An explanation about the functioning of LiDAR lasers. We discuss the different measuring principles that are used by lasers and the possibilities for application that arise from it. The principles are: phase comparison, pulse back-mixing method and ToF (Time of Flight).

How does a LiDAR work?

To be able to measure the distance to an object or surface with a laser, it uses LiDAR (LIght Detection of Laser Imaging And Ranging) technology. The LiDAR laser emits a laser pulse to an object or surface. The pulse is then reflected. The distance is calculated based on the elapsed time between the emission of the laser pulse and receiving the reflection. 

Schematic explanation of the operation of LiDAR laser

The measuring principles of a LiDAR sensor

Phase comparison
Pulse back-mixing method
Time of Flight
Operation
1. Emits light at a certain wavelength. 2. Determines the receiving time with a comparator for a received signal. 3. Determines the phase shift (φ) between the emitted and received signals.
1. Emits a sequence of laser pulses. 2. Determines the time of receiving of the reflection signal. 3. High frequency sampling by counting emitted signals.
1. Emits a single light pulse and measures the time until the moment a reflection is received. 2. Determines the time of receiving with a comparator in order to calculate the distance.
Benefits
Very high measuring accuracy
– High-range for objects with low reflection – Small surfaces possible
– Short measuring time for objects with good reflection – High measuring frequency – Suited for scanning systems
Cons
Not optimal for moving objects
Long measuring time for surfaces with bad reflection. Not optimal for moving objects.
Configuring comparison tresholds, depending on ambient lighting. The measured value is dependent on the reflection of the object.
Measuring distance
Low: 0 to 50 m
High: 5 to 2000 m
Average: 5 tot 100 m (905 nm diode). Up to 10,000 m (1550 nm diode).
Measurement accuracy
High: ±3 mm
Low: ±100 mm
Average: ±100 mm ±5000 mm (1550 nm diode)
Measuring frequency
Low: 0.5 to 5 Hz
Low: 1 to 5 Hz
High: kHz area (905 nm diode) Hz area (1550 nm diode)

Application examples for a LiDAR laser

In addition to LiDAR lasers, there are also many other laser products. For example, Sensor Partners has an extensive range of distance lasers. The distance lasers from Sensor Partners can be used in many different industrial environments. Below are some examples of possible applications and which type of laser is most suitable.

Positioning containers in a loading bridge

Depending on the desired measuring range, the LAM 70 series and LAM 300 series can be used to prevent collisions or to position containers in ports or docks. With the help of these lasers, the operator of the harbor crane knows the exact position of the container relative to the crane. Another option for these series is to measure distances for mooring ships. For example, the LAM 70 can measure up to 270 meters (with reflector)!

Determining parking facilities

With the LAM 300 series from Sensor Partners, remaining parking spots can be measured in parking lots or truck rest areas. The laser measures the distance to the back of the last car or truck in a row, so that the number of free parking spaces behind the vehicle can be calculated.

Position detection of moving objects

To detect the position of objects with a high temperature, the LAM 70 series offers a suitable solution. The distance lasers can be used to determine the position of objects such as trains at train stations and other boarding places. The lasers provide assistance in decelerating the train to ensure that it is stopped at the correct position. Sensor Partners offers a reliable solution here in supporting automated trains.

Road management system

The LAM 70 and LAM 300 series can be used for traffic management. The lasers measure the distance to a vehicle to determine traffic jams or speed of passing vehicles, but also to detect tailgating. The laser detects the vehicle at two moments: the set distance and the moment it drives underneath the laser. These lasers are ideal for use in traffic because they are eye-safe (for the drivers) and have a high switching frequency that can keep up with fast passing traffic.

Level measurement in silos

There are applications, for example in a transshipment terminal, where it is necessary to determine the degree of filling of a silo. Think of silos that are filled with animal feed. When a new load of animal feed arrives, it must be distributed to the silos where sufficient storage capacity is available. By monitoring this with the laser distance sensors, the operator can read which of the silos is free and how many tons of animal feed can be dumped there.

Would you like to know more about the distance lasers from Sensor Partners? Feel free to contact one of our experts!

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