LiDAR
The automotive industry has a clear vision: Vehicles of the future should be able to move about in traffic completely autonomously. In doing so, the car must be able to perceive its surroundings much better than it does today. Bühler, with its coating technology, is part of this development. Coated sensors will be the eyes of the vehicles of the future.
August 2019
Since its invention driving a car has entailed a person maneuvering a steering wheel while peering over it to decide where the machine should go. Of course, more cognitive skills and strategies come into play to handle the many eventualities that one encounters in traffic and which require intelligent decisions. Events such as when a chicken crosses the road, a motorcycle rider passes from the right in heavy traffic, or an oncoming vehicle cuts a turn too sharply. All of these events are perceived by the driver and a decision is made based on past experience.
For some time now, the automotive industry has been researching how traffic situations, with all of the various participants, can be made safer. Emergency braking assistance, improved rearview mirrors, and intelligent headlights have been developed for this purpose. These are functions that assist people during driving and help them to better anticipate and overcome dangers.
“Today, the industry is facing another revolution. The car, more and more, is expected to be able to not only assist the driver, but also to make decisions for them,” explains Dr. Steffen Runkel, Head of Optics at Bühler Leybold Optics. “Adaptive cruise control slows down when the car comes too close to the vehicle in front of it, the blind spot assistant warns of vehicles approaching from the side, the lane assistant notifies the driver when the car unintentionally drifts to the edge of the lane.”
The technology that makes it possible for the car to be equipped with additional optical nerves comes from the semiconductor industry. Sensors scan the environment and estimate distances or perceive objects – the vehicle learns through them to perceive the environment itself.
Sensors are only as good as their coating Sensors are placed in various locations in a vehicle depending on their area of application. A laser beam is sent out to illuminate the sensor’s field of vision. The light reflected back by the surroundings is captured and evaluated by a detector. This is how the sensor detects the size and distance of the object. One challenge for this technology is that the sensor detects the reflected light waves that are important for the use of the detector. All other distracting light waves, such as sunlight, need to be kept away from the detector. The selection of light waves is done with the help of what is called a band-pass filter, which consists of a certain sequence of nanometer-thin optical layers.
Bühler Leybold Optics, in Alzenau, Germany, specializes in this area. Nearly 20 years ago, its HELIOS technology was developed and is used to manufacture exactly this type of filter. “The technology is based on the sputtering method. To do so, a material like silicon or tantalum is used for the coating and is referred to as the target. It is placed as a block in the sputter cathode,” explains Dr. Runkel. “With the help of an energetic plasma, individual ions are created which bombard the target material. This ejects individual silicon or tantalum atoms out of the target material which in turn condense on the filter. By adding oxygen gas, these layers oxidize and become transparent. This results in several nano-meter-thin layers of various materials. Depending on the composition, they filter different wavelengths.”
The HELIOS technology has advanced so far today that the filters produced can sort out the light waves with great differentiation. They work in the light spectrum from ultraviolet to infrared by applying up to 800 layers of various optical materials to a filter. Another decisive factor is that a HELIOS system can coat several work pieces simultaneously, thus increasing production volumes. This makes the production of filters much more cost-effective.
The car is expected to be able to not only assist the driver, but also to make decisions for them.
Dr. Steffen Runkel, Head of Optics, Bühler Leybold Optics
“When we think about the future, our technology is very well suited for manufacturing optical sensors in autonomous vehicles,” says Dr. Runkel. “It is clear that a car can only drive by itself if it completely detects its environment.” Of course, it takes more than just optical sensors. A self-driving vehicle must evaluate all the information generated by the sensor in real time and convert it into an appropriate action. “Therefore, a self-driving car needs additional intelligent software programs based on artificial intelligence that can make the correct decisions,” explains Dr. Runkel. The euphoria of the industry that both public and private vehicles can be completely self-driven in the future is still somewhat contained.
Despite extensive research, the conversion to self-driving traffic will probably take a bit longer than originally planned as objects are still being misidentified. “If a truck coming from the left is not recognized as a truck but as a bridge, then the system is still incorrect.
Even street signs can currently be detected by the camera system with only about 90 percent accuracy. So far, there is no system that can reliably see all eventualities,” explains Klaus Herbig, Head of Product Management Optics at Bühler.
This hardly stops the automotive industry from continuing to believe in the vision. Not least thanks to the technical feasibility of LiDAR technology, which is now within easy reach. LiDAR (short for light detection and ranging) is a method related to radar that works with light rays instead of radio waves. “LiDAR emits a laser beam that is reflected by the object and captured again. One of the challenges here is that the laser beam must scan the entire environment. In comparison to conventional sensors, LiDAR not only detects objects, it also classifies them and determines the distance and movement relative to the vehicle. An additional difficulty is the reliable coverage of distances of up to 250 meters in any weather conditions,” says Dr. Runkel.
The first prototypes of LiDAR systems have already been installed on the roofs of cars. They are arranged in boxes at various angles so that they can capture all of the surroundings. However, such systems could only reach market maturity when the components are smaller and can be integrated into existing car components, such as headlights. “Currently the entire industry is working in high gear on this, both established companies as well as many start-ups. There are about 100 start-ups around the world that have their own ideas of how LiDAR technology could work in cars in the future,” says Dr. Runkel.
LiDAR itself is not new. The technology is already used in satellites and various military applications. “In these areas, a system could cost several thousand euros,” explains Herbig. “In the automotive industry, we are talking about much higher quantities. In the premium class, such a device could cost even a bit more, but once we approach the mid-size or compact class, then we are talking about the 100-euro range.” Within the Optics department Herbig is responsible for recognizing trends in the market in a timely manner. “This is crucial for us so that we can further develop our solutions according to the needs of our customers. For example, in order to reduce the costs in production, high volumes and a high level of automation are the critical factors that differentiate our-selves from the competition,” he explains.
Currently the entire industry is working in high gear on lidar technology.
Dr. Steffen Runkel, Head of Optics, Bühler Leybold Optics
However, the Bühler Leybold Optics team in Alzenau will only be able to tackle these further developments once it is clear how such a technology will be used in large numbers. “Many of our customers are currently researching in this area. For us, it is therefore crucial that we maintain our contacts and cooperate with our customers to provide them with the coatings needed in this area. We are the experts in optical thin-film coating,” Herbig says. Bühler Leybold Optics is well connected within the industry and is in regular contact with research institutions in Germany, France, and Belgium. “We are also in contact with several automotive manufacturers and their suppliers,” Herbig explains. “We offer them the opportunity to test their creative ideas and developments in our application center in Alzenau.”
The application center was established a year and a half ago, and includes a 1,200-square-meter test area, a high-tech lab, and a highly modern research and development area. Due to the high demand, Bühler just set up two HELIOS systems from the latest generation there.
There is also a DLC machine right next to them (DLC stands for diamond-like carbon) which is used for manufacturing items such as cameras for night vision. These support the driver to detect potential risks earlier in darkness and in difficult light conditions. The forward-facing cameras need to withstand enormous loads, like stormy weather and use in heavy traffic.
The DLC can coat the outer camera window to make them very resilient. For customers of Bühler, the application center is a huge added value, especially for those who do not yet have a lot of experience with optical thin-film coating technology. “Many of these ideas are still in the early stages, but they will soon be implemented in one way or another,” explains Dr. Runkel. “We are talking about the car of the future that learns to see through a variety of smart sensors based on optical technologies.”
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