Lidar: the core technology to promote intelligent perception
LiDAR (Light Detection and Ranging) technology is a high-precision ranging technology that detects the distance of objects through laser beams. In recent years, with the rapid development of autonomous driving, unmanned aerial vehicles, geographic information systems (GIS) and other fields, laser radar technology has gradually come into the public view and become the core component of intelligent perception systems.
1. Operating principle of laser radar
The basic principle of lidar is similar to radar, but the difference is that it uses laser beam instead of electromagnetic wave to detect the distance of objects. When the laser beam irradiates the target object, the laser will reflect. Lidar calculates the distance of an object by measuring the time difference between the laser emission and the reflected signal received, and combining the speed of light. This process can be completed in a very short time, and the three-dimensional space information of objects can be obtained by continuously transmitting and receiving laser pulses.
Different from the traditional laser rangefinder, the laser radar can achieve 360 degree omnidirectional scanning coverage through rapid scanning of multiple laser beams. This enables the lidar to simultaneously sense multiple objects around vehicles, pedestrians, road facilities, etc., thus providing rich environmental awareness data.
2. Optical technology applied to lidar
The core technology of lidar is the laser transmitting and receiving system, which involves the application of several optical principles and technologies.
Laser emission system
The laser emission system of lidar uses laser diode (LD) or pulse laser source. These laser sources can emit high intensity light pulses in a very short time, usually in the wavelength range of 800 to 1550 nm. Choosing the appropriate wavelength is to obtain the best detection effect under different environmental conditions. For example, a longer wavelength can penetrate more substances, which is suitable for applications in complex environments, while a shorter wavelength is conducive to more accurate distance measurement.
Laser receiving system
The receiving system of laser radar is mainly composed of photodetectors (such as avalanche photodiodes, photodiodes, etc.), which are used to capture the laser signal reflected from the target object. The sensitivity of the receiving system is crucial to the performance of the lidar, which determines its performance in low reflectivity objects (such as rain, dust, leaves) or low light environment.
After receiving the optical signal, the lidar will analyze the reflected signal through the signal processing system to calculate the distance, shape, size and other data. These data can draw the 3D model of the surrounding environment in real time in the form of 3D point cloud.
Beam scanning technology
In order to achieve 360 degree omni-directional scanning, the laser radar usually adopts rotary or solid-state scanning technology. In a rotary lidar, the laser transmitter rotates around an axis to scan the entire environment. The angle of each scan is very accurate, so high-precision spatial data can be obtained. The solid-state lidar electronically adjusts the emission direction of the laser, avoiding the need for mechanical rotation, reducing the volume, and improving the stability.
Waveform analysis and filtering technology
The signal processing part of the lidar will apply waveform analysis technology to extract effective information from complex reflected waves. Filtering technology is also used in the signal processing of laser radar to remove noise, reduce errors and improve the accuracy of data. For example, when the reflected signals of multiple objects are received at the same time, the radar needs to distinguish the echo of each object through an efficient algorithm to achieve high-precision object recognition and distance measurement.
3. Main applications of laser radar
The laser radar technology has been widely used in many fields, especially in the automatic driving technology. The laser radar is regarded as an indispensable core sensor.
Automatic driving
In autopilot, the laser radar helps the autopilot system perceive the surrounding environment by providing high-precision 3D maps and real-time data. Through laser radar, autonomous vehicles can accurately identify other vehicles, pedestrians, traffic signs, obstacles, etc., providing reliable data support for the decision-making system, so as to achieve safe automatic driving.
UAV and Remote Sensing
The UAV equipped with lidar can carry out efficient mapping in areas with complex terrain or inaccessible areas. Lidar can accurately measure the height difference of the ground and draw a detailed three-dimensional topographic map, which is widely used in forest monitoring, mineral exploration, urban planning and other fields.
Environmental monitoring and geological exploration
Laser radar is also widely used in environmental monitoring and geological exploration. Through laser radar scanning, scientists can monitor the changes of landform after the earthquake, or evaluate the hydrological conditions of river basins. In addition, the lidar is also used for 3D modeling of forests and monitoring forest health.
4. Challenge and development trend of lidar
Although lidar is widely used in many fields, it still faces some challenges. First of all, the cost of laser radar is high, especially in the high-precision and high-performance laser radar. Secondly, the detection accuracy and reliability of lidar may be affected in poor weather conditions (such as heavy rain, snow, haze, etc.).
However, with the continuous development of technology, the price of lidar is gradually declining, and its performance is also continuously improving. In the future, the laser radar technology is expected to achieve a wider application, especially in the fields of intelligent transportation, smart cities, and driverless driving.
5. Conclusion
As an important optical technology, lidar is promoting the rapid development of intelligent perception and automation technology. Through accurate distance measurement, 3D environment modeling and efficient data processing, laser radar provides powerful technical support for automatic driving, UAV mapping, environmental monitoring and other fields. Despite certain challenges, the development prospect of lidar technology is still broad and will play an important role in more industries and application scenarios in the future.