Under the direction of Susumu Noda of Kyoto University in Japan, a group of researchers has presented in optics its revolutionary 3D lidar system without mechanical components. This advanced system is able to fit in the palm of your hand and has the ability to measure the distance of objects with low reflectivity and automatically track the movement of said objects.
"With the implementation of our lidar system, robots and vehicles will have the ability to navigate safely and efficiently in dynamic environments, without losing sight of low-reflectivity objects such as black metallic cars," says Noda. "Incorporating this technology into vehicles, for example, would provide an additional level of safety to autonomous driving."
It was thanks to the development of an innovative dual-modulation photonic crystal laser (DM-PCSEL), an original chip-based light source, that this new system became possible. This remarkable advance could lead to the design of a fully integrated solid-state 3D lidar system on a single chip.
“The DM-PCSEL combines electronically controlled, non-mechanical beam scanning with flash illumination used in flash lidar to capture a full 3D image with just a flash of light,” explains Noda. "This unique source allows us to achieve flash and scanning illumination without components
mobile devices or large external optical elements, such as lenses and diffractive optical elements.
Scan fusion with flash illumination
Lidar systems use laser beams to illuminate objects and calculate their distance by measuring the time it takes for the rays to travel, reflect, and return (ToF). However, most lidar systems in use or under development require moving parts such as motors to scan the laser beam, making them larger, more expensive and less reliable.
Flash lidar is a non-mechanical methodology that uses a single, wide, diffuse beam of light to illuminate and calculate the distances of all objects in its field of view. However, flash lidar systems have difficulty measuring the distances of objects with low reflectivity, such as black metallic cars, due to their low reflectance. Additionally, they require external lenses and optical elements to create the flash beam, which increases their size.
The team of researchers developed the DM-PCSEL light source to overcome these barriers. Said light source includes a flash source capable of illuminating a wide field of view of 30°×30°, and a beam scanning source that allows punctual illumination with 100 narrow laser beams.
By integrating the DM-PCSEL into the 3D lidar system, the researchers were able to measure the distances of multiple objects at once using broad flash illumination, while selectively illuminating low-reflectivity objects with a more concentrated beam of light. To be able to perform distance measurements and automatic tracking of objects with low reflectivity, the researchers equipped the system with a ToF camera and developed sophisticated software that uses beam scanning illumination.
Accurate measurement of objects with low reflectivity
"Our 3D lidar system, based on DM-PCSEL, allows us to simultaneously measure objects with high and low reflectivity," highlights Noda. «The lasers, the ToF camera and all associated components necessary to operar the system, they were mounted compactly, resulting in a system that occupies less space than a commercial card.
The researchers tested the effectiveness of the new system by using it to calculate the distances of low-reflectivity objects arranged on a laboratory table. They also demonstrated that the system was capable of automatically recognizing objects with low reflectance and tracking their movement using a selective illumination approach.
The research team now aims to demonstrate its practical application in real situations of autonomous movement of robots and vehicles.
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