Why is night vision green?

July 3, 2020

 

Firstly, night-vision isn't just a thing in your favorite first-person shooter. It's present in everything from the surveillance cameras to military periscopes and ordinary smartphones. In fact, part of the reason night vision has so many applications it's because it's not just one specific piece of technology rather it comes in several different forms that can be deployed depending on the use case. But what man people think when they hear the words "night vision" is something called image intensification of image enhancement. This is a stereotypical green form of night vision that you may associate with the military or you see in action movies speaking of which that green color is used on purpose because your eyes are more sensitive to green than other colors.

Who and When Invented Night Vision?

The first breakthrough in modern military night vision came in the 1930s at the result of early research in television and the development of an image tube that could be used to convert infrared images into visible displays. Recognizing the military significance of this invention the army began pursuing their own research. The effort resulted in the familiar sniper scope of World War II. In today's terms, a sniper scope is a rather primitive night-vision device but its popularity helped pave the way for the more sophisticated near-infrared systems of the future. In the 1950s army, night-vision experts were successful in developing light amplifying tubes that did not require the cumbersome and power-consuming infrared light source. It was at night vision laboratory in Virginia, where the first imaging intensifiers, thermal imaging devices, and infrared searchlights were invented. The first Generation image tube which needs no light source scored a tremendous success in Vietnam where it was put to the test in conditions of night combat. 1 Generation image intensifiers accomplished two important objectives in the late 1960s and early 1970s. They satisfied an urgent need on the battlefields of Southern Asia and proved the effectiveness of passive night vision. But, of course, they had their drawbacks. They were too costly and too heavy and cumbersome for some applications.
A shortcoming of the first generation tube at the upper left was largely surmounted with the recent introduction of two second-generation image intensifier tubes. Not only they are lighter and cheaper but in several respects superior to their 1 generation predecessors. This development signified a major advance in the army's night-vision technology; costs were reduced increasing the potential of broad army issues. Generation 2 nearly eliminates the problem inherent in the 1 generation device: the momentary blinding of the user by light emitted from tracer bullets.
Another item that stood to benefit by the second-generation pew is the multi-purpose night-vision goggles. It was designed to give the individual soldier around-the-clock mobility, a capability of performing, a variety of combat, and support tasks during darkness. What is more, googles ideally suited for night driving. They permitted driver a field of view of 40 degrees and the visibility of up to 100 meters in the moonlight and 50 meters in straight light at speeds up to 35 miles per hour. The goggles were envisioned to be of great value with the performance of a variety of other nighttime tasks including air rescue and medical aid. A monocular version of the goggles was a handheld pocket scope. It was designed to be used as a personal night viewer for patrol local surveillance, weapon fire, and general orientation in darkness. The pocket scope can also be employed to detect enemy use of infrared lights.

What about the green vision?

Image enhancement works being able to detect low levels of light and then amplify it. When photons, the tiny particle that makes up light, enter an image enhancer they first hit a special layer called a photocathode which releases electrons. These electrons then hit a second layer called a microchannel plate which multiplies the electrons before they hit the phosphor screen. Well, that then converts them back into the light because there are now so many more electrons you get a brighter image, so you'll have an easier time getting into someone's base and killing all their nudes.
But hold on a second, what if there isn't enough light for thermal enhancers to "see" at all? This is where thermal imaging comes in. Instead of detecting light thermal cameras detect heat that comes off of a different object since they can see infrared light. The heat causes things to emit photons in the infrared or IR spectrum and although humans can't see infrared light these special cameras take advantage of it in several different ways. Our cameras produce images called thermograms which sometimes look like a rainbow where different colors represent different temperatures. Thermograms are useful for everything seemingly from medicine to construction but they are very specifically handy for night vision. It's really easy to pick out different objects such as people or animals due to their different colors standing out on a screen.
Thermal cameras often can achieve the same level of detail as their image-enhancing counterparts. They have the big advantage of being able to pick out things that might be hard to see with a normal image enhancer. For example, a firefighter trying to locate people that need to be rescued in a burning building or a hunter picking out prey deep in the woods hiding behind foliage or cops trying to locate the hiding fugitive. And speaking of thermal imaging, some cameras can even create their own infrared light in a process called active illumination where they are actually light up the surroundings with IR radiation. Because this additional infrared energy reflects off of whatever the cameras pointed at this strategy can result in much higher resolution images. Great for things like surveillance cameras where you really want to get a positive ID on that purp that tried to steal your slushie machine.
To sum up, the big reason why night vision is green is that the screen that is used for image-intensification inside the device itself is mainly made out of phosphor. One more important thing to remember, a night vision is green because human eye can differentiate more shades of green, than any other color.