by Alex Circelli
Night Vision Goggles
Night Vision Goggles
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Conventional night vision goggles do not work in absolute darkness. Image Intensifying devices use light amplification and require some available light to function. These devices increase visibility by amplifying the light from 2,500 to 5,000 times that of normal visual range. However, the image does not go straight to the eyes. It is first sent to the image intensifier, (often called the "third eye" of the goggles) where the image is turned green before being transmitted to the user's eyes. The signature green hue of night vision goggles is due to a change in the contrast. Humans can see the color green better than any other color of the visible spectrum. Green night vision helps the human eye make out objects and make out distances in dark situations.
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The first thing you probably think of when you see the words night vision is a spy movie you've seen, in which someone straps on a pair of night-vision goggles to find someone else in a dark building on a moonless night. And you may have wondered "Do those things really work? Can you actually see in the dark?"
The answer is most definitely yes. With the proper night-vision equipment, you can see a person standing over 200 yards away on a moonless, cloudy night! Night vision uses optics in two very different ways, depending on the technology used.
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Infrared Light- This works by collecting the tiny amounts of light, including the lower portion of the infrared light spectrum, that are present but may be imperceptible to our eyes, and amplifying it to the point that we can easily observe the image.
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Refraction - The limited light from the object will have to be magnified and projected on to an electronic sensor (CCD) . This means that a lens will have to be used and lenses use refraction of light for them work. Don't forget that the more glass the light passes through the more is obsorbed and so less light to form the image.