Negating The Night
By
Michael Gething
-
April 3, 2020
The US Army begun introducing the head-mounted ENVG-Binocular and the FWS-I thermal sight (shown mounted on the M249 SAW) into service in November 2019.
The variety of night vision systems for maritime and land forces is wider then everConducting military operations at night without any form of night vision system today is virtually unthinkable. Not so very long ago, Night Vision (NV) capability, be it Image Intensification (I2) or Thermal Imaging (TI), for maritime, ground or airborne applications, came as individual items of kit with the soldier, sailor or airman providing the interface with the weapon system, via the Mk1 Human Brain.
In today’s digital battle space, whether on a naval vessel, an airborne platform, a main battle tank (MBT) or armoured fighting vehicle (AFV) or just a four-man infantry unit on the ground, it seems everything comes with Night Vision.
Spurred on by the various regional conflicts of the last 30 years, NV capability is reaching new heights, or more accurately, distances and resolutions. The two main technology threads that power NV systems – I2 (the amplification of whatever light is available) or TI (the detection of radiant heat from infrared [IR] sources) – are bracketed within the category of EO/IR (electro-optic/infrared) sensors, which also includes laser products.
Technology re-cap
I2, now principally used for night-vision goggles (NVGs), involves the collection and conversion of ambient light photons from the visual and near infrared (V/NIR) part of the spectrum from 0.4 to ~0.9 microns, into electrons that are then multiplied by a cascading process before being reconverted back into visible light, within a small (usually 18mm-diameter) tube. As with all technology, I2 has evolved and today’s tubes are Gen3, with a thin barrier film on the microchannel plate (MCP) within the tube.
The down side of I2, as experienced by forces operating in open country or mountainous terrain (such as in Iraq and Afghanistan), is the lack of sufficient (usually urban) ambient light. Thus NVGs, powered by I2, were rendered almost ineffective on moonless nights or when occluded skies blanked out starlight.
The Dragon-C640 (Compact) thermal sight uses an uncooled LWIR 640×512 FPA, allowing a longer detection range.
TI is based on a photon detector made of an exotic material such as indium antimonide (InSb) or mercury cadmium telluride (MCT, CMT or HgCdTe) for the sensing detector’s focal plane array (FPA), and required cryogenic cooling to deliver the sensitivity required for imaging, as well as optics and processing elements. Such systems usually concentrate on either the mid-wave infrared (MWIR) spectrum of 3-5 microns or the long-wave infrared (LWIR) spectrum of 8-12/14 microns.
Cooled detectors require an appropriate mechanism, which adds to its size and weight. However, the last decade has seen the rapid evolution of uncooled detectors for smaller TI-powered NV systems, notably hand-held fire-control systems (FCS), thermal weapon sights and head-mounted cameras.
As with I2, there is a drawback to TI. While it can produce an image in total darkness, the distance TI can ‘see’ depends on the atmospheric conditions across different parts of the spectrum: MWIR is generally considered applicable for hot and humid climates; while LWIR is more suitable to cooler, drier climates. Thus performance can depend on the climate in the combat zone and, of course, the ‘fog of war’.
FPA
The other element, when considering TI, is the resolution of the image, defined by the number of pixel elements in the detector’s FPA; and the number of pixels therein depends on their size (or pixel-pitch).
Some 17 years ago, the most common FPA format was 320×240, with a pixel pitch of 25 or 30 microns, depending on the detector material. Thus, the more pixels there are in an FPA, the better the image resolution and, depending on the optics, the longer the range. A reduction in pixel-pitch results in a higher pixel counts.
So, in 2002, a 640×480 FPA with a 20 micron pixel pitch was considered High Definition (HD); today it is considered as Standard Definition (SD). Production detectors with pixel pitches of 17, 15 or 12 microns are now commonplace, with 10 and seven microns emerging.
Detectors
At the DSEI exhibition in September 2019, Leonardo displayed the SLX-Superhawk – an MWIR detector with a cooled FPA and pixel-pitch of just eight microns, providing a 1,280×1,024 pixels.
It is claimed that the SLX-SuperHawk is able to capture better than HD-quality images in total darkness by detecting temperature differences as small as 1/50th of a degree.
As a means of penetrating the dust, haze and smoke encountered on the battlefield, detectors tuned to the short-wave infrared (SWIR) spectrum (~0.9 to 3 microns) as well as the visible-to-near-infrared (V/NIR) spectrum (0.4 to ~0.9 microns) as used by daylight cameras, have been evolved.
These use reflected ‘light’ and are better able to penetrate atmospheric detritus, with the added advantage that bright light or flashes will not degrade performance.
