The principle of lidar is simple. LiDAR (Light Detection and Ranging) is a technology that uses laser pulses to measure distances, size and direction of objects. This process enables accurate 3D maps of the environment.

Introduction to 3D LiDAR sensor technology: principles, applications and future developments

Q: How does distance determination with LiDAR work?

In the time-of-flight principle, the distance to an object is determined by measuring how long it takes for light pulses emitted by a transmitter to be reflected and received by a receiver. The time between emitting and receiving the reflected photons provides insight into the distance to the object. This determines the distance to the object very accurately.

Q: What is a Point Cloud of a LiDAR?

A Point Cloud is a collection of millions of data points generated by a LiDAR sensor. These points represent the 3D structure of the environment and are updated several times per second to form a dynamic and detailed image.

Q: What is a solid-state LiDAR?

A solid-state LiDAR has no moving parts. The laser diodes and receivers are integrated on a chip (ASIC), which increases reliability and reduces wear and tear. These sensors are more compact, but often have a smaller opening angle and detection range.

Q: What is a hybrid solid-state LiDAR?

A hybrid solid-state LiDAR combines fixed components with limited mechanical motion, such as rotating mirrors. This provides a good balance between performance, cost efficiency and durability. They are often based on ASIC technology and offer a wide field of view and high resolution.

Q: What is a mechanical LiDAR?

Currently, the most widely used LiDAR sensor is still the mechanically rotating variant. In this, the laser channels are arranged vertically in an array mounted on a rotating platform. A motor rotates this platform, creating a 360° horizontal field of view. Traditional manufacturing of mechanical LiDAR systems is complex and time-consuming, resulting in relatively large dimensions and a higher purchase price.

Q: What are the strengths and weaknesses of different LiDAR types?

Mechanical: Large field of view (360°), but sensitive to wear and more expensive to manufacture. Solid-state: Compact and rugged, but limited range and field of view. Hybrid solid-state: Best balance of performance, cost and lifetime.

Q: Can LiDAR technology be integrated with existing production lines and assets?

Yes, LiDAR sensors are versatile and can often replace one or more traditional sensors. They improve machine efficiency and performance and can reduce system complexity.

Q: What applications can LiDAR sensors be used for?

LiDAR is applied in: Autonomous vehicles Automated Guided Vehicles (AGVs) Autonomous Mobile Robotos (AMRs) Drones Industrial Automation Stationary applications Service robots Security Logistics and warehouse management

If an industrial vehicle could drive itself, how would it perceive the world around it? As humans, we use our own eyes to pick up light and determine the distance, size and direction of objects.
The most commonly used technology for this is a 3D laser sensor, also called a LiDAR sensor.

What is a LiDAR and what does a LiDAR system consist of?

A LiDAR system consists of a laser, a receiver and a processor.

**How does LiDAR calculate the positions of objects and what role does time of flight in that?**

The LiDAR projects beams of light in different directions. When a beam hits the surface of an object, it is reflected back and picked up by the receiver.

By calculating the duration it takes light to travel back and forth, the processor determines the exact distance to the object. Because the speed of light is constant, this allows the distance to be determined very accurately. This principle is called Time of Flight (TOF).

So how can LiDAR systems combine high performance with reliability?

The key technical properties for a LiDAR sensor are range, resolution and accuracy.

The main factors influencing this are the number of laser channels, signal processing and efficiency of the transmit-receive module.

With the angle at which the laser is pointed and the distance measurement, we can calculate the position of the object.

Over time, it creates a collection of millions of data points that together form a detailed 3D image of the environment: a so-called Point Cloud. In order to safely drive autonomously in complex traffic situations, this Point Cloud are renewed at least ten times per second.

The way a LiDAR sensor generates a Point Cloud depends greatly on the type of sensor used.

The three main types of LiDAR sensors

LiDAR technology is available in several versions, each with unique features and application areas. Choosing a particular type of sensor depends on factors such as desired field of view, resolution, detection range, robustness and cost.

Solid-state LiDAR

Sensors with no moving parts, more compact and reliable, but with limitations in range and viewing angle. A solid-state LiDAR has no moving parts and therefore requires many laser channels to provide the same performance as mechanical variants. The many laser channels currently make the production of a solid-state LiDAR very expensive.

Mechanical LiDAR

Currently, the most common type of LiDAR sensor is still a mechanically rotating LiDAR. These are sensors with moving parts.

The laser channels are vertically aligned in an array. A motor rotates the mechanical rotating platform on which the laser array is mounted to achieve a 360° (horizontal) field of view.

Due to the limited number of vertical lasers, the density of the Point Cloud decreases as distance increases. The horizontal resolution also causes the Point Cloud in the horizontal plane in terms of density decreases as distance increases. To increase the resolution and detection range, you can add more transmit-receive modules and thus increase the number of laser channels. Another option is to run the motor more slowly. This will increase your horizontal resolution.

