Current Status and Development Trends of Foreign Individual Soldier Thermal Imaging Equipment

Under modern warfare conditions, to meet the operational requirements of individual soldiers in high-tech warfare, the technological enhancement of individual equipment has become an inevitable choice. As the "eyes" of the soldier, it must possess universal visual capabilities in conditions of day, night, and low visibility, which has made thermal imagers the preferred high-tech equipment for individual soldiers.

The use of individual soldier thermal imaging equipment involves relatively simple platforms, and the components required can be purchased from the international market. The development threshold is relatively low, allowing many countries to research and produce such equipment. Countries capable of independently developing and producing core components for such equipment include: the United States, the United Kingdom, France, Germany, Israel, Russia, Japan, Canada, Sweden, Switzerland, the Netherlands, Spain, Turkey, Poland, Bulgaria, Singapore, South Korea, and others.

Currently, infantry combat has evolved from traditional models, such as cooperation between infantry units and individual soldiers, simple coordination between infantry and artillery, infantry and tanks, and air-ground operations, as well as independent operations by individual soldiers, to joint operations involving various branches and services, including the Air Force, Navy, Army Aviation, Armored Corps, and Artillery. The infantry has also transformed from a direct firepower combat unit into a unit responsible for information acquisition and firepower operations. To this end, countries such as the United States and Europe are developing and equipping individual soldiers with thermal imaging equipment that offers more functions and advanced capabilities. In addition to enhancing the soldiers' day-and-night combat capabilities, these systems integrate with individual soldier information systems and tactical internet networks to enable joint operations with other branches, services, and friendly forces. To meet the requirements of joint operations, individual soldier thermal imaging equipment has progressed from merely providing observation, search, and targeting functions to becoming comprehensive optoelectronic systems that integrate capabilities such as visible light, low-light vision, laser group/fusion, ranging, computation, wireless transmission, and fire control calculations. At the application level, individual thermal imaging equipment is evolving into micro/small multifunctional thermal imagers and optoelectronic fire control systems integrated with light weapons. At the system level, individual thermal imaging equipment is gradually being incorporated into the "Future Soldier" combat systems actively being developed by various countries.

1.The Role of Infrared/Thermal Imaging Technology

In the military field, infrared/thermal imaging technology primarily serves the following three functions:

1)It enables imaging observation, reconnaissance, surveillance, guidance, and other operations during nighttime and under low-visibility conditions. It offers long effective ranges and can penetrate light fog and smoke, providing the capability to achieve "one-way transparency" by gaining an information advantage in complete darkness or conditions of poor visibility.

Figure 1: The advantage of "one-way transparency" offered by infrared/thermal imaging devices in combat operations under total darkness

As shown in Figure 1, infrared/thermal imaging devices provide an advantage of "one-way transparency" in combat operations under complete darkness. In pitch-black nighttime conditions, visible light (Visible) cannot produce an image of the scene (left). However, at the same time and location, clear thermal images (Thermal) can be obtained in the long-wave infrared spectrum, allowing the identification of personnel, vehicles, roads, and forests.

Figure 2: The capability of infrared/thermal imaging devices to penetrate haze

As shown in Figure 2, infrared/thermal imaging devices possess the ability to penetrate haze. Under hazy conditions, the buildings in front of and behind the tower located 4.9 km away (Tower 4.9 km) are faintly visible in the visible light image (left). However, in the mid-wave infrared image (right) captured by a 640 × 480 indium antimonide (InSb) thermal imager at the same time and location, these buildings are clearly discernible.

Figure 3: The capability of infrared/thermal imaging devices to penetrate dense smoke

As shown in Figure 3, infrared/thermal imaging devices possess the ability to penetrate dense smoke. In the visible light image of a room with dense smoke billowing out the door (left), only the thick smoke and the haze spreading outside the house are visible. However, in the long-wave infrared image (right) captured at the same time and location, the person standing inside the room, who was obscured by the smoke in the visible light image, as well as the details on the left side of the house, become clearly visible. This demonstrates that long-wave infrared radiation can penetrate smoke, making the scenes blocked by it appear "transparent."

