What is LiDAR?

Lidar combines radar ranging with camera angular resolution to provide accurate depth sensing to complete the image (figure 1).

The visual part represents the visibility, object classification and lateral resolution of the camera or driver.

Darkness and weather conditions such as snow, dust or rain can weaken these capabilities.

The radar part represents the return of the RF signal.

This signal is not affected by weather conditions and darkness, and can also measure distance.

The lidar section can complete the sensing picture by providing further object classification, horizontal resolution, ranging and dark penetration. 

How does lidar work? 

The basic elements of the lidar system include the square wave transmitting system, the target environment, and the optical receiver system used to explain the distance of external elements in the environment.

The lidar sensing method uses light in the form of pulsed laser to measure the range by analyzing the time-of-flight (ToF) of the return signal (figure 2).

Signals in the digital domain

The circuit solution of lidar is to solve the problem of signal reception through automobile cross-resistance amplifier.

The input terminal is used to receive the negative input current pulse of the photodetector (figure 3).

Laser diodes transmit digital pulse signals through a piece of glass.

The signal is also reflected onto the D2 photodiode.

The processing of the signal provides the transmission time and the electronic delay built into the system.

After hitting the object, the digital optical signal pulse will be reflected back to the optical system.

The returned pulse is mirrored to the second photodiode D1.

The electronic part of the D1 signal path is the same as the D2 signal path.

The flight time can be calculated when the two signals arrive at the microcontroller (MCU).

Market snapshot

The automobile lidar system uses pulsed lasers to measure the distance between two cars.

The automobile system uses lidar to control the speed and braking system, thus responding to the sudden change of traffic conditions.

Lidar plays an important role in semi-automatic or fully automatic vehicle auxiliary functions such as collision warning and avoidance system, lane maintenance assistance, lane departure warning, blind spot monitor and adaptive cruise control.

Automotive lidar is replacing the radar system in the early automotive automation system.

The ranging of the lidar system can range from a few meters to more than 1000 meters.

Self-driving cars have been widely used, and the lidar imaging system will further improve this situation.

Radar, cameras and lidar equipment are still the technology of choice for semi-autopilot and fully autopilot. The price of lidar is also falling, and the market is accelerating this change.