And again, this isn't
(15:06):
just the the visible light, the ambient visible light that's
out there, but also the infrared light. So um, because
those photons, you know it doesn't you know, the photons,
It doesn't matter if it's visible or not. UM. And uh,
the more light that's hitting certain areas, that the brighter
it's going to be for whatever it is you're looking at.
(15:27):
So if you're looking at something that's that's fairly reflective, um,
you're gonna be able to see it in higher definition
than you could with something that is not as reflective. Now,
there are different ways of actually achieving this too. You
can have a various they're various generations of this technology,
(15:48):
all right. So the earliest generation of this technology actually
involved shining infrared light at the objects you're looking at
through the through the night vision goggles, right, So when
that that infrared light was reflected, then you would be
able to see it, right, because these goggles were not
(16:09):
so sensitive as to be able to take just the
ambient light. Right, if you did that, you would probably
get you you might be able to see marginally better
than you would if you had just use your regular vision.
But using this infrared flashlight, essentially you could illuminate the
scene and be able to see it through the night
vision goggles. But if you did not have the goggles,
(16:31):
because infrared light falls outside the visible spectrum, any independent
observer wouldn't be able to tell what you were doing. Yeah, now,
I UM I did some research on the the US
military website about the history of of night vision and apparently,
um they sent about three hundred sniper scopes over to
(16:54):
be used in the Pacific theater during World War Two,
but they didn't get used very much because of the
way that the technology worked. Um they really could see
less than a hundred yards. Yeah, they weren't very effective, right,
because again, since it's dependent upon a reflected ray of
infrared light, if it's you know, the rays starting to
(17:17):
dispersees as it goes out, Right, it's not not a
not a concentrated like a laser beam. Yeah, it's not
a beam. It does disperse and diffuse as it goes out.
So the further away your target the less likely you're
going to be able to see it, and even with
a really really advanced version. That's, by the way, it's
called active infrared because you're actively beaming infrared radiation out
(17:39):
in order to try and see stuff coming back through
the monitors. Um if because because you're relying on that reflection,
if it's too far away, you're not gonna be all
se very well. So obviously a sniper rifle, where at
least in theory, you want to be able to put
your snipers at a good distance away from the targets
(18:00):
to maximize their effectiveness and minimize the chance that they
will be targeted. Um it doesn't. It's not so effective
if you know your your distance is cut down that dramatically. Yeah. Plus,
the first generation wasn't exactly um useful for someone like
a sniper, considering the batteries were huge and the i
R emitters had to be carried on flatbed trucks. It's
(18:23):
hard to put one of those up in a tree. Yeah. Yeah,
it turns out that also all of these are going
to involve having a power supply of some sort. But
for the active infrared it requires either more more energy
because you're not you're not just for your your actual
night vision device, whether it's a scope or goggles or whatever,
but also for the emitter. By the way, that generation
(18:45):
is normally referred to as generation zero for a night vision.
Generation one was the first generation using passive infrared system. Now,
this was the kind of of night vision goggles or
scope that could just use the ambient light in the area,
although it needed a good amount of the ambient light.
(19:06):
So moonlight or starlight. It's funny you should say starlight. Yeah,
that's what it was called. Yea in the U. S.
Army they called it starlight. Uh, the without the moon
or stars, you wouldn't be able to see very much.
So on an overcast night it would not be terribly useful. Yeah,
but on a clear day you could see forever. You
got a clear day, you don't need night vision. Okay,
(19:29):
starlight first star I see tonight. Um, so yeah, it
was better than Generation zero. Still still pretty far acry
from what we have today. Although interestingly, if you were
to go out and buy a pair of night vision goggles,
you know, a consumer brand version would probably be Generation one,
(19:51):
I would guess, you know that's the military tends to
reserve the more the more advanced forms generations. It's they
could be generation two as well. Generation two where they
had better UH image intensive fire tubes, which meant that
they could use them in extreme low light conditions. So
(20:12):
on a moonless night, you could use these and it
would be strong enough to be able to to amplify
that light. So you can see. Generation three is what
you can find in the U. S Military now, UM,
and that is they used a new kind of photo
cathode called gallium arsenide, so it's even more sensitive than
the previous ones, which means that you know, it's it's
(20:33):
not that the UH they've really advanced the technology that much.
They just found a material that that emits electrons much
more readily than others. Yeah. As a matter of fact,
I believe we talked about gallium arsenid when we talked
about transistors. I believe we did some months back. Yeah,
and then we have generation four, which is yet more
(20:54):
improvements UH and it works both in UH in low
and high level light environments, which that's important too, because
some sometimes you're in an environment where you're gonna have
more light than UH than well, let's take two separate
nights Okay, we have one night where let's say there's
a lot of moonlight, Uh, there's starlight. There might even
be some some lights set up in whatever it is
(21:17):
you're looking at, Like let's say it's an enemy encampment.
Let's say you're sniper looking at an enemy encampment. Uh.
