12 Platform one Researchers in China have developed a compact, lightweight single-photon airborne Lidar system, which can acquire high-resolution 3D images with a low-power laser, writes Nick Flaherty. The system, developed at the University of Science and Technology at Hefei in China, could make singlephoton Lidar practical for air and space applications such as environmental monitoring, 3D terrain mapping and object identification. Single-photon Lidar uses detection techniques to measure the time it takes laser pulses to travel to objects and back. It is particularly useful for airborne applications because it enables highly accurate 3D mapping of terrain and objects even in challenging environments such as dense vegetation or urban areas. “Using single-photon Lidar technology on resource-limited UAVs or satellites requires shrinking the entire system and reducing its energy consumption,” said researcher Feihu Xu. “This employs the lowest laser power and the smallest optical aperture, while still maintaining good performance in terms of detection range and imaging resolution.” The airborne single-photon Lidar system works by sending light pulses from a laser towards the ground. These pulses bounce off objects and are then captured by very sensitive detectors called single-photon avalanche diode (SPAD) arrays. These detectors provide enhanced sensitivity to single photons, enabling more efficient detection of the reflected laser pulses so that a lowerpower laser can be used. To reduce the overall system size, the researchers used small telescopes with an optical aperture of 47 mm as the receiving optics. Measuring the time of flight of the returned single photons makes it away with default settings. Scanning the image at a sub-pixel level and using a 3D deconvolution algorithm enabled a resolution of 6 cm from the same distance away. The investigators also conducted daytime experiments with the system aboard a small airplane over several weeks in Yiwu City, Zhejiang Province, China. These experiments successfully revealed detailed features of various landforms and objects, confirming the functionality and reliability of the system in real-world scenarios. The team is now working to enhance the performance and integration of the system, with the long-term goal of installing it on a spaceborne platform such as a small satellite. Lidar Single-photon Lidar maps challenging terrain possible to calculate how long it takes for light to travel to the ground and back. The detailed 3D images of the terrain can then be reconstructed using computational imaging algorithms. “A key part of the new system is the special scanning mirrors that perform continuous fine scanning, capturing subpixel information of the ground targets,” said Xu. “Also, a new photon-efficient computational algorithm extracts this sub-pixel information from a small number of raw photon detections, enabling the reconstruction of super-resolution 3D images despite the challenges posed by weak signals and strong solar noise.” A pre-flight ground test showed the system was able to perform Lidar imaging with a resolution of 15 cm from 1.5 km August/September 2024 | Uncrewed Systems Technology Single photon mapping from a UAV (Image courtesy of the Hefei University of Science and Technology)
RkJQdWJsaXNoZXIy MjI2Mzk4