To make the night battlefield "transparent", how important are night vision glas

Panoramic night vision devices are a more advanced type of night vision equipment in modern military gear. They feature an ultra-wide field of view of 97 degrees, which significantly enhances the ability to gather information at night, aiding in rapid enemy situation assessment and decision-making for targeted strikes. Due to their higher weight and cost, these night vision devices are typically only equipped by the most elite special forces.

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Night Vision Goggle Technology Army Competition

This year, L3Harris Technologies signed a contract worth $256 million with the U.S. Army to produce Enhanced Night Vision Goggle - Binocular (ENVG-B) and Ground Panoramic Night Vision Goggle-18 (GPNVG-18). These two types of night vision devices have an ultra-wide field of view of over 120 degrees, with almost no blind spots, enabling soldiers to quickly assess enemy situations and conduct precise strikes in complex nighttime environments. The company anticipates that the contract will span 10 years, with a total value reaching $1 billion upon completion.

Soldiers will use the ENVG-B to enhance the unit's situational awareness in night and low-light conditions, combining fused white light and thermal technology to achieve precise targeting and identification capabilities. Statistics show that the Army is currently in service with approximately 13,000 of these binocular devices.

The enhanced reality feature of the goggles allows users to lock onto targets without having to look down at maps or radios to access key information. It can also switch from white hot vision to black hot and contour modes, maintaining accuracy under all battlefield conditions and lighting levels. Other key features include the ability to switch to monocular vision, a 40-degree field of view, and data display with waypoints, tracking, and battlefield imagery.

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It can be said that the ENVG-B is a key solution to ensure that a unit remains ahead of its peers. The night vision device was used by Navy SEALs in the movie "Zero Dark Thirty," which brought it into the spotlight. The high profile of this equipment also reflects its importance in real combat scenarios.Interestingly, night vision goggles are not exclusively enjoyed by the authorities; they are also available for sale on the renowned e-commerce website eBay, with prices around 500 RMB. However, the quality is something one must discern for themselves.

The design, which incorporates a four-lens system, results in a relatively heavy weight, and with the addition of extra battery accessories, the total weight is approximately 2 kilograms. Therefore, a specialized support frame is necessary to secure the device at the front and sides of the helmet.

The integration with a helmet gives it a rather futuristic appearance. Moreover, because the four-lens night vision device provides a split image to the human eye, prolonged viewing would undoubtedly be disorienting, which could affect combat effectiveness. Thus, a four-lens panoramic night vision device must achieve seamless image stitching technology; without a processor capable of image stitching, a four-lens night vision device is simply not viable for practical use in combat.

In the trend of military high-tech iteration, China's People's Liberation Army Airborne Corps has also begun to equip itself with this advanced wide-field helmet-mounted night vision device. The domestically produced four-lens panoramic night vision device is very similar to the U.S. military's GPNVG-18, featuring a revolutionary ultra-wide field of view that is usable both day and night.

The People's Liberation Army Navy's Jiaolong Commando Unit has used the new panoramic night vision device in exercises. This four-lens panoramic night vision device not only has a science fiction-like appearance but also, when combined with a helmet, provides a broader field of vision. The full-color low-light night vision surveillance system camera's sensitivity is increased by six times, and the observation distance is doubled, further enhancing the efficiency and effectiveness of night operations.

However, it must be acknowledged that although we have placed more emphasis on the procurement of night vision equipment in recent years, the main products are still the BBG011A, BBG191-3, and the multifunctional night vision goggles of the individual soldier system. The latter, with a sensor strip at the front for enhancement, has reached a level of performance that is usable, creating a gap with the so-called digital night vision devices currently on the market, indicating there is room for improvement.Stylish four-eyed night vision goggles can allow troops to see targets up to 200 meters away during night operations, but this equipment is too heavy. In the near future, however, night vision filters may be used, thanks to a new type of ultra-thin material that can capture both infrared and visible light simultaneously.

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The Principle of Low-Light Night Vision Devices

Returning to the principle of night vision, if the image you see through night vision is green, then the device is likely a low-light night vision device. So, how do traditional night vision devices see in the dark? There are two types of traditional night vision devices: low-light night vision devices and infrared thermal imagers.

The core component of a night vision device is the image intensifier tube (often abbreviated as the image intensifier tube), which can enhance weak light from stars and moonlight through the photoelectric effect, eventually forming an image on a monochrome fluorescent screen, which happens to be green.

In front of the image intensifier tube, there is a set of ordinary glass lenses responsible for collecting and converging ambient light and nearby infrared radiation; the collected light enters the image intensifier tube, where the components are divided into three layers.

The first layer that light encounters is the photoelectric cathode, which uses the photoelectric effect to allow photons to hit and release electrons from the back, thus converting light into electricity at the first layer. With more control over electrons, a current is applied to the tube, using the first layer as the negative electrode, and a positive electrode is placed behind the third layer, causing electrons to accelerate and move backward along the electric field.