The traditional way to produce a mechanical LiDAR sensor is a complex and time-consuming manufacturing process. As a result, mechanical LiDARS are often large in size and relatively expensive to purchase.

Hybrid solid-state LiDAR

An alternative to the mechanical LiDAR is the hybrid solid state LiDAR, which operates with two mirrors rotating within a limited angle. This combination of fixed components and limited mechanical motion - in the form of rotating mirrors - provides a good balance between performance and cost efficiency....

The heart of this hybrid LiDAR consists of a rotating polygonal mirror and a swinging mirror. The polygonal mirror provides horizontal scanning, while the swinging mirror deflects the beams vertically.

Thus, one laser can create a scanning pattern similar to that of a mechanical LiDAR with multiple lasers.

To scan a full image with a single laser requires an extremely high speed. Whereas a mechanical LiDAR spins ten or twenty times per second, the mirror of an ASIC-based single-laser LiDAR must spin hundreds to thousands of times per second.

What is Field of View?

For applications in autonomous vehicles, drones and stationary security solutions, a LiDAR sensor must have a wide field of view (Field of View, FoV) cover. The FoV refers to the horizontal and vertical viewing angles within which the LiDAR sends out and receives back its laser pulses.

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What is the ideal LiDAR solution?

We can say that the fewer moving parts integrated into a sensor, the longer the lifetime of the sensor could theoretically be. This is because mechanical parts are always subject to wear and tear, which limits the lifetime of the sensor to a greater extent than the lifetime of the electronics components.

Image: ThePandar 128is a mechanical LiDAR with the transmitter and receiver modules integrated on a rotating platform.

For a traditional mechanical LiDAR, where the transmitter and receiver modules are integrated on a rotating platform, this is certainly the case. Here, as a rule, the lifetime is limited by the motor and bearings that keep the platform in place and rotating. In addition, producing such a rotating platform is very complex. The construction must be perfectly balanced to reduce friction on the shaft of the motor and bearing. This is important to prevent heat build-up and wear on these mechanical parts from drastically reducing the lifetime of the sensor. When constructing laser arrays with transmitter and receiver diodes, the precise alignment of the diodes is a particularly complex and largely manual part of the manufacturing process, making it costly.

An ideal solution would be a LiDAR sensor with no moving parts. In other words, a solid-state LiDAR sensor. The caveat to this is that a solid-state LiDAR sensor also has its limitations. In particular, the electronics and optics of a solid-state LiDAR sensor are more complex than those of a mechanical LiDAR sensor, making the production cost of a solid-state LiDAR relatively high. Another limitation is that a solid-state LiDAR often has a limited aperture angle and smaller sensing range than a mechanical LiDAR. This is because, in particular, the transmitter module is a chip on which a matrix of very small laser diodes are integrated.
Due to their size and optical power, these laser diodes have a smaller range than the individual (larger) laser diodes stacked together in a mechanical LiDAR.

Image: solid-state LiDAR FTX

There are then two options for further building the sensor. For hybrid solid-state sensors that require a large sensing range but not a 360° field of view, the laser pulses emitted by the transmitter ASIC are guided into space by means of 2 rotating mirrors, and the reflections also return to the receiver ASIC by means of the same two mirrors.

Pictured above: ASIC

This is a very robust and relatively simple construction because you only have two small mirrors as moving parts inside the sensor. This simplifies the construction and mechanics of the sensor, which benefits production. This way of building the LiDAR sensor means that this type of sensor can be produced relatively cost-effectively, without sacrificing performance.

Image: theOT128is a new generation of mechanical lidars based on innovative ASIC technology.

Mechanical LiDAR sensors with 360° field of view also using the innovative transmitter and receiver ASICs from hybrid solid-state LiDAR sensors are very much on the rise. The ASICs are integrated on the rotating platform as we know from the traditional mechanical LiDAR sensors. Again, the advantage is that the assembly, construction and manufacturing of the rotating platform has become a lot less complex. In addition, by using the ASICs, the size and weight of the rotating platform can be drastically reduced. This in turn benefits the load on the bearings and motor that must carry and rotate the platform. The result is a smaller LiDAR sensor that offers the same performance as a traditional mechanical LiDAR, but at a drastically lower cost.

The innovative ASICs bring together the best of both worlds. Currently, in many situations, the best LiDAR solution is an ASICs-based hybrid solid-state or mechanical LiDAR sensor.

3D LiDAR sensors are among the most important innovations in the sensor market in recent decades. Developments within the LiDAR market are rapid: they are becoming better, more compact and more affordable. Therefore, it is only a matter of time before they are used on an increasingly large scale in a variety of applications.

The versatility of LiDAR sensors makes them widely applicable. In many cases, they can already now take over the functions of one or more traditional sensors with a single sensor. In some situations, it is even now possible to switch to a LiDAR sensor because they can significantly improve the efficiency and performance of a machine or application. At the same time, the cost and complexity of those systems can be reduced and simplified.