Solid-state LiDAR addresses transportation infrastructure monitoring
Toshiba Corporation has announced an updated version of its solid-state LiDAR in the smallest volume availble, along with industry-leading resilience to wind and vibrations. It supports a maximum detection range of 200m, plus, according to a Toshiba survey, higher resolution than any other sensor on the market of similar size. The upgraded performance of the new LiDAR device will help to accelerate progression towards autonomous driving. It will also open up application opportunities for monitoring transportation infrastructure, in such areas as early detection of road subsidence or landslides, snow cover, or fallen objects on roads.
Current methods for monitoring transportation infrastructure rely on cameras, but their performance is degraded by low light levels and adverse weather conditions. Toshiba’s upgraded solid-state LiDAR offers an alternative with superior performance, as it realizes clear, long-distance, robust 3D scanning and object detection across a wide variety of lighting and weather conditions. It is also extremely compact, measuring only one-third the size of the earlier prototype announced back in July 2020, and is the industry’s smallest on record.
“We have developed technologies essential for a compact, high-resolution, long-range solid-state LiDAR that is robust and simple to implement. Major demand for such a versatile product is anticipated in both the autonomous driving and transportation infrastructure monitoring applications,” said Akihide Sai, Senior Research Scientist at Toshiba’s Corporate Research & Development Center.
Pivotal to the compact LiDAR unit were the innovations that Toshiba made to its silicon photo-multiplier (SiPM) light-receiving chips to enhance the image resolution attained. Each SiPM consists of light-receiving cells controlled by transistors. The new chips have smaller transistor modules, and eliminate the buffer layers protecting the transistors. Instead, newly developed insulating trenches are placed between the transistors and the light-receiving cells. The potential issue of reduced light sensitivity due to use of smaller transistors has been solved via the addition of a high-withstand voltage section to raise the voltage input to the light-receiving cell (as described in Figure 1).
These innovations have reduced the size of the SiPM by 75% while elevating its light sensitivity by 50% compared with the July 2020 predecessor. More SiPMs can now be arrayed in the same package – thereby boosting the resolution to 1200 x 80 pixels (which is a 4x improvement).
Figure 1: Toshiba’s new SiPM incorporates much smaller transistors, a high voltage input section, plus insulating trenches.
Toshiba has also ensured that the new LiDAR unit exhibits the durability that is essential for outdoor use in all weather conditions. A temperature compensation mechanism automatically adjusts the voltage input applied to the light-receiving cells, in order to mitigate the effect of external temperature changes. This means that heightened SiPM performance is maintained despite any ambient temperature fluctuations. In addition, by utilizing its expertise in high-density component mounting, Toshiba has reduced the overall size of the LiDAR projector and receiver to a 350cc volume (as shown in Figure 2).
Figure 2: (Left) Toshiba utilized high-density mounting know-how to build the LiDAR unit. (Right) Toshiba’s LiDAR prototype is the world’s smallest, 350cc in volume.
Toshiba will continue to contribute to safer transportation by promoting its advanced LiDAR technologies for autonomous driving and transportation infrastructure monitoring. Continued R&D activities will lead to further improvements in the detection range, image resolution and miniaturization of its LiDAR solutions – allowing new possibilities to be explored in robots, drones, and small security devices.
Figure 3: A demo of obstacle detection using Toshiba’s new LiDAR in an outdoor and sunny daytime setting. The LiDAR successfully circled a cardboard placed at 50m ahead and accurately measured the distance. (Low speed frame rate (1fps). Fixed angle. Detection range: ~ 300m)
Video 1: Toshiba’s new LiDAR provided a clearer detection of three obstacles in an outdoor and nighttime setting than a camera and an infrared camera. (Low speed frame rate (1fps). Fixed angle. Detection range: ~ 200m.)
Video 2: Change the shooting angles and Toshiba’s new LiDAR can detect objects from a car parked at 20m ahead to a building located 300m ahead. (High speed frame rate (20fps). Change of angles. Detection range: 20~300m. Outdoor and sunny daytime condition.)