Highly sensitive lidar sensor has no mechanical parts

October 12, 2016 // By Christoph Hammerschmidt
Advanced driver assistance systems and autopilot systems depend greatly on the quality of their sensors. A meaningful complement to existing radar-camera combination is Lidar, but in practice, lidar sensors are regarded as too expensive for the extremely cost-conscious market of volume cars. The Fraunhofer Institute for Microelectronic Systems (IMS) now has developed an innovative lidar sensor that combines an all-electronic approach with high sensitivity, enabling more cost-effective systems in the future.

Cameras have proved unreliable under difficult lighting situations – we remember the infamous fatal accident earlier this year when a vehicle in autopilot mode crashed into a crossing truck. “A lidar sensor probably would have identified the obstacle correctly and thus the system could avoid the crash”, comments Werner Brockherde who oversees Fraunhofer IMS’ CMOS Image Sensor department. According to the researcher, lidar in combination with other components sets out the conditions for future self-learning systems that can brake and steer automatically. In automated vehicles, lidar therefore will have at least a complementing function besides radar and camera and help the systems to properly identify the surroundings of the vehicle.

In traditional lidar systems, a single laser beam is deflected to a rotating mirror. Through the rotation of this mirror, the system can capture data from the surroundings in a 360-degree angle around the sensor. Such sensors however are clumsy and, due to its high degree of mechanic parts, failure-prone. Brockherde and his colleagues at Fraunhofer IMS therefore use highly sensitive lidar sensors that do not require any a rotating mirror, and, actually no moving parts at all. The “Flash Lidar” developed by IMS transmits a single laser flash to acquire all the reflexes from the surroundings. The scientists utilize so-called Single-Photon Avalanche Diodes (SPADSs) also developed at the Duisburg, Germany based Fraunhofer institute. “We do not illuminate just a point but a rectangular measurement field”, explains Brockherde.

The sensor and the processing circuitry is integrated on a single chip, resulting in a very space-saving and low-profile design. Carmakers could therefore easily place the sensor between rear view mirror and windscreen or inside the headlight casing, claims Brockherde.

The design goal is a range of 100 meters for the Flash Lidar technology. Brockherde expects the first systems utilizing the novel sensors to enter series production in 2018.

Besides automotive, the sensors could also be used in many other application fields