Micro Mirrors Expand Field of View in Intel’s New MEMs LiDAR CameraMarch 10, 2021 by Jake Hertz
LiDAR is cropping up in manifold variants, and for scanning LiDAR, MEMs micro-mirrors are a key factor in determining the field of vision.
LiDAR is certainly a buzzword nowadays in autonomous vehicle and robotic marketing—and for good reason. This technology has forged computer vision innovations, the most recent being aboard the Mars Perseverance rover.
Another announcement that speaks more specifically to the design-level details of LiDAR comes from Intel and STMicroelectronics, which have teamed up with the recent release of a high-resolution MEMs LiDAR camera.
Breakdown of the Intel RealSense LiDAR Camera L515. Image used courtesy of Intel
As part of the success of this new device, ST points to its micro-mirror scanning technology, which the company claims is the "world's smallest" of its kind. This MEMs mirror is said to enable the new LiDAR camera to spatially scan an environment, yielding high-resolution imaging for a host of industrial applications like 3D scanning, robotic bin picking, logistics, and volumetric measurements to name a few.
MEMs LiDAR Taps Into Quasi-mechanical Scanning
To better understand the details of this announcement, it may be helpful to review the basics of MEMs LiDAR technology (PDF), which is classified as "scanning LiDAR" (as opposed to non-scanning LiDAR).
Scanning LiDAR steers a laser beam over a wide area to effectively capture a large field of view (FOV). This process in itself can either take the form of mechanical or non-mechanical scanning. The former utilizes moving parts in the laser system while the latter does not.
From left to right: flash LiDAR, optical phased array (OPA) LiDAR, motorized scanning LiDAR, and MEMS LiDAR. Image used courtesy of Wang et al. (PDF)
For many applications, MEMS LiDAR has proven to be a useful solution