2)It passively receives infrared radiation signals generated by temperature differences, emissivity differences, or reflectance differences of scenes (including targets and backgrounds) across different infrared bands or wavelengths. This capability enables the identification of camouflaged targets, perception of target status, and detection of stealth targets. With its strong concealment and low susceptibility to interference, it facilitates the achievement of tactical surprise.

Figure 4: The capability of infrared/thermal imaging technology to identify camouflaged targets

As shown in Figure 4, infrared/thermal imaging technology possesses the capability to identify camouflaged targets. The principle of low-light imaging relies on the reflection of visible light from the surfaces of scenes and objects for image formation. When the surface reflections of the scene and objects are similar, identification becomes difficult (left). In contrast, the principle of thermal imaging is based on the infrared radiation emitted by scenes and objects themselves. As long as there are differences in temperature or surface emissivity between the scene and objects, detection and identification become possible. In the long-wave infrared image of the same time and scene, a person standing in the woods wearing camouflage can be clearly identified (right), because the camouflage clothing cannot replicate the temperature and surface emissivity of the surrounding environment.

Figure 5: The Capability of Infrared/Thermal Imaging Technology to Perceive Target Status

As shown in Figure 5, infrared/thermal imaging technology possesses the capability to perceive target status. In the visible light image, a pickup truck can be seen (left). In the long-wave infrared image captured at the same time and location (right), not only is the pickup truck visible, but it is also evident that its engine is very hot while the rear wheels show minimal heat. This indicates that the truck is parked but its engine has been idling, and the parking duration is approximately the time it takes for the rear wheel surfaces to reach thermal equilibrium with the ground.

Figure 6: Long-Wave Infrared Image of a Storage Tank Farm

As shown in Figure 6, this is a long-wave infrared image of a storage tank farm. The heat from the oil warms the tank roofs, causing the grayscale of the roofs to reflect the fill levels of the tanks. Storage tanks with white roofs contain a larger amount of oil, while those with black roofs contain less oil or are even empty.

3)It offers advantages such as high precision, compact size, lightweight design, and low power consumption, making it easy to integrate into various weapon systems and platforms.

2. Scenarios for Individual Soldier Combat Operations

In modern localized warfare, typical operational scenarios for individual soldier thermal imaging equipment include observation and reconnaissance, target designation and laser guidance, small arms aiming, sniper operations from pre-established fixed positions, precise engagement of targets behind obstacles or within blind spots using small arms, and integration into "Future Soldier" combat systems.

2.1 Battlefield Observation and Reconnaissance

Individual soldiers use portable thermal imagers for observation and reconnaissance under nighttime and low-visibility conditions, and they can also be employed to detect camouflaged targets. In fact, thermal imagers are equally effective during daytime operations. When a portable thermal imager is relatively heavy, it can be mounted on a tripod for stable use (as shown in Figure 7).

Figure 7: The "Sych-4" Handheld Laser Rangefinder-Thermal Imager Equipped by the Russian Army

As shown in Figure 7, the "Sych-4" handheld laser rangefinder-thermal imager equipped by the Russian Army features a design that allows it to be mounted on a tripod, which is characteristic of portable systems.

2.2 Target Designation and Guidance for Strikes

Beyond observation and reconnaissance, handheld thermal imagers (Figure 8) can also be integrated with components such as angle measuring devices, satellite positioning systems, laser rangefinders, and laser target designators (Figure 9). This combination enables the determination of target angular coordinates and distance, allowing for the guidance of semi-active laser precision-guided munitions to accurately engage high-value targets.

 Figure 8 A soldier can stably use a handheld thermal imager for observation and reconnaissance by holding it with both hands. The image shows the French "Sophie" handheld thermal imager.

