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Home | Features | US Night Vision: Enhanced and Ubiquitous
 
US Night Vision: Enhanced and Ubiquitous

Glenn Goodman looks at the night vision systems being fielded to US dismounted forces

The U.S. Army recently began fielding in April and May, a next-generation night-vision goggle that represents a leap ahead in battlefield technology for its dismounted soldiers. The helmet-mounted, flipdown monocular device, called the Enhanced Night- Vision Goggle (ENVG), combines an imageintensifier tube like those used in existing U.S. Army NVGs for the first time with a lightweight, low-power thermal imaging camera incorporating an “uncooled,” long-wave infrared (IR) sensor. This exploits the strengths of the two types of sensors in a single, integrated system.

The ENVG blends the two types of sensor imagery in front of the soldier’s eye using an optical fusion approach. The U.S. Army already has been funding industry work for several years on a follow-on system that would use a digital fusion approach offering additional advantages while retaining size, weight and power comparable to the ENVG. Called the ENVG (D), it could be ready for fielding in three years. In addition, the service is currently fielding a new-generation of thermal weapon sights featuring uncooled IR sensors for its dismounted soldiers, and they are both also being purchased by the U.S. Marine Corps.

The Enhanced Night-Vision Goggle (ENVG), combines an imageintensifier tube like those used in existing U.S. Army NVGs for the first time with a lightweight, low-power thermal imaging camera incorporating an “uncooled,” long-wave infrared (IR) sensor. This exploits the strengths of the two types of sensors in a single, integrated system. © DoD

The Enhanced Night-Vision Goggle (ENVG), combines an imageintensifier tube
like those used in existing U.S. Army NVGs for the first time with a lightweight,
low-power thermal imaging camera incorporating an “uncooled,” long-wave
infrared (IR) sensor. This exploits the strengths of the two types of sensors in a
single, integrated system. © DoD

CURRENT NIGHT-VISION GOGGLES

The image-intensifier tubes used in NVGs and rifle sights gather the minute amounts of visible light present in the night sky from the Moon or stars as well as invisible near-IR radiation. The vacuum-packed tubes amplify the light energy and convert it to green, illuminated, highresolution imagery of the area being viewed in the darkness out to a range of 150 meters in the latest Army models.

The AN/PVS-14 has become the standard U.S. Army and Marine Corps infantry NVG. The PVS-7 it is displacing has a binocular eyepiece that protrudes from the soldier’s face. The PVS-14, which uses a single 18mm tube like the PVS-7D, covers only one eye, making it easier for the soldier to adjust his or her eyesight to changing light conditions. The lightweight device weighs only 0.4 kg and operates using a single commercial AA battery for 15 hours. The PVS-7D by comparison weighs 0.68 kg and requires two AA batteries. The PVS-14 can be helmet-, head- or rifle-mounted. It provides the state of the art in NVG performance with its low-light sensitivity.

ITT Night Vision and L-3 Communications (formerly Northrop Grumman) Electro-Optical Systems are the world’s most advanced producers of Generation 3 image-intensifier tubes for NVGs. Gen 3 tubes, which use a gallium-arsenide photocathode as their light input surface, can operate effectively under starlight conditions with no moon. The latest Gen 3 tubes produced by the two companies provide a capability in “overcast starlight” conditions, defined as cloudy with no moon. They also feature an automated “gated” power supply. Instead of using continuous power, with autogating the photocathode is turned on and off to reduce the electron flow at high light levels. This keeps the tube from producing a washed-out image and reduces the “halo” or image blooming that occurs using NVGs in the dark around bright light sources, such as vehicle headlights. Auto-gating also allows soldiers to move in and out of buildings in urban areas without having to remove their goggles.

As a result of the huge demand for NVGs for U.S. Army troops and Marines in Iraq and Afghanistan, ITT and L-3 continue to produce PVS-14 NVGs at a high rate under open-ended contracts awarded in Sept. 2005. Mark Richter, the Marine Corps’ program manager for the Marine Expeditionary Rifle Squad (MERS), noted that his service’s acquisition requirement for NVGs had grown from 125,000 to 625,000 sets since Sept. 11, 2001.

SMALL IR SENSORS

In contrast to image-intensifier tubes, IR sensors highlight the temperature differences between objects and their backgrounds, offering much longer range and the ability to see through smoke, dust, haze, adverse weather and total darkness. IR sensors typically produce black-and-white video that is fed to a display. Until recent years, the large size and weight of such thermal sensors limited their applications to vehicles and aircraft. A key weight and cost contributor was the need for a cryogenic cooler. IR detectors had to be cooled to very low temperatures to achieve the sensitivity required to distinguish temperature differences at long range. The advent of uncooled IR sensors reduced the size and cost of thermal cameras while retaining acceptable performance for applications such as dismounted infantry.

The U.S. Army’s first-generation Thermal Weapon Sights (TWS), produced by Raytheon and fielded in light, medium and heavy versions in 2002-2006, use a cooled IR sensor. They are mounted atop M-16/M4 rifles, M240/M249/M2 machine guns and other crew-served weapons. In 2004, the U.S. Army awarded full-rate production contracts for second-generation TWS-II models with uncooled IR sensors to BAE Systems and DRS Technologies and the service is qualifying Raytheon to be a third production source for TWS-IIs. The first U.S. Army unit to receive TWS-IIs was fully equipped in the spring of 2006.

