Ultra-thin night vision filter could make bulky goggles a thing of the past
New ultra-thin night vision filters could one day turn regular glasses into night-vision devices.
Researchers have unveiled a revolutionary night vision technology that may transform everyday life, potentially making cumbersome and heavy night vision goggles a thing of the past. A new ultra-thin infrared filter, lighter than cling wrap, could be integrated into regular eyewear, allowing users to see both infrared and visible light simultaneously.
Night vision devices have traditionally been reserved for military use, hunting enthusiasts, or photographers due to their bulk and weight. The average person isn’t likely to go for a night-time jog with an extra kilo on their forehead.
Researchers at the ARC Centre of Excellence for Transformative Meta-Optical Systems, or TMOS, think bulky night vision could be a thing of the past. Soon, filters weighing less than a gram, integrated into regular glasses, could make night vision accessible for everyone. Imagine safer night-time driving, walking, and working without cumbersome headlamps.
From bulky goggles to night vision glasses
The technology leverages a special material called a lithium niobate metasurface to improve night vision. This material enhances infrared light and converts it into visible light through a process called non-linear upconversion. In simple terms, this means boosting the energy of light particles. Unlike traditional night vision systems that need many heavy, bulky parts and cooling systems, this new approach is much simpler. The light filter would be lightweight and work at room temperature, making it more practical for everyday use.
Traditional night vision involves infrared photons passing through lenses and encountering a photocathode to transform them into electrons. These electrons are then amplified and reconverted into photons, producing a visible image. Night vision is green because green is considered to provide the best balance between contrast and visibility in the dark. So, the amplified electrons land on a phosphor-coated screen. Still, this setup is cumbersome and blocks visible light.
In contrast, the metasurface technology requires fewer parts. Photons pass through a single resonant metasurface where they mix with a pump beam. This metasurface enhances photon energy, converting low-frequency photons directly into the visible spectrum.
Not-so-impossible technology
The technology utilises lithium niobate, which is fully transparent in the visible range. It makes the process far more efficient by reducing angular data loss. In this context, angular data loss refers to the loss of visual information that occurs when light particles spread out at different angles. By reducing this loss, the technology ensures the conversion of more infrared light into clear, visible images, enhancing the overall quality and effectiveness of the night vision system.
“People have said that high-efficiency up-conversion of infrared to visible is impossible because of the amount of information not collected due to the angular loss that is inherent in non-local metasurfaces. We overcome these limitations and experimentally demonstrate high-efficiency image up-conversion,” said lead author Laura Valencia Molina.
Co-author Rocio Camacho Morales highlights the practical applications, stating, “This is the first demonstration of high-resolution up-conversion from 1550 nm infrared to 550 nm visible light in a non-local metasurface. These wavelengths are crucial as 1550 nm is common in telecommunications and 550 nm is highly visible to the human eye.”
The researchers add that this technology may open new opportunities in biological imaging, autonomous navigation, and surveillance. “The miniaturization of night vision technology is a key example of the potential of meta-optics,” they added.
The findings appeared in the journal Advanced Materials.
