Night fighting capability is enabled by twin technologies of image intensification and thermal imaging. These technologies are being used separately or in combination and have evolved over succeeding generations to enable effective night fighting.

Image intensification. Image intensification is a complex conversion of energy particles that occurs within a vacuum tube. An image-intensifier system works by collecting photons through an objective lens, converting them to electrons via a photocathode, increasing the electrical energy with a microchannel plate (MCP), converting the electrical energy back to light using a phosphor screen and presenting the image for viewing through an eyepiece lens. The aim is to increase the intensity of existing light for an optical system to enable to operate in low-light conditions.

Thermal Imaging (TI). TI technology detects objects based on heat emitted by them. The warmer the object, the more infrared long-wave light it radiates and the more detectable it is. A special lens focuses the infrared light emitted by all of the objects in view which is scanned by infrared-detector which in turn forms a detailed temperature pattern called a thermogram in about onethirtieth of a second. The thermogram is then converted into electric impulses which are then displayed as an image in varying colours. There are two common types of TI devices - Un-cooled and Cryogenically cooled. Un-cooled is the most common TI device which can operate at room temperature, is completely quiet and activates immediately. Cryogenically cooled is more expensive but has an incredible resolution and sensitivity and can discern a difference as small as 0.1 C from more than 300 m away.

Combination of Image Intensifiers and Tls

Night vision devices (NVD) would be more effective if the image intensifier and the TI is combined to bring out the best design features of both. The current family of uncooled TIs are much lighter, as compared to the earlier generation, thus it is possible to use them in user mounted applications. Coupling them with image intensifiers has resulted in ‘Sensor Fusion’, which produces a much better image due to the combination of the best design features of image intensifiers and TIs. Such a combination enables the user to view a much greater part of the light spectrum, from visible to near- infrared to long-wave infrared. This type of sensor fusion has led to the development of new night-vision technologies and devices like the enhanced night-vision goggle (ENVG) that combines a thermal imager with an image intensifier. The image intensifier works like a standard NVG in this system but image from the thermal sensor is through a video display. Both the inputs are then optically overlaid to provide a fused image. Developments are on to combine the video output of a thermal imager directly with the video output of an image intensifier. These new devices would then display a complete digitally fused image through HMD (head-mounted/helmet display) in a device known as the digitally enhanced ight-vision goggle (ENVG-D).

US Army’s ENVG and FWS-I. The system enables the soldier to observe and manoeuvre in all weather conditions, during limited visibility and under all lighting conditions due to the data fusion of image intensifiers and TIs. The system features a fused TI for better target recognition in degraded visual environments (dust, smoke, zero illumination, subterranean, etc.); inclusion of augmented reality aspects from the Nett Warrior display and wireless interconnectivity with the Family of Weapon Sight-Individual (FWS-I). The FWS-I when mounted on a soldier’s weapon, will transmit its sight picture through radio to the ENVG III, which is mounted on a soldier’s helmet. The FWS-I is designed for the M4 and M16 rifles and is mounted on these rifles in front of day sights that have already been bore-sighted. A variety of modes will allow soldiers to see in their goggles only the image from the ENVG III itself, only the image from the FWS-I, or a combination of the two. Using a ‘picturein-picture’ mode, the image from the FWS-I is displayed at the bottom right of the image that is coming from the goggle. The ENVG-B can see a man size target with 80 per cent probability at 150 m (threshold) and 300 m (objective) and with 50 per cent probability at 300 m (threshold) and 550 m (objective).

The ENVG family represents helmet-mounted nightvision goggles that blend image intensification and long wave infrared sensors for combat at night, in bad weather, and in smoke and dust. Harris (now with L3 Technologies) and L3 Insight are building ENVG II,while BAE Systems and Leonardo DRS are building ENVG III.

