Find Us In Booth W60

What is LiDAR and how does it work?

Table of Contents

What is LiDAR? And what does LiDAR stand for?

LiDAR stands for Light Detection and Ranging. It is a remote sensing technique that measures distances and creates precise three-dimensional maps of the environment using laser light.

The method works by directing laser beams at a target and then measuring the time it takes for each beam to return to the sensor. A LiDAR system can generate accurate and precise three-dimensional representations of the target by estimating the distance travelled by each laser beam.

How does LiDAR work? Different LiDAR working principle

Time of Flight

The principle of ranging is currently mainly based on the time of flight (time of flight) method, which uses the time interval between the pulse signal emitted by the transmitter and the reflected pulse signal received by the receiver to calculate the distance to the target object. Please find the indication of Time of Flight principle for details. 

Time of Flight LiDAR
Time of Flight Principle

Distance = Speed of Light*(t2 – t1)/2

Time of Flight LiDAR is mainly used for perception unit for autonomous driving, robotics, V2X and surveying application. Learn more details >>. 

FMCW - Frequency Modulated Continuous Wave

Taking triangular wave frequency modulated continuous wave as an example to introduce its ranging/speed measurement principle. Blue is the frequency of the transmitted signal, red is the frequency of the received signal. The emitted laser beam is repeatedly modulated, and the signal frequency is constantly changing. The laser beam hits an obstacle and is reflected. The reflection affects the frequency of the light. When the reflected light returns to the detector, compared with the frequency when it was emitted, the difference between the two frequencies can be measured, which is proportional to the distance. Calculate the position information of the object. The frequency of FMCW’s reflected light changes according to the speed of the moving object in front. Combined with the Doppler effect, the speed of the target can be calculated.

what is LiDAR - FMCW LiDAR work principle
Triangular LiDAR Principle

AMCW - Amplitude-Modulated Continuous-Wave

Amplitude-modulated continuous-wave (AMCW) lidars are similar to basic time-of-flight systems in that AMCW lidars emit a signal and measure the time it takes for the laser light to reflect back. But the difference is that time-of-flight systems emit only one pulse, while AM CW LiDAR achieves modulation by changing the pole current in the laser diode to adjust the intensity of the emitted light.

Triangular LiDAR

what is LiDAR triangular lidar
Triangular LiDAR Principle

During each ranging, the LiDAR’s pulse modulated laser emits an infrared laser signal, which generates a reflected light spot after irradiating the target object. The light spot is received by the LiDAR’s image acquisition and processing system after passing through a set of optical lenses and is then solved in real time by the LiDAR’s embedded signal processing module. The distance between the target object and the LiDAR and the relative azimuth values are output from the communication interface.

Doppler LiDAR

Doppler LiDAR (Light Detection and Ranging) is a sophisticated technology that measures the speed and direction of objects by using the Doppler effect applied to light waves, typically lasers. Here’s how it works:

  1. Emission of Light: Doppler LiDAR systems emit laser light towards a target. This light is usually in the infrared spectrum and is invisible to the naked eye.

  2. Reflection and Return: The light pulses bounce off particles (like dust, moisture, or other atmospheric constituents) or objects and return to the LiDAR system. The time taken for the light to return is measured to calculate the distance of the object.

  3. Frequency Shift: When the light wave bounces off a moving object, its frequency changes. This phenomenon is known as the Doppler effect. If the object is moving towards the LiDAR system, the frequency of the reflected light increases (shifts to blue). If the object is moving away, the frequency decreases (shifts to red).

  4. Speed and Direction Calculation: By analyzing the change in frequency (or wavelength) of the returned light, the LiDAR system can calculate the speed and direction of the object relative to the LiDAR’s position.

  5. Data Processing: The processed data can provide detailed information about the speed and movement of objects or particles in the atmosphere. This information is essential for applications like meteorology (to study wind patterns), autonomous vehicles (for obstacle detection and navigation), and aircraft navigation systems.

How Doppler LiDAR Calculates Wind Speed and Direction

What can we use LiDAR and its data for?

how is lidar data collected?

