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What is LiDAR and how does it work?

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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