Figure 9 The "Sophie" Handheld Thermal Imager

As shown in Figure 9, the "Sophie" handheld thermal imager (right) can be integrated with devices such as an angle measuring instrument, satellite positioning system, laser rangefinder, and laser target designator. This combination enables soldiers on the front lines to conduct reconnaissance, determine target positions, and guide semi-active laser precision-guided munitions to strike high-value "point targets."

2.3 Special Operations and Nighttime Combat

Helmet-mounted thermal imagers not only address soldiers' needs for observation and reconnaissance during nighttime (as well as daytime) and low-visibility conditions but also free up their hands to operate weapons and equipment, such as aiming and firing small arms or driving vehicles. To enhance soldiers' shooting accuracy, a laser indicator emitting near-infrared laser light (e.g., with a wavelength of 808 nm) can be mounted on the firearm. Simultaneously, the helmet-mounted thermal imager integrates a low-light night vision module (Figure 10). This allows soldiers to see the near-infrared spot projected by the firearm's laser indicator onto the target through the low-light night vision module's image, effectively aiming at the target and enabling them to fire. This targeting method is referred to as indirect aiming.

Figure 10 The U.S. Monocular AN/PVS-20 Enhanced Helmet-Mounted Night Vision Device

As shown in Figure 10, this is the U.S. monocular AN/PVS-20 enhanced helmet-mounted night vision device. It integrates two modules within a single housing: a low-light night vision module (top) and an uncooled long-wave infrared thermal imager (bottom). When not in use, the entire unit can be flipped upward. This design addresses the need to free the soldier's hands and enables observation under nighttime and low-visibility conditions. The soldier's weapon is equipped with an integrated laser indicator, which, combined with the low-light night vision module, facilitates indirect aiming and precision shooting.

2.4 Aiming and Firing with Small Arms

There are two main factors that contribute to the improved accuracy of small arms with optical sights:

Enhanced visibility-The objective lens of an optical sight has an aperture roughly one order of magnitude larger than the human eye, allowing it to gather more photon energy and produce a brighter image.

Improved clarity and distance measurement-Optical sights provide magnification (typically around 8×) and are equipped with mil-dot reticles to measure the distance to the target, enabling corrections based on ballistic tables.

Thermal scopes (Figures 11 and 12), in addition to offering the functionality of optical sights, address the challenges of observation, aiming, and precision shooting under nighttime (as well as daytime) and low-visibility conditions.

Figure 11 An MP7 submachine gun equipped only with a thermal sight, allowing the soldier to conduct precision shooting at targets both day and night.

Figure 12 A thermal sight used in combination with an optical sight, enabling the soldier to conduct precision shooting at targets both day and night.

Under nighttime or low-visibility conditions (such as smoke, dust, fog, haze, etc.), the human eye cannot see targets, making it impossible for individual soldiers to use the optical sights mounted on small arms for searching, aiming, and firing. Therefore, if the capability to observe and search for targets during both day and night, as well as in low-visibility conditions, is available, the combat effectiveness of individual soldiers can be enhanced.

The small arms equipped by individual soldiers include assault rifles, submachine guns, light machine guns, sniper rifles (Figure 13), rocket launchers, recoilless rifles (Figures 14, 15), portable anti-tank missile systems (Figure 16), and anti-aircraft missile systems (Figure 17). As the operational targets and engagement ranges of these different small arms vary, light, medium, and heavy weapon thermal sights have been developed to be compatible with them.

Figure 13 A Three-Person Combat Team of the French Army

As shown in Figure 13, this image depicts a three-person combat team of the French Army. One soldier is equipped with a FR-F2 7.62 mm caliber sniper rifle fitted with a "Sword" observation-fire control sniper rifle scope, capable of delivering precise point lethality against targets within 800 meters. Another soldier is armed with a "Minimi" light machine gun equipped with a thermal sight, providing area suppression against targets within 1,000 meters. The third soldier carries a "FAMAS" assault rifle, tasked with providing cover for the sniper and machine gunner.

