Night Vision Technology

Summary

Night vision technology allows for better night vision than is possible with the human eye alone. It uses light amplification and thermal-imaging components incorporated into goggles, cameras, binoculars, and other devices to improve vision under low-light conditions.

Definition and Basic Principles

Night vision technology uses light-amplifying and thermal-imaging devices to enhance human vision performance in low light. These devices can include cameras, goggles, binoculars, and spotting scopes. This technology amplifies ambient light through photoelectric techniques or thermal imaging, which uses the energy released in the infrared spectrum in the form of heat.

Night vision devices use a photocathode that collects photons, which are light particles present even in dim light. These photons strike a photocathode, which then emits electrons. Photocathodes can be made of a variety of coated metallic materials. These electrons are multiplied by a microchannel plate and then transformed into green light using a phosphor screen. Green light works well because of the sensitivity of the human eye to these wavelengths. There are variations on this technology, including early night vision systems that project infrared light and then amplify the reflected light.

Background and History

The groundwork for the development of night vision technology was laid by early scientists such as Heinrich Hertz, who described the photoelectric effect in 1887. The discovery that electrons are emitted when light strikes metal was further developed by German physicists Max Planck and Albert Einstein in the early twentieth century. Their work confirmed the particle nature of light and provided the foundation for future applications, which included night vision technology.

William E. Spicer was a cofounder of the Stanford Synchotron Radiation Lightsource and was instrumental in developing light amplification. His work paved the way for the first generation of night vision goggles and had applications in medical imaging technology. Spicer’s work provided the basis by which light in the infrared spectrum, which is not visible to the human eye, can be detected, amplified, and transformed into visible green light. All of the night vision devices rely on this basic technology.

As a result of the research done by Spicer night vision goggles were developed for use by the military during World War II in the 1940s. England, Germany, and the United States developed sniper scopes using infrared cathodes. These devices used an infrared beam to generate reflected light from the surroundings that were then amplified by the scope. These devices had the disadvantages of low range and the enemy's ability to detect the infrared beam. Early devices using an infrared beam to create reflected light are called active night vision devices and are referred to as generation zero.

Militaries around the world continued to work on improved night vision technology. Generation one devices, the next iteration, improved on the light amplification so that ambient light could be used without the need to use an infrared beam. These systems did not work well on very dark or cloudy nights. Early night vision devices were large and created a distortion of images. The Starlight scope used in Vietnam is an example of this generation of devices. Generation zero and generation one night vision devices are now available to the general public.

As technology advanced, the next generation of night vision devices became more sensitive by adding microchannel plates, which further amplified the signal. A microchannel plate is manufactured from lead oxide cladding glass. Generation two devices have less distortion and increased brightness. Generation three night vision technology incorporates gallium arsenide cathodes, which further increases sensitivity. Generation four devices, which are typically used for military applications, incorporated changes to the microchannel and added gating. Gating is a system that switches on and off to allow for rapid response to changes in light. For example, if night vision goggles are on and a light is suddenly switched on, the user can see under the lighted conditions.

Thermal imaging has been made possible with improved sensitivity and light amplification. It also creates images using infrared wavelengths that are emitted as heat. However, not all night vision devices can detect thermal energy.

How It Works

To understand how night vision technology works, it is important to have a basic understanding of light and how the human eye responds to light. Before the twentieth century, there was an ongoing debate about whether light was a wave or a particle. Sir Isaac Newton favored a particle theory, which was later substantiated by Henrich Hertz, Max Planck, and Albert Einstein. However, the modern understanding of light is that it behaves like both a wave and a particle.

For the purpose of understanding night vision technology, the photoelectric effect forms the basis for these devices. When particles of light called photons strike metal, electrons are emitted. Specialized photocathodes are coated with various materials to make them more sensitive. The technical specifications of the photocathodes have improved over the generations since the 1940s, partly because of the use of different materials and coatings. The function of the photocathode in a night vision device is to convert the light into electrons. In low-light conditions, night vision devices can detect infrared light that is not detectable by the human eye.

The electrons are then converted into visible light by a phosphor screen, which then converts the electrons back into green light visible to the human eye. Later devices added a microchannel plate, which amplified the electron energy while preserving the pattern or image. The microchannel plate is an array of tiny glass tubes. The electrons enter and are confined in each tube as they travel through, which results in the preservation of their entering pattern. While traveling through the microchannel plate, the electrons are further amplified by the application of voltage across the microchannel plate. This allows for more energy to enter the phosphor screen and a subsequently brighter image. Infrared light travels from the environment to the photocathode, where it is translated into electrons, which enter the microchannel plate. The amplified signal then strikes the phosphor screen, which turns the energy into green light that the viewer can see.

The human eye is most sensitive to visible light, with wavelengths of about 400 to 700 nanometers (nm). Infrared light is in the 700 nm to 1 millimeter (mm) range. Infrared is further divided into near-infrared IR-A with 750 to 1400 nm wavelength range, medium wavelength IR-B of 1,400 to 3,000 nm range, and long wavelength or far IR-C with wavelengths of 3,000 nm to 1 mm. The long wavelengths are used in thermal imaging devices. Infrared light is not detected by the human eye, so night vision devices are used to transcribe this light into visible green light. The human eye is particularly sensitive to green light. For example, 0.001 watts of green light will appear bright, while 0.001 watts of blue light will appear dim.

