Unique, chip-based light source enables combination of scanning lidar with 3D flash lidar – Zoo House News

Our roads could one day be safer thanks to a whole new system that overcomes some of lidar’s limitations. Lidar, which uses pulsed lasers to map objects and scenes, helps autonomous robots, vehicles, and drones navigate their surroundings. The new system represents the first time that the capabilities of traditional beam-scanning lidar systems have been combined with those of a newer 3D approach known as flash lidar.

In Optica, Optica Publishing Group’s journal of high-impact research, researchers led by Susumu Noda of Kyoto University in Japan describe their new non-mechanical 3D lidar system that fits in the palm of your hand. They also show that it can be used to measure the distance of poorly reflecting objects and to automatically track the movement of these objects.

“With our lidar system, robots and vehicles will be able to reliably and safely navigate through dynamic environments without losing sight of poorly reflective objects such as black metal cars,” said Noda. “Incorporating this technology into cars, for example, would make autonomous driving safer.”

The new system is possible thanks to a unique light source the researchers developed, called a dual modulated photonic crystal laser (DM-PCSEL). Because this light source is chip-based, it could eventually enable the development of an all-solid-state 3D lidar system on the chip.

“The DM-PCSEL integrates non-mechanical, electronically controlled beam scanning with flash illumination used in flash lidar to capture a full 3D image with a single flash of light,” said Noda. “This unique source allows us to achieve both flash and scanning illumination without moving parts or bulky external optics such as lenses and diffractive optics.”

Combination of scanning and flash lighting

Lidar systems image visible objects by illuminating those objects with laser beams and then calculating the distances to those objects by measuring the beams’ time-of-flight (ToF) — the time it takes for light to travel to objects to be reflected be and then return to the system. Most lidar systems in use and under development rely on moving parts, such as motors, to scan the laser beam, making these systems bulky, expensive, and unreliable.

A non-mechanical approach, known as flash lidar, simultaneously illuminates and evaluates the distances of all objects in the field of view with a single broad, diffuse beam of light. However, flash lidar systems cannot be used to measure the distances of poorly reflective objects such as black metal cars because very little light is reflected from these objects. These systems also tend to be large because of the external lenses and optics needed to create the flash beam.

To address these critical limitations, researchers developed the DM-PCSEL light source. It features both a flash source capable of illuminating a wide field of view of 30°×30° and a scanning beam source that provides spot illumination with 100 narrow laser beams.

They incorporated the DM-PCSEL into a 3D lidar system that allowed them to measure the distances of many objects simultaneously with wide flash illumination while selectively illuminating poorly reflective objects with a more concentrated beam of light. Researchers also installed a ToF camera to perform distance measurements and developed software that enables automatic tracking of the movement of poorly reflective objects using beam-scanning illumination.

Measuring objects with different reflectivities

“With our DM-PCSEL-based 3D lidar system, we can detect highly reflective and poorly reflective objects at the same time,” said Noda. “The lasers, ToF camera and all associated components required to operate the system have been assembled in a compact manner, resulting in an overall system footprint smaller than a business card.”

The researchers demonstrated the new lidar system by using it to measure the distances of poorly reflecting objects placed on a table in a laboratory. They also showed that the system can automatically detect poorly reflective objects and track their movement through selective lighting.

The researchers are now working to demonstrate the system in practical applications such as the autonomous movement of robots and vehicles. They also want to see if replacing the ToF camera with a more optically sensitive single-photon avalanche photodiode array would allow objects to be measured at even greater distances.