Whether on television or in the movies, you've probably seen spies or soldiers using special glasses to see in the dark. We call those special glasses night vision goggles and today's Wonder of the Day takes a closer look at how they work!
If you're WONDERing whether night vision goggles really work or are just the stuff of movies, the answer is a definite “Yes, they really do work!" The best night vision goggles can help you see a person standing over 200 yards away on a cloudy, moonless night.
Before we discuss the two types of technology, it's important to understand something about light. Did you know that not all light is visible? It's true! The light we can see — called visible light — is only a part of the overall electromagnetic spectrum (all types of light). There are other types of light, such as infrared and ultraviolet light, that can't be seen by the naked eye.
If you want to see in the dark, there are a couple of ways you can go about it. The first way requires a type of technology called image enhancement. This basically means that equipment takes what is there and makes the most of it.
Even in the darkest of conditions, there are tiny bits of light present. Some of this light may be infrared light that isn't visible to the naked eye. Night vision goggles using image enhancement technology collect all the available light, including infrared light, and amplify it so that you can easily see what's going on in the dark.
Hot objects, including human bodies, emit some heat in the form of infrared light. Night vision goggles using thermal imaging technology capture the infrared light being emitted as heat by objects in the field of view. In this way, you can see an image of what's going on in the dark based upon the amount of heat being generated by various objects.
Thermal imaging works well when trying to detect people in the dark. It's also better suited for conditions approaching absolute darkness. Most night vision equipment, however, uses image enhancement technology.
Night vision technology has many uses for the military and law enforcement agencies. For example, it can be used to find people in the dark, as well as for and surveillance. Night vision can also be used for hunting and watching animals after dark.
If you've ever seen a night vision image, you've probably noticed that it always has a green glow. That's intentional. When available light is captured and amplified, it's turned into electronic information that has to be transmitted to the eyes.
In essence, this electronic information is colorless. Why aren't the pictures black and white then? Night vision goggles are made with screens that produce green pictures, because human eyes are more sensitive to green light and it's easier to look at green pictures for long periods of time than it is to look at black and white pictures.