Future Developments

US Army has also given $391.8 million three-year contract to L3 Insight during May, 2018 for the ENVG-B. The ENVG family represents helmet-mounted night-vision goggles that blend image intensification and long wave infrared sensors for combat at night, in bad weather, and in smoke and dust. Harris (now with L3 Technologies) and L3 Insight are building ENVG II, while BAE Systems and Leonardo DRS are building ENVG III. ENVG III weapon sights also has an improved resolution and a wider field of view which enables rapid target acquisition.

Night Vision Devices-Some examples

Elbit Systems - USA

AN/PVS-14 Night Vision Monocular (F6015). Manufactured by Elbit Systems of America – Night Vision (previously Harris Night Vision), the Mil Spec AN/PVS-14 Monocular Night Vision Device (F6015) is designed for the individual soldier for a variety of ground-based night operations. It features the superior performance of the Gen 3 Mil Spec F9815 YG image intensifier tube with a variable gain control to achieve an optimum balance in the images seen by both eyes. The dark adapted unaided eye provides situational awareness and vision of closerange objects, while the night vision aided eye provides long-range vision of potential threats and targets. The AN/PVS-14 can be weapon mounted on a MIL-STD-1913 weapon rail mount behind a standard collimated dot sight, such as the EoTech. This sight provides a central aim point while retaining the AN/PVS-14’s 40° field of view. When fitted with the 3X magnifier, the unit fits similarly behind the collimated dot sight. This configuration provides the soldier with a 3X night scope, significantly increasing the range of the AN/PVS-14 for weapon firing.

L3 Technologies

L3/Insight LA-5B/PEQ. The L3/Insight LA-5B/PEQ is the high power variant of the standard issue AN/PEQ-15 (ATPIAL) Advanced Target/Pointer Illuminator Aiming Laser. It is a compact, self-contained laser aiming system that features three functions: Visible Aiming Laser, Infrared Aiming Laser, Infrared Illuminator. The battle-proven LA-5B/PEQ is a weaponmounted system that easily attaches to any M1913 Picatinny Rail with a standard rail grabber mount. The co-aligned infrared and visible aiming lasers are easily adjustable; making for a simple zero procedure (zero one, and the other moves with it).

AN/PVS-31 Binocular Night Vision Device (BNVD). The AN/PVS-31 BNVD is compact, lightweight, dual tube Gen3 goggle which is to replace the legacy AN/PVS-15. Weighing just under one pound (about half a kg), this system is almost as light as a monocular but packs in the same features. It is specially designed for special forces. The AN/PVS-31 has the latest Gen3 image intensifier tubes, providing unmatched clarity in resolution. It can run on a single onboard AA battery or a remote battery pack mounted behind the helmet for extended use. The AN/PVS-31 has independent pivoting tube housings that allow the operator to run the goggle in a binocular or monocular configuration. The ability to pivot the tube housings against the helmet surface creates an overall lower profile, increasing operator safety and equipment life.

FLIR Monocular NVD (MNVD)

Armasight is a multi-purpose night vision monocular. It can be hand held, head mounted, helmet mounted, or weapon mounted. With a 51° field of view (also available with 40°), it provides a large visual field without the requirement of moving the monocular. The MNVD uses advanced multi-coated optics and is built to last with a compact composite housing. Operating from a single AA alkaline battery or CR123A battery, the MNVD can run up to 40 hours. The MNVD-51 uses a unique 51° FOV lens and is available in the multiple tube options.

BAE Systems

ENVG III/ FWS-I Night Vision Mobility and Targeting System. ENVG III and Family of Weapon Sight-Individual (ENVG III/FWS-I) provides dismounted soldiers with a solution that allows them to navigate and rapidly acquire and engage targets in all light levels and conditions. With both units integrated, weapon sight imagery and aiming point can instantly transmit into the goggle – for a tactical edge during close combat missions. With a 12-micron thermal technology produces sharp thermal images by day or night. The Rapid Target Acquisition (RTA) technology aids the shooter by providing the ability to simultaneously display the weapon sight imagery and aiming point in the goggle, allowing the user to aim the weapon at targets without shouldering it. This system is similar to the system US Army is developing.