How do night vision goggles work?

Night vision binoculars and goggles

Night vision technology lets you see much more in the dark than your natural night vision is capable of. This equipment is becoming a bigger part of many consumer electronics, military equipment and other devices.

Many different kinds of night vision devices (NVDs) are available today, each with its own unique purposes.

What are night vision goggles?

Night vision goggles (NVGs) are wearable electronic devices that help you see more in low light. They cover both eyes and provide a hands-free alternative to other devices.

While consumer-grade products are available, night vision goggles are mostly used in military, law enforcement and security settings. Military-grade goggles cost thousands of dollars — sometimes tens of thousands — much more than the typical household device.

Binoculars, monoculars, cameras and scopes with night vision tech are generally more popular with the average consumer than night goggles.

While some night vision devices include magnification, goggles generally allow objects to appear about as close as they would to the naked eye. This makes it easier for the wearer to walk and maneuver during use.

Types of night vision goggles

All night vision devices (NVDs), including goggles, use different types of night vision to help you see in the dark. Some use more than one type.

The following four methods provide an introduction to the most popular technologies used in night vision goggles and other devices:

1. Image intensification

2. Thermal imaging

3. Active illumination

4. Digital night vision

Image intensification

Also called image enhancement, image intensification gathers the available light around you and makes it easier to see.

Here's how this night vision works:

1. Photons (particles of light) come in through a lens and enter the battery-powered intensifier tube. In low-light settings, these photons can be gathered from the moon, stars or faint artificial lighting.

2. A special component inside the intensifier tube (the photocathode) converts the photons into electrons — charged particles in atoms.

3. The photocathode amplifies or increases the number of electrons.

4. A phosphor screen changes the electrons back into photons. (Many night vision goggles look green because they use a green-tinted phosphor screen to make the new image easier to see.)

5. The "upgraded" excited photons enter your eyes and make the low-light scene look brighter and more intense.

Image intensification requires at least a little light, so it won't work in complete darkness.

Thermal imaging

Humans can see as many as 10 million different colors. That might sound like a lot, but it's only a small slice of all the radiation on the electromagnetic spectrum.

Visible light is the only part of this spectrum that you can see on your own.

Thermal imaging lets you "see" infrared radiation (IR), which is invisible to the naked eye. This is the radiation that's associated with heat. The warmer something is, the more infrared radiation it emits.

Thermal infrared night vision goggles work by translating invisible heat into images or colors you can see. Unlike image intensification, thermal imaging works in total darkness — as long as something gives off heat.

Some thermal units display warmer objects as warm colors (red, orange and yellow) and cooler objects as cool colors (blue and purple).

Other thermal goggles display the image in black and white, where hotter objects look brighter and cooler objects look darker.

Active illumination

Active illumination uses image intensification differently. Instead of collecting infrared heat signals, the device shines its own beam of near-infrared light, which is closer to visible light. Many home security cameras use this type of night vision.

Active illumination is sometimes known as active infrared.

You can think of it as an invisible flashlight. You can't see the device's beam of near-infrared light, but once it bounces back onto the image sensor, it makes the scene light up like a flashlight would.

Digital night vision

Digital night vision devices don't have to use intensifier tubes like traditional, analog NVDs. Instead, they use chips called image sensors.

These optoelectronic components collect light and convert it into a digital signal. The signals are then processed and sent to an LCD screen so you can view the enhanced image.

Two common chips are CCD sensors and CMOS sensors.

CMOS sensors tend to cost less and use less power. This makes them a popular choice for digital night vision equipment, along with photography devices like cell phones, HD video cameras and digital SLR cameras.

Personal security cameras, like doorbell cameras, often combine digital night vision with active illumination.

Some digital NVDs are now capable of color night vision. This is made possible by boosting visible light or combining it with colorless infrared signals.

Night vision binoculars, monoculars and scopes

Night vision binoculars and monoculars may not have the hands-free perk of goggles, but they offer something many goggles don't: long-distance magnification.

Both binoculars and monoculars make distant scenes appear much closer, but the exact magnification power varies between models.

The number of eyepieces is the biggest difference between night vision binoculars and monoculars. Binoculars are built for use with both eyes, while monoculars can only be used with one eye at a time.

Most consumer-grade night vision scopes are purchased by recreational hunters and attached to the top of their hunting rifles. Since animals naturally produce a lot of heat, thermal NVDs are particularly useful when an animal is hidden or far away.