Figure 14 The "Carl Gustav" Recoilless Rifle

As shown in Figure 14, the left image depicts the M3 variant of the "Carl Gustav" recoilless rifle equipped with the French "Sword" day-and-night thermal imaging sight. This configuration enables targeting and firing under both day and night conditions, as well as in low-visibility environments.

Figure 15 The M3 "Carl Gustav" recoilless rifle equipped with an optical sight.

Figure 16 FGM-148 "Javelin" Portable Anti-Tank Missile Weapon System

As shown in Figure 16, the fire control system (Command Launch Unit) of the FGM-148 "Javelin" portable anti-tank missile weapon system employs a long-wave infrared thermal sight with scanning imaging technology. This enables target acquisition under both day and night conditions, as well as in low-visibility environments, facilitating the calculation and programming of firing parameters for missile launch.

Figure 17 FIM-92 "Stinger" Portable Anti-Aircraft Missile Weapon System

As shown in Figure 17, the FIM-92 "Stinger" portable anti-aircraft missile weapon system is equipped with the AN/PAS-18 thermal sight, enabling the infrared seeker of the missile to acquire targets before launch under both day and night conditions, as well as in low-visibility environments.

To maximize the effectiveness of thermal sights, their operational range should exceed or at least match the firing range of the small arms they are paired with. Consequently, thermal sights are typically categorized into three types based on their operational range: Light Weapon Thermal Sights (LWTS), Medium Weapon Thermal Sights (MWTS), and Heavy Weapon Thermal Sights (HWTS). An example is the AN/PAS-13E series of thermal sights (Figure 18) produced by Raytheon in the United States.

Figure 18 AN/PAS-13E Series Uncooled Thermal Sights Manufactured by Raytheon of the United States

As shown in Figure 18, the AN/PAS-13E series of uncooled thermal sights produced by Raytheon in the United States form light (LWTS), medium (MWTS), and heavy (HWTS) uncooled thermal sights by incorporating different infrared optical lenses and uncooled infrared focal plane detectors. These sights feature dual fields of view and a 3x electronic zoom function, making them suitable for various small arms with different effective ranges. In addition to serving as thermal sights, they can also be used independently as handheld thermal imagers.

2.5 Sniper Operations

Sniper operations refer to a combat method in which infantry use sniper rifles to conduct precise strikes against targets within their line of sight, typically at distances around 1,000 meters. For example, on November 11, 2012, during daylight hours, a British Army sniper successfully eliminated two Taliban soldiers at a GPS-measured distance of 2,475 meters using an L115A3 sniper rifle. However, conducting sniper operations under conditions of day, night, or low visibility requires the use of a thermal sight (Figure 19). The efficiency of target acquisition with a sniper rifle thermal sight alone is limited. Therefore, snipers often rely on a handheld thermal imager to search for targets, provide directional cues, and measure distances.

Figure 19 Scenario of a Two-Person Team Conducting a Sniper Operation

As shown in Figure 19, in a two-person sniper team scenario, the sniper (left) uses a High-Performance Coaxial Sniper Rifle Thermal Sight (HISS-XLR), which has limited efficiency in target search. Therefore, the spotter (right) employs a Recon V handheld thermal imager to search for targets, provide azimuth guidance, and measure distances.

2.6 Optoelectronic Aiming–Laser Rangefinding–Fire Control System for Small Arms

Currently, there is also a demand for equipping small arms with an optoelectronic aiming–laser rangefinding–fire control system. The main reason is that as engagement distances increase (e.g., beyond 2,000 meters), the combat effectiveness relying solely on human observation and aiming significantly decreases. The small arms optoelectronic aiming–laser rangefinding–fire control system (Figures 20, 21) not only addresses soldiers' needs for observation and precise ranging under nighttime (as well as daytime) and adverse weather/low-visibility conditions, but also solves the calculation and display of firing parameters. This enables even ordinary soldiers to conduct precision shooting with small arms, making it a crucial component of the individual soldier system.