The second layer is called the microchannel plate, which serves to amplify the electrical signal. It is evenly distributed with many tiny channels spaced a few micrometers apart, each channel being a few micrometers long. These channels are not straight but are inclined at an angle of 8 degrees, so when electrons are vertically injected, they collide with the channel walls, each collision producing more electrons and triggering a chain reaction. When one electron enters the channel, thousands of electrons rush out. This army of electrons, under the influence of the electric field, heads towards the third layer. To avoid interference from air molecules on the electrons, the interior of this tube is vacuum-sealed.The third layer is the green fluorescent screen. When electrons hit the phosphor, they excite green fluorescence, and the more electrons there are, the stronger the light becomes. This enhanced electron then becomes enhanced light, allowing us to see images at night. Since the human eye is more sensitive to green, this color has been continued in use.

In films and TV series, night vision devices are very sensitive to strong light; turning on a light can render an agent wearing night vision goggles blind. However, the current fourth-generation night vision devices can automatically adjust the amplification current according to the intensity of the incoming light, being able to adapt to both bright and dim light environments.

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Thermal Imaging Night Vision Device

As long as the temperature of a substance is above absolute zero, the atoms and molecules inside the object are engaged in thermal motion and release thermal radiation to the outside. Thermal radiation is a natural way for objects to emit energy, with wavelengths ranging from radio waves to gamma rays. When objects are at lower temperatures, the radiation is mainly concentrated in the infrared band, and at very high temperatures, the radiation may include visible light and even ultraviolet bands. Thermal imaging night vision devices, also known as infrared thermographs, can convert invisible infrared thermal radiation into visible images.

The objective lens of a thermal imaging night vision device is usually made of germanium glass, which still has good light transmission in the far-infrared band. It can collect the infrared radiation emitted by objects. Then, lenses are used to focus the infrared light onto an infrared absorbing layer that can detect infrared radiation, such as microbolometers.

The surface of the microbolometer is covered with micro-bridges arranged in an array. When the infrared signal is focused onto the detector, the absorbing layer absorbs the infrared energy, causing a temperature change. These temperature changes lead to changes in the resistance value of the thermosensitive layer, which is then converted into an electrical signal output.

The signal processing unit further processes the electrical signal, converting it into a thermal image represented by different colors for different temperatures. These images display the temperature distribution of different objects in the scene.

The advantage of thermal imaging devices is that they do not require an external light source and can operate in completely dark environments. They can also observe objects through obstacles such as fog, rain, and dust. The disadvantages are that the device observes temperature; as long as the target temperature is the same as the background, it will not be displayed, making it susceptible to environmental thermal noise. Secondly, high-end low-temperature cooled thermal imaging devices need to operate below 0°C, consuming more power and having a larger volume.Ultra-Thin Night Vision "Night Vision Lens"

Researchers in Australia published in "Advanced Materials" a "metasurface-based upconversion technology" that can create thinner night vision filters capable of capturing both infrared and visible light simultaneously.

This technology eliminates the need for cooling and bulky optoelectronic conversion devices, effectively avoiding thermal noise. Moreover, this technology can capture both visible and infrared light at the same time, making the night vision images more realistic and comprehensive, directly enhancing the overall quality of the night vision images. The developers say that in the future, when going out at night, we can simply clip a night vision filter onto our glasses.

The technology does not require the conversion of photons into electrons, thus discarding complex electronic and mechanical devices.

The researchers initially studied the deposition of gallium arsenide coatings onto the lens surface, hoping to enhance the night vision effects of the lenses. Later, they found that gallium arsenide was insufficient in processing light, so they switched to using lithium niobate to coat the lens with a "metasurface." This surface features artificially designed periodic arrangements of tiny structures. This metasurface is extremely thin, with a thickness far less than the wavelength of light (subwavelength scale), allowing researchers to manipulate light waves at the microscopic level, achieving effects similar to lenses, beam shapers, polarizers, and optical wave filters.

They calculated and designed a "nonlinear upconversion enhancement metasurface" based on Fourier transform, with a thickness of 200nm, a width of 500nm, and a spacing of 379nm. When short-wave infrared light of the target frequency enters this metasurface, it undergoes a "nonlinear upconversion process," converting two or more low-energy invisible photons (infrared) into one or more high-energy photons (visible light).

This process is also known as "sum-frequency generation," which merges the energy of two or more low-frequency light rays through the action of a special medium to produce a high-frequency light ray, with the entire process adhering to the law of energy conservation. Traditional sum-frequency generation experiments typically require equipment such as lasers and prisms, but now the entire process is completed in one step through a specially designed metasurface.Actual night vision effect, stripe width is 50 micrometers.

It is precisely because this night vision technology only requires coating on the lens surface that researchers believe that as long as imaging quality and conversion efficiency can continue to be improved in the future, this achievement will have a broad application prospect.