In October 2019, Israel’s SCD (Semi Conductor Devices) announced orders worth in excess of $15 million for its InGaAs (indium gallium arsenide) SWIR-based solutions, including its in-production Cardinal 1280 detector (with a 10 micron pixel-pitch).
The company notes its SWIR technology includes low-light level capability for night vision, based on its advanced low-noise ROIC (Read-Out Integrated Circuit). Over the past two years, SDC reports an increased demand for EO/IR systems based on the SWIR spectrum.
An example of a V/NIR spectrum detector is in the Nocturn camera range from Photonis USA, using the company’s Lynx CMOS (Complementary Metal Oxide Semiconductor) solid-state imaging sensor with 1,280×1,024 resolution.
Imagery
Driven by the need for improved NV capability and the spread of digital communications, allowing imagery to be transmitted electronically, the technology and application of both types of detecting systems has evolved. Over the past decade, the problem of bringing both image sources together in one picture, with the goal of a consolidated image that overcomes the drawbacks of the individual systems, has been addressed.
The combination of I2 visible imagery and thermal imagery into one complementary TV-like picture – known as image fusion or, more accurately, image blending – merges two different views of the world, to provide a tactically significant picture.
The visible image is most like what we are used to seeing with our eyes and provides higher resolution than current uncooled thermal imagers. This makes the overall picture ‘readily understandable’.
The thermal imager, however, is sensitive to differences in the temperature of objects in view, thus people (and other mammals) tend to stand out strongly in the picture due to their body warmth. This provides for very fast detection of individuals (and active objects such as military vehicles) that is not available in visible imagery.
However, the problem is that an I2 image is not electronic while TI, by the nature of its creation, is fully digital, allowing imagery to be displayed on any of a number of digital displays and transmitted into a network via wireless data links if required.
The initial response was to overlay a thermal image onto the I2 image, while developing an alternative fully-digital detector in place of the I2 source.
One emerging technology is that of the EBAPS (Electron Bombarded Active Pixel Sensor), pioneered by US manufacturer, Intevac. This takes the photons from the scene, focuses them onto a photocathode and the resulting photoelectrons are then accelerated across a vacuum gap and proximity-focused on the back-illuminated CMOS anode to produce digital image intensified (DI2) imagery with very little background noise.
As with all technological solutions to problems, the technology employed boils down to ‘horses-for-courses’: the application most suitable to the mission. So, having outlined the basic technology available for night vision systems, let us consider some examples of how it has been applied.
Naval applications
Maritime use of EO/IR night vision is widespread, covering command-and-control (including navigation) and weapon fire-control systems (FCS) for surface combatants; long-range and close-in surveillance for all sizes of warship, down to RIB-sized vessels; plus on-board monitoring of the immediate vicinity of the ship itself.
For surface combatants, a typical EO/IR fire-control director is the MSP500/600 series from Germany’s Rheinmetall Defence Electronics. It uses a Saphir LWIR 640×480 thermal imager, alongside a daylight camera and laser rangefinder. This has been adopted by the German Navy and exported to customers including Malaysia.
For longer-range surveillance, IRST (infrared search-and-track) systems are available. The VAMPIR family from Safran’s Sagem, operating in the MWIR spectrum, has been widely procured beyond France, with export customers including Australia and South Korea. Italy’s Leonardo (formerly Selex ES) offers its Silent Acquisition and Surveillance System (SASS) IRST, with both MWIR and LWIR channels, serving with the Italian and Turkish navies.
Typical of an on-board monitoring system is the Gatekeeper panoramic surveillance and alerting system from Thales Nederland, housed with other sensors in the I-Mast 400 integrated mast. It comprises three or four non-rotating sensor heads located around the vessel, each with three pairs of uncooled LWIR 320×240 FPA and HD TV cameras, offering 360deg coverage against asymmetric threats such as swimmers. It is in service on Holland-class OPVs of the Belgian and Netherlands navies.
For sub-surface vessels, pure optical periscope systems are being progressively replaced by optronic masts. L3 KEO (formerly Kollmorgen) has a TI variant of its Model 76 periscope using an MWIR 640×480 thermal imager, which has been widely exported; while the UK end of Thales produces the CM10 series of optronic masts, with an MWIR thermal imager (or image intensifier option) for the Astute-class of SSNs for the Royal Navy and the Soryu-class SSK boats for Japan.
Land applications
Virtually every operational task conducted by ground forces now has an NV element: NVGs, hand-held targeting devices, night-vision binoculars (NVB), weapon FCS on MBTs and AFVs, reconnaissance and surveillance, and night driving/navigation.
