All about automotive lidar
10 days ago
- #autonomous-vehicles
- #sensor-technology
- #robotics
- Lidar is a sensor technology used in autonomous vehicles and robotics for environmental perception.
- Lidar measures distance, bearing, reflectivity, speed, and ambient light by bouncing light off surfaces.
- Distance measurement (ranging) can be done via time-of-flight (direct or modulated) or parallax methods.
- Direct time-of-flight pulsed lidar measures the time for light to return, with accuracy enhanced by interpolation and matched filters.
- Photodiodes like APDs and SPADs are used in pulsed lidar for high-speed light detection, each with unique advantages.
- SPAD macropixels and multi-shot ranging improve dynamic range and signal strength in lidar systems.
- Amplitude-modulated and frequency-modulated (FMCW) lidar offer alternative ranging methods with trade-offs in cost and performance.
- Bearing discernment in lidar is achieved via arrays or beam steering, with trade-offs in resolution, cost, and field of view.
- Common beam steering methods include spinning, MEMS mirrors, optical phased arrays, and Risley prisms.
- Lidar wavelength choices (near-infrared vs. 1550 nm) impact eye safety, detector sensitivity, and performance in adverse weather.
- Laser sources for lidar include VCSELs, edge-emitting diodes, and fiber lasers, each suited for different applications.
- Common lidar issues include beam angle calibration errors, range offsets, pixel crosstalk, and encoder hysteresis.
- Lidar is often mistakenly capitalized as 'LiDAR,' but lowercase is preferred as the technology becomes commonplace.