light detection and ranging (opt. sensor) (LIDAR)
Light Detection and Ranging (LIDAR) is a technology developed for automotive applications that takes autonomous driving a significant step forward. Lidar technology is a laser-based radar technology for detecting and determining the distance to people, motor vehicles, traffic signs, road boundaries, trees and other objects located in front of, behind and to the side of the vehicle. The technology supports various driver assistance systems. In addition, lidar systems that use the Doppler effect can be used to measure speed.
Lidar systems operate according to the time-of-flight method and, with their short-range radars and long-range radars, form the basis for advanced driver assistance systems. They support traffic sign recognition, automatic distance control, pedestrian detection, lane departure and lane change assistants, parking assistants and several other assistance functions. The systems are equipped with various sensors that, together with video cameras and radar technology, form an integral part of the autonomous driving of the future. Such a system consists of various radiation sources, usually laser diodes and laser sensors with which the laser beams reflected from objects are received. The receiving devices have avalanche photodiodes( APD), photomultipliers or PIN diodes that detect the reflected laser beams and feed them to a downstream signal processing unit consisting of a variable gain amplifier( VGA) and an A/D converter.
The short laser pulses are reflected from objects at different distances, and converted into short duration voltage pulses by the APD diode. Since the reflected signals can vary greatly in amplitude and have only a small amplitude, they are amplified in image intensifiers or photomultipliers before digitization. Because of the short-duration laser pulses, A/D converters with extremely high sampling rates are required for digitization, since these have a direct influence on the accuracy of the distance measurement. A/D converters in lidar systems achieve sampling rates of 3 GS/s at an actual bit rate of 7. Modern systems can generate high- resolution 3D representations with a measurement resolution of 0.1°. These representations can be processed in driver assistance systems and used for automated and autonomous driving.
Lidar systems, unlike radar systems and digital cameras, work in all weather conditions and in all daylight. With their long range, lidar systems can still detect objects at a distance of 250 meters. Conceptually, there are different lidar systems, which differ in the illumination zone. With flash lidar, for example, the entire field of view is illuminated by a single lidar light flash. Scanning lidar systems, on the other hand, work with a directed laser beam that is guided across the field of vision and scans it in a grid pattern. The lidar beam can also be scanned using a MEMS mirror, Micro Electro Mechanical System (MEMS).
The systems are used in automotive technology in driver assistance systems, in toll systems for vehicle recognition and in military vehicles. The lasers of the lidar systems belong to laser class 1 and are therefore non-hazardous and intrinsically safe. In addition to automotive technology, lidar systems can also be used to measure chemical concentrations. These lidar systems are called differential absorption lidar.