June 1, 2021
Achieving safer, more reliable data with interference immunity
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Before a vehicle can drive itself, it needs to be able to see what’s going on around it. LiDAR sensors are essentially the “eyes” of autonomous vehicles (AVs). LiDAR sensors detect everything going on around them, near and far, and create a real-time 3D map that the vehicle’s control center can then use to make critical decisions on how the vehicle should respond to its environment – slow down, speed up, change direction, stop.

So, what happens when something interferes with the LiDAR’s ability to accurately record its surroundings? Well, it’d sort of be like driving blindfolded.

While LiDAR allows AVs the ability to measure distances more accurately than cameras, they also present a new set of challenges – light interference.

If external light sources are able to enter the LiDAR system and either blind or confuse the sensor, it could lead to wonky driving behaviors and may even result in a serious accident.

To safely put autonomous driving technology on the road, AVs need to be equipped with LiDAR sensors that are immune to any form of interference, guaranteeing an accurate and precise record of the vehicle’s external environment no matter what conditions present themselves.

At Baraja, our ability to achieve interference immunity is one of the many advancements that sets our Spectrum-Scan™ LiDAR sensors apart from other manufacturers. Paired with our range capabilities and versatility, we are one of the first LiDAR manufacturers to present a sensor ready to hit the open road today.

How does interference occur?

LiDAR sensors detect their surroundings by sending light into the external environment and then receiving that same light after it has hit and bounced off of an object. This process provides the LiDAR with detailed information about the objects surrounding it, including size, velocity, distance, and reflectivity. That information is translated into a single point within the sensor’s output, or pointcloud.

In controlled conditions, the LiDAR can make an extremely accurate replication of its environment. However, when external influences present themselves, such as powerful headlights or direct sunlight, the foreign light sources can flood the LiDAR’s lens and potentially oversaturate the detector.

Oversaturation of detectors leads to an increased amount of noise in the signal. This has two potential impacts for the customer. First, increased noise level leads to false positive returns, which could lead to false detection of objects in the scene, or secondly the LiDAR needs to filter out the noise in turn reducing the sensitivity of the system, leading to possible missed detections on weaker targets.

Another form of LiDAR interference is one that comes from other LiDAR sensors. Signals from other LiDAR systems, whether it’s of the same model or from a competitor, can inadvertently transmit signals directly into another LiDAR system. Without suitable protecting features in place, the receiving LiDAR may then accept the signal as true information, leading to inaccuracies in the LiDAR pointcloud.

When LiDAR interference occurs, the receiving LiDAR could misinterpret the signal as an object when, in reality, there is nothing there. When these false objects, or “phantom points,” make their way into the pointcloud, the vehicle could respond to the imaginary point by swerving away or activating its emergency breaking, creating obvious issues with the driving experience.

Achieving interference immunity

Using a combination of anti-reflection coatings and intrinsic properties of prism-like optics, along with our random modulation continuous wave (RMCW) ranging approach, we have created one of the first LiDAR sensors that is immune to light interference.

For an external light source to infiltrate the Spectrum-Scan™ LiDAR sensor, it needs to know where to enter and when. Incoming light sources must hit the lens at the exact angle at which the original signal was transmitted. To make it even harder, the beam only has a 0.5 – 2 microsecond acquisition window to hit at exactly the right angle. In the unlikely case that another light source does hit the correct angle at the right moment, the prism-like optics of the Spectrum-Scan™ sensor will deflect away any wavelengths that differ from the one transmitted at that angle.

Lastly, a unique layer in the Spectrum-Scan™ sensor interference “security” system is code matching. With our random modulation continuous wave (RMCW) ranging approach, we are able to embed each transmitted wave with a randomized code unique to each system. In the extremely rare case that an external light source hits the LiDAR lens at the right time, right angle and right wavelength, it must then provide the detector with the exact code combination before it is detected as a real return.

Some LiDAR manufacturers use frequency modulated continuous wave (FMCW) for their ranging, which provides some level of immunity, but is ultimately less effective than RMCW. An independent study found RMCW to be twice as robust against AV interference than FMCW.

Further, our sensors can generate virtually infinite code combinations, enabling us to assign a unique code for every individual LiDAR sensor, eliminating the possibility of interference between any two Spectrum-Scan™ LiDAR sensors.

Through these multiple layers of protection, we have been able to eliminate the possibility of false or inaccurate readings and achieve true interference immunity.

Why immunity matters

While many LiDAR manufacturers are addressing concerns of interference from sunlight, headlights and other external sources, few are discussing the problems of LiDAR-to-LiDAR interference. LiDAR interference isn’t prominent in today’s driving conditions, but soon our roads will be filled with AVs and smart infrastructure that will all be transmitting and receiving their own LiDAR signals. For safe adoption of autonomous technology, AVs must be equipped with LiDAR sensors that are immune to interferences from ALL external light sources.

At Baraja, we are focused on the future and fitting AVs with LiDAR sensors that provide consistently reliable data and is impermeable to interference – regardless of external conditions.

If you’re looking to achieve safe and reliable L4 autonomous driving for your fleet of vehicles, invest in a sensor system that will provide your vehicle with the clarity and consistency it needs to make smart and accurate decisions. Spectrum-Scan™ LiDAR is years ahead of the competition, offering interference immunity, exceptionally detailed long-range vision and scalable versatility.

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