Night Vision Goggles Explained: How do they work?

Night Vision Goggles Explained

This is one piece of equipment that you may want to consider adding to your arsenal of protection preps. Before the days of electricity, when war was waged with swords and muskets, battles would end when the sun went down because no one could identify friend from foe. Once the sun rose the battle would begin again. Night vision has change what the enemy can do at night. It was first used by the Germans in World War II, giving them a superior tactical advantage with devastating effects. The ability to see at night is a very valuable resource. It allows you to flee or fight under the cover of night.

If you want to get a good pair of night vision goggles, then you need to understand how they work. It might also help you decide on their advantages as compared to that of a flashlight or an infrared scope. So if you want to understand how it’s actually possible to handle the dark night, you’re in the right place.

Night Vision Goggles Explained

Light and heat

Do you think that you can see everything if there’s light? Well, what if we told you there are some types of lights you can’t actually see? Apart from the sunlight that makes everything visible, infrared and ultraviolet are also part of the electromagnetic spectrum, but they’re invisible.

But some night vision scopes and goggles can pick up even the faintest fragments of light, including infrared, enhancing them until the threshold to visibility is surpassed. Then, you will be able to see things around you, thanks to what it’s known as image enhancement.

Other night goggles use thermal imaging, a technology that picks up the heat waves emitted by objects. These heat waves are translated as infrared light, which is what the goggles actually pick up. However, there are hot objects, like animals and humans, as well as cold objects like buildings or trees, so these will appear differently.

The theory

Night vision goggles that use image enhancement have three important parts: a photocathode in front, near the lens, a photomultiplier located near the middle and a phosphor screen at the end, near your eyes.

All types of light are made out of subatomic particles called photons which pass through the front lenses. Doing so, they hit the photocathode, which is a sort of miniature solar panel with a surface that’s sensitive to light. The purpose of this screen is to transform the photons into electrons, which actually means it transforms light into electricity.

Traveling further inside the night goggles, these electrons meet the photomultiplier which is put there to actually multiply their number. So now you’ve got an increased number of electrons traveling further back in the goggles to your eyes, where they meet the phosphor screen. This screen has the opposite role of the photocathode, converting the electrons into photons.

But since there are more electrons now, there will also be an increased number of photons or light particles that reach your eyes. And that’s why you can actually see in the dark, thanks to night goggles that enhance the surrounding light.

The practice

But things are never as simple as that in practice, hence the vast array of different night vision devices on the market. However, night goggles have the advantage of a 1x magnification, meaning they won’t actually make an object seem larger, they’re just increasing the number of light particles picked up from the environment. That means you’ll get an accurate depth perception so you can easily move around.

Another important part of these night goggles are the lenses and how qualitative they are. An all-glass lens that has multiple layers of coating render brighter images than cheap, plastic lens that isn’t coated at all or has just a layer of coating. Besides, the bigger the lens diameter, the more photons can pass through the lenses, so you can end up seeing more details.

The focusing mechanism that comes between the photocathode and the photomultiplier has an important purpose too. This is used to make sure that neither of the electrons gets lost along the way, focusing them precisely through the multiplier or image intensification tube, as it’s also called.

Red light! Greenlight!

Another interesting fact about the image enhancement technology is that it renders just green images, though the light it picks up is called infra-RED. How can that be, if you’re using infrared and if the objects reflect the entire light spectrum? The reason is that once they pass through the photocathode, the newly formed electrons don’t “remember” the color. In fact, these electrons carry a sort of light that corresponds to the black and white spectrum only.

Once they are converted to photons again, the phosphor screen is what makes the light appear green. So why not just pick some other chemical element, or simply allow our eyes to perceive just the white and black colors? The answer is that green is a very eye-friendly color, that’s easy to look at for prolonged periods of time.

No light!

But up until now we only discussed image enhancing night goggles that work great when it’s not actually pitch black, and there’s at least some infrared light floating around. In the case of no light particles to multiply, these night goggles are rendered useless, and you need thermal imaging.

That’s what firefighters use for finding their way through buildings that overflow with a dark, stifling smoke. As we’ve said before, these types of night goggles simply pick up a difference in temperatures, rendering different colors according to that. Red means an object is extremely hot, and blue that it’s mostly cold, with various degrees in between, reflected by corresponding shades of warm and cool colors.

Objects that are hot emit an infrared radiation, not an infrared light, so it has a lower frequency, but this can be transformed into light too. These goggles have a CCD or CMOS sensor that picks up this sort of radiation, which is decoded and transformed into photons.

That said, night goggles are an immense use for various activities. If you want a pair just for hiking, boating or camping, then goggles which use the image enhancement technology are great. If you need them for search and rescue, as well as other professional applications, thermal imaging might be better. So now it’s your turn: which sort of night vision are you after? Has this article cleared the way night goggles work? Let us know in the comments.

 

Guest Post

About the author: Mike is a passionate hunter and his favorite grounds are Alaska and British Columbia. He’s also an expert in hunting gear and he is one of the most reliable resources when it comes to choosing the right tools for the job. He also writes for OpitcGearLab.com


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