LiDAR Laser Sensor Classification And Scanning Methods

LiDAR Laser Sensor actively emits laser light and can obtain information such as the distance, orientation, speed and contour of an intruding target with high precision and high resolution. It has been widely used in fields such as urban security and industrial security. This article briefly introduces the mainstream domestic and foreign security lidar manufacturers and their product technical specifications. Combining the needs of different security applications, the principles, characteristics and current situation of lidar under different technical systems are discussed from three aspects: ranging scheme, scanning method and light source selection. Finally, the application trends and development prospects of security lidar are summarized and prospected. In order to meet the needs of consumer security applications, security lidar will further develop in the directions of low cost, high performance, serialization, miniaturization, solid state, chipization and multi-source integration.

Depending on whether there are moving components inside the system, lidar can be divided into mechanical lidar and solid-state lidar. Among them, the implementation methods of solid-state lidar include micro-electromechanical system (Micro-ElectroMechanical System, MEMS), Flash technology and OPA technology.

According to the beam control characteristics in the scanning mode, lidar can be divided into scanning lidar and non-scanning lidar. Among them, non-scanning lidar achieves target imaging by covering the scene with light, such as Flash area array lidar. Appropriate scanning methods can enable security lidar to obtain a larger field of view and resolution, while making the entire structure more stable. Therefore, the choice of scanning technology greatly affects the life cycle of lidar, which in turn determines whether security lidar under this system can be mass-produced. Among them, long detection range and large field of view are key indicators of security lidar, and they also determine the application prospects of security lidar in the future.

1. Mechanical LiDAR Laser Sensor
Mechanical lidar refers to the use of mechanical rotation to achieve laser scanning. The motor drives the single-point or multi-point ranging module to rotate to achieve a full 360° or other large-angle area scanning. The working principle of mechanical lidar is shown in Figure 1. It has the advantages of simple principle, easy driving and large scanning field of view. It was the first to be widely used and became the scanning solution for mainstream security lidar products on the market. Taking into account factors such as lenses, mechanical structures, and circuit boards, many points ranging modules usually cannot be optimized in terms of size and weight. Therefore, when the motor drives the module to rotate for a long time, the bearings are easily worn. This makes traditional mechanical scanning criticized in terms of life and reliability, and the cost caused by wear increases. It is also a very real problem. Therefore, the early security market mostly adopted dimensionality reduction and low-cost solutions, that is, using low-beam line laser radar in conjunction with other sensors. It has a compact appearance and a large scanning field of view, and is suitable for scenarios such as building protection and regional perimeter protection.

Fig. 1 Working principle of traditional mechanical LiDAR

Currently, the biggest challenge facing LiDAR design is achieving performance and robustness while achieving mass production at a reasonable cost. However, mechanical lidar cannot be widely promoted in the security field due to its redundant core electronic components, which makes it difficult to reduce its size and cost. To this end, the core components of lidar are integrated into application-specific integrated circuit (ASIC) chips to reduce the size of the lidar signal processing circuit and reduce power consumption and cost. This is to realize the mass production of multi-line lidar. an important trend.

2.MEMS LiDAR Laser Sensor
MEMS laser radar replaces the traditional mechanical rotating device with a MEMS micromirror integrated on a silicon-based chip. The micromirror reflects the laser to form a wider scanning angle and a larger scanning range. Its working principle is shown in Figure 2. MEMS micro-mirrors are innovators of traditional mechanical lidar and will lead the miniaturization and cost reduction of lidar. The galvanometer scanning method avoids the direct rotation of the ranging structure, enables solid-state scanning of the lidar, and makes the lidar compact.

Fig. 2 Schematic of MEMS.（a）Working principle of MEMS LiDAR；（b）MEMS scanning mirror

Relying on the advantages of MEMS micro-mirrors, the industry regards MEMS lidar as the fastest technology to be implemented. At present, Leishen Intelligent LS20/LS21 series MEMS solid-state lidar has been used in fields such as intelligent security and disaster monitoring. However, the shortcoming of the MEMS micro-mirror is that its scanning angle is small, and an additional angle is required to achieve large field of view scanning. In addition, the amount of laser light it can project is limited, making it difficult to achieve "long-distance detection". In general, MEMS lidar technology solutions are not mature enough and need further improvement. It is believed that with the development of MEMS micro-mirrors, the application prospects of MEMS lidar will be broader.

3.Flash LiDAR Laser Sensor
Flash lidar is a non-scanning radar. It emits area array light onto the target, uses the area array detector to detect the scattering of the incident light by the target, and outputs an image with depth information. Its working principle is shown in Figure 3. Although Flash lidar is low-cost and has good stability, its detection range is relatively short, so its application scenarios are limited. In the field of security, Flash laser radar has been widely used. Using 3D Flash lidar for target detection, segmentation and tracking, the results show that Flash lidar is suitable for perimeter surveillance and on-site security fields. However, in fields such as environmental monitoring, object observation, and hazard prevention, real-time detection of objects or people will be limited by scanning characteristics, resulting in data distortion. Using a sensor system built with 3D Flash lidar, highly variable moving objects can be tracked in real time and with high accuracy over medium to long distances. The experimental process and results are shown in Figure 4. In addition, with the development of small components, the cost of area array detectors is reduced, and Flash lidar is easy to miniaturize, and its applications in the security field will be more.

Fig. 3 Working principle of Flash LiDAR

Fig. 4 Working scenario and experimental results of Flash LiDAR. （a）Experimental setup with real-time tracking on PC and Flash LiDAR on pan-tilt head；（b）point cloud of scenario；（c）intensity view of scenario with person marked center；（d）range view of scenario with person marked center

4.OPA LiDAR Laser Sensor
As a new type of beam pointing control technology, OPA scanning technology has become a research hotspot in recent years. It has the advantages of no inertia devices, stable accuracy and controllable direction. Its working principle is shown in Figure 5. Several transmitting units form a transmitting array. The exit angle of the laser beam is changed by adjusting the phase difference of each transmitting unit in the transmitting array, thereby achieving mutually reinforcing interference in the set direction, thereby preparing High intensity pointing beam. S3, “the world’s first solid-state lidar sensor.” S3 uses OPA scanning method and is only palm-sized. The product and its principle are shown in Figure 6. The S3 series products have been used in fields such as intrusion monitoring and access control.

Fig. 5 Working principle of OPA

Fig. 6 Working principle of Quanergy S3 LiDAR

Optical phased array technology with high integration can meet the development needs of all-solid-state and miniaturization of security lidar. However, there are currently two main factors that restrict the mass production of OPA security lidar: first, side lobes are easily formed during actual scanning, which will affect the range and angular resolution of the beam; second, the processing difficulty is high. Therefore, OPA security lidar technology is still immature, and it is difficult to achieve productization at this stage.

Contact information:

If you have any ideas, feel free to talk to us. No matter where our customers are and what our requirements are, we will follow our goal to provide our customers with high quality, low prices, and the best service.