LiDAR (light detection and ranging) uses lasers to create detailed pictures of an environment and is increasingly integrated in autonomous vehicles for situational awareness. In this instance, scientists from Oxford, Cambridge and University College London (UCL) used LiDAR to create a granular representation of a busy London street. Holographic details from the street, such as road signs, can then be relayed directly to the driver’s eyes using AR when line of sight is blocked by other traffic or trees, for example.
"Head-up displays are being incorporated into connected vehicles, and usually project information such as speed or fuel levels directly onto the windscreen in front of the driver, who must keep their eyes on the road," said lead author Jana Skirnewskaja, a PhD candidate from Cambridge's Department of Engineering. "However, we wanted to go a step further by representing real objects in as panoramic 3D projections."
Using LiDAR, the researchers scanned Malet Street, a busy thoroughfare on the UCL campus in central London. Millions of pulses were sent out from multiple positions along Malet Street and the LiDAR data was then combined with point cloud data, building up a 3D model. This technique, known as terrestrial laser scanning, was carried out study co-author Phil Wilkes, a geographer who normally uses LiDAR to scan tropical forests. The work is described in Optics Express.
"This way, we can stitch the scans together, building a whole scene, which doesn't only capture trees, but cars, trucks, people, signs, and everything else you would see on a typical city street," Wilkes explained. "Although the data we captured was from a stationary platform, it's similar to the sensors that will be in the next generation of autonomous or semi-autonomous vehicles."
The optical setup is capable of projecting multiple layers of holograms with the help of advanced algorithms. The holographic projection can appear at different sizes and is aligned with the position of the represented real object on the street. For example, a hidden street sign would appear as a holographic projection relative to its actual position behind the obstruction, acting as an alert mechanism. The team is now working to miniaturise the optical components used in the holographic setup so it can be fitted to a car. Once the setup is complete, vehicle tests on public roads in Cambridge will be carried out.