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MEMS micro-mirrors improve Lidar sensing for vehicles

CEA-Leti research leads to improved MEMS micro-mirrors for vehicles. This innovative technology aims to detect car tires (15cm high) from a distance of 100 meters. These research results emerged from the European Vizta project and are protected by three new patents.

Published on 10 November 2022

​MEMS micro-mirrors for automobile Lidar are tiny (2mm wide) but essential components that reflect a laser beam and direct it thanks to their up-down-left-right mouvements. This helps Lidar sweep an area and detect vehicles, pedestrians and obstacles.

Cheaper micro-mirrors and improved Lidar range

The innovations developed by Leti are protected by three patents. These improvements will increase Lidar range and security as well as reduce energy consumption and manufacturing costs. 

To improve the mechanism used to move the mirrors, the researchers replaced the traditional electrostatic or electromagnetic solutions with a PZT piezo-electric solution that only requires 20V (versus 150V for an electrostatic mirror). This innovative solution also eliminates the need for bulky magnets, which are required for an electromagnetic mirror.

Very Large Scale Integrated manufacturing process suitable for CMOS

These innovative micro-mirrors were designed to work at 1550nm in order to limit ocular risk and support the high-power laser beam required for long-range Lidar applications. To achieve this improvement, researchers replaced the habitual gold reflector with layers of Bragg deposited on silicon. This solution offers two advantages: first, the reflectors are four times less absorbent and thus less prone to overheating by the laser, which makes it possible to increase incident power. And second, these layers can be deposited with CMOS compatible processes thus reducing the cost of manufacturing.

Successful testing with an industrial partner

To reinforce ocular safety for pedestrians, the researchers added a self-diagnostics function that could enable the laser to switch off when the mirror is not moving. The research carried out as part of the Vizta framework also includes an optical characterization bench, packaging and a dedicated electronics pilot interface. The mirrors were integrated into an industrial partner's existing 3D Lidar system and their compatibility with the desired goal was confirmed. Mirror control will continue to be improved in order to scan specific parts of a scene with greater precision.

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