I. Laser Emission System
One of the core components of a lidar system is the laser emitter. It typically employs either solid-state lasers or semiconductor lasers. Solid-state lasers rely on solid materials such as crystals or glass fibers as the gain medium to generate laser light, while semiconductor lasers utilize the properties of semiconductor materials, such as PN junctions made of GaAs (gallium arsenide) or InP (indium phosphide), to achieve laser emission. The laser emitter needs sufficient power, stable output, and narrow pulse width characteristics to ensure that the laser pulse can propagate over long distances and accurately measure distance.
II. Scanning System
The scanning system is a key component of lidar's omnidirectional detection capability. Traditional scanning methods include:
1. Mechanical scanning: The laser beam is continuously scanned at a preset angle and rate by a rotating component driven by a motor, such as a rotating mirror driven by a motor or the entire mechanical structure rotating, covering a 360° field of view.
2. Solid-state scanning: Using MEMS (microelectromechanical systems) technology, such as MEMS mirrors, the direction of the laser beam can be oscillated at high speed and with small amplitude to achieve fast and efficient electronic scanning.
3. Flash scanning: This method does not rely on mechanical or electronic scanning. Instead, it uses a large-area laser array to emit multiple pulses at once, covering the entire field of view to form a static three-dimensional image.
III. Optical Components
The optical components include optical lenses at the transmitting end and optical elements at the receiving end. The lens system at the transmitting end is mainly used to focus and guide the laser pulse, ensuring its straight-line propagation in space. The receiving end includes a receiving lens, optical filters, and photodetectors. The receiving lens is responsible for converging the returning laser pulse, the optical filter is used to remove background noise and incoherent light, allowing only the laser echo of interest to pass through, and the photodetector (such as an APD or PIN diode) converts the received optical signal into an electrical signal.
IV. Reception and Signal Processing
The receiver of a lidar system is responsible for capturing the reflected laser signal and converting it into a processable electrical signal. This process includes time difference measurement, which calculates the target distance by recording the time interval between the emission and reception of the laser pulse. The signal processing unit contains a time-to-digital converter (TDC), a signal amplifier, and a series of advanced digital signal processing devices for real-time decoding and processing of these electrical signals, extracting useful information such as distance, intensity, and velocity, and generating high-quality point cloud data.
V. Data Processing and Output
The pre-processed data enters the data processing unit, where point cloud generation, 3D modeling, target classification, and tracking are performed. By processing the point cloud data using efficient algorithms, not only can an accurate 3D model of the environment be constructed, but also specific target attributes, such as object shape, texture, and even dynamic behavior, can be identified. Finally, the LiDAR system transmits the processed data to the host system via a dedicated interface (such as a CAN bus, Ethernet interface, or custom protocol) for further analysis and decision-making.
VI. Additional Modules
LiDAR may also contain other key modules, such as:
1. Power Management System: To ensure the stable operation of the lidar, an efficient and reliable power management system is essential, which includes functions such as voltage conversion, current control, and overheat protection.
2. Environmental adaptability design: including temperature control system, dustproof and waterproof packaging, etc., to ensure that the lidar can work normally in various environments.
3. Positioning and attitude perception: By combining data from GPS, inertial measurement unit (IMU) or other sensors, the radar's own motion state is accurately estimated and compensated, thereby improving measurement accuracy.
In summary, the internal structure of a lidar system is a highly integrated and precisely coordinated system, encompassing multiple key technological aspects such as laser emission, scanning mechanisms, optical transceivers, signal processing, and adaptation to the external environment. With the advancements in hardware miniaturization and software intelligence, future lidar systems will further improve performance, reduce costs, and expand application areas, becoming one of the cornerstones of intelligent sensing technology.
