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| Night Vision Technology in New Method |
Converting infrared (IR) to visible light (VIS) for vision applications. a) A scheme of a nonlinear upconverter for infrared imaging where light from an infrared source illuminating an object is consistently converted to visible light by lens L1, captured by lens L2, and then seen in a conventional silicon-based camera. b) All rays coming from different angles must be converted with the same efficiency by the ideal upconverter or H(k) = constant.
Researchers at the Excellence Center for Advanced Optics in Meta-Optic Systems (TMOS) have made significant strides in developing a new approach to night vision technology. They have developed an infrared filter, thinner than a piece of stretch film, which could be worn on regular glasses in the future, allowing simultaneous viewing of both visible and infrared light spectra.
Military personnel and hunters, who are not reluctant to carry large lenses or binoculars for multiple purposes, have been the primary users of night vision equipment. This is a consequence of the mass and weight of the technology.
A typical person wouldn't plan to go for a night run with an extra kilogram strapped to their forehead.
Thus, shrinking the size of night vision could result in widespread use. With the development of night vision filters that are lighter than a gram and fit over a pair of regular glasses like a film, new practical applications have become possible.
Consumer night vision goggles with simultaneous visible and infrared vision could lead to safer driving at night, safer night walks, and less hassle working in low light conditions that currently require bulky and often uncomfortable headlamps.
Researchers at the Australian National University, in a paper published in Advanced Materials, demonstrate advanced infrared vision using nonlinear upconversion technology with a nonlocal lithium niobate metasurface.
To produce more electrons than possible with traditional night vision technology, infrared photons must first pass through a lens, then through a photocathode that converts the photons into electrons. Finally, the electrons must pass through a microchannel plate. The electrons are converted back into photons passing through a phosphor screen, producing an enhanced visual representation detectable by the human eye.
Cryogenic cooling is required to prevent thermal noise from worsening for these elements. As mentioned above, a top-of-the-line night vision system is large and heavy. Additionally, these devices often block visible light.
The area covered by meta-surface-based upconversion techniques significantly decreases because they use fewer components. After passing through a single resonance metasurface, photons are combined with a pump beam.
Without the need for electron conversion, the resonance metasurface increases photon energy and draws them into the visible light spectrum. Additionally, it operates at room temperature, eliminating the need for large, heavy cooling systems.
Furthermore, because they capture images from both spectra side by side, traditional infrared and visible imaging systems cannot provide similar images. Imaging systems can capture both visible and invisible in a single image using upconversion technology.
The technology used by the researchers initially included a gallium arsenide metasurface; their work is improving on this. The new metasurfaces, composed of lithium niobate, which is entirely transparent in the visible spectrum, are significantly more efficient. Additionally, the photon beam covers a larger surface area, reducing angular data loss.
Lead author Laura Valencia Molina says, "It is claimed that the nature of nonlocal metasurfaces' angle loss makes it impossible to efficiently convert infrared to visible due to the amount of information lost. We are overcoming these limitations and experimentally demonstrating high-efficiency image upconversion."
According to co-author Rocio Camacho Morales, this is the first instance of high-resolution upconversion imaging from visible 550 nm light to infrared 1550 nm light on a nonlocal metasurface. These wavelengths were chosen because 550 nm is visible light, to which the human eye is highly sensitive, and 1550 nm is commonly used for infrared in telecommunications.
Future research will aim to broaden the spectrum of wavelengths the device can detect to achieve wideband infrared imaging and explore image processing, including edge detection.
According to Principal Investigator Dragomir Neshev, these studies hold great promise for industries such as surveillance, autonomous navigation, and biological imaging, among others. Industry 4.0 and the impending extreme miniaturization of technology largely depend on meta-optics and the work done by TMOS, as evidenced by the decreasing size, weight, and power requirements of night vision technology.