Lt. Col. James Smith, product manager for sensors and lasers at the U.S. Army’s Program Executive Office- Soldier, said, “TWS-II provides greater range in a package that is about 40 percent of the weight, uses roughly half the power [fewer AA batteries] and costs substantially less than the TWS.” The weights of the light, medium and heavy TWSII models are 0.88 kg, 1.32 kg and 1.68 kg, respectively.

Soldier feedback on the ENVG’s performance has been extremely positive. Though the ENVG weighs more than the PVS-7D and PVS-14, soldiers find it well-balanced, with the goggle on the front of the helmet and its battery pack on the back. © DoD

Soldier feedback on the ENVG’s performance has been extremely positive.
Though the ENVG weighs more than the PVS-7D and PVS-14, soldiers find it
well-balanced, with the goggle on the front of the helmet and its battery
pack on the back. © DoD

IMAGERY FUSION

ITT won the contract in 2004 to be the sole producer of ENVGs for the Army. The ENVG weighs 0.91 kg, including a single 16mm image-intensifier tube and four AA batteries. With ENVG’s optical fusion approach, the thermal camera and the image-intensifier tube simultaneously sense the same scene in parallel, and the IR video is overlaid on the image-intensifier imagery. The combined imagery is aligned and displayed through a monocular eyepiece assembly. The soldier actually can view either type of imagery alone or a variable blend of both by turning knobs on the device, which facilitates recognizing man-size targets that might not be discerned using a single type of sensor.

Soldier feedback on the ENVG’s performance has been extremely positive, Smith said. Though the ENVG weighs more than the PVS-7D and PVS-14, soldiers find it well-balanced, with the goggle on the front of the helmet and its battery pack on the back.

Reliability shortfalls during 2006 testing in harsh environmental conditions required a significant redesign of the ENVG that delayed fielding nearly a year, he said, but subsequent operational testing was completed successfully. Production deliveries began in March, and the first U.S. Army to receive ENVGs was fully equipped recently [2nd Qtr (Apr-May-June) CY2008]. Smith said the U.S. Army’s acquisition objective is around 61,000 sets.

Achieving digital sensor fusion in an ENVG (D) would provide added advantages, particularly the ability to transmit the fused imagery that the soldier sees to a platoon leader or company commander, or to a command post for intelligence exploitation, via wireless communications. But achieving that digital fusion capability in a device no heavier than the ENVG with comparable resolution entails formidable technology challenges. For example, digital fusion requires greater battery power, Smith said. Moreover, the two types of imagery have to be integrated pixel by pixel, with the result presented on a miniature display in front of the soldier’s eye, yet miniature displays have lacked high enough resolution to accommodate the output of an image-intensifier tube.

As a result, the ENVG (D) could end up combining an uncooled IR sensor with a digital low-light-level camera operating in the visible light to near-IR spectrum, rather than with an image-intensifier tube, and integrating digital video imagery from both, he said. Another approach has involved bonding an electro-optical detector on the back end of the image-intensifier tube to convert its output to digital video.

Smith said his office has pursued multiple industry contracts, both at the component and the system prototype level, to mature the key technologies required for ENVG (D) development. “We have been turning digital prototypes now for the last couple years, and the technology has advanced every year,” he noted. “You can watch the key metrics, whether it’s weight, power or target resolution, and all of those continue to improve.” He predicted that the ENVG (D) could be fielded by 2011.

The participating companies include BAE Systems, DRS, ITT-Raytheon, L-3 and two small specialized firms, Intevac Inc. and Kopin. Intevac produces extremely lowlight- level imaging sensors, while Kopin fabricates miniature liquid crystal displays.

The U.S. Marine Corps, Richter said, does not plan to procure ENVGs but will continue to use PVS-14 NVGs while waiting for the U.S. Army to fully develop the ENVG (D). The Corps is procuring medium and heavy TWS-IIs through the Army, but not the light version. Instead, it conducted its own competitions for a clip-on Independent Weapon Night Sight for its individual riflemen’s M16A4s in both thermal and image-intensified versions (IWNS-T and IWNS-I2), and Insight Technology, won both contracts last Autumn. Both devices look like palm-size video cameras and are used in combination with the Marine Corps’ standard Rifle Combat Optic (RCO) magnified telescopic sight, the TA31F Advanced Combat Optical Gunsight (ACOG) produced by Trijicon.

The ENVG will replace the PVS-14 as the primary night-vision system for the U.S. Army’s developmental Land Warrior integrated modular fighting ensemble for dismounted soldiers, Smith said. The TWS already is interoperable with Land Warrior. “It ports out an RS-170 video stream that feeds into the Land Warrior [monocular] display,” he noted. In addition, a key performance parameter of the ENVG (D), Smith said, is that its output be interoperable with both Land Warrior and the follow-on Ground Soldier System ensemble planned as part of the U.S. Army’s Future Combat Systems.

 
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