Auto Lidar: Optical Choices And Challenges

Auto lidar (for the autonomous-vehicle revolution), is one of the hottest hot topics today in optics and photonics. But what kind of lidar? The technology’s deceptively simple five-letter name packs in a complex array of choices, from spinning car-top sensors to tiny solid-state lidar scanners largely still on the drawing boards.

Angular resolution is the big thing that separates it from other onboard sensors. If you want object classification, you need to know that you’re seeing what the object is, at close range or long range. Lidar’s 0.1 degree angular resolution allows that to happen, in contrast to systems like radar. Lidar also has some advantages over camera systems, which have trouble in low-lighting and variable-lighting conditions that can temporarily “blind” the camera. Lidar does share one key disadvantage of cameras, however: Both suffer in adverse weather conditions.

The highest-level division in the auto lidar market is between time-of-flight (ToF) lidar, which pulls a distance measurement from the flight time of the laser pulse, and frequency-modulated continuous-wave (FMCW) systems, which extracts time and velocity information from the frequency shift of returning light. ToF lidar is a very simple concept, but it’s very complex to make a high-resolution lidar out of this. FMCW’s more information-rich data stream is potentially attractive, but has complexities of its own.

Read more