Why Do Night Vision Goggles Have 4 Lenses?

You may have noticed that the night vision goggles that the US military used in taking down Bin Laden, and as featured in such military films such as Zero Dark Thirty, had four different lenses. What makes them different from the others that only rely on just two lenses or a single lens in the form of monocular and similar devices? That’s what we are going to discuss in the following post.

The Problem With Monocular and Binocular Night Vision Devices

More conventional night vision devices, such as monocular and binoculars are problematic because they only offer a limited FOV or field of vision. This produces a tunnel vision-style effect and also is hampered by several depth-perception problems. All of these issues are not exactly things the military or even law enforcement needs to deal with when they are involved in special missions and tactical moves after nightfall.

The Basics of Night Vision

To help understand why 4 lenses are used rather than one though, we need to discuss briefly how night vision technology works. Night vision devices such as goggles utilize a tech known as image intensification. This extracts all low-level light and then converts the light’s photons into electricity while amplifying the signal and then displaying the enhanced image onto a green phosphor screen.

Another form of night vision goggles that you may be familiar with is the FLIR or Forward-Looking Infrared System. These do not boost or amplify anything at all. Rather, they create a false-color display of the infrared radiation signature picked up from what’s in your field of vision. Why have we mentioned this? It all comes back to the four lenses goggles.

When Both Systems Are Combined

When you use FLIR and image intensification together, you have a particularly effective and efficient combination. You have the benefit of night vision for longer range spotting in normal conditions, with the infrared that augments its vision capabilities when you are in low light conditions.

The best example of this combined creation is the Ground Panoramic Night Vision Goggle designed by L3 Warrior Systems. The same model was used in taking down Bin Laden. Yes, it looks a little silly or like something from a cheesy sci-fi flick, but it offers the best field of vision.

More About the GPNVG-18

Known as the GPNVG-18 for short, this is a great example of a night vision goggle that uses four lenses rather than 2. It is mounted onto a helmet and provides a 97-degree horizontal FOV for target identification and observational purposes.

The central intensifier tubes on it work in the same way as night vision goggles, producing a conventional binocular-style, overlapping image. While the two additional tubes at either side give offset views of the outer edges of the main central image. It is basically like using two pairs of binoculars held side by side in front of you.

So, although it looks a bit silly, this piece of kit allows the user to see dark corners quicker at just a quick glance rather than needing to turn completely to face them.

 

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