The article on LiDAR Major Components discusses the three essential elements that make up a LiDAR system: the laser source, the receiver, and the apertures for pointing the system.
1. Laser Sources:
LiDAR systems typically use diode lasers or diode-pumped solid-state lasers. Diode lasers are efficient and inexpensive but lack energy storage, meaning they cannot perform Q-switching. These lasers also tend to have broader line widths and beams, making them suitable for applications where these traits are advantageous. On the other hand, solid-state lasers provide narrower line widths and beam divergence, which are closer to the diffraction limit. Solid-state lasers can also be Q-switched to generate higher peak power. Another type, fiber lasers, offers high efficiency but limited gain area, making them ideal for higher-duty-cycle operations.
2. Receivers:
LiDAR receivers can either be a single detector or an array of detectors. Older LiDAR systems relied on single detectors, but recent advancements have made high-bandwidth arrays more common. These arrays can measure range in each pixel based on the reflected laser pulse, providing greater accuracy and efficiency. Coherent LiDAR systems benefit from using the local oscillator (LO) to increase the signal-to-noise ratio (SNR) in the receiver. This is particularly useful for direct detection systems, which may employ amplification techniques to boost SNR.
Linear-mode avalanche photodiodes (LMAPDs) are a type of detector that generates multiple electrons for every photon received, improving detection accuracy. Geiger-mode APDs, in contrast, provide a maximum electron count when one or more photons are detected.
3. Apertures:
The optical system in a LiDAR must accurately direct both the transmitter and receiver components. These apertures may be shared between transmission and reception or separate. Mechanical beam-pointing systems, such as mirrors that can tilt, are often used, but recent developments have explored non-mechanical beam-pointing techniques, including optical phased arrays, similar to those found in microwave systems. These arrays allow the phase front of the electromagnetic wave to change without moving physical components, offering enhanced control over beam pointing.
These components enable LiDAR systems to perform accurate measurements of distances, angles, and velocities.
