Night-vision device

A night-vision device (NVD), also known as a night optical/observation device (NOD) or night-vision goggle (NVG), is an optoelectronic device that allows visualization of images in low levels of light, improving the user's night vision. These tools are very helpful for seeing in the dark.

The device enhances ambient visible light and converts near-infrared light into visible light which can then be seen by humans; this is known as I² (image intensification). Unlike thermal imaging, which looks at heat, night vision works by using available light.

A night vision device usually consists of an image intensifier tube, a protective housing, and an optional mounting system. Many NVDs also include a protective sacrificial lens, mounted over the front/objective lens to prevent damage by environmental hazards, while some incorporate telescopic lenses. An NVD image is typically monochrome green, as green was considered to be the easiest color to see for prolonged periods in the dark.

These devices were first used for night combat in World War II and came into wide use during the Vietnam War. Today, they are commonly used by military and law enforcement agencies, but are also available to civilian users for applications including aviation, driving, and demining.

History

In 1929, a scientist named Kálmán Tihanyi invented a special camera in the UK that could see in the dark using infrared light. During World War II, night-vision devices were first used by the German Army as early as 1939. They tested these devices on tanks and for soldiers on the ground.

The United States also developed night-vision devices during this time. These early devices needed extra infrared light to work and were used by soldiers during wars like the Korean War.

After World War II, scientists made night-vision devices that could work with natural light, like moonlight. In the 1960s, the US Army made devices that could see in very dark conditions. Over the years, these devices got better, with newer versions improving clarity and lasting longer.

Figure of merit

Figure of merit (FoM) is a way to measure how well a night-vision device works and how clear the picture is. It uses how many lines a person can see in a small space and the quality of the picture.

In the late 1990s, new ideas in technology made the picture quality better. By 2001, experts found that the type of tube used did not matter as much, so they stopped using it for rules about sending these devices to other countries. The government says that as long as someone can see clearly at night, the device works well.

Fusion night vision

Fusion night vision mixes two special ways to see in the dark. It uses something called image intensification, which boosts the tiny bits of light you can’t normally see, and thermal imaging, which shows heat. This helps you spot things that are warm, like people or animals, even better.

There are different ways to use fusion night vision. You can see only the boosted light, only the heat, or both together. Some devices can even make hidden objects stand out by showing their heat. These tools are a bit heavier and need more power than regular night vision devices, but they help you see clearly and find warm objects easily.

Out of band

Out of Band (OOB) refers to night vision technologies that work outside the 500-900 nm NIR (near infrared) range. These devices can use special tubes or clip-on tools to see in different light conditions.

OOB devices can be helpful on starlit nights because they can make use of any available light, including ultraviolet or short-wave infrared light. They can also see 1064 nm light, which is useful for marking targets with certain lasers. OOB light is hard for many common night vision devices to see, making it harder for others to notice friendly forces using special lights or lasers. Some OOB devices can also detect common laser rangefinders.

Wide field of view

Night vision devices often have a smaller field of view (FoV) than our natural vision. For example, the common AN/PVS-14 has a FoV of 40 degrees, which is less than what humans normally see with one eye (95°) or both eyes together (190°). Because of this, users need to move their heads to see everything around them. This is especially important when flying, driving, or in situations that need quick decisions, like CQB. Because of these limits, many SF/SOF operators sometimes prefer regular light instead of night vision for certain tasks. To fix this, researchers have worked hard to create night vision devices with a wider field of view.

Panoramic night vision goggles

Panoramic night vision goggles (PNVG) make the field of view wider by using more sensor tubes. However, this makes the goggles bigger, heavier, and more complex. One example is the GPNVG-18 (Ground Panoramic Night Vision Goggle). These goggles, inspired by the aviation AN/AVS-10 PNVG, offer a field of view of 97°.

Examples:

• GPNVG-18
• AN/AVS-10

Foveated night vision

Foveated night vision (F-NVG) uses special WFoV optics to widen the field of view through an intensifier tube. The fovea is the part of the retina that helps with clear central vision. These devices let users look "straight through" the tubes so that light through the center of the tube reaches the foveal retina, like in regular night vision goggles. But the wider view can mean lower image quality and some edge distortions. Examples include:

• WFoV F-NVG retrofit AN/PVS-15 goggles
• WFoV BNVD (combined F-NVG and DIT-NVG variant of AN/PVS-31A)

Diverging image tube

Diverging image tube (DIT) night vision makes the field of view wider by angling the tubes slightly outward. This helps see more on the sides but can cause distortion and lower image quality. With DIT, users are not looking through the very center of the tubes, so the clearest images are not seen, and light through the center does not reach the fovea.

Examples:

• AN/PVS-25 (2000s).
• WFoV BNVD: a version of the AN/PVS-31A that combines F-NVG and DIT-NVG. The foveal WFoV optics widen each tube's FoV from 40° to 55°, and the angling of the tubes creates a 40° overlap in the center and a total 70° FoV. It has a FoM of 2706, better than the FoM in both the GPNVG-18 and the standard AN/PVS-31A.
• Noise Fighters Panobridge: a mount that connects two AN/PVS-14 monoculars and lets them be angled outward or positioned straight.

Digital

Some night vision devices, like the ENVG (AN/PSQ-20) models, have digital thermal overlays. These were introduced in the late 2000s and let the image be sent, but they are bigger, heavier, and use more power.

High-sensitivity digital camera technology allows night vision goggles to use a camera and screen instead of special light boosters. This can give good quality at a lower cost. In 2022, SiOnyx made digital color night vision goggles called "Opsin." They are about the same size and weight as an AN/PVS-14 but need a separate battery pack. They don’t last as long on a charge and aren’t as sensitive to light, but they can handle bright light and see more types of light.

Other technologies

Scientists have developed several new ways to see in the dark. One idea replaces the glass in night-vision devices with a special ceramic plate, making the device work better. Another idea is a very thin night-vision contact lens that uses a material called graphene, but it still needs more work before it can be used.

Researchers also made a new type of infrared detector that can see certain kinds of invisible light. This technology might be good for watching places for a long time because it could be cheaper and easier to make, but it is not yet available for everyday use.

Other materials can also help see in the dark, and scientists are exploring a special film that can be placed on regular glasses. This film uses a tiny structure to change invisible light into visible light, so both kinds of light appear together in one picture without needing to cool the device.

Soviet Union/Russia

The Soviet Union and, after 1991, the Russian Federation made their own special tools that help people see in the dark. These tools are called night-vision devices. After 1960, the Russian and Soviet armies used models named 1PNxx. The letters PN mean "night sight" in Russian. These tools work with different guns and have special parts that can be swapped out.

Some of these night sights are used with small guns, big rifles, and hand-held launchers. There are also special night sights made to find and see faraway targets. These use light pulses to spot enemy tools that help them see in the dark.

Legal restrictions

Different countries have different rules about night-vision devices. In Belgium, it is not allowed to attach these devices to guns. In Germany, using them on guns is only allowed for hunting wild boars. Iceland allows people to own these devices but not to use them for hunting.

In India, people need special permission to own or sell night-vision scopes for civilian use. The Netherlands does not control ownership, but you need a permit to attach them to guns, especially for hunting wild boars in the Veluwe area.

In the United States, rules vary by state. Some states ban the use of night-vision devices for hunting, while others have specific limits. For example, in California, having a device made for use on guns can be against the law. Minnesota also has rules about using these devices while hunting animals.