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
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
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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