What is LiDAR, and How Does it Work?

A great many vehicles these days use cameras, radar, and sensors to enable a wide array of advanced driver assistance systems (ADAS), ranging from blind-spot warning to rear cross-traffic alert—all designed to help prevent a collision from occurring. However, a next-generation technology known as LiDAR allows vehicles to "see" their surroundings even better. This technology makes the on-road experience safer for today's drivers and promises to further the development of autonomous vehicles into the future.

LiDAR Point Cloud Projected on Image

What Is LiDAR?

LiDAR stands for "light detection and ranging." In general terms, this technology uses infrared light or lasers to create a three-dimensional image of an environment. NASA initially developed LiDAR to monitor the positions and paths of satellites in space, but as the technology scaled down and continued to develop, new terrestrial-based applications emerged relating to automotive safety technology and autonomous vehicle systems development.

LiDAR's central premise is to act as a vehicle's eyes to always see in all directions. With a real-time ability to map the world in 360 degrees, LiDAR helps vehicles identify objects on or near the roadway to avoid collisions with pedestrians, cyclists, animals, and other vehicles, stationary or moving.

How does LiDAR Work?

A LiDAR sensor utilizes the same kind of laser used in everyday applications, such as retail barcode scanners, light shows at concerts and sporting events, and home security systems. This kind of laser technology is safe to the eye and has been in use for decades.

The LiDAR sensor on a vehicle emits single particles of light, known as photons, that strike nearby objects such as cars, pedestrians, and trees. The photons then bounce back to the sensor. The LiDAR system records each photon's roundtrip data, measuring distance and time to every object in the vehicle's vicinity.

A LiDAR sensor will fire anywhere from eight to 108 laser beams in a series of pulses. Each laser beam pulse emits billions of photons per second. With so many data points and calculations processed almost simultaneously, LiDAR accurately highlights objects, gives them shape, and shows their movement. A computer algorithm then assembles these shapes and forms a complete picture of the world around the vehicle.

A rotating or spinning LiDAR sensor located at the top of the vehicle will capture a 360-degree field of view at a rapid rate of speed to provide a complete image of the vehicle's surroundings. Conversely, solid-state LiDAR sensors are fixed in place and point in a single direction with 90 to 120 degrees field of view. It takes several fixed sensor units to achieve coverage comparable to a single spinning unit. LiDAR sensors can be placed in various locations, including a vehicle's roof, within the rearview mirror housing, behind the grille, or at the rear window or tailgate of a vehicle.

LiDAR has a range of 250 to 400 meters, allowing it to identify objects and their positions well before reaching them. This allows a vehicle's ADAS or autonomous system to process the information and react accordingly.

LiDAR vs. Camera-Based Systems

LiDAR offers several advantages over camera-based systems. While cameras provide a flat representation of the environment in two-dimensional form, LiDAR renders a three-dimensional view of the world that is much more realistic and accurate.

Also, since LiDAR is its own light source, low-light situations do not affect its operation. It can see objects at night as well as it can see them during the day. In contrast, camera-based systems need sufficient light to function optimally, sometimes becoming unreliable during nighttime use.

Other factors that can lessen a camera's ability to see include optical illusions and the inability to make precise distance measurements. Also, a camera requires more computing power and generally runs hotter than a LiDAR sensor.

In the end, an ADAS system or autonomous vehicle will benefit most when LiDAR and camera-based systems are used in tandem to monitor a vehicle's surroundings.

The Disadvantages of LiDAR

Although LiDAR is considered a game-changer for those developing ADAS systems and autonomous vehicles, some are skeptical of its potential. The downsides of LiDAR include:

  • Sensors can have difficulty differentiating between objects that are similar in size and shape, which means threats and non-threats can be confused with one another.
  • LiDAR images are recreations rather than photos, so a vehicle system is susceptible to tampering and manipulation; LiDAR has a decreased level of security as compared to actual images from a camera.
  • Artificial Intelligence (AI) and machine learning are not inherent to LiDAR; camera-based systems are more aligned with ADAS technology that learns over time.
  • LiDAR sensors are significantly more expensive than camera and radar systems.

Summary

Whether LiDAR systems will continue to advance ADAS and autonomous driving into the future is yet to be seen. But there is no doubt this technology helps cars "see" the surrounding world better. Which, for many, means improved roadway safety and a more confident driving experience.