Application of Laser Range Sensor

In front of us, we learned about the principle and characteristics of several major ranging/distance sensors. Among them, laser ranging sensors have enjoyed great advantages due to their strong anti-interference ability and high precision. Since their inception, they have achieved great development. Industry has played a huge role.

Shortly after the world’s first ruby laser was introduced in 1960, laser ranging technology with its main function of precision ranging was born.

The first ruby laser

After more than 50 years of development, its development is roughly reflected in two aspects: First, the application of various new technologies and equipment to improve the distance measurement accuracy and the amount of observation data; secondly, to improve the degree of automation of the ranging system and reduce manpower and material resources. Consumption. Specifically:

1. In ranging accuracy, from the initial level of meters to the decimeter level, centimeter level, the current international most advanced stations can reach the millimeter level.

2. In terms of distance measurement capability, the distance from the first farthest 1000 to 2000km has been raised to 20,000km and even 36,000km. The laser measurement of the moon has achieved a distance of 380,000 km.

3. In the ranging frequency, from the first time per second to the current 1000 to 2000 times per second, higher frequency laser ranging (such as 10 kHz ranging) is also under test.

4. At the wavelength of distance measurement, monochromatic distance measurement systems are still widely used at present, and some stations are also using dual-color/multi-color laser ranging systems. The dual-wavelength laser ranging system no longer requires the modification of the atmospheric physical parameters and the atmospheric model, and only the measurement result itself can modify the atmospheric delay, and better data accuracy can be achieved.

5, in the degree of automation, from the initial artificial visual tracking, to today's computer control, automatic tracking.

Application of Laser Range Sensor in Cosmic Space Exploration

Space laser ranging technology plays an important role in monitoring the motion of continental plates, deformation of crust, rotation of the earth, improving the gravitational field and the gravitational constants of the Earth, determining the regularity of earth and ocean tide changes, and monitoring space debris. It is also one of the main methods for precise positioning observation of high-precision satellites. It is one of the highest single-point sampling accuracy among various modern positioning observation methods, and is one of the technical means of supporting International Earth Rotation and Reference System Service (IERS). Satellite laser ranging technology has achieved remarkable results in the following applications and has broad application prospects.

Precisely measuring the orbit of laser satellites

The accuracy of the orbit determined by the satellite's laser observation data can reach 1cm in 3 days and 2 to 2.5cm in radial orbit.

Accurate Measurement of Earth's Gravitational Field Model and Its Time Variation

In the process of studying the positional change of the earth's centroid, laser technology determines the most accurate gravitational constant of the earth, GM, and its measured value is: GM = 39,860.4415km3/s2; the use of laser satellites with different orbit inclinations and altitudes to accurately determine the Earth's gravity The field model determines the seasonal variation of the low-order spherical harmonic coefficients of the Earth's gravitational field; at the same time, it also obtains the periodic changes in the location of the Earth's centroid, including seasonal and interannual variations. The latest measurement is: J2=-2.6 *10-11/year (epoch 1986.0); The change in Earth's gravitational field reflects the complex movements and interactions within the Earth's interior and in all spheres (including the ocean, atmosphere, groundwater, ice, etc.) and has important research value.

Accurate determination of earth rotation parameters

The Earth's rotation parameter (ERP) defines the Earth's rotation axis and its directional motion over time and its rotational speed in the celestial sphere reference frame. Earth rotation parameters include polar shifts and changes in day length (LOD). The accuracy of the Earth's polar shift component (XP, YP) measured by laser tiger measurement technology has now reached 0.1 to 0.2 mas; the accuracy of the measurement of day length (LOD) has now reached 0.1 ms.

Monitoring global crust movement

The long-term observation data of the laser can accurately determine the geocentric coordinates of the ground station. The resolution of the high-precision station coordinates makes it possible to monitor the movement of the plate. Using the data obtained from laser ranging technology, station speeds and station-to-station baseline rate of change for more than 40 stations have been estimated. If the station is located in the rigid part of the plate, its station speed represents the plate movement. The relative motion between plates can be solved by using the rate of change of the station baseline and the station speed.

High-accuracy measurement of sea level and ice cover topography

The combination of laser ranging technology with other space technologies (such as GNSS, radar altimeters, SAR, etc.) will enable measurement of millimeter-level sea level and ice sheet topography.

Space debris orbit determination and monitoring

The use of laser ranging technology can accurately determine the space debris, determine the location of debris orbits, and provide precise orbit information for space debris monitoring and space collision warning systems.

Application of Laser Distance Sensor in Military Field

Lightweight portable pulse laser rangefinder

Lightweight portable pulsed laser rangefinders include hand-held and forward-looking reconnaissance for infantry and artillery reconnaissance and FAC dual purpose laser rangefinder target indicators. The above-mentioned systems require agility, repetition, lightness, small size, use of battery packs as a power source, high reliability and maintainability, and low cost of a single product.

