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Everyone’s familiar with the term night vision, one way or another. You’ve most likely seen soldiers wearing one of these funny-looking devices, whether in a movie or from raw combat footage. And you’re probably wondering – how do night vision goggles work?
Night vision goggles work by capturing any available light and then amplifying it to produce a visible picture.
But the more specific manner by which an NV device works depends on the type of technology used – there are 3 main kinds:
- Image Intensification (Passive NV) – This is arguably the most widespread NV tech out there and the way they work is that these devices gather any available light and amplify it to deliver an image that’s visible to the human eye.
- Active Illumination (Active NV) – Here, infrared illuminators (IR) send an infrared beam on surrounding objects that then returns to the device producing an image that you can see.
- Thermal Imaging – Instead of relying on any natural light sources (i.e. the moon), thermal imaging technology collects the infrared light that warm objects emit (such as humans, animals and even cars) and turns it into a visible image.
That’s just a general overview of the different types of NV tech and how they work though.
What Are the Different Types of Night Vision and How Do They Work?
So let’s now take a closer look at each particular kind and what kind of pros and cons they might have!
1. Image Intensification (Passive Night Vision)
Image intensification NV devices require some kind of outside light source to produce visible light.
They do that via a specific tube named image-intensifier tube that catches infrared light, amplifies it and converts it into visible light.
In essence, this tube converts the electromagnetic particles known as photons into electrons, then into multiplied electrons and finally back to photons again, albeit in greater numbers.
But for all of this to take place, a particular set of pieces has to be put together.
This is how image intensification works:
- First, the objective lens of the NV goggles catches light from the surrounding area in the form of photons
- Then the photons go to the image-intensifier tube where a special light-sensitive surface (photocathode) transforms the photons into electrons
- Next, the newly-formed electrons enter a photomultiplier that multiplies the number of electrons when they exit it
- After that, the multiplied electrons hit а screen made of phosphor, which then releases photons as a reaction between the electrons and the phosphors
- The typical night vision green image then appears as a result of the phosphors and it can be seen via the ocular lens (that can be used to put on focus and magnify what you see) at the end of the device
And these are the core elements of a night vision monocular (binoculars/goggles are just about identical):
- Objective lens
- Focusing mechanism
- Phosphor screen
It’s also worth noting that as the name suggests, image intensifiers need at least some sort of light available for them to multiply.
Image Intensifiers – Pros:
- Stronger and more durable than thermal imaging
- Have a bigger field of vision
- Provide a more natural visible image
Image Intensifiers – Cons:
- Useless during the day
- Dust, shadows and camouflage can conceal your target/s
2. Active Illumination (Active Night Vision)
Active illumination is an NV technology that relies on image intensification combined with NIR (near-infrared) or SWIR (shortwave infrared) rays.
The infrared illumination comes in the form of beams within the 700 – 1000 nm range, which is slightly below the spectral range that we can see.
Essentially, active illumination NV devices project an infrared beam that bounces off objects to give you a visible image.
The idea is that you’ll be able to see in very dark conditions thanks to the infrared light that’s directed at things in front of you.
For example, your TV remote control uses an identical infrared light, while low-light cameras basically have the same active illumination technology as active NV devices.
On a side note, this type of night vision tech was initially used by the US military back in WWII.
However, it’s no longer used for such purposes because enemy forces can spot the infrared beams coming from the device, thus giving away your location.
Active Illumination – Pros:
- Generally provides a more high-res image than other NV technologies
- Helps you to see in almost pitch-black darkness
Active Illumination – Cons:
- More complex than image intensifiers, thus typically heavier
- The infrared light can be detected by other devices to give out your location (if that’s important to you)
3. Thermal Imaging
Thermal imaging is somewhat different from the other two main types of NV as it relies on sensors that detect heat-emitting objects.
This type of NV tech utilizes the top-end spectrum of infrared light (heat emits this light) and as a result, a human body will emit more of this IR light than something like a tree.
As you can already see, this is in contrast to the light reflection method used by active illumination for instance.
That’s why some night vision experts argue that thermal imaging isn’t night vision technology in the purest sense of the word.