If you're using a device that's meant for low light environments,
you might not be able to see anything anyway, because
all of that light just overwhelms the device, and so
you all you see is just a big, you know,
green screen. Uh. So you need to have one that
(21:38):
can work in both kinds of situations. Um. So yeah,
that's your basic that's your basic. Uh. Image enhancement style
night vision. Chris and I are about to wrap up
this discussion about night vision, but before we get to that,
let's take another quick break to thank our sponsor. Now,
(22:06):
I guess we can move on to the the thermal devices,
which again can look at you can look at stuff
and see the energy it's giving off, the light it's
giving off even though light uh, an outside source of
light isn't necessarily present. M And this has to this
(22:26):
involves the whole concept of excitation. Yeah, yeah, Now, you
have to have a special type of lens to use
when you're working with thermal imaging basically to identify the
infrared light. And you've got to what happens is once
the light is focused through the lens, UM I phased
array of infrared detector elements scans it UM basically trying
(22:51):
to create a pattern called a thermogram, which shows you
the different ranges in temperature UM. And this can be
done pretty quickly, about one of a second. Yeah, so
like okay, thirty frames a second essentially, so yeah, and
considering that film is twenty four frames a second, that
is that's Yeah, it's fast enough so that you can
(23:12):
get a good view. So even if something's in motion,
you should be able to get a pretty good view
of it. Yeah. And then and then, very much like
the other style, it creates a thermogram UH and then
translates it into an electric impulse UM just like that,
and then it's sent to a signal processing unit which
(23:33):
is basically UH electronic circuit board UM and UH. Instead
of converting electrons to photons, it actually creates a display
of information UM. So it's more like a computer than
it is an ocular system with the other one. Yeah,
(23:53):
you wouldn't have a lens. You would have a monitor
of some site, some type. Now that motor might be small, Yeah,
so it could be a motor they then probably Yeah,
it could even fit into a headset or or binoculars
or whatever. Um. Yeah, this is the what I was
talking about with the the documentary Predator, where you've got
the different colors representing different temperatures. So if you've ever
(24:15):
watched any ghost hunting shows where they use thermal detectors
to try and see if there are cold or warm spots,
that's what they're using. By the way, just so just
side note, the air can actually retain heat for a
good amount of time. So let's say that you're with
a big crew of people down in a cold basement
(24:37):
and you've set up a bunch of lights and stuff,
and you're filming some things, and then you turn the
lights off and you go and you turn on the
thermal imaging detector and you see this hot spot in
the air that could possibly be generated by someone who
had been standing there for about five or ten minutes,
or even a light that had been turned on. Not
necessarily a paranormal, uh ghostly presence Okay, rant Over, I
(25:01):
was actually going to use blue Thunder as an example.
Like they used to they would fly outside and hover
outside the window and they could see the shapes where
people were. Which is funny because when you when you
mentioned it like that and the movies and tv uh,
when a person moves across the room, the heat stay,
you know, stays with the person. It's identifiable human shape.
(25:24):
It's very very much defined to that particular shape. It
seems like in the case of since the air can
retain heat, it seems like they would leave a trail
of some Yeah, depending on how where residual pattern as
much as the roadrunner does with a little cloud of dust.
It takes off well if you're if you're moving, if
you're moving steadily through the environment, you're probably not leaving
(25:47):
much of a trail. But if you have been staying
in a position and then start moving, then it wouldn't
be so quick as to you wouldn't see like a
clearly human defined red shape. Um move from h from
a position that had been standing in for like twenty
minutes and then move across the room. It wouldn't you know,
(26:08):
it wouldn't be in an immediate effect you would still
be able to see at least the residual heat that
was left behind. Now, it might be enough so that
you can clearly tell which one is the human and
which one's just the space that the human was in,
but it's not gonna be, you know, just totally clear cut. Um.
So I'm sorry. I was just gonna say. So if
you're if you're looking at a show and they're showing
(26:32):
a colored image of you know, night vision, basically that's
thermal image and if you're looking at the monochromatic green
screen version, that would be the image ence, So you
know now which one is which, right, So let's why
are you able to see the heat? That's the question. Well,
let me let me talk about some atoms here. Now
(26:52):
you've probably heard us talk about how atoms are. Uh,
normally they're moving. Yes, it's really only if you're at
zero kelvin, when you have no molecular movement, when you
have no movement on the atomic scale, absolutely, thank you,
absolute zero. Yes, uh, Because you know, atoms are always moving,
even in in solid material like a block of marble.
(27:17):
The atoms within that block of marble are moving. They're
not moving necessarily at the same speed as say, uh,
oxygen gas is moving, but they are moving, and atoms
have a specific state, an energy state that they are
naturally found in the ground state. No, no, not that
(27:39):
kind of state. The ground state is what we call it.
