Introduction
This article is targeted at beginners who want to explore the working principle of digital lidar sensors and their capabilities. By reading this article, you should have a foundational understanding of what lidar is and why it has such great potential.
What is lidar?
Lidar is an acronym for "light detection and ranging". As the name suggests, lidar is a method that uses light to calculate the distance to a certain point. Because a lidar sensor uses a laser to produce the light, lidar is sometimes referred to as 3D laser scanning.
In the end, the measured points are combined into a model, called a point cloud. This point cloud is defined as a set of points in a 3D space and can be viewed on a computer or smartphone. Unlike an image from a camera, users can navigate around a point cloud in 3D, because the distance to the individual points is known. This depth information is of great value to many industries, like automotive, robotics, and infrastructure.
In many ways, lidar is similar to radar, with the key difference being that it uses light waves instead of radio waves. Although the first lidar has been introduced in the 1960s, significant improvements have been made in the last decade. Besides that, modern sensors are getting cheaper, more reliable, and more capable every year. This leads to the integration of lidar across many industries and the creation of a variety of use-cases.
How does lidar work?
The built-in laser rapidly emits laser pulses at a wavelength of around 900nm. At some point, the light beam gets back-scattered (reflected) to the sensor where it is detected by a photo sensor. The time elapsed - from emitting to detection - is monitored precisely. Given the time the lidar beam traveled, the distance to the object is calculated.
To generate a point cloud that provides detailed information, however, a single point is not sufficient. Therefore, multiple laser beams are aligned vertically with different orientations and emitted simultaneously. This is referred to as the number of channels. For instance, Ouster produces sensors with up to 128-channel resolution. To gain horizontal information, this array of lasers is spinning continuously.
The method explained above is used on Ouster OS-series sensors. However, other ways to move laser beams in different directions exist. These include a stationary laser paired with a moving mirror to steer the light, or true solid-state lidar that does not rely on any moving parts at all.
Applications
Due to the ability to extract 3D information from the point cloud, lidar is an adequate replacement for cameras in many cases.
For years, lidar technology has already been used to investigate the atmosphere and important parameters like upper winds, clouds, and aerosols. A currently widespread use case is 3D mapping and infrastructure inspection. In the automotive industry, lidar integration in self-driving cars is common. Ouster also partnered with many companies that develop autonomous robots for warehouse or delivery applications.