This is how thermal imaging works:
- Initially, a lens captures and focuses the IR light that emits from the heat of the objects around you
- After that the captured and focused IR light is scanned by IR detector components, which then produces a thermogram
- Next up, electric impulses are created from the newly-formed thermogram
- These electric impulses are then transferred to a signal-processing circuit board that turns the info captured by the IR detector components into readily available data for the display
- Ultimately, all the data is sent to the display where you see the final image with varying colors depending on the heat emitted
And since thermal imaging doesn’t actually need any external source of light, it produces images even in total darkness and even when there’s light smoke, fog and rain.
Apart from that, thermal imaging devices can be categorized into 2 main groups:
- Un-cooled – This is the type of your typical thermal imaging device that offers convenience and ease of use.
- Cryogenically-cooled – These thermal imaging devices offer superb resolution and sensitivity, although they’re more expensive and more fragile.
It’s also worth noting that thermal imaging won’t let you see objects behind walls as we’re often led to believe in movies and video games.
Because solid objects such as walls are opaque and they have their own heat signature.
Thermal Imaging – Pros:
- Produces visibility in complete darkness
- Works just as good in broad daylight
- Enables you to see through light fog, dust, smoke etc.
Thermal Imaging – Cons:
- Larger and heavier
- More expensive
- Long boot time
How Does Digital Night Vision Work?
- First, the image enters the device via the objective lens
- Next, a charge-coupled device (CCD) sensor (or alternatively a complementary metal-oxide-semiconductor (CMOS)) processes the image through millions of small pixels
- Then, the CCD sensor creates an electric signal out of the image
- Finally, the CCD sensor converts the signal into a visible image that you can see on the device’s LCD display
This technology is quite straightforward indeed and as the name suggests it doesn’t have intensifier tubes or anything of the sort.
It’s all digital – you’re even looking through an LCD screen so you’re directly looking at the image per se.
In fact, your typical digital night vision device relies on the following main parts:
- Objective lens
- CCD or CMOS sensor
- IR illuminator (only on some models)
- Block of electronic image processing
Other than that, the image quality is similar to standard Gen 2 NV technology, although some digital NV devices also come with an infrared illuminator.
Digital Night Vision – Pros:
- Can be used in daylight without any concerns
- Gives you way less image distortion
- Low price
Digital Night Vision – Cons:
- Needs light to perform adequately
- Not the best image quality
What Are The Different Types of Night Vision Devices?
There are six types of night vision devices that you can come across:
Let’s now dive into these different devices to give you a better idea about each type.
This is definitely the most widespread type of NV device that consists of 2 eyepieces and in some cases an IR illuminator in.
The best thing about NV goggles is the fact that you can get them in a hands-free version, which is priceless if you’d like to stay mobile during your nighttime explorations.
The hands-free nature of some night vision goggles is also the reason why military personnel uses them so often – from helicopter pilots to commandos.
Night vision cameras are basically more advanced surveillance cameras that also work in dark conditions.
They rely on infrared light to capture visible images in the dark as they can be installed both outdoors and indoors.
Apart from being used for home surveillance and security, NV cameras can also be found in some military vehicles.
Scopes a.k.a. telescopic sights utilize a single-eyepiece that can be used hand-held or hands-free (e.g. mounted on a gun).
This particular kind of night vision devices is typically used by soldiers and hunters who’d like to improve their aim when there’s little light outside.
Moreover, night vision goggles for hunting have scopes that can help you see and aim at your prey when it’s almost pitch black outside.
And depending on the generation (Gen 1, Gen 2, Gen 3 etc.) you can get a pretty quality image out of scopes, although that comes at a price (you’d have to pay more).
In essence, night vision glasses are just sunglasses that have tinted lenses.
Thus, most models come with a yellow tint since the color yellow is the most optimal option when it comes to seeing in low light scenarios.
One neat thing about yellow-tint glasses is that this color also shields the eyes from any light glare.
A monocular NV device consists of a single eyepiece or in other words, it’s one-half of a binocular.
