Before we conclude which LiDAR mode is superior, we must first understand how these two LiDAR modes work.


What is a ToF or FMCW LiDAR?


ToF Lidar

The principle of the ToF (time of flight ) LiDAR is straightforward to understand. The laser emits a laser pulse, and the timer records the emission time. The sensor receives the return light, and the timer records the return time. The distance is then calculated by dividing the product of the speed of light and time of flight by 2.




FMCW Lidar

 The frequency modulated continuous wave(FMCW) principle can also be used for ranging to avoid the challenges caused by high-peak laser pulses. The distance to the object is measured using frequency modulation, where the emitted laser beam is repeatedly modulated and "chirped," and the frequency of the signal changes repeatedly. When the laser beam hits an object, the frequency of the reflected light will change depending on relative motion. This difference is called the Doppler effect or Doppler shift, which the LiDAR system can use to calculate the object's speed.




Pros and Cons of ToF LiDAR

Pros: ToF LiDAR has been introduced to the public for a while now, and it has become more powerful, accurate, and, most importantly, affordable.

Cons: Although more and more companies are making LiDAR, it is still considered High Cost. It is also unable to accurately to measure distance through heavy rain, snow, and fog.


Pros and Cons of FMCW LiDAR

Pros: Better Ambient Light Immunity, Better Eye Safety, Better Signal to Noise, and potentially better range. 

Cons: FMCW cannot measure lateral velocity simultaneously in one shot, and the most significant disadvantage of FMCW Lidar is that FMCW is still far from automotive-grade, reliable, and readily compared with ToF LiDAR.



FMCW may show a promising future, but ToF LiDAR currently is still the overall best choice for ADAS.