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New MEMS Mirror Integrated in LiDAR Systems can Supplement Human Vision

Advanced technologies literally take the wheel in self-driving vehicles, enabling passengers to relax and enjoy the ride.

When integrated into a LiDAR sensor, the MEMS mirror from Fraunhofer IPMS will equip vehicles with a 3D vision of their surroundings. Image Credit: © Fraunhofer IPMS.

But these systems have to fulfill rigorous safety standards. For instance, a self-driving vehicle should be able to detect obstacles and other similar dangers and apply the brakes during emergency situations.

A vehicle like that could be fitted with a novel microscanner mirror developed by the Fraunhofer Institute for Photonic Microsystems (IPMS). This mirror conducts a 3D scan of the vehicle surroundings to a range of more than 200 m. When the mirror is incorporated into a LiDAR system, it can prevent the requirement for human vision and play a crucial role in the safety of autonomous driving.

The current generation of vehicles already includes a wide range of sophisticated driver-assistance systems. In the days to come, it will become mandatory to install evasive steering support and other similar emergency systems in the latest vehicles, presenting new opportunities for the introduction of autonomous driving.

However, even in the forthcoming vehicle generations, people will still need to watch their surroundings and respond in hazardous situations. But this scenario is likely to change with the advent of light detection and ranging (LiDAR) systems, which quantify the distance between other objects and the vehicle.

These systems can scan the surrounding region for any sign of potential dangers and substitute for the human eye. Therefore, such systems represent a crucial step on the way toward safe autonomous driving.

A research team from Fraunhofer IPMS in Dresden has designed a new kind of microscanner mirror, which represents a crucial element of LiDAR systems that perform a 3D digital vision. This mirror is utilized to steer the laser that produces a 3D scan of the surrounding region.

The microscanner mirror is already being used by AEye—a company specializing in LiDAR systems in autonomous vehicles—in its 4Sight LiDAR sensor.

With our technology platform, we’re able to meet design specifications for new microscanners suitable for use with LiDAR. LiDAR systems are able to scan the surrounding area in three dimensions and therefore detect pedestrians, cyclists or other vehicles.

Dr Jan Grahmann, Research Associate, Fraunhofer IPMS

Our MEMS mirror splits the laser beam in two dimensions and focuses the light on the object that is being measured. By measuring the time of flight of the reflected light, it is also possible to determine the distance to the object as a third dimension,” added Dr Grahmann.

To explain this in more detail, the procedure is as follows: light emitted from a laser diode or another laser source is focused toward a microscanner mirror fixed to the LiDAR system transmitter. Following this, the mirror scans the surrounding region in two dimensions.

To establish the third dimension, a LiDAR sensor captures the light reflected from the object. The following applies in this case: if more light is captured by the LiDAR sensor, the distance to the object can be established more precisely. An evaluation algorithm performs this particular task. The distance to all scanned positions in the vehicle surroundings creates a 3D point cloud that denotes the LiDAR field of vision.

Robust, Proof Against Material Fatigue, Resistant to Temperature and Shock

The MEMS scanner is composed of monocrystalline silicon—a material that has many benefits. For example, the material is strong, impervious to material fatigue, and also has a high temperature and excellent shock resistance.

A reflective coating in the silicon intensifies the light reflection. The chip is integrated with positioning technology, which makes it possible to constantly monitor where the laser beam is steered by the mirror and which position is being quantified. This consequently allows for correction to the point of operation.

The LiDAR sensor within the vehicle is typically installed behind the rear-view mirror, and from this place, it directly scans the surrounding region via the windshield. The system can be employed to conduct a 3D scan in the infrared range, supplementing the vision of the passengers or driver.

Our MEMS mirrors are typically up to 5 millimeters in size. For specialized applications, larger mirrors are an option; but with increasing size, you lose the benefits of MEMS. Alongside the microscanner mirrors, we also supply the requisite packaging and the drive electronics.

Dr Jan Grahmann, Research Associate, Fraunhofer IPMS

All components can be designed to customer specifications, thereby guaranteeing that they can be integrated in different LiDAR systems. We also develop, for example, MEMS scanners for head-mounted displays and industrial robots,” he continued.

Designed by Fraunhofer IPMS, the microscanner mirrors work, for instance, at wavelengths usual for LiDAR applications—905 to 1550 nm. The aperture size has a significant effect on the operating range.

With AEye’s smart LiDAR sensors, operating ranges of more than 200 m can be achieved. AEye has fully tested the MEMS scanners from Fraunhofer IPMS, and these scanners are now installed in the former’s LiDAR system.

At present, advanced driver-assistance systems featuring LiDAR technology are still about providing greater comfort and enhanced safety. There are five levels of autonomous driving, each of which involves a different degree of driver invention. Now, there’s still some way to go before fully autonomous driving becomes a reality, but our technology will help advance this process.

Dr Jan Grahmann, Research Associate, Fraunhofer IPMS

The following step will be to create the microscanner mirrors in greater volumes and prepare this advanced technology for large-scale production.


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