laser radar

A radar that uses a laser as a radiation source. Lidar is a combination of laser technology and radar technology. It consists of transmitter, antenna, receiver, tracking frame and information processing. Emitters are various types of lasers, such as carbon dioxide lasers, Nd-doped yttrium aluminum garnet lasers, semiconductor lasers and solid-state lasers with adjustable wavelengths. The antenna is an optical telescope; The receiver adopts various forms of photodetectors, such as photomultiplier tubes, semiconductor photodiodes, avalanche photodiodes, infrared and visible light multi-detector devices, etc. Lidar works in two modes: pulse or continuous wave. Detection methods are divided into direct detection and heterodyne detection.

Lidar can be used to measure the trajectories of various military flying targets. Such as tracking and measuring the initial stage of missiles and rockets, tracking and measuring the low elevation angle of aircraft and cruise missiles, and accurately determining the orbit of satellites. Laser radar is combined with infrared, television and other photoelectric equipment to form ground, shipboard and airborne fire control systems to search, identify, track and measure targets. Because lidar can obtain the three-dimensional image and velocity information of the target, it is beneficial to identify the stealth target. Lidar can monitor the atmosphere, telemeter the pollution and poisons in the atmosphere, and also measure the temperature, humidity, wind speed, visibility and cloud height of the atmosphere.

Application of lidar

● Wang Mengmin Xuecai

The principle and structure of lidar are similar to laser rangefinder, which is a detection system working in infrared to ultraviolet spectrum. Generally, it is called pulsed laser radar that uses laser pulses for detection, and it is called continuous wave laser radar that uses continuous wave laser beams for detection. At present, lidar with fire control, reconnaissance, guidance, measurement, navigation and other functions has been developed in the world.

Master of biochemical warfare: land-based lidar

The detection and prevention of chemical and biological warfare agents has always been one of the key projects concerned by the military. The traditional detection method is mainly carried by soldiers, and it is slow, inefficient and easy to be poisoned while walking. It is reported that Russia has successfully developed the "KDKHR- 1N" long-distance ground poison lidar detection system, which can detect and determine the oblique distance, center thickness, height from the ground, center angle coordinates and poison-related parameters of poison aerosol cloud in real time, and send an alarm to the army control system through wireless technology in time to take corresponding anti-virus measures. In this regard, the German military has also developed a more advanced "VTB- 1" telemetry lidar, which uses two 9 micron-1/micron CW CO2 lasers, which can be adjusted at 40 frequencies, and uses the principle of differential absorption spectrum to remotely measure chemical warfare agents, which is both safe and reliable.

Master of Flight Collision Avoidance: Airborne Lidar

Aircraft, especially helicopters, are prone to collide with hills or buildings on the ground when patrolling at low altitude, which is a major problem that many countries in the world attach importance to and try to solve. In recent years, the United States, Germany and France have vigorously developed helicopter obstacle avoidance lidar, which has successfully solved this problem. The earliest "obstacle avoidance radar" developed in the United States for helicopter flying at ultra-low altitude uses a solid-state laser diode transmitter and a rotating holographic scanner to detect the vast airspace in front of the helicopter. The ground obstacle information can be displayed on the airborne head-up display or helmet display in real time, thus ensuring the pilot's safe flight. Subsequently, the "Hellas" lidar successfully developed by Germany was even better. It is stereoscopic 1.54 micron imaging with a field of view of 32 degrees ×32 degrees. It can detect wires or obstacles with a diameter of 1 cm within a distance of 300 -500 meters, which can ensure flight safety. The pod "Clara" lidar jointly developed by France and Britain has many functions. Using CO2 laser, we can not only detect the tiny obstacles in front of the helicopter, such as posts and cables, but also track the terrain, target ranging and moving target indication to ensure flight safety. This kind of lidar is also suitable for aircraft.

An Expert in Capturing Underwater Targets: Ocean Lidar

The traditional way to alert, search, identify and track underwater targets is to use large and heavy sonar, which usually weighs 600 kilograms to dozens of tons. With the development of marine lidar, the airborne blue-green laser transmitting and receiving equipment, the detection of underwater targets is simple, convenient and accurate. Especially on the third generation laser radar successfully developed after 1990s, the functions of GPS positioning and altitude determination are added, and the automatic control of route and altitude is realized. For example, the "Alarm" airborne mine detection lidar developed by Northrop Company in the United States can work 24 hours a day and can accurately detect suspicious targets such as underwater mines. The underwater imaging lidar developed by Kaman Space Company in the United States has more advantages, which can display the shape and other characteristics of underwater targets and accurately capture them, so as to take emergency measures and ensure navigation safety.

In addition, lidar can also be widely used to counter electronic warfare, anti-radiation missiles, ultra-low altitude penetration, missile and shell guidance and mine clearance.