90 Focus | Thermal imaging features in thermal imagery faster than a human. Imagery captured in the IR spectra can be invisible to people lacking at least several months of experience in thermal analysis, and by extension an autonomous gimbal can track and react to moving objects quicker than a remote operator, even if the latency in control signals between a UAV and its ground station was lost somehow. That means gimbals for uncrewed thermographic surveys often integrate powerful GPUs for onboard image processing and AI, with many manufacturers even graduating to the latest SoC (system-on-chip) for providing packages of intelligent, contextdependent capabilities with their sensors. Coupling them with the imagers eliminates the risk of losing those capabilities if, say, a gimbal is installed in a different uncrewed vehicle without those processors, or if a system that relies on cloud-based processing is jammed or loses its data links for other reasons. It also enables fast processing and outputting of analytical reports that can be shared with other interested parties – a vital feature for disaster response and some defence work. SWaP While thermal camera r&d continues to develop detectors with higher resolutions than the widespread 640 x 512, and narrower pixel pitches even than the 12-17 µm found in current thermal imagers to achieve better image quality, uncrewed systems engineers are largely demanding thermal cameras with less weight, smaller sizes and lower power consumption, far more than they want improvements in image quality. This is largely because uncrewed vehicles integrate an increasingly wide array of sensors and electronics. For example, UAVs could soon be expected to carry two EO/IR/laser gimbals, GNSS-IMU navigation systems, optical or radar solutions for GNSSdenied navigation, an SWIR camera for navigating through fog during take-off and landing, multiple radios for redundant real-time downlinking, and multiple transponders for air traffic compliance. To reduce the SWaP taken up by thermal imagers, companies reserve their r&d resources for developing detectors with narrower pixel pitches. While (as mentioned) a smaller pixel pitch can give better image quality, the more important benefit for system integrators is that, when contrasting two thermal cameras with the same resolution, the one with the smaller pixel can be made lighter and more compact. Certain applications will prove more suited for thermal cameras with longer range – as mentioned, MWIR cameras are in high demand among military integrators for this reason – but designing cameras for range often drives up the size, weight and power needed for the lens, which is already one of the biggest components in a camera. An uncooled LWIR camera might be highly sensitive but it will still need a large-aperture lens to achieve longrange sensing. Lenses of f/1 to f/1.2 are often used in LWIRs for uncrewed systems (the f-number being the ratio of the focal distance to the aperture size, and a measure of the clarity and speed of the device). Cooled UAV MWIR cameras however, being extremely sensitive to minute thermal differentials, can work using lens apertures of f/4 to f/5. That reduction in the size of the lens in turn reduces the size of the gimbal or other multi-sensor housing. In addition to accounting for a thermal camera’s physical peripherals, some companies are increasing the power efficiency of their thermal cores by December/January 2024 | Uncrewed Systems Technology Multi-spectral cameras combining IR and other spectra can enable multi-faceted surveys of critical geospatial events such as wildfires (Courtesy of Overwatch Imaging) Thermal camera and gimbal makers are sizing their IR detectors and lenses to SWaP-optimise sensors for UAV integrations (Courtesy of AVT Australia)
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