What is light detection and ranging (LiDAR)? Combining radars ranging capability with the angular resolution of cameras, LiDAR provides accurate depth perception sensing to complete the picture (Figure 1).
Figure 1 Camera, radar and LiDAR are three technologies of choice for vehicle autonomy. Source: Analog Devices Inc.
The vision portion represents a camera or the driver’s visible capability, object classification, and lateral resolution. Darkness and weather occurrences—such as snow, dust, or rain—lessen the abilities. The radar portion represents the return of an emitted radio-frequency signal. This signal penetrates weather and darkness while supplying a distance measurement. The LiDAR portion completes the sensing picture by providing further object classification, lateral resolution, distance measurement, and darkness penetration.
How does it work
The fundamentals of the LiDAR system include a square wave light-emitting system, an environment of interest, and a light receiver system that interprets the distance of the external element in the environment. The LiDAR sensing method uses light in the form of a pulsed laser to measure ranges with the analysis of the time-of-flight (ToF) of the returning signal (Figure 2).
Figure 2 Each LiDAR transmit unit has a triangular “view.” Source: Bonnie Baker
The drawing of the distance depends on the optical digital signal.
Signals in digital domain
The LiDAR circuit solution addresses the signal receiving challenges with an automotive transimpedance amplifier. The input stage accepts a photo detector’s negative input current pulses (Figure 3).
Figure 3 The electronics comprise one laser diode emitter and two photodiode receivers. Source: Bonnie Baker
The laser diode transmits digital bursts through a piece of glass. This signal also reflects to the D2 photodiode. The processing of this signal provides the time of transmission with the electronic delays built into the system.
The digital light signal pulses out to an object and reflects back to the optical system. The returned pulse mirrors to a second photodiode, D1. The D1 signal path has the same electronics as the D2 signal path. Both signals arrive at the microcontroller unit (MCU) to calculate the ToF.
Snapshot of the market
Automotive LiDAR systems use pulsed laser light to measure the distance between two vehicles. The automotive system utilizes LiDAR to control vehicle speed and braking systems in response to sudden changes in traffic conditions. Semi or fully autonomous vehicle assistance features LiDAR in collision warning and avoidance systems, lane-keep assistance, lane-departure warning, blind-spot monitors, and adaptive cruise control. The automotive LiDAR is replacing the earlier automotive radar systems in automated systems. The distance range of LiDAR systems is from a few meters to more than 1,000 m.
Figure 4 The automotive LiDAR market is segmented into semi-autonomous and autonomous vehicle applications. Source: Allied Market Research
Autonomous cars are here to stay, and the LiDAR imaging systems further complete the picture. The current technologies of choice in semi and fully autonomous driving are radar, camera, and LiDAR equipment. The LiDAR price is coming down, and the market is accelerating toward this change.
Bonnie Baker is a seasoned analog, mixed-signal, and signal chain professional and electronics engineer. She has published and authored hundreds of technical articles and blogs in industry publications. Baker is also the author of the book “A Baker’s Dozen: Real Analog Solutions for Digital Designers” as well as coauthor of several other books.
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