Figure 20 U.S. Army MK-47 "Striker" 40mm Automatic Grenade Launcher

As shown in Figure 20, the U.S. Army's MK-47 "Striker" 40mm automatic grenade launcher is an area-suppression weapon with an effective range of 2,200 meters. It is equipped with the AN/PWG-1 Lightweight Video Sight, which integrates a television camera, a third-generation low-light night vision device, a laser rangefinder, a ballistic computer, and a display. Together with the AN/PAS-13 Heavy Thermal Weapon Sight (top left), it forms a complete distributed optoelectronic aiming-laser rangefinding-fire control system.

Figure 21 XM25 Grenade Launcher

As shown in Figure 21, the XM25 grenade launcher employs an integrated optoelectronic aiming, laser rangefinding, and fire control system. This system addresses the calculation and display of firing parameters, enabling ordinary soldiers to conduct high-precision shooting with small arms under nighttime (as well as daytime) and low-visibility conditions.

When a small arms fire control system is composed of a "three-optics" sight, the shooter can detect and identify targets through visible and infrared channels, measure distance using a laser rangefinder, and have the data processed by a ballistic computer to generate firing parameters. The aiming point is then directly displayed on the screen, allowing even ordinary soldiers to achieve high-precision shooting akin to that of professional snipers.

In 2014, the U.S. Department of Defense (DARPA) initiated the Computational Weapon Optic (CWO) program to develop the "Super Smart Scope" (3S). This scope is equipped with advanced thermal imaging and night vision capabilities to enhance situational awareness and targeting precision (Figure 22). It also integrates a ballistic computer, Applied Ballistics software, and radio synchronization features, among others.

Figure 22 The U.S. Department of Defense's Development of the "Super Smart Scope" under the Computational Weapon Optic (CWO) Program

As shown in Figure 22, the U.S. Department of Defense, under the Computational Weapon Optic (CWO) program, is developing the "Super Smart Scope." This scope integrates multiple functions, including visible light, low-light vision, thermal imaging, laser rangefinding, a ballistic computer with Applied Ballistics software, and radio synchronization. This enables even ordinary soldiers to conduct high-precision shooting similar to that of professional snipers.

To achieve precise shooting at targets within the line of sight or behind obstacles with small arms, obtaining accurate distance measurements to the target is essential. Therefore, integrating a laser rangefinder into the thermal sight becomes the optimal choice. Once the target's distance is measured, firing parameters can be calculated, allowing the thermal sight to naturally evolve into a small arms electro-optical fire control system. With such an integrated electro-optical fire control system on small arms, ordinary soldiers can also engage in precise shooting at both line-of-sight and beyond-visual-range targets. To this end, the United States has developed the "Target Acquisition Day/Night Fire-Control system" (TA D/N FCS) for the XM25 grenade launcher. Its prototype was originally developed for the now-canceled XM29 "Objective Individual Combat Weapon System" (OICW), as shown in Figure 23.

Figure 23 The XM29 "Objective Individual Combat Weapon System" (OICW), a Trailblazer in Global Individual Soldier Weapon Development

As shown in Figure 23, the XM29 "Objective Individual Combat Weapon System" (OICW), which has led global trends in individual soldier weapon development, primarily consists of three major components: a 5.56 mm small-caliber assault rifle (lower), a 20 mm automatic grenade launcher (middle), and an integrated electro-optical fire control system (upper).

The "Target Acquisition Day/Night Fire-Control System" (TA D/N FCS) integrates a visible light sight, an uncooled thermal imaging module, a laser rangefinder/laser spot marker, temperature and pressure sensors, a ballistic computer, and a fuse-setting device. The thermal imaging video is projected onto the visible light sight via a mirror, while data such as laser ranging measurements, crosshair reticles, and aiming correction points are overlaid on the thermal imaging module's micro-display for the soldier's observation. This design meets the requirements for day and night combat operations, as illustrated in Figure 24.

Figure 24 The U.S. military has deployed the XM25 grenade launcher equipped with the "Target Acquisition Day/Night Fire-Control System" (TA D/N FCS) in the Afghanistan theater for operational validation.

