How does Night Vision Device (NVD) work?
Everyone tends to be curious to know about the technology behind the night vision device In this post, we will know the science behind the working of NVD which enables our soldier to keep an eye on the enemy or guard the border areas. Let's begin,
Section of NVD
- The main purpose of a night vision goggle is to amplify the dim light that it receives to such an extent that it is possible to see in the dark.
- The NVD mainly have 3 section which enables the boosting of light and those are- Photocathode, Photomultiplier, Phosphorus screen.
- Firstly the Dim light from a night scene enters the lens at the front section known as the photocathode. As we know the light is made of photons (particles of light) of all colors.
- After the photons enter the goggles, they strike a light-sensitive surface called a photocathode. Its purpose is to convert photons into electrons.
- These electrons then move towards the mid-section of the NVD, amplification by a photomultiplier takes place here. To make it simple i.e. each electron entering the photomultiplier results in many more electrons leaving it.
- The last section is the screen made of the phosphor. The electrons leaving the photomultiplier hit a phosphor screen. As the electrons hit the phosphor, they create tiny flashes of light.
- You all must be wondering then how come we see an image which is continuous if electrons are striking in parts? The answer is the number of electrons is too many. Relate this to the television screen.
- Since there are many more photons than originally entered the goggles, the screen makes a much brighter version of the original scene
The question that intrigued me was why is everything green when we view through night vision Google?
- Even at night, the photons that hit the lens at the front of night vision goggles are carrying the light of all colors.
- But when they are converted to electrons, there's no way to preserve that information. Effectively, the incoming, colored light is turned into black and white.
- Why, then, don't night vision goggles look black and white?
- The phosphors on their screens are chosen for this purpose only to make green pictures because our eyes are more sensitive to green light.
- It is Scientifically proven that watching at green screens for long periods is easier than to look at black and white ones.
- Hence, night vision goggles have their characteristic green glow.
Hope this post will serve the purpose of explaining the functioning of NVD in detail.
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