LiDAR Laser Sensor in The Security Field Application

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.

With the development of science and technology and the improvement of safety awareness, more and more Laser Sensor Detection Technologies are used in the security market. Traditional security methods use active and passive sensors for detection to realize applications such as sound monitoring, video surveillance, infrared alarm and access control identification. LiDAR (Light Detection and Ranging, LiDAR) is an intelligent sensor for active environment perception. Compared with traditional cameras and passive infrared detection technology, it is not limited by conditions such as lighting environment and target characteristics, and has strong anti-interference. Compared with Laser beam technology can provide information such as the dynamic position of the target, has positioning and tracking functions, and is highly flexible; compared with traditional radar technologies such as millimeter wave and microwave radar, its operating wavelength is shorter and can accurately obtain information such as target distance and speed. ,High-resolution. It can be seen that lidar has obvious advantages in the security field, has a wide range of application scenarios, and plays an important role in urban security and industrial safety. Traditional surveying-level lidar is usually bulky and expensive, which limits its large-scale promotion and application in the security field. The market demand for lightweight and low-cost lidar is increasing. In addition, the particularity of the security field has some special requirements for lidar hardware design, performance indicators and software algorithms: perimeter protection of sensitive areas requires high detection rate and low false alarm rate; monitoring environment for target protection, Its light source is required to be concealed and safe for human eyes; building protection under harsh conditions requires it to be stable and reliable with a high level of protection.

In order to meet the special needs in the security field, research on key lidar technologies is continuing to deepen. The main differences between LiDARs of different technical systems lie in the ranging scheme, scanning method and light source selection. These three aspects directly determine the core parameters such as human eye safety, detection performance and scanning field of view. They are the key to achieving low power consumption and miniaturization. The key to low-cost mass production of consumer-grade security lidar. The future development trend of the security industry will be all-round and all-weather "intelligent identification-intelligent early warning-real-time processing", which requires the system to be more intelligent and integrated while having high performance. Combining lidar technology with technologies such as artificial intelligence and mobile Internet can achieve diversified development of security technologies and products.

As the "eyes" of smart security, the outstanding feature of security lidar lies in safety protection. First of all, it can detect intrusion targets and provide security warnings at the same time; secondly, it has a high security level and meets the needs of human eye safety and light source concealment; finally, it has a high protection level and can work stably and reliably in harsh environments. Based on the physical parameters it detects, such as distance, grayscale, speed and angle, security lidar can calculate the target's orientation, distance, width and depth in real time and is used in different types of security scenarios. For example, ranging lidar can be used in fields such as industrial safety detection and building protection to monitor target areas and achieve safe distance warnings; speed lidar can be used to monitor speeding traffic vehicles and accurately classify violations to ensure road safety. Safety. In addition, lidar can use information such as distance, angle, and grayscale to achieve target imaging, and is suitable for target tracking and recognition and other fields. Security lidar is widely used in areas such as perimeter protection, industrial monitoring, intrusion warning, and cultural relic protection.

Fig. 1 Application scenarios. （a）Perimeter protection；（b）industrial monitoring；（c）intrusion warning；（d）cultural relic protection

In recent years, with the rapid development of security lidar, its application scenarios have become more and more extensive, from indoor and outdoor building protection to intelligent traffic control, to aerial anti-UAV (Unmanned Aerial Vehicle, UAV) early warning, etc. For intrusion targets in different security scenarios, security lidar has a high detection rate and can determine the attributes of the intrusion target, determine location information, and provide timely warnings. The detection targets in different security scenarios are shown in Table 1. It can be seen that the intrusion targets targeted in security application scenarios are mainly crowds. Therefore, to a certain extent, this requires security lidar to meet the requirements of light source concealment and human eye safety. This enables covert protection and security monitoring of detection targets. In order to cope with the ever-changing complex environment, in the security field, integrators and end customers pay more attention to the detection accuracy of intrusion targets, such as recognition effect and positioning accuracy, as well as low false alarm rate and false negative rate. However, the key factor affecting the false alarm rate and false alarm rate of security lidar is not the measurement accuracy, but the stable and reliable anti-interference ability and protection ability of security lidar. As shown in Figure 2, in complex forest scenes, using drones equipped with lidar to detect intrusion targets may lead to misjudgment due to the complexity of factors such as temperature and humidity in the working environment. Therefore, security lidar should have the characteristics of high protection level, strong anti-interference ability and good environmental adaptability to ensure normal use in harsh environments.

Fig. 2 Drones equipped with security LiDAR for detecting intrusion target in forest scenario

Traditional lidar is mostly used in industries such as high-precision engineering surveying and industrial surveying. The ranging accuracy can reach millimeter level, while the angle measurement accuracy is generally 0. 001° or even lower. It adopts a multi-wire harness mechanical structure. With the loss of internal moving parts, the service life is reduced, the maintenance cost is increased, and the stability is poor, which greatly limits the promotion and application of lidar in the security field. Among the mainstream foreign security lidar products, Flash means area array flash, OPA means optical phased array, and ρ is the target reflectivity. Compared with traditional lidar, it has small size, obvious cost advantages, good stability, and is easy to promote mass production. Mainstream commercial security lidar manufacturers include Germany's SICK and Japan's HOKUYO. The security lidar products of these companies are mature 2D single-line lidar, which are widely used in industrial fields and occupy the mainstream of the security market. The security field does not have high requirements for the measurement accuracy of laser radar. The measurement accuracy is generally at the centimeter level, and the angle measurement accuracy is about 0. 1°. In recent years, high-performance, low-cost solid-state lidar launched by companies such as Quanergy and Ouster in the United States has gradually become an indispensable product in the field of lidar smart security applications.

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