In modern warfare, from the previous single infantry and artillery to independent warfare and development to joint operations of special forces consisting of infantry, artillery, and Marine Corps, the weapon system has also gradually adopted multi-functional integrated high technology from a single ground and artillery. Therefore, the laser range finder is also developed from a portable, hand-held device with a single ranging function to a laser ranging, an infrared sighting day/night sighting device, a laser ranging, a target indication, an infrared infrared target laser infrared target indicator, and the like.

Ground vehicle pulsed laser rangefinder

Ground vehicle pulsed laser rangefinders include tanks, Infantry Fighting Vehicles (IFVs), fire control, air defenses, artillery or missile guided fire control, and current developments of ground vehicle laser rangefinders—target indicators. The main technical performance: the maximum measuring range of 4 ~ 10km, ranging accuracy ± 5 ~ 10m, the target resolution of about 20m, the repetition rate of 0.1 ~ 1Hz, beam angle of 0.4 ~ 1mrad.

The application of the laser range finder in the tank fire control system is to provide the ballistic path's super elevation angle correction information and the azimuth correction information and distance information caused by the upwind or target movement. Infantry combat vehicles use laser rangefinders to measure whether targets are within the distance of anti-tank missiles, followed by gun fire control and target sorting.

Penetration of empty artillery and missile defense laser rangefinders

The air defense pulse laser range finder and the self-protected infantry tank air defense pulse laser range finder should work according to the requirements of the fire control system and the combat system, and the airborne high speed manoeuvres are within the range and distance rates. The goal is to provide stable tracking information and distance information to counter the threats of armed helicopters, stealth aircraft and cruise missiles, and anti-radiation missiles.

This requires the laser rangefinder to provide a relatively high data rate (high laser pulse rate) and a very high distance accuracy, such as the maximum range of 4 ~ 20km, ranging accuracy of ± 2.5 ~ 5m, repetition rate of 6 ~ 20Hz The beam angle is 0.5~2.5mrad.

Airborne pulse laser rangefinder

The on-board pulsed laser rangefinder can be used to equip armed helicopters with missile-command guidance and equipped with fixed-wing aircraft for blocking targets such as supported opto-electronic aircraft and intercepting aircraft and missile attacks.

The main technical performance of the airborne pulse laser range finder is that it has a long range, high range accuracy, high repetition rate, and small beam spread angle. At the same time, the onboard equipment should be small and lightweight and should be shared with aviation indicators.

Therefore, the laser must use high-efficiency circulating liquid as a cooler to meet the high operating speed requirements, or else use gas or mixed gas boost cooling.

Shipborne pulse laser rangefinder

The development of ship-borne pulsed laser rangefinders has evolved from lightweight portable, vehicle-mounted and air-defense laser rangefinders. It includes two major categories of surface carrier and submarine periscope.

The surface-borne pulsed laser range finder has the same technical performance indicators as the on-board fire control and air defense laser range finder, and it must be adapted to the loading requirements of seaborne air, sea surface, and sea salt fog on the ship's environment. The requirements for volume, weight, electrical efficiency, maintenance capability and cost are not harsh.

Therefore, a large number of naval vessels currently equipped with conventional fire control and air defenses, such as cover (silent radar) ship-based aircraft recovery and infrared thermal imaging, television and other tracking systems, all-weather surveillance and tracking of air targets and other unique ships Applications are emerging and their application prospects are quite extensive.

Submarine periscope pulse laser range finder currently uses two combinations. The first one installs a laser range finder, an image intensifier, and a thermal imager in its periscope, and distance indicators, trigger buttons, etc. are installed above the operator. Or nearby.

The advantage is that the loss of laser light in the transmission light path is small, but the light beam drifts, it is not easy to capture the target; the second part is to install the three parts above the bottom of the periscope, the installation, debugging and disassembling of the whole system are very convenient, but the laser adopts this method. The beam passes through a 12m long periscope tube and 15 to 20 lenses, which causes a large loss of energy.

Cloud high pulse laser rangefinder

The instrument used to measure the vertical height of clouds using a pulsed laser range finder is called a cloud high laser range finder. This type of laser range finder is mainly used to measure the height of clouds at the airport. It can also be used to measure the height of clouds at satellite launch points and provide safe meteorological data for aircraft take-off and landing or satellite launch.

This type of pulsed laser distance meter can provide reliable meteorological data for the security of leading military bases, airports or military satellite launch points (close distances) and is an indispensable instrument for modern warfare; if it is used for large international airports, small commercial civilian use Airport and civilian communication satellite launch points (close distances) provide safe weather data for aircraft take-off and landing or satellite launch, which will have enormous economic and social benefits for the national economic construction and the improvement of international reputation.

Application of Laser Distance Sensor in Intelligent Transportation

Some possible applications of laser ranging technology in IOT-based intelligent transportation mainly include: laser speed sensors, automobile collision avoidance systems, traffic flow monitoring, model drawing, illegal monitoring of vehicle pedestrians, and other applications in precision monitoring and measurement.

Car crash detector

In general, laser distance sensors of most existing automotive crash prevention systems use a laser beam to contactlessly identify the distance between a car in front of or behind a target car, when the car distance is less than a predetermined safety distance The car anti-collision system can make emergency brakes to the car, or issue an alarm to the driver, or comprehensively judge the speed and distance of the target car, car braking distance, response time, etc., and can respond to the car's driving in real time, which can greatly reduce traffic accidents. . The advantages of using it on the highway are even more obvious.