The U.S. military has integrated the "Target Acquisition Day/Night Fire-Control System" (TA D/N FCS) into the XM25 grenade launcher. During operation, the soldier aligns the center of the crosshair with the target's aiming point, performs laser ranging, selects the desired burst distance relative to the target, and the system automatically programs the grenade's fuse with the calculated firing parameters before launch. By connecting to an external GPS receiver to obtain target coordinates, the system enables precise strikes against targets behind obstacles.

If the "triple-optics" sight is combined with an electrically controlled mount and a control link, it can form a remote-controlled sniper rifle weapon station. This eliminates the need for soldiers to remain concealed in pre-set positions for extended periods, allowing them to conduct sniper operations from a safe location, as shown in Figure 25. The "triple-optics" sight is a crucial component of future individual soldier weapon systems, enabling both direct aiming and firing through the thermal sight and indirect aiming and shooting via the display screen.

Figure 25: Combining the "Triple-Optics" Sight with an Electrically Controlled Mount and Control Link to Form a Remote-Controlled Sniper Rifle Weapon Station

As shown in Figure 25, integrating the "triple-optics" sight with an electrically controlled mount and control link enables the creation of a remote-controlled sniper rifle weapon station. This eliminates the need for soldiers to remain concealed in pre-set positions for extended periods, allowing them to conduct sniper operations from a safe location. In the depicted system, the remote-controlled large-caliber sniper rifle weapon station employs a distributed architecture for its triple-optics sight.

2.7 "Future Soldier" Combat System

The "Future Soldier" combat system is an integrated informatized equipment system for individual soldiers. By connecting to the tactical internet, it transforms the soldier into an information and combat node within the broader operational network. This system addresses challenges such as battlefield situational awareness, operational planning, coordinated/joint combat execution, and logistical support, while maximizing the combat effectiveness of individual soldier weapons. In Germany's "GLADIUS" New Future Soldier Program, the system includes eight types of thermal imaging equipment (Figure 26).

Figure 26 Germany's "GLADIUS" New Future Soldier Program

As shown in Figure 26, the system composition of Germany's "GLADIUS" New Future Soldier Program includes a core system featuring "Night vision goggles with an IR module," reconnaissance equipment comprising three types of thermal imagers, and weapon accessory equipment (thermal sights) consisting of seven models configured for six types of small arms.

France's "Future Soldier" combat system is known as the "Integrated Infantry Equipment and Communications (FELIN) System," which also incorporates multiple models of thermal imaging equipment. This system addresses both coordination and joint operations among individual soldiers (Figures 27–29) and joint operations between individual soldiers and other military branches. Examples include battlefield target designation and guiding aerial firepower or artillery strikes for precise engagement of targets.

Figure 27 France's FELIN Individual Soldier Weapon System

As shown in Figure 27, the "triple-optics" sight is a critical component of future individual soldier weapon systems. The image depicts France's FELIN individual soldier weapon system, where the soldier can operate the thermal sight via buttons located on the forward grip of the assault rifle while aiming.

Figure 28 Thermal Sight of the French FELIN Individual Soldier System

As shown in Figure 28, the thermal imagery from the French FELIN individual soldier system's thermal sight can be transmitted to the helmet-mounted display, enabling soldiers to conduct indirect aiming and firing with the FAMAS assault rifle.

Figure 29 French "Future Soldier" Combat System

As shown in Figure 29, this is an operational scenario of the French "Future Soldier" combat system-the "Integrated Infantry Equipment and Communications" (FELIN) system. A soldier lying on the ground uses a "JIM MR" handheld thermal imager for observation, directing another soldier standing behind a tree for cover to engage targets with a "FAMAS" assault rifle equipped with a "Sword" day-and-night sight.