LiDAR (Light Detection and Ranging) data is collected using a process that involves emitting light pulses and measuring the time it takes for them to return after hitting an object or surface. This technology is often used to create detailed three-dimensional information about the shape of the Earth and its surface characteristics.

Some LiDARs, like wind measurement LiDARs use Doppler Effect to measure the moving speed of the aersols in the air to measurement wind speed for renewable and atomospheric monitoring projects. 

LiDAR data can be applied across different industries and fields.

Autonomous Vehicles

LiDAR systems are crucial for autonomous vehicles, as they provide precise information about the vehicle’s surroundings. The data gathered by LiDAR helps self-driving cars detect obstacles, navigate safely, and make informed decisions on the road, such as Automated Forklift or AGV

automated guided vehicle automated forklift SFL CDD16
Automated Forklift

Mapping and Surveying

LiDAR is commonly used for topographic mapping and surveying. It provides highly accurate and detailed elevation data, which is valuable for creating maps of land surfaces, including forests, wetlands, and urban areas.

>>Learn more about LiDAR surveying applications. 

LiDAR Surveying Deliverables

Forestry and Agriculture

In forestry, LiDAR helps measure forest biomass, canopy structure, and tree height, aiding in forest management and conservation efforts. In agriculture, LiDAR helps monitor crop health, optimize irrigation, and assess land suitability for farming.

>>Learn more about LiDAR Forestry surveying applications. 

LiDAR Forestry Survey

Energy Sector

In the energy sector, LiDAR is used to assess the potential of wind and solar energy projects. It helps in the planning and design of wind farms and solar power plants by providing detailed information about the terrain and sunlight availability.

LiDAR Application for Renewable Projects

Civil Aviation

Doppler LiDAR systems are used to measure wind shear around the aircraft glide path and vortex generated by giant aircraft like A380 or B747. This information is critical for air traffic control and pilots, particularly during takeoff and landing.

LiDAR systems can detect and map obstacles like buildings, towers, and natural terrain features around airports. This information is vital for creating obstacle limitation surfaces, which are essential for flight safety.

Molas 3D Doppler Scanning Wind LiDAR Improves The Civil Aviation Safety and Efficiency
LiDAR For Civil Aviation

LiDAR can also be applied for disaster management, archaeology, and environment monitoring. 

Disaster Management

LiDAR can be used to assess the impact of natural disasters such as floods, earthquakes, and landslides. It helps in disaster planning and mitigation by providing accurate information about the affected areas.

Archaeology

LiDAR technology is used in archaeology to detect and map ancient structures and landscapes. It helps uncover hidden archaeological sites without the need for extensive excavations.

Environmental Monitoring

LiDAR is used to monitor environmental changes, such as deforestation, erosion, and changes in land cover. It provides valuable data for researchers studying climate change and its impacts on the environment.

Different LiDAR Technology & types

Lidar is a system that integrates three technologies: laser, global positioning system (GPS), and IMU (inertial measurement unit). Compared with ordinary radar, lidar has higher resolution, better concealment, and stronger anti-interference ability. Advantage. With the continuous development of science and technology, the application of lidar is becoming more and more widespread. It can be seen in fields such as robots, driverless cars, and unmanned vehicles. If there is demand, there will be a market. As the demand for lidar continues to grow, As the number of laser radars increases, the types of laser radars have also become dazzling. Lidars can be divided into different types according to their use functions, detection methods, load platforms, etc.

LiDARs classified by functions

Ranging LiDAR Techology

Ranging LiDAR determines the distance between the measured object and the test point by emitting a laser beam to the measured object, receiving the reflected wave of the laser beam, and recording the time difference. Traditionally, lidar can be used in the field of industrial security detection, such as the laser walls seen in science fiction movies. When someone breaks in, the system will respond immediately and issue an early warning. In addition, laser ranging LiDAR is also widely used in the field of surveying and mapping. However, with the rise of the artificial intelligence industry, laser ranging radar has become an indispensable core component of the robot. When used with SLAM technology, it can help the robot perform real-time positioning and navigation and achieve autonomous walking.

Laser speed measurement LiDAR technology

Laser speed LiDAR measures the moving speed of an object. By performing two laser ranging measurements on the measured object with a specific time interval, the moving speed of the measured object is obtained.