Traffic monitoring and contouring

This method of use is generally fixed to a gantry at a high speed or at an important intersection. Laser emission and reception are perpendicular to the ground and are aligned with the middle of a lane. When a vehicle passes, the laser ranging sensor can output the measured value in real time. The relative change in the distance value, in turn, depicts the contour of the car being tested.

This measurement method generally uses a ranging range of less than 30 meters, and requires a relatively high laser ranging rate, generally required to reach 100 Hz.

This can achieve very good results for monitoring on important road sections. It can distinguish various models and the sampling rate of the body height scan can reach 10 centimeters. The high limit of traffic flow, limit length, vehicle type, etc. can be distinguished in real time, and the results can be quickly output.

When no vehicle arrives, the laser ranging sensor measures a distance constant, which is the distance from the laser ranging sensor to the ground. When a vehicle passes under the laser ranging sensor, the distance value changes, and when the distance value is again To the constant, we think that there is a car passing. According to this method, we can monitor the flow of traffic through some road sections.

The commonly used method is a statistical average method for traffic flow over a period of time, with a large estimation component, and the video statistics method has many practical difficulties. Therefore, the laser ranging statistical method provides traffic statistics. A feasible solution.

Pedestrian Illegal Monitoring

Since the beam of the laser ranging sensor is not a substantial obstacle, the use of a laser ranging sensor to monitor the road will not hinder the normal operation of the traffic.

Therefore, in some road sections that are forbidden to stop or prohibit pedestrians from passing through the vehicle, laser beams are used to carry out fixed launches at certain heights in parallel with the road or to scan at a certain angle. When there is a vehicle that illegally parks a red light or a pedestrian crosses the guardrail illegally, laser ranging The distance value can be changed to alarm or warning.

This kind of application beam is not necessarily too wide, but it generally requires a relatively long range distance to ensure the protection distance of the length of a certain road segment. The intelligent traffic violation monitoring system constructed in this way will find great application in the traffic internet of things.

Laser speed sensor

Laser ranging sensor is the earliest form of laser ranging technology in the field of traffic management. Because of its excellent performance, it has gradually gained popularity in practical applications. The laser distance measuring sensor is a laser distance measurement principle. It is a laser distance measurement with a specific time interval on the object to be measured, and the distance of the measured object is changed during this time interval to obtain the movement of the measured object. speed.

Laser speedometer is divided into fixed and mobile two kinds, fixed type is generally fixed on the roadside or gantry, with a relatively small angle to the arrival of the car, generally measured by the license plate reflection, measurement accuracy is relatively high, can Achieves ± 1 km/h, speed range up to 250 km/h, ranging range is not too large in this application, generally 80 to 100 meters.

The mobile laser speedometer has relatively high operating requirements, and the general beam divergence angle is greater than 3 mrad. In view of the principle of laser speed measurement, the laser beam must aim at the plane and the laser beam's plane reflection point, and because the vehicle is moving, the body plane Not much, and the speed requires a certain time, only as a temporary speed, forensics applications.

The laser ranging sensor has a small beam divergence angle, which is convenient for speed measurement and forensics. Unlike radar Doppler anemometers, it is impossible to ascertain the speeding specific vehicle in multi-lane measurement, and since the laser speed sensor emits near-infrared light waves, It cannot be probed by radar detectors, electronic dogs, etc., and is not easily disturbed by radar noise in the urban area.

In the hottest unmanned area at present, it is also a place for laser ranging sensors.

One of the prominent features of Google’s driverless cars is the rotary laser rangefinder above the roof. The rangefinder emits 64 laser beams to help cars identify potential hazards on the road. The intensity of this laser is relatively high, and it is possible to calculate the distance of an object within 200 meters and create an environment model.

Google Unmanned Car

According to Sebatian Thrun, the chief engineer responsible for the driverless car project, the core of the entire system is the Velodyne 64-beam on the roof. When the device rotates at high speed, it emits 64 laser beams to the surroundings. When the laser hits the surrounding objects and returns, the distance between the vehicle body and the surrounding objects can be calculated.

The computer system then draws a detailed 3D topographic map based on these distance data, and then combines it with a high-resolution map to generate different data models for onboard computer systems.

The laser rangefinder on the top of the car is the core of the whole system

3D terrain map drawn by the driverless system

to sum up

In fact, the range of application of laser ranging sensors is far from these, it is also widely used: electricity, water conservancy, communications, environment, construction, geology, policing, fire, demolition, navigation, railways, anti-terrorism/military, Agriculture, forestry, real estate, leisure/outdoor sports and other fields.

At present, the laser ranging technology is more and more in the direction of miniaturization, simple structure, high precision and high application range. Especially with the development of digital processing technology, laser ranging technology will become more perfect. Such as the introduction of advanced background noise suppression technology and triangulation technology, laser ranging sensors can work better under more complicated conditions. We believe that with the development of technology, laser ranging sensors and laser ranging technology will surely become more and more widely used.