LIDAR, which stands for Light Detection and Ranging, is a technology which is being used more and more in modern vehicles. In this post we’re going to look at how it works, how it’s already being used, and some interesting future applications.
The Hughes Aircraft Company first introduced a LIDAR-like system in 1961, just after the invention of the laser. It was developed for the purposes of satellite tracking, and had the ability to calculate distances by measuring the time taken for a light signal to return. This core function has proved to have many useful applications, from Agriculture to Video Games, and is increasingly used on modern vehicles.
How Does LIDAR Work?
Typically, a LIDAR sensor sends pulses of light waves into the environment. The pulses will reflect off objects and surfaces in the surrounding area, and a sensor will detect the returning light. The sensor will calculate the time taken for the pulse to return to the sensor, and from this calculate the distance to the object the light has reflected off. LIDAR sensors will repeat this process millions of times per second, and this allows for a detailed 3D image of the surrounding area to be created in real-time.
The LIDAR sensors used on vehicles will fire anywhere from 8 to 108 laser beams in a series of pulses, with each beam pulse emitting billions of photons per second. This process generates a huge amount of data points, and the resulting calculations are processed almost simultaneously. Because of this LIDAR can accurately determine the shape and size of objects and track their movement.
LIDAR sensors can be solid state or rotating. Spinning sensors will often be located at the top of the vehicle and are designed to capture a 360-degree field of view. Solid-state LIDAR sensors on the other hand are fixed, and point in a single direction with 90 to 120 degrees field of view. Solid-state sensors are cheaper to produce, but several fixed sensor units are required to achieve the coverage that a single spinning unit can provide. LIDAR systems usually have a range of somewhere between 250 and 400 metres. This allows the system to identify objects and their positions well before reaching them.
What Does LIDAR Do on My Vehicle?
LIDAR sensors are used, alongside RADAR and Cameras, to help the vehicle's systems ‘see’ the world around your vehicle. If your vehicle has adaptive cruise control, parking assistance, automatic emergency braking, or blind spot monitoring, the chances are that LIDAR sensors are part of those systems.
Adaptive Cruise Control (ACC) automatically adjusts the vehicle speed to maintain a safe distance from vehicles ahead. LIDAR sensors will often be used to prompt the system to decelerate when it detects the car is approaching another vehicle ahead, then accelerate when traffic allows it to.
Parking assistance features, like Mercedes Benz’ Parktronic ™, will often use LIDAR sensors alongside cameras to help determine usable parking spaces and aid you in parking without collisions.
Autonomous Emergency Braking (AEB) systems will often use LIDAR alongside radar sensors and cameras, and aim to detect risks of collision ahead of the vehicle. A ‘Forward Collision Warning’ alerts the driver and, if they fail to react, the system applies the brakes automatically to reduce the impact speed or avoid the crash altogether. Early AEB systems functioned at lower speeds, and were only sensitive enough to avoid collisions with other vehicles. However more recent systems operate up to motorway speeds, and can detect pedestrians and cyclists. Most new vehicles have AEB fitted as standard. In fact, since 2019, it’s no longer possible to get a five-star Euro NCAP safety rating without it.
Some Blind Spot Monitoring systems also use LIDAR scanners to capture the presence of objects or vehicles in the driver’s blind spot and alert the driver to their presence. Sensors are the eyes of any blind spot monitoring system, and a blind spot system will generally use two or more sensors to cover different sides of the vehicle. When something enters into the "view" of the sensor at or above a specific speed, the sensor will trigger the indicator. Indicators come in many forms, but most will use a combination of visual LED lights and an audible alarm to notify you.
What Next for LIDAR on Cars?
As LIDAR sensor technology continues to come down in cost, we are seeing it used in more and more contexts. The iPhone 12 Pro has a LIDAR sensor, and it’s inclusion is based on improving camera focus accuracy and speed. It is also being used to enhance Augmented Reality (AR) apps, as LIDAR can be used to mesh out 3D objects and spaces. Layering photo imagery on top of these 3D images, a technique called photogrammetry, is also possible. The ability to use these types of techniques to provide drivers with layers of information via an HUD (Heads Up Display) is not too far away.
LIDAR is also a key technology in the journey towards fully autonomous vehicles. LIDAR and cameras are the two main contenders as the key sensor for autonomous vehicles. LIDAR is far better at judging distances than cameras, as well as being able to detect surfaces that are reflective or textured. Cameras also require significant computing effort, such as complex neural networks, to gauge distance between objects, by aggregating different camera feeds or a single feed over time.
The most common view is that the best option is a hybrid, using both LIDAR’s superior vision and cameras’ colour, object and text recognition, to obtain a clear picture of the surrounding environment. Though it is worth noting that Elon Musk has described LIDAR (in the context of autonomous vehicles) as “a fool’s errand” and “unnecessary”, LIDAR could reach an accessible price faster than cameras can become truly usable and reliable. LIDAR would then be likely to become universal in autonomous vehicles as a cheap, dependable and very accurate distance sensor, at the very least in conjunction with cameras.