There are two main categories of lidar speed measurement methods. One is based on the principle of lidar ranging, that is, the target distance is continuously measured at a certain time interval, and the target distance can be known by dividing the difference between the two target distances by the time interval. The speed value and the direction of the speed can be determined based on the positive or negative value of the distance difference. This method has a simple system structure and limited measurement accuracy, and can only be used for hard targets with strong reflective lasers.

Another type of speed measurement method uses Doppler frequency shift, and the LiDAR uses this technology is call doppler LiDAR. Doppler frequency shift means that when there is a relative speed between the target and the lidar, there will be a frequency difference between the frequency of the received echo signal and the frequency of the transmitted signal. This frequency difference is the Doppler frequency shift. This technology is widely used for wind and atomospheric monitoring LiDARs

Imaging LiDAR

Laser imaging radar can be used to detect and track targets, obtain target orientation and speed information, etc. It can complete tasks that ordinary radar cannot complete, such as detecting submarines, mines, hidden military targets, etc. It is widely used in military, aerospace, industrial and medical fields.

Atmospheric detection liDAR

Atmospheric detection LiDAR is mainly used to detect molecules in the atmosphere, the density of smoke, temperature, wind speed, wind direction and the concentration of water vapor in the atmosphere, in order to monitor the atmospheric environment and forecast disastrous weather such as storms and sandstorms. 

Learn more about Atmospheric detection lidar.

Tracking LiDAR

Tracking LiDAR can continuously track a target, measure the coordinates of the target, and provide the target’s movement trajectory. It is not only used in artillery control, missile guidance, external ballistic measurement, satellite tracking, penetration technology research, etc., but also in the fields of meteorology, transportation, scientific research and other fields.

LiDARs classified by work mediums

Solid LiDAR

The peak power of solid-state lidar is high, the output wavelength range matches existing optical components and devices, and the long output range matches existing optical components and devices (such as modulators, isolators and detectors) and atmospheric transmission characteristics, etc., and The ease of implementing a master oscillator-power amplifier (MOPA) structure, coupled with conductors such as high efficiency, small size, light weight, high reliability and good stability, has given priority to solid-state lidar applications in airborne and space-based systems. In recent years, the focus of lidar development has been diode-pumped solid-state lidar.

Gas LiDAR

Gas lidar is represented by CO2 lidar. It works in the infrared band, has small atmospheric transmission attenuation and long detection range. It has played a great role in atmospheric wind field and environmental monitoring. However, it is large in size and uses mid-infrared HgCdTe detection. The device must work at a temperature of 77K, which limits the development of gas lidar.

Semiconductor LiDAR

Semiconductor lidar can work continuously at a high repetition rate. It has the advantages of long life, small size, low cost and little damage to the human eye. It is widely used in Mie scattering measurements where the backscattering signal is relatively strong, such as detecting cloud base height. Potential applications of semiconductor lidar are measuring visibility, obtaining aerosol extinction profiles in the atmospheric boundary layer and identifying rain and snow, etc. It can be easily made into airborne equipment. Currently, the CT25K laser cloud meter developed by Finland’s Vaisala Company is a typical representative of semiconductor cloud measurement lidar, and its cloud base height measurement range can reach 7500m.

LiDARs classified by Number of Lines

Single line LiDAR or 2D LiDAR scanner

Single-line lidar or 2D LiDAR scanner is mainly used to avoid obstacles. It has fast scanning speed, strong resolution and high reliability. Since single-line lidar reflects faster in angular frequency and sensitivity than multi-line and 3D lidar, it is more accurate in testing the distance and accuracy of surrounding obstacles. However, single-line LiDAR can only scan in a plane manner and cannot measure the height of objects, which has certain limitations. Currently it is mainly used in service robots, such as our common sweeping robots.

2D LiDAR Point Cloud

Multi line LiDAR or 3D LiDAR scanner

Multi-line lidar, or 3D LiDAR scanner, is mainly used for automotive, robotics, or surveying LiDAR imaging. Compared with single-line lidar, it has made qualitative changes in dimensionality improvement and scene restoration, and can identify the height information of objects. Multi-line lidar is conventionally 2.5D and can be 3D. Currently, the main ones launched in the market are 16-line, 32-line, 128-line,or even more. But the price of the 3D LiDAR sensors has significantly dropped as well.