Subsequently, only one of your eyes will benefit from seeing in a low-light setting, which I’m personally not a fan of.
But hey – if you prefer to carry less weight then a monocular might be superior to a binocular.
Everyone’s familiar with binoculars and it’s the same thing in night vision terms – a dual eyepiece with magnification capabilities.
The great about them is the fact that you’ll see the exact same image with both eyes (as opposed to monoculars).
However, the dual-tube system and everything else adds weight so they’ll logically be heavier.
Why is Green Used in Night Vision?
Because the green color provides the most accurate and distinguishable image since our eyes can recognize more shades of green than any other color out there.
When creating night vision devices, engineers have tested various colors and unsurprisingly green is the most optimal choice for a monochrome (single color) model.
The human eye is apparently most sensitive to light wavelengths close to 555 nanometers that happens to be… yes, the color green!
Basically, our eyes are most sensitive to green light so you’ll see best when in a darker, low-light setting when the picture is green.
Another reason for using green is that it helps make the display of the device a bit dimmer and that can preserve battery life.
But fear not if you’re not a fan of green – color night vision technology is already here as it provides an incredible full-color image in almost pitch-black conditions.
^ This is Gen 4 night vision devices can offer in terms of viewing distance!
How Far Can Night Vision Goggles See?
Up to 500 yards (450 meters) if you’re using a quality Gen 4 NV device.
With that in mind, the average detection range is around 300 yards or 200 it’s cloudy and moonless outside.
Note – there’s a difference between detection and recognition range!
Here’s what the difference is:
- Detection range – This is when an object becomes visible and distinguishable (e.g. you’re able to a person from the background)
- Recognition range – This term stands for when you can classify the object (e.g. is it a man or a woman)
Regardless, there are many variables that come into play when it comes to how far you can see using an NV device.
Perhaps the biggest variable is how large the object is since there’ll be quite a bit of difference when it comes to detecting a mouse or a bear.
Can Night Vision Goggles See In Pitch Black?
Yes, but only devices that come with a built-in infrared illuminator.
An IR illuminator is an integral part if you’d like to see anything in total darkness as there would be no external light for your device to collect and amplify.
Thermal imaging is another brilliant technology that works in absolute darkness as it detects heat and doesn’t require any light.
Still, some people don’t consider thermal imaging “real” night vision although it’ll most definitely help you to spot any heat-emitting objects when no light is present.
Are Night Vision Goggles Legal?
Yes, using night vision goggles is perfectly legal across the US.
The only exception is California although the law there forbids the use of sniper scopes so you should be fine using NV goggles.
In the state of Cali it’s illegal to use infrared technology on your NV device, be it scopes or binoculars.
The law in this particular state forbids the use of:
- Active infrared scopes (with magnification)
- Passive infrared scopes (with magnification and an infrared illuminator)
So if you’re night-vision goggles don’t have an IR illuminator (or anything to do with IR for that matter) and they use passive light (e.g. image intensification technology), you should be fine.
As for Europe, it seems that some of the more developed countries prohibit the use of night vision systems that are mounted on firearms so you should be fine using NV goggles.
However, always consult with a lawyer if you’re unsure as to avoid any legal repercussions.
Who Invented Night Vision Goggles?
The night vision technology was invented during the 1930s in Germany by a company called AEG.
This is when the first generation of NV devices was born (known as Gen 0) as they were used for military purposes in the German army.
However, the photoelectric effect that most NV devices rely on was initially discovered back in 1887 by the German physicist Heinrich Hertz.
So we can argue that night vision technology was first “conceived” all the way back in the 19th century, again – thanks to the Germans.
Interestingly enough, Albert Einstein himself expanded on the photoelectric effect in the early 20th century to explain this phenomenon with the help of quantum theory.
So, the way night vision goggles work (and most other NV devices) is quite simple at its core:
- It collects all the available external light and greatly amplifies it to deliver a visible image that you can interpret.
It’s thermal imaging that works a bit different though as it uses the heat emitted by objects (instead of light) to produce an image.
What is your favorite night vision technology though?
Let us know by leaving a comment in the comment section below!