Wednesday, August 17, 2022

RMCW LiDAR

Baraja is an automotive LiDAR company headquartered in Australia which specializes in pseudo-random modulation continuous wave LiDAR technology which they call "RMCW". A blog post by Cibby Pulikkaseril (Founder & CTO of Baraja) compares and contrasts RMCW with the more-commonly-known FMCW and ToF LiDAR technologies.

tldr; There's good reason to believe that pseudo-random modulation can provide robustness in multi-camera environments where multiple LiDARs are trying to transmit/receive over a common shared channel (free space).

Full blog article here: https://www.baraja.com/en/blog/rmcw-lidar

Some excerpts:

Definition of RMCW

Random modulated continuous wave (RMCW) LiDAR is a technique published in Applied Optics by Takeuchi et al. in 1983. The idea was to take a continuous wave laser, and modulate it with a pseudo-random binary sequence before shooting it out into the environment; the returned signal would be correlated against the known sequence and the delay would indicate the range to target. 

Benefits

... correlation turns the pseudo-random signal, which to the human eye, looks just like noise, into a sharp pulse, providing excellent range resolution and precision. Thus, by using low-speed electronics, we can achieve the same pulse performance used by frequency-modulated continuous wave (FMCW) LiDARs... .

... incredible immunity to interference, and this can be dialed in by software.

RMCW vs. FMCW vs. ToF

... [FMCW and RMCW] are fundamentally different modulation techniques. FMCW LiDAR sensors will modulate the frequency of the laser light, a relatively complicated operation, and then attempt to recognize the modulation in the return signal from the environment.

Both RMCW and FMCW LiDAR offer extremely high immunity from interfering lasers – compared to conventional ToF LiDARs, which are extremely vulnerable to interference.

Spectrum-Scan™ + RMCW is also able to produce instantaneous velocity information per-pixel, also known as Doppler velocity ... something not [natively] possible with conventional LiDAR... .

 

Baraja's Spectrum OffRoad LiDARs are currently available.


Spectrum HD25 LiDAR samples (specs in image below) will be available in 2022.