When an autonomous car drives on a road, it needs to know where the obstacles around it are. Is there a pedestrian crossing? A cyclist? A stopped vehicle? To answer those questions It uses sensors capable of building three-dimensional maps of the environment in real time.
Among them stands out a technology known as LiDAR, a type of radar that uses laser light instead of radio waves. These types of devices emit laser pulses and measure how long it takes for them to return after reflecting off an object. Since the speed of light is known, this time allows the distance to be calculated with enormous precision. By repeating this process millions of times per second, the system generates a three-dimensional point cloud that represents the environment. It’s a bit like a bat building an image of the world using sound echoes. The difference is that here the “echoes” are flashes of light.
Thanks to this technology, self-driving cars can identify roads, buildings, pedestrians or traffic signs even in complex conditions. The same happens with military tanks when detecting obstacles and missiles when determining targets. but it exists an important limitation: the information obtained is usually reduced mainly to the geometry of the scene and they know very little about what exactly they are seeing.
Now, scientists from the University of Toronto and the telecommunications company Ciena have developed a new system capable of going much further. In addition to measuring distance, you can simultaneously determine the speed of an object and obtain information about the properties of its surfaceall using a single measurement. The advance has been described in Optics.
Although the authors, led by David Lindell, highlight civil applications such as robotics, autonomous driving or industrial inspection, it is difficult not to think about the military potential of such a technology. On a modern battlefield it is not enough to detect that an object exists several kilometers away. Also It is important to determine whether it is an armored vehicle, a drone, an artillery piece, or simply a harmless obstacle. And do it in low visibility conditions caused by smoke, fog, dust or rain.
The brain of the system is a device called a coherent optical modem. While a conventional optical modem is limited to sending and receiving the light that circulates through a fiber optic cable, a coherent optical modem not only detects that the light has arrived, but also analyzes its characteristics. This equipment is essential for modern telecommunications and its use in large data centers is essential.
Lindell’s team’s idea was simple: if these devices can analyze light so precisely to transmit the Internet, perhaps they could also be used to “read” the environment. The result is a LiDAR capable of capturing much more information than conventional systems. The laser used not only measures how long it takes for the light to return. Also analyzes how certain properties of that light change after interacting with the surface of an object. These small modifications contain information about the materials and their properties.
One of the most interesting aspects of the system is that it takes advantage of a property of light called polarization. Polarization describes the orientation of light waves as they travel. When light hits different surfaces, that orientation changes differently depending on the material. A metal sheet, a plastic surface, or a rough wall leave different “footprints” in the reflected light. It is something similar to throwing a ball against different surfaces. The bounce reveals information about what it has collided with. Analyzing these alterations is how the system can obtain clues about the composition and texture of the objects.
The interesting thing is that this property works even through the “noise” that particles suspended in the air can produce. That means the system could perform better in difficult conditions such as fog, heavy rain, dust or glare. This is an especially valuable capability for autonomous vehicles, industrial robots and remote surveillance systems, where atmospheric conditions can significantly degrade the performance of current sensors.