Issue 54 Uncrewed Sytems Technology Feb/Mar 2024 uWare uOne UUV l Radio and telemetry l Rheinmetall Canada medevacs l UUVs insight DelltaHawk engine l IMU focus l Skygauge in operation l CES 2024 report l Blueflite l Hypersonic flight

14 Platform one February/March 2024 | Uncrewed Systems Technology Researchers in the US have developed a new technology that uses meta-optical devices to perform thermal imaging (writes Nick Flaherty). The spectro-polarimetric decomposition system uses a stack of spinning metasurfaces to break down thermal light into its spectral and polarimetric components. This allows the imaging system to capture the spectral and polarisation details of thermal radiation in addition to the intensity information that is acquired with traditional thermal imaging. The metasurfaces are ultra-thin, structured surfaces that can manipulate light in complex ways. After engineering spinning, dispersive metasurfaces with tailored infrared responses, the researchers developed a fabrication process that allows these metasurfaces to be used to create large-area (2.5 cm- diameter) spinning devices that are suitable for imaging applications. The resulting spinning stack measures less than 10 x 10 x 10 cm and can be used with a traditional infrared camera. This approach provides richer information about objects, which could broaden the use of thermal imaging in fields such as autonomous navigation. “Our method overcomes the challenges of traditional spectral thermal imagers, which are often bulky and delicate due to their reliance on large filter wheels or interferometers,” said Zubin Jacob, who led the research at Purdue University. “We combined meta-optical devices and cutting-edge computational imaging algorithms to create a system that is both compact and robust, while also having a large field of view.” The researchers showed the new system can be used with a commercial thermal camera to successfully classify various materials – a task that is usually a challenge for conventional thermal “Integrating these large-area meta-optical devices with computational imaging algorithms facilitated the efficient reconstruction of the thermal radiation spectrum,” said Wang. “This enabled a more compact, robust and effective spectro-polarimetric thermal imaging system than was previously achievable.” Using the spectro-polarimetric information acquired with the system, the team accurately distinguished the different materials and objects. They also demonstrated a three-fold increase in material classification accuracy compared with traditional thermal imaging methods. The researchers are also trying to enhance the technique’s spectral resolution, transmission efficiency, and speed of image capture and processing. They also plan to improve the metasurface design to enable more complex light manipulation for higher spectral resolution. Another aim is to extend the method to room-temperature imaging using improved materials, metasurface designs and anti-reflection coatings. Metasurfaces Thermal imaging using metasurfaces cameras. The method’s ability to distinguish temperature variations and identify materials based on spectropolarimetric signatures could help boost safety and efficiency for a variety of applications, including autonomous navigation. “Traditional autonomous navigation approaches rely heavily on RGB cameras, which struggle in challenging conditions like low light or bad weather,” said researcher Xueji Wang at Purdue, who worked on the project. “When integrated with heat-assisted detection and ranging technology, our spectro-polarimetric thermal camera can provide vital information in these difficult scenarios, offering clearer images than RGB or conventional thermal cameras. Once we achieve real-time video capture, the technology could significantly enhance scene perception and overall safety.” Spectro-polarimetric imaging in longwave infrared is crucial for applications such as night vision, machine vision, trace gas sensing and thermography. However, these imagers are currently bulky, and limited in spectral resolution and field of view. The metasurfaces are ultra-thin, structured surfaces that can manipulate light in complex ways