A simplified version of the "Future Soldier" combat system enables the concept of "see it, shoot it" by integrating thermal sights with helmet-mounted displays. This allows soldiers to engage targets without needing to raise and aim their rifles (Figures 30 and 31). In urban or jungle environments, where visibility is often poor or sightlines are limited, targets may appear at close range, leaving little time for traditional aiming. With this system, soldiers can shoot as soon as they see the target-truly achieving "see it, shoot it."

 Figure 30 Integrating Thermal Sights with Helmet-Mounted Displays to Achieve "See It, Shoot It"

Figure 31 Integrating thermal sights with helmet-mounted displays enables "see it, shoot it" capability for heavy machine gun fire.

Individual Thermal Imaging Equipment in the United States

The U.S. military places significant emphasis on enhancing the operational capabilities of individual soldiers. This is reflected not only in the development and production of a diverse range of small arms tailored for various purposes but also in the extensive array of thermal imaging equipment for individual soldiers. This includes portable thermal imagers, handheld thermal imagers, thermal weapon sights for small arms, clip-on thermal sights, thermal imager monoculars, thermal imager binoculars, clip-on thermal imagers, and helmet-mounted thermal imagers, among others.

The advancement of second-generation thermal imaging technology in the United States has overcome the limitations imposed by the size, weight, cost, and reliability constraints of first-generation thermal imaging technology. As a result, U.S. individual thermal imaging equipment has achieved world-leading levels in all aspects, including structural diversity, model variety, functional performance, scale of deployment, and practical operational use. The key manifestations of this leadership are as follows:

1) Coverage of Three Atmospheric Transmission Windows
The U.S. military has developed and deployed individual thermal imagers with spectral response ranges covering all three atmospheric transmission windows: short-wave infrared (1 μm–2.5 μm), mid-wave infrared (3 μm–5 μm), and long-wave infrared (8 μm–14 μm).

2) Parallel Development of Multiple Technological Pathways
To ensure the success of the second-generation individual thermal imager program, the United States has pursued a strategy of developing multiple technological pathways in parallel. In terms of imaging methods, the approaches include optomechanical scanning imaging, electronic scanning imaging, and staring imaging. Regarding infrared focal plane detectors, both cooled and uncooled types have been advanced. From the perspective of detector materials, quantum-type materials such as mercury cadmium telluride (HgCdTe), indium antimonide (InSb), platinum silicide (Pt:Si), lead selenide (PbSe), and indium gallium arsenide/gallium arsenide (In₁₋ₓGaₓAs/GaAs) have been utilized, alongside thermal-type materials such as barium strontium titanate (BST), lead zirconate titanate (PZT) ceramics, vanadium oxide (VOₓ), and amorphous silicon (α-Si) thin films. Historically, the most mature technology-the 6-stage thermoelectric cooler-cooled 40×16-element HgCdTe TDI focal plane detector with optomechanical scanning imaging-was developed first and saw large-scale production and deployment. The uncooled focal plane detector technology, which carried certain technical risks, was only adopted for large-scale production and deployment after reaching maturity.

3)Two Technological Approaches to Uncooled Long-Wave Infrared Focal Plane Arrays

To maintain global leadership in thermal imaging technology, the United States initiated classified research and development on uncooled long-wave infrared focal plane array (FPA) technology in the late 1980s. To ensure the success of this technology, the U.S. pursued two parallel technological approaches: hybrid ferroelectric FPA technology and integrated microbolometer-type vanadium oxide (VOx) FPA technology. By the early 1990s, when this research was declassified, breakthroughs had been achieved in both uncooled FPA technologies-the ferroelectric type using barium strontium titanate (BST) ceramic materials and the microbolometer type using vanadium oxide (VOx) thin films. Thermal imagers utilizing these two types of uncooled FPAs were successfully developed, mass-produced, and fielded, giving the United States a lead of approximately 15 years in uncooled thermal imaging technology. Subsequently, uncooled long-wave infrared FPA technology based on amorphous silicon (α-Si) thin-film materials was also successfully developed, with corresponding thermal imagers entering mass production and deployment. Today, ferroelectric, vanadium oxide, and amorphous silicon uncooled FPA technologies represent the three mainstream approaches.

