But the detector, a passive device for registering stimuli, makes up just half of a lidar sensor. The sensor as a whole is based on an echolocation principle similar to the biological sonar that allows dolphins and bats to find their way – and their prey – in the dark. To do so, they generate sound waves that are reflected back to them by obstacles and potential food sources. The time the sound takes to bounce back tells the animals where a given object is positioned in relation to themselves. Bats even make use of the associated Doppler effect to work out which way a tasty moth is flying and how rapidly its wings are beating.
Lidar systems use bursts of laser light, each lasting just billionths of a second, as the equivalent of sound waves. Together with ZF, Hamburg-based firm Ibeo is developing a new generation of lidar sensors, using lasers that operate in the infrared range at wavelengths of 850 or 885 nanometers. Light at these wavelengths is invisible to the human eye, and not intense enough to do any harm. Compared with other sensors, lidar systems can produce accurate results over very long ranges. The laser sensors can detect objects – both motionless and moving – surrounding the vehicle at distances of up to 300 meters.