LiDAR Principle

There are four main types of laser radars based on the ranging principle: time of flight (ToF), frequency modulated continuous wave (FMCW), triangulation ranging and phase method. The two main measurement methods are ToF and FMCW. The lasers of laser radars can be divided into 1550nm (far-wave infrared, SWIR) lasers represented by fiber lasers and 905nm (near infrared, NIR) lasers represented by semiconductor lasers. Among them, near-infrared lasers can be divided into edge-emitting lasers (EEL), vertical cavity surface-emitting lasers (VCSEL) and solid-state lasers according to different light-emitting principles. The detectors in laser radars, namely photodetectors, can be divided into four categories: PINPD (PIN photodiode), APD (avalanche photodiode), SPAD (single photon avalanche diode), and SiPM (silicon photomultiplier tube). APD is the current mainstream.