Applications of night vision technology

While top-of-the-line night vision goggles still cost a lot of money, consumer-level NVDs continue to become more accessible.

Night vision tech is now used in areas such as:

• Hunting

• Home security

• Professional security and surveillance

• Dash cams and in-car backup cameras

• Military

• Law enforcement

• Aviation

• Hiking, camping and navigation

• Bird and nature watching

• Stargazing

• Rescue operations

READ MORE: How does human eyesight work?

Generations of night vision devices

Like other technology, night vision has improved a lot over time. These advancements can be separated into five generations:

Generation 0

Generation 0 is the oldest type of night vision, first used during World War II. It involves projecting a beam of infrared light (active illumination) to help see in the dark.

The images tend to be fuzzy and dim by today's standards, so it isn't used much anymore.

Generation 1

Generation 1 devices were the first to gather infrared light from their surroundings (passive infrared). This offered some improvements, but it still had drawbacks.

For example, the technology didn't work well on nights with little or no moonlight.

Generation 2

Generation 2 night vision devices were a big upgrade over the previous two versions. One breakthrough was the microchannel plate, a thin glass surface in the intensifier tube. It helped create more electrons as they traveled through the tube.

Unlike the previous generation, Generation 2 devices are still effective when there's very little ambient light.

Generation 3

Generation 3 is similar to Generation 2, but the intensifier tubes are more sensitive to light.

This is mostly because the photocathode (part of the intensifier tube) is made of gallium arsenide. This chemical compound is also used in things like cell phones, solar panels and lasers.

In night vision devices, gallium arsenide helps create more electrons and boosts low-light performance.

Generation 3 NVDs are still widely used today.

Generation 4

Generation 4 NVDs use the latest and most advanced night vision technology. Right now, they offer the clearest images with the best illumination in darkness.

However, the complex technology can make these NVDs more susceptible to damage. This is why the military tends to use Generation 3 devices in many settings.

It's also why Generation 4 is sometimes called Generation 3+ or Generation 3 Filmless instead.

This "filmless" part of the name comes from the fact that these devices don't need microchannel plates, unlike Generations 2 and 3.

Frequently asked questions (FAQs)

Do night vision goggles work in total darkness?

Thermal imaging goggles can work in complete darkness because they detect heat rather than visible light particles (photons).

On the other hand, some image intensification goggles can work in near-total darkness, but not complete darkness. Their intensifier tubes rely on photons to function, so there has to be at least a little light in the area to work.

Is night vision always green (or black and white)?

Not anymore. Many types of night vision products generate images that look either green or black and white, but some devices now combine technologies to give you full-color night vision.

This full-color option is gaining popularity in doorbell cameras and other personal devices.

Is night vision infrared?

Many night vision devices rely on infrared light, but not all of them.

Some devices only use the available visible light (the light you can see with your eyes) to light up a scene. Others automatically switch back and forth between visible and infrared light.

These devices can also pick up near-infrared light, which is closer to visible light than thermal infrared radiation.

Can you get a night vision camera on your phone?

Some specialty manufacturers do make phones and plug-in devices that include active IR or thermal night vision cameras.

True night vision isn't currently a feature of mainstream phone models. Instead, popular manufacturers usually include a night photo mode. This gathers more visible light by keeping the camera's shutter open for a few moments.

Unlike true night vision devices, you need to hold the camera very still while you use night photo mode — at least for now. The technology is still improving.

How far can night vision binoculars see?

In the right conditions, many night vision binoculars can help you see things several hundred yards away in darkness. Some high-end options advertise night viewing distances of 1,000 yards or more.

This exact viewing range varies by model. Some binoculars have ranges of less than 100 yards, so they're better suited for use in smaller areas.

When were night vision goggles invented?

The first infrared night vision systems were invented by the German army before World War II. But these Generation 0 devices were far from portable — they had to be carried on a truck.

The first model of night vision goggles (as we think of them today) was the SU-50. They were developed a few decades later, closer to the time of the Vietnam War.

Night vision goggles weren't invented by one person alone. They were the collective work of many defense and military researchers leading up to the mid-1960s.

The future of night vision

Night vision technology has seen major breakthroughs since it was invented less than a century ago. Today, this technology is more accessible than ever, and there's a good chance you already own at least one device that utilizes it.

Over time, night vision tech could become integrated into even more everyday devices, giving more people the once-unthinkable power to see in the dark.

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Page published on Tuesday, February 23, 2021

Page updated on Tuesday, December 10, 2024

Medically reviewed on Monday, December 2, 2024