WEBVTT - How Does Night Vision Work?

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<v Speaker 1>I am Scott and I'm Then and we're from car Stuff.

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<v Speaker 1>get your podcast. Welcome to brain Stuff from how Stuff Works. Hey,

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<v Speaker 1>brain Stuff, this is Christian Seger. So night vision seems

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<v Speaker 1>like a pretty cool idea, right, I mean, you see

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<v Speaker 1>it all the time in movies. Some secret agent type

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<v Speaker 1>straps on a pair of goggles, sneaks into a luxurious

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<v Speaker 1>supervillain compound and mows down enemies under the cover of darkness,

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<v Speaker 1>or the Predator stocks Arnold Schwarzenegger killing his platoon one

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<v Speaker 1>by one by one. And as you're watching all this,

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<v Speaker 1>you may occasionally ask yourself, Hey, do those goofy looking

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<v Speaker 1>goggles really work? Well? The answer is yes, absolutely. With

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<v Speaker 1>a good night vision device or n v D, you

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<v Speaker 1>can see a person standing over two hundred yards or

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<v Speaker 1>a hundred and eighty three meters away on a moonless,

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<v Speaker 1>cloudy night. And whether we're talking goggles, scopes or cameras,

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<v Speaker 1>Most of these devices rely on one or two types

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<v Speaker 1>of night vision, image enhancement that's the green looking one,

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<v Speaker 1>and thermal imaging, which is the bluish gray stuff. They

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<v Speaker 1>both produce results, but work in different ways. Thermal imaging

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<v Speaker 1>captures the upper portion of the infrared light spectrum. Objects

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<v Speaker 1>emit this as heat rather than reflecting it as light.

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<v Speaker 1>Hotter objects, such as the bodies of secret agents, emit

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<v Speaker 1>more of this light than cooler objects like buildings, trees,

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<v Speaker 1>or you know, dead bodies, and that's what you're seeing

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<v Speaker 1>when you use thermal imaging, essentially a measure of temperature

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<v Speaker 1>from negative four degrees fahrenheit to three thousand and six

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<v Speaker 1>hundred degrees fahrenheit. The magic, or well, you know, the

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<v Speaker 1>science starts at the lens, which focuses the infrared lightmitted

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<v Speaker 1>by all of the objects in view and uses a

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<v Speaker 1>phased array of infrared detector elements to create a temperature

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<v Speaker 1>pattern called a thermogram, which is translated first into electric

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<v Speaker 1>impulses and then into data for the display, where it

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<v Speaker 1>appears as various colors depending on the intensity of the infrared.

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<v Speaker 1>Then there's image enhancement. This collects tiny amounts of light,

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<v Speaker 1>including the lower portion of the infrared light spectrum and

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<v Speaker 1>amplifies it. Devices using this approach rely on an image

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<v Speaker 1>intensifier tube to collect and amplify light, both the infrared

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<v Speaker 1>kind and the visible stuff. Image enhancers use a photo

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<v Speaker 1>cathode to convert photons into electrons and high voltage to

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<v Speaker 1>amplify those electrons in a micro channel plate or an

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<v Speaker 1>m c P before they hit a screen that's coated

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<v Speaker 1>with phosphors. Here's the crazy part. These electrons maintain their

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<v Speaker 1>position in relation to the micro channel they passed through,

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<v Speaker 1>which provides a perfect image. Since the electrons stay in

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<v Speaker 1>the same alignment as the original photons. When they hit

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<v Speaker 1>the screen, their energy excites the phosphors, releasing photons. Those

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<v Speaker 1>phosphors create the green image you see when you look

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<v Speaker 1>through a night vision scope. Check out the brain Stuffed

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<v Speaker 1>channel on YouTube, and for more on this and thousands

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<v Speaker 1>of other topics, visit how staff works dot com.