3D LiDAR Point Cloud

LiDARs classified by scanning methods

LiDAR classifications are diverse, and this article will introduce the classification of LiDARs according to scanning methods.

Mechanical LiDAR Technology

The transmitting and receiving modules of the mechanical rotating Lidar rotate in a macro sense. Multiple groups of laser line beams are arranged in the vertical direction. The transmitting module emits laser lines at a certain frequency, and dynamic scanning is achieved by continuously rotating the transmitting head.

Mechanically rotating Lidar’s discrete transceiver components requires manual optical path alignment during the production process, which is time-consuming and labor-intensive, and has poor mass production. At present, some mechanical rotating lidar manufacturers have taken the chip route, integrating multi-line laser emitting modules into one chip to improve production efficiency and mass production, reduce costs, reduce the size and volume of rotating parts, and make it easier to process automotive regulations.

LS C16 Mechanical LiDAR Structure Inside
Pros of Mechanical LiDAR
  • Technology is mature
  • Fast scanning
  • 360 degree scan
Cons of Mechanical LiDAR
  • Poor mass production: complex optical path debugging and assembly, low production efficiency
  • Expensive: By increasing the number of transceiver modules to achieve a high scanning channels, the cost of components is high.
  • Difficulty with automotive standard regulations: The rotating parts are large in size/weight and difficult to meet the stringent requirements of automotive standard regulations.
  • The shape is not easy to integrate into the car body

Hybrid Solid State LiDAR scanner

Hybrid solid-state lidar uses “micro-moving” devices to replace macro-mechanical scanners to achieve laser scanning at the LiDAR transmitter on a microscopic scale. The reduction in rotation amplitude and volume can effectively improve system reliability and reduce costs.

MEMS LiDAR scanner
What is MEMS LiDAR scanner? What does MEMS stand for?

MEMS stands for MicroElectroMechanical Systems. LiDAR that uses MEMS mirror-based scanning technology is called MEMS LiDAR, which has unique benefits over other types of laser scanners in terms of size, speed, and cost, making them perfect for LiDAR in a wide range of applications. 

MEMS galvanometer is a silicon-based semiconductor component, which is a solid-state electronic component. It integrates a very compact micro-galvanometer on a silicon-based chip. Its core structure is a very small cantilever beam – the mirror is suspended on the A pair of torsion bars on the front, back and left oscillate at a certain harmonic frequency, and the rotating micro-mirrors reflect the laser light to achieve scanning. The silicon-based MEMS micromirror has good controllability and can achieve fast scanning. Its equivalent line beam can be as high as one to two hundred lines. Therefore, when the same point cloud density is required, the number of laser emitters of the silicon-based MEMS Lidar is lower than that of the mechanical rotating one, with smaller dimensions and high reliability as well. 

Pros of MEMS LiDAR
  • MEMS micro-vibration mirrors get rid of mechanical motion devices such as bulky motors and multiple transmitting/receiving modules. Millimeter-sized micro-vibration mirrors greatly reduce the size of lidar and improve stability.

  •  

    MEMS micro-mirrors can reduce the number of laser emitters and detectors, greatly reducing costs

Cons of MEMS LiDAR
  • The limited optical aperture and scanning angle limit Lidar’s ranging capabilities and FOV. A large field of view requires multi-subfield splicing, which requires high point cloud splicing algorithms and point cloud stability.

  •  

    Impact and vibration resistance is questionable at the stage

Rotating scanning mirror LiDAR scanner

As the first mass-produced L3 level autonomous passenger car, the lidar equipped on the Audi A8 is a rotating scanning mirror lidar. Unlike mechanical rotating lidar, its laser transmitting module and receiving module are stationary, and only the scanning mirror is mechanically rotating. The laser unit emits laser light to the rotating scanning mirror (Mirror), which is deflected forward (scanning angle 145°). The light reflected by the object is received by the detector on the lower left through the optical system.

Pros of Rotating scanning mi