4)Development of Five Generations of Uncooled Focal Plane Arrays

To sustain leadership in individual soldier thermal imaging technology, the United States has continuously advanced through five generations of uncooled FPA technology (see Figure 1), marked by detector format and pixel pitch:

First Generation: Pixel pitch of 51 μm × 51 μm, with formats such as 320 × 240.

Second Generation: Pixel pitch ranging from 25 μm to 35 μm, with formats including 320 × 240, 160 × 120, and 640 × 480/512.

Third Generation: Pixel pitch of 17 μm × 17 μm, with formats such as 320 × 240, 640 × 480/512, and 1024 × 768.

Fourth Generation: Pixel pitch of 12 μm × 12 μm, with formats including 206 × 156, 320 × 240, 640 × 480/512, and 1024 × 768.

Fifth Generation: Pixel pitch of 5 μm × 5 μm, with formats such as 1280 × 720.

Throughout these generations, the Noise Equivalent Temperature Difference (NETD) of uncooled FPAs has improved from approximately 100 mK in the first generation to as low as 10 mK in the latest generation (while maintaining a relative aperture around f/1).

The United States has developed a comprehensive range of focal plane array (FPA) specifications, including:

160 × 120 (Quarter VGA)

320 × 240/256 (Half TV format, or Half VGA)

640 × 480 (Full TV format, or VGA)

1024 × 768 (Quasi-High Definition TV format, or QXGA)

1920 × 1080 (High Definition TV format, or HDTV).

Figure 1 The United States' Continuous Development of Five Generations of Uncooled Focal Plane Array Technology

As shown in Figure 1, to ensure leadership in individual soldier thermal imaging technology, the United States has continuously advanced through five generations of uncooled focal plane array (FPA) technology. The figure illustrates the technological evolution from 1996 to 2012.

5) Development of Common Components, Modules, and Complete Systems for Individual Soldier Thermal Imaging

The United States has simultaneously developed common components, common modules, and complete common systems for individual soldier thermal imaging. The image processing software has been designed to be user-configurable and customizable, significantly reducing size, weight, and power consumption. This approach effectively meets the "Size, Weight, and Power" (SWaP) constraints of individual soldier thermal imagers.

6)Diversified Forms of Individual Thermal Imagers
The development of uncooled thermal imaging common components and modules has lowered the technical barriers for the research, development, and production of individual thermal imagers. This enables small and medium-sized companies to design and manufacture a wide range of devices, including portable thermal imagers, handheld thermal imagers, monocular thermal scopes, binocular thermal scopes, thermal weapon sights, and helmet-mounted thermal imagers. The number of models available exceeds 100, while simultaneously enhancing the reliability, lifespan, and tactical usability of these systems.

7)Development of Versatile Application Software for Individual Thermal Imagers
Advanced and feature-rich application software has been developed and implemented for individual thermal imagers. These include various modes of non-uniformity correction, multiple reticle/crosshair options, thermal image rangefinding capabilities, diverse image processing modes, pseudocolor and "intelligent coloring," radiometric temperature measurement, fusion of thermal images with visible/low-light images, and storage of thermal video and frame-captured images. These advancements significantly improve image quality while expanding and refining functional capabilities.

8)Integration of Multiple Sensors with Thermal Imagers
Individual thermal imagers now integrate various sensors, such as visible-light cameras, laser rangefinders, laser designators, GPS receivers, micro-gyro assemblies, barometric altimeters, and inclinometers, thereby extending their functionality.

9)Incorporation of Built-In Storage
Built-in storage has been added to individual thermal imagers, enabling the recording of video and images as well as post-mission playback.

10)Addition of Bluetooth or Wi-Fi
The integration of Bluetooth or Wi-Fi in individual thermal imagers allows for wireless remote control, sharing of recorded video or images over networks, and playback on network-enabled devices such as smartphones, tablets, and televisions.