That's the ground state energy level. That's the amount of
energy and atom has normally if no other outside forces
or energies are acting upon it. Okay, so you've got
the ground state energy level. That's when all the electrons
are at their normal electron shell. This is from the
(28:00):
nucleus of the atom. When you add energy to an atom,
then you excite the electrons until they start to have
so much energy that they'll pop into outer electron shells
further out from the nucleus, and the more energy you
pour in, the further out they get. Okay, So when
(28:21):
you remove that energy, when that energy is when the
electrons get to a point where the energy is as
decreased enough so that the the electrons are going to
go back toward the nucleus. They have to give off
some kind of energy for that to happen. You all right,
So you think of it almost like you have a
a balloon and you over inflate that balloon. When you
(28:45):
let out the uh, the air, than that balloon is
gonna deflate some. Right, it's gonna come back down to
a smaller size, and if you keep it open, it's
gonna go all the way down to flat. Well, the
electrons are gonna start moving back towards the nucleus. They
give off photons when they do this, and depending upon
the material uh that in question, you'll get different different
(29:08):
kinds of photons within the spectrum of light. So some
things are going to give off light that is actually visible,
especially if you pour enough energy into it. That's why
Let's say you've got a toaster oven and you've got
a toaster oven going on full blast, and you look
in and you see the little toaster oven coils have
turned red. That's actually photons being given off by these atoms.
(29:30):
And uh, if you were to pour even more energy
into it, if you were to crank it up a notch,
those coils might start to glow even brighter and different colors.
So if they went from red to orange, that would
mean that you have even more energy that's being given off, right,
that you've you've poured more into it and it's and
it's giving off higher energy photons. So, uh, all materials,
(29:54):
all all things are giving off at least some kind
of photon energy when the because the whole idea of
movement and excitation, and the more it gives off, the
brighter it's going to be. So that's that's what the
thermal night vision goggles are detecting. When when they're going
when the lights being pulled through that lens, when the
(30:14):
lens is directing that light to the the sensors, it's
detecting the the photons that are given off, the thermal
infrared photons that are given off by things just because
of the excitation of atoms. So that's what we're actually
looking at. That's why you can be in a completely
isolated room. You could be in a cave deep below
(30:37):
the Earth's surface where there's there's no ambient light whatsoever,
and still be able to see based upon the what's
around you. Now, the less the less stuff gives off heat,
then the less you're gonna be able to see, the
less the less excitation is there. So if you're in
a cave where there's nothing else living in there, it
(30:57):
may you know, the thermal the thermal gogs may not
do you any good except to let you see where
your feet are in relation to the rest of you.
So that might be more useful to carry, say a flashlight. Yes, yes,
that might be a good idea to carry a flashlight
or a headlamp even better. And um, yeah, so that's
(31:17):
kind of the basics of night vision. It's pretty cool stuff.
I don't know, have you ever had an opportunity to
actually look through any sort of night vision stuff? No,
not really, I just haven't been exposed to it. Um.
But you can use it for all kinds of different things.
Of course, the military applications are obvious, um. But you
can use it for uh, you know, photography, um, for spelunking.
(31:40):
You know, that was an excellent uh suggestion, you know,
all kinds of sports and things where you might be
out on hunting, you know, out in the woods. There
are a lot of cam quarters out there that have it. Now,
there's also cars that have displays that include night vision
uh a night vision elements so that you see better
(32:01):
when you're driving a night and and they're in fact
cars that use different versions of it. There's some that
use the thermal version where they're really detecting the heat
of things, so that you can get an idea if
there's something in the road, like a person or an animal,
but those are only gonna show you things that are
again active. Really Uh. Then there are other kinds that
(32:22):
use the the the image enhancement style. Um. And there
are even some that use the active image enhancement. So
when you turn on your head lights, you're actually beaming
not just visible light, but infrared rays as well, infrared radiation.
So uh, the the system and those cars picks up
the reflection, just like we were talking about in the
(32:44):
generation zero image enhancement. Night vision he uses that same principle.
And now that of course means that the range is limited,
just as we were talking about earlier. And if it's
a foggy night, it doesn't work so well because the
fog will reflect that h that radiation back before it
can hit something more substantial, so you'll just end up
(33:06):
It's just like fog, right, It's just like if you
were to put your high beams on the fog bank there. Yeah,
and and in that case, the night vision might not
help you out unless you have well, if you have
the thermal one it might, but the the the image
enhancement style not so not so useful in that situation.
(33:27):
And that's it for another classic episode of tech Stuff.
I hope you guys enjoyed this. It's always fun to
look back in the stretches of time and revisit some
of these topics that I've talked about in the past.
I occasionally take these and make new episodes out of them,
so you never know when I might revisit this topic
and talk about the advances that have been made since
(33:48):
two thousand eleven. If you have any suggestions for future episodes,
why not go to tech Stuff podcast dot com. That
website has all the different ways to contact us. Remember
to check out our merchandise store over at t public
dot com slash tech stuff for all your tech stuff
merchandise needs. Every purchase goes to help the show and
we greatly appreciate it. And uh, that's it for me.
(34:11):
I'll talk to you again really soon for more on
this and thousands of other topics because it how stuff works.
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Karah Preiss
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