How does the thermal goggles know what is warm and what is cold? And why doesnt the army use thermal over nightvision any day?
In: Engineering
You know how a hot piece of metal glows? Well, everything glows based on its temperature. Just like a hotter thing glows whiter, a less hot thing glows redder.
So “red” that it passes red. It doesn’t glow in visible light at all. It glows in *infrared* light – a light that is past red and invisible to humans. In fact, it’s difficult to detect at all, since your camera will also be glowing with that light.
But, with some smarts (and often a lot of money) we can solve this problem and make a camera that sees this glow. Such a camera is called a “thermal camera”.
Therms have a lot of limitations. Some combination of being very expensive, having a low framerate (so the video looks really choppy), heavy, using a lot of energy, and producing very low resolution pictures. Partly because of this, it can also be hard to make out normal stuff like trees or rocks in thermals, so if all you saw was thermals you might trip. These limitations come mostly from the fact that your camera is also hot, or alternatively it needs to be cooled down. Both of these come with downsides – big ones.
Everything around us emit light based on their temperature. We call that blackbody radiation.
Room temperature objects **do** emit energy in the form of light. But its frequency is low enough that it falls outside the visible spectrum and into infrared (and lower bands of the electromagnetic spectrum).
Heat an object up and, you guessed it, it starts to glow. That’s when the radiation emitted starts dipping into visible light. At first, it’s red hot. Afterwards, it becomes glowy white. That’s when that radiation is so intense it leaves the visible spectrum and turns into ultraviolet light. That’s the stuff the Sun emits, by the way.
Thermal cameras simply allow you to see outside the visible spectrum.. The human body is significantly warmer than any other object or landscape around at any given time, so it’s ideal for spotting people.
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