Applications and Products

Military Applications. Military organizations used night vision technology in World War II and remain at the forefront of new developments. Military applications include night vision goggles for military personnel, sniper scopes, reconnaissance, and vehicle navigation. The advances that led to thermal imaging were on display in the media during the Gulf War in 1991. Those who may have watched the coverage of this war on television will remember the pictures with greenish images and periodic flashes of bright green corresponding to tracers and explosions.

Thermal forward-looking imaging (FLIR) devices are installed on vehicles and helicopters. Night vision devices are available to personnel for survival purposes. This technology has continued to be employed in weapons-aiming devices. Data collection and communications technology have been added to some night vision devices to improve military communication and reconnaissance.

The US Army started fielding and training with its enhanced night vision goggles (ENVG-III) and goggle-binoculars that allowed for increased depth perception through the ability to use both eyes as well as access to clearer images in 2019. ENVG-III uses wireless technology to link its systems to a rifle-mounted device called a family of weapon sights–individual. The linkage helps improve soldiers’ situational awareness and maneuverability.

Law Enforcement. Law-enforcement applications are similar to military applications and include surveillance, weapons aiming, recording, and identification of suspects in situations of low light. Thermal imaging is used to identify illegal marijuana-growing operations, which are sometimes located in ordinary urban neighborhoods. The heat lamps used in growing the plants make it possible for law enforcement to identify these operations by air. A helicopter equipped with thermal imaging equipment can detect an increased heat signature coming from the roof of the house that contains the growing operations. FLIR is also used on law-enforcement vehicles. Night vision technology is also used in search-and-rescue operations by law enforcement and other agencies.

Photography. Some photographers are using night vision cameras to create artistic images. To address the green images created by this technology, the photographers employ digital-editing techniques. The resulting images are unique works of art.

Recreational Use. Recreational use of night vision technology has expanded as the older generation of devices has become less expensive. Newer generations are still mostly used by the military and law enforcement because of the higher costs of these advanced devices. Spotting scopes, binoculars, and cameras are used by hunters, campers, hikers, and anglers. Night vision devices are used for wildlife viewing and photography.

A unique activity that uses night vision goggles is dining in the dark. The servers use night vision goggles to provide a meal for diners who do not have night vision goggles. The idea is to make the meal more of an adventure and to enhance the dining experience. Some companies use this as a team-building activity.

Scientific Research. Scientists use night vision devices to study nocturnal animals and other phenomena that might not otherwise be visible to the human eye. This has opened up a new area of study for wildlife biologists. In some parks, night vision technology is used to study wildlife and vehicle collisions to determine ways to reduce these incidents, which are dangerous to both humans and animals.

Astronomical research has also benefited from the use of night vision technology. The National Aeronautics and Space Administration (NASA) has used night vision technology to acquire images with the Hubble Space Telescope and the Mars Rovers. This technology is also being offered to amateur astronomers to enhance the images that can be acquired.

Careers and Course Work

Manufacturers and distributors of night vision technology utilize a variety of personnel. For technical jobs in this field, a solid mathematics background is necessary. Understanding of physics, electronics, optics, photonics, and software is important for some career paths.

Automatic data processing equipment technicians (ADPE) are used in the night vision technology industry. This type of technician requires two years of technical training. ADPE technicians work with engineers and other personnel in a range of activities including assembly, design, and troubleshooting.

Software engineers should have a Bachelor of Science degree in a field such as physics, mathematics, or engineering. Some jobs require a Master’s degree. Strong computer programming skills are also required.

The night vision technology industry employs engineers in various areas. Electrical engineers and manufacturing engineers are two examples. A Bachelor’s degree and a strong understanding of mathematics are required. Fields of study will vary between the various engineering programs.

Researchers in night vision technology will often have a Master’s degree or Doctorate in physics, engineering, mathematics, or another related field. Research in this field is done by universities, industry, and the military.

Social Context and Future Prospects

The development of night vision technology changed the way wars are fought. Before this technology was available, most militaries avoided night operations. Militaries have competed to stay at the forefront of night vision technology research to maintain a tactical advantage. Night vision technology has been credited with the success of Desert Storm in 1991, giving the US military an advantage in the conflict. The 2011 capture of Osama bin Laden exposed the military’s highly modified night vision goggles. 

As this technology continued to advance into solid-state formats, scientists explored additional communications and analysis features to allow real-time communication between soldiers. Remote surveillance and reconnaissance using thermal imaging became more widely used. Night vision technology was used to acquire astronomic images. NASA used thermal and infrared imaging in its missions to Mars.

In the twenty-first century, thermal imaging systems were marketed to consumers for night driving, heavy equipment operators, maritime applications, and pilots. As the costs of these systems decline, they are likely to become available for the general public and become a standard option in passenger vehicles.

As the 2020s progressed, manufacturers and designers of night vision technology made more advancements in producing night vision goggles and systems that allowed the user to see images in color rather than the traditional, monochromatic green display. By employing a semiconductor imaging sensor in conjunction with a decoding algorithm, the device could produce a colored digital image. Engineers behind such technology argued that more naturally colored images obtained through night vision systems allowed soldiers and law enforcement personnel to better detect and interpret specific details faster, enabling improved vision adjustment during and after use. Improved imaging, the use of artificial intelligence and practical advances, such as wireless connectivity, a reduction in size and weight, and longer battery life, have also advanced night vision technology.

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