Night Vision Goggles: Explained + Density Effects

[Great Smoky]

Can somebody explain how night vision and/or a black light work? I know it does something where it enhances dark colors to an infrared light spectrum. Would the same concept work for object or fluid density? For example, if I was wearing this night vision goggles and see oil on the floor, will it be brighter when it is more dense versus when it is less dense, etc.?

 

[chrisbaird]

No, night vision googles see radiated infrared light, which is dependent on the object's temperature, not its density. If the oil on the floor was hot, then it will be brighter. Everything literally glows infrared light just like a heated toaster element glows red (it's called black body radiation). The hotter an object, the more infrared light it gives off. Our eyes are tuned to see visible sunlight reflecting off objects, which obviously fails is in the dark off night. But night-goggles see the infrared radiation that is emitted by object naturally. This is useful because warm-blooded animals and machines that have been running (such as trucks) are much hotter than the environment and therefore are very bright in an infrared image. The important point is that standard infrared cameras (such as in night goggles) don't do anything special. The infrared radiation coming from the landscape already exists where there is a camera or not. The camera just forms the radiation into an image through the use of a lens, then records the image, and then re-displays it on a screen that emits visible light s0 a human can see it. The hard part of actually getting an infrared camera to work is the fact that the camera parts themselves have a temperature and are glowing infrared radiation, which can swamp out the actual signal.

 

[Drakkith]

There are multiple designs that use different methods to allow night vision. See here for more: http://en.wikipedia.org/wiki/Night_vision

A black light works differently: http://en.wikipedia.org/wiki/Black_light