22. April 2016
The new age of automobiles will be defined by one major change: Drivers are optional. Technology giants and car companies are pushing the pedal to the metal to develop the first commercially available driverless car. They’re handing the wheel to technology that can see things humans can’t, can better prevent accidents, and could rewrite traffic patterns. And it all starts with light.
Light detection and ranging — LiDAR for short — works with a number of other systems to make driverless cars safer, more responsive, and more aware than any human driver. Similar to RADAR, where sound is using for sensing and detection, LiDAR uses light. The concept was developed over 50 years ago, coinciding with the invention of lasers and the resulting growth in applications. The basic technology has evolved over the years to today, where it is used to generate a detailed, 360-degree map of an environment, to spot artifacts of ancient civilizations, improve street maps, and it is expected to be able to scan the human body in the future. It even helped safely navigate the retired Space Shuttle through the busy streets of Los Angeles.
Even though LiDAR was theorized and developed over 50 years ago, the momentum toward driverless cars has put the technology in the media spotlight. At the forefront of this revolution is the Google Self-Driving Car, which has driven more than 1 million miles using this LiDAR technology.
Your new chauffeur — LiDAR
LiDAR uses light to measure distances. A LiDAR-based detection system emits thousands of bursts of light every second in every direction, similar to how radar emits radio waves and sonar uses sound waves. Those light rays reflect off objects in the 360-degree area around the car — other vehicles, buildings, pedestrians, bikes, etc. — and bounce back to the sensor, where an onboard computer records the amount of time each individual wavelength took to travel out and back.
Using that data, the distance between the car and its sarroundings is calculated, thus creating a 3D map of the car’s surroundings, including the shape and size of nearby objects. The car’s other sensors use that mapping data to stop, go, position itself on the road, and park. It could even allow driverless cars to travel at closer intervals on highways, possibly reducing traffic-related problems.
In the safe lane, thanks to glass
All the decisions a driverless car has to make about distance, speed, other cars, and pedestrians happen in fractions of a second — much faster than a human could respond. Accomplishing this is even more complex than it sounds.
Remember, the road is a busy and often dirty place, and these systems and their components must work in full sunlight, rainy conditions, and dusty or dirty environments. LiDAR systems use specialty laser glass, which produces a solid light beam that stays coherent without diverging or degrading in the environment.
But not any light will do — light of specific wavelengths can damage the eye if absorbed by the tissue. SCHOTT has developed laser glasses that generate light pulses between 1.5 and 2 µm, found in the communications band and considered eye safe. That’s critically important for those walking by on busy city streets, and the light between these two wavelengths is still considered coherent, focused, and reliable for LiDAR applications.
Though LiDAR systems can use crystalline materials to produce lasers, glass seems to be a preferable choice to manufacturers because of efficiency, beam quality, and accuracy. Other diode systems typically have more divergence and a poorer beam profile, which can degrade the accuracy of the measurements, and the lasers produced from yttrium aluminum garnet-based systems can damage the eye, which usually means these materials are not used in open environments. Plus, laser glass boasts a long and consistent lifespan, and unlike crystals, the light produced from glass will not diverge and degrade over years of constant use.
More than just your car’s navigation
LiDAR is being installed in driverless cars, and city planners are using it to create 3D maps of neighborhoods and roadways, as well. But that’s not all.
Today, scientists are employing it to see the tree density of forests, and even how many leaves are on a tree. Soldiers equipped with LiDAR-equipped range finders gain better awareness on the battlefield, as well.
Your next trip to the doctor’s office might be for a LiDAR scan, and not an X-ray. But before you even get to the doctor’s office, LiDAR systems in your car of the future will keep you — and other drivers and pedestrians — safe. The technical achievements of laser glasses may make better 3D mapping possible, and the robustness and strength of the glass ensures you’ll make your appointment safely every time.