I2-powered NVGs proliferate worldwide with US-developed goggles being predominate. The most numerous legacy products are probably the AN/PVS-7 and AN/PVS-14 NVGs, or derivatives thereof, produced by L3 Warrior Systems and L3 Harris (the night vision business of which [originally ITT] was acquired by Elbit Systems of America in September 2019, following the merger of L3 Communications and the Harris Corporation).
Speaking to
Asian Military Review earlier this year, an L3Harris spokesman said that “our legacy PVS-14 is still a big seller”, noting that the company had recently received “a large foreign order” for this product.
I2 tubes
In the United States, I2 tubes are manufactured by L3 Warrior Systems and Harris, although exportability of these tubes is restricted by Figure of Merit (FOM) regulations, as well as ITAR restrictions.
There are other non-US manufacturers, mainly in Europe, where the Franco-Dutch company Photonis has emerged as a principle developer and producer of a whole range of II tubes, adopted by many users, especially where ITAR-free products are required. By way of example, Germany has selected the company’s 4G high-FOM I2 tubes for the 1,700 Theon Sensors NYX NVBs being procured from Greece to improve night driving manoeuvrability.
FCS systems
Virtually all I2-powered night vision adjuncts to MBT/AFV gunfire FCS have now been replaced with TI technology.
Initially this was by retrofit to systems mounted ‘under armour’ but new generation FCS units use TI only. However, in recent years, ‘above armour’ systems have emerged, not only for main armament FCS applications but also for external weapon stations and the Reconnaissance, Surveillance and Target Acquisition (RSTA) role on lighter AFVs and recce vehicles.
Typical of current generation FCS systems on offer for MBT/AFV is the Commander’s Open Architecture Panoramic Sight (COAPS) day/night target acquisition and independent surveillance system from Elbit Systems of Israel.
This is a dual-axis sight with additional fire-control functions for stationary and mobile platforms. The 360° panoramic sight is synchronised with the gunner’s main sight and provides a hunter-killer capability. Sensors within COAPS include a continuous-zoom thermal imager (both MWIR and LWIR are both offered with a 640×512 FPA resolution, with a 1024×768 option for MWIR and 1280×1024 option for LWIR), a daylight colour CCD TV camera, and an eye-safe laser rangefinder.
Moving to the hand-held target acquisition sector, SAFRAN’s Sagem JIM (Jumelle Infrarouge Multifonction) range is typical. The long range JIM LR model features a cooled MWIR detector with a 320×240 FPA, while the JIM UC uses an uncooled LWIR detector with a 640×480 FPA. The former weighs some 2.8kg while the latter (somewhat smaller as a result of its uncooled detector) is 0.5kg lighter.
Weapon Sights
Slightly smaller are the thermal weapon sights (TWS), use of which is becoming more the rule than the exception. The US AN/PAS-13 TWS family, produced in several versions by several contractors (including BAE Systems, Leonardo DRS and Raytheon) has become ubiquitous around the world.
In Europe, Safran’s Sagem market the Sword range of thermal sights derived from the French Army FELIN project while the UK’s, Excelitas Qioptiq offers its Dragon thermal sight range. Both ranges use uncooled LWIR detectors.
As developments evolve, the US Army has been working on a new Family of Weapon Sights – Individual (FWS-I) for the M4 carbine and M249 squad automatic weapon. It produces IR imagery in all weather conditions, under all lighting conditions and has the ability to see through fog, dust and smoke.
US Army data indicates recognition of a man-sized target at night to have a 70 percent probability at 960 metres, and through smoke or other obscurants a 90 percent probability at 300m.
A screen image of the OMNI VIII standard of the green phosphor I2 tube, familiar to many users, which is giving way to a white phosphor tube in some applications.
Additionally, FWS-I can wirelessly transmits the weapon sight crosshair and thermal imagery to the new Enhanced Night Vision Goggle-Binocular (ENVG-B), providing a Rapid Target Acquisition (RTA) capability.
ENVG-B comprises a dual I2 tube binocular system for improved situational awareness and depth perception, using higher resolution, white phosphor tubes (replacing the traditional green phosphor) providing better contrast; plus a fused thermal imager for better target recognition in degraded visual environments (such as dust, smoke, zero illumination and subterranean).
The wireless interconnectivity with FWS-I, allows soldiers to accurately engage without shouldering the weapon and significantly reducing exposure to enemy fire.
Roll-out of the ENVG-B and FWS-I was announced on 1 November 2019, indicating that the 2nd Armoured Brigade Combat Team (ABCT) of the US Army’s 1st Infantry Division, had become the first unit equipped, fielding the equipment in September. The FWS-I is being produced by BAE Systems and Leonardo DRS; while the ENVG-B is produced by L3 Warrior Sensor Systems (part of L3Harris).
by Michael Gething
