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 helps people see in very little light. These tools make it easier to see when it is dark.

The device makes use of the small amount of light that is around and changes near-infrared light into light that humans can see; this is called I² (image intensification). Unlike thermal imaging, which looks at heat, night vision uses whatever light is available.

A US Navy aviator uses a pair of helmet-mounted AN/AVS-6 vision goggles. The effect on the natural night vision of the eye is evident

A night vision device usually has an image intensifier tube, a case to protect it, and sometimes parts to attach it to other things. Many NVDs also have a special lens on the front/objective lens to keep them safe from dirt and weather, and some have telescopic lenses. The picture from an NVD is usually monochrome green, because green is the easiest color to see for a long time in the dark.

These devices were first used for night combat in World War II and became common during the Vietnam War. Today, they are often used by military and law enforcement groups, but people can also buy them for things like flying, 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 in 1939. They tested these devices on tanks and soldiers.

A cut-open and depotted AN/PVS-5, showing the components of a night-vision device. This device was manufactured in 2nd generation (5A to 5C) and 3rd generation (5D)

The United States also made night-vision devices at this time. These early devices needed extra infrared light to work and were used by soldiers in 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.

Generation II, III and IV devices use a microchannel plate for amplification. Photons from a dimly lit source enter the objective lens (on the left) and strike the photocathode (gray plate). The photocathode (which is negatively biased) releases electrons, which are accelerated to the higher-voltage microchannel plate (red). Each electron causes multiple electrons to be released from the microchannel plate. The electrons are drawn to the higher-voltage phosphor screen (green). Electrons that strike the phosphor screen cause the phosphor to produce photons of light viewable through the eyepiece lenses.

Figure of merit

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

In the late 1990s, new technology improved picture quality. By 2001, experts learned that the type of tube used was not as important, so they stopped using it for rules about sending these devices to other countries. The government says that if 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 image intensification, which makes very weak light visible, and thermal imaging, which shows heat. This helps you see warm things like people or animals more clearly.

You can choose to see only the weak light, only the heat, or both together. Some devices can show hidden objects by making their heat stand out. 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 use special tubes or clip-on tools to see in different light conditions.

OOB devices can be useful on starlit nights because they can use any available light, including ultraviolet or short-wave infrared light. They can also see 1064 nm light, which helps when 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 show less than what our eyes can see. For example, the common AN/PVS-14 shows only 40 degrees, while humans see about 95° with one eye and 190° with both eyes. Because of this, users need to move their heads to see all around them. This is important when flying, driving, or making quick decisions, like in CQB. Because of these limits, many SF/SOF operators sometimes choose regular light for some tasks. Researchers work to make night vision devices show more.

Panoramic night vision goggles

Panoramic night vision goggles (PNVG) make the view wider by using more sensor tubes. But 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, show a view of 97°.

Examples:

GPNVG-18
AN/AVS-10

Foveated night vision

Foveated night vision (F-NVG) uses special WFoV optics to make the view wider 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 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 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 made in the late 2000s and let the image be sent, but they are bigger, heavier, and use more power.

High-sensitivity digital camera technology lets night vision goggles use a camera and screen instead of special light boosters. This can give good quality for less money. 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 created new ways to see in the dark. One idea swaps the glass in night-vision devices for a special ceramic plate, which can make them work better. Another idea is a very thin night-vision contact lens made from a material called graphene, but it still needs more work before it can be used.

Researchers also made a new infrared detector that can see certain kinds of invisible light. This technology might be useful for watching places over 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. Scientists are studying 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 show up together in one picture without needing to cool the device.

Soviet Union/Russia

The Soviet Union and, after 1991, the Russian Federation made special tools to 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 changed.

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.

Legal restrictions

Different countries have different rules about night-vision devices. In Belgium, you cannot attach these devices to guns. In Germany, you can only use them on guns for hunting wild boars. Iceland lets people own these devices but not 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.