For decades U.S. warfighters have benefitted from advanced night-vision technology, allowing pilots to fly low-level missions on pitch-black nights and ground forces to conduct operations against adversaries in the dark. Traditional Night Vision Goggle (NVG) systems provide the wearer with enhanced visibility in low-light conditions by exploiting the natural near-infrared (NIR) illumination from moonlight or starlight. These systems use a multi-step process called image intensification, which involves converting NIR photons to electrons, amplifying electrons, and converting them into visible photons presented to the wearer.
But current night-vision goggle (NVG) technology requires cumbersome binocular-like optics mounted on a helmet, offering a limited field of view (FOV) and putting unhealthy strain on the wearer’s neck. Building on recent scientific advances in photonics and optical materials pioneered in DARPA’s Defense Sciences Office (DSO), a new effort seeks to develop next-generation NVGs that are as lightweight and compact as a pair of regular eyeglasses or sunglasses.
Recent advances in materials science and nanofabrication open up the possibility to replacing the bulk refractive optics and image intensification technologies with ultrathin planar optics and planar image intensifiers. These advances show promise in disrupting the current tradeoff between enhanced capabilities and large induced neck torque, leading to low-torque direct-view NV systems.
DARPA announced its Enhanced Night Vision in eyeglass form (ENVision) program in Jan 2021. ENVision aims to create lightweight NVGs that offer a wide FOV across multiple infrared (IR) spectrum bands without needing separate optics for each IR band. The goal is to enable night vision through fog, dust, and other obscurants as well as provide thermal vision – all via a single flat lens.
“Our warfighters experience significant neck strain from current NVGs caused by the weight of the optics extending 4-5 inches in front of their helmets,” said Rohith Chandrasekar, program manager in DARPA’s Defense Sciences Office. “If you’ve never worn NVGs for hours at a time imagine wearing a baseball cap all day with a two-pound weight attached to the front of the bill – that gives you a small sense of the stress experienced. Extended use of such systems leads to a condition where the neck no longer has energy to keep the head upright requiring warfighters to use their hands to lift and point their heads. NVG wearers also have to swivel their heads frequently for peripheral vision since current optics only provide a 40-degree field of view compared to the 120-degree wide view we have with our eyes, which only makes use of NVG systems more painful.”
Current NVG systems are bulky (lengths of ~10 cm) and heavy (>1 kg), which moves the center of gravity away from the head and induces a large torque on the wearer’s neck. In the short term, this torque greatly limits agility, and over prolonged use can lead to acute and chronic neck injury. Additionally, traditional NVG systems are limited in field-of-view (FOV) to ~40° and are typically limited to a narrow NIR bandwidth, both of which greatly limit situational awareness.
Besides the weight and field-of-view constraint, current NVGs provide only a narrow segment of the IR portion of the spectrum (typically near-IR) that limits what types of threats the viewer can see at night. Efforts to expand FOV and IR bandwidth to date have involved increasing the number of optics, which increases weight. The ENVision program is designed to break the paradigm that increased performance can only be achieved by an increase in weight.
“DARPA investments over the past decade have led to breakthroughs in the areas of planar optics, detection materials, and novel light-matter interactions,” Chandrasekar said. “ENVision will leverage these advancements, amongst others, to develop enhanced night-vision devices in lightweight eyeglass form factors.”
The DARPA ENVision program seeks to leverage these advancements and expand their capabilities to develop enhanced direct-view NV systems with the following capabilities:
• lightweight systems in near-eyeglass form factors;
• extended visual access beyond NIR to include short-wave (SWIR, 1.5-3 µm), midwave (MWIR, 3-5 µm), or long-wave infrared (LWIR, 8-12 µm) through a common aperture, and;
• expanded FOV to near natural eyesight (100°)
Optical specialists have attempted to widen the fields of view for today’s night-vision goggles, but improvements come at the cost of increased systems size, weight, and wear-and-tear on the user. The ENVision project seeks to explore the next technical leap in night-vision technologies by achieving direct vision of the infrared through photon upconversion.
NV systems use a multi-step process, the physics to directly upconvert IR photons to VIS in a single step has been known since the invention of the laser in 1960. Direct photon upconversion involves the absorption of two or more photons and the re-emission of a photon of higher energy. As a separate thrust, ENVision will take the next technical leap forward and investigate the possibility of achieving direct vision of the infrared through photon upconversion. Photon upconversion-based night vision would eliminate the need for multiple components and could lead to even simpler, all-optical NVG systems in the future.
“This will further simplify NVG systems by advancing from the multi-step conversion currently used to a single step up-conversion process,” Chandrasekar said. “Some of these processes even conserve the momentum of photons, which, in theory, could enable night vision without the need for any optics.” The ENVision program focuses on developing prototypes of multi-band, wide-FOV night vision systems and investigating methods to amplify photon up-conversion processes from any IR band to visible light.
Currently, these processes are inefficient and are limited in the bandwidth of light that can be upconverted simultaneously. Yet recent advances in material systems such as polaritonic structures and sensitized core-shell nanoparticles have opened up new avenues in exploring photon upconversion. The process of photon upconversion-based night vision would eliminate the need for several components and could lead to even simpler, all-optical night-vision systems in the future, such as night vision contact lenses, DARPA researchers say.
Planar optics and planar image intensifiers could enable direct vision of several infrared bands through one common aperture. Structured materials such as diffractive optics and metamaterials enable one to embed optical functionalities far beyond those of traditional refractives into one optical element.
While wide field of view, broad bandwidth, and high imaging quality all are achievable individually, combining these traits in practice remains a challenge. In addition to planar optics, image intensification is necessary to convert the often weak infrared light into visible photons detectable by the naked eye.
Officials of the U.S. Defense Advanced Research Projects Agency (DARPA) in Arlington, Va., awarded a $3 million contract to Raytheon BBN Technologies Corp. in Cambridge Mass., and a $2.3 million contract to UC San Diego in Sep 2021. for the Enhanced Night Vision in eyeglass form factors (ENVision) project.
Researchers at Raytheon Technologies Corp. and the University of California at San Diego will develop night-vision devices far smaller and lighter in weight than today’s night-vision goggles, which would be about the same size and weight as a typical pair of eyeglasses. Today’s night-vision goggles also burden the wearer with a narrow field of view and generally have limited spectral access to the near-infrared spectral band, which limits situational awareness.
This drawbacks from refractive optics for imaging, and image-intensifier tubes — two technologies in modern night-vision systems that have remained largely the same since their inception. Instead, the DARPA ENVision program seeks to overcome these limitations by developing enhanced direct-view night-vision systems that are of a size and weight near those of typical eyeglasses.
Raytheon BBN and UC San Diego researchers will develop small and lightweight night-vision eyeglasses to extend visual access beyond near infrared to include shortwave, midwave, and long-wave infrared spectral bands through a common aperture, giving users access to spectral ranges from 1.5 to 12 microns. These night-vision eyeglasses, furthermore, are to widen the user’s field of view to natural eyesight of about 100 degrees.
The ENVision program will last for four-years in two two-year phases, and has two technical areas: prototypes and upconversion. Those participating in the first technical area will develop prototypes of enhanced night vision systems in eyeglass form-factors, while those in the second technical area will investigate broadband direct photon upconversion.
SUNY Polytechnic Institute awarded in May 2022
SUNY Polytechnic Institute announced Professor of Nanoscale Engineering Dr. Shadi Shahedipour-Sandvik has received $699,000 from Defense Advanced Research Projects Agency (DARPA) as part of a research effort lead by SRI International and in collaboration with Vanderbilt University.
With two phases of the Enhanced Night Vision in Eyeglass Form (“ENVision”) project, if a second phase is funded, SUNY Poly anticipates receiving a total $1.4 million in funding as part of the overall $6 million initiative, which seeks to address challenges with current night vision (NV) systems that limit the wearer’s agility and comfort.
SUNY Poly researchers will focus on developing image intensifier components, which will reduce the size and weight of an NV system, and therefore the strain on their user.
“On behalf of SUNY Poly, I am thrilled to congratulate Dr. Shahedipour-Sandvik for this DARPA/SRI International grant, in collaboration with Vanderbilt University, that will support the development and fabrication of a planar-image-intensifier system for enhanced dual-band night vision goggles, providing an excellent example of how SUNY Poly’s research can have a tangible impact on real-world technologies that provide enhanced capabilities and save lives,” said Acting President Dr. Tod A. Laursen, in a statement
The four-year research effort at SUNY Poly will center around the use of III-Nitride ultra-wide bandgap materials to create an image intensifier system that is slimmer and less weight than image intensifiers that currently contribute to NV systems’ ability to allow the wearer to see in the dark, SUNY Poly said.
Combined with Vanderbilt University’s meta-optics research to enable a wider field of view and enhanced infrared-based vision, the new systems are expected to be more effective while also remaining lightweight to reduce the wearer’s neck strain, especially when used for long periods of time.
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