This article compares Frequency Modulated Continuous Wave (FMCW) and Time of Flight (ToF) for LiDAR. In summary, FMCW is better in longer term but ToF is still better now.

What are FMCW and ToF?

Lidar can take on several different modalities, which can be classified by their dependence on incoherence or coherence of the laser source which is used. Each of these methods uses the optical path of the target reflector to effectively modulate the envelope intensity of the detected signal. Time-of-flight (pulsed) and amplitude-modulated continuous-wave (AMCW) sensors detect range by measuring temporal properties of the received light intensity. Frequency-modulated continuous-wave (FMCW) and optical coherence tomographic (OCT) sensors map properties of the received optical field (amplitude and phase) into intensity and attempt to leverage the knowledge of both the amplitude and phase in order to detect range.

Applicaiton Comparisons

First, many LiDAR companies claims that FMCW is better than ToF. recent papers1–5 have presented a number of marketing claims about the benefits of Frequency Modulated Continuous Wave (FMCW) LiDAR systems.

References

  1. Aurora Team, “FMCW Lidar: The Self-Driving Game-Changer”, www.medium.com, April 9, 2020
  2. Philip Ross, “Aeva Unveils Lidar on a Chip”, IEEE Spectrum, December 11, 2019.
  3. Timothy Lee, “Two Apple veterans built a new lidar sensor — here’s how it works”, arsTECHNICA, October 2, 2018.
  4. Jeff Hect, “Lasers for Lidar: FMCW lidar: An alternative for self-driving cars”, LaserFocusWorld, May 31st, 2019.
  5. “Aeva launches ‘4D’ LiDAR on chip for autonomous driving”, www.optics.org, December 16, 2019.
  6. Phillip Sandborn, “FMCW Lidar: Scaling to the Chip-Level and Improving Phase-Noise-Limited Performance”, Electrical Engineering and Computer Sciences, University of California at Berkeley, Technical Report No. UCB/EECS-2019–148, December 1, 2019.
  7. “Technology readiness level”, Wikipedia
  8. A Gschwendtner, W Keicher, “Development of Coherent Laser Radar at Lincoln Laboratory”, MIT Tech journal, Vol 12, #2, 2000.
  9. C. Patel, “Stability of Single Frequency Lasers”, IEEE J Quantum Electronics, v4, 1968.
  10. Voxtel Laser Rangefinders, www.voxtel-inc.com, June 2020
  11. P Suni et al, “Photonic Integrated Circuit FMCW Lidar On A Chip”, 19th Coherent Laser Radar Conference
  12. https://www.novuslight.com/fmcw-the-future-of-lidar_N9691.html
  13. https://www.laserfocusworld.com/home/article/16556322/lasers-for-lidar-fmcw-lidar-an-alternative-for-selfdriving-cars
  14. https://www2.eecs.berkeley.edu/Pubs/TechRpts/2019/EECS-2019-148.pdf

Tech Leader/PM who focuses on 3D (Imaging/Photonics/Sensing, LiDAR/ToF) and 3A (AV/Auto, AR/VR, AIoT/5G)…. linkedin.com/in/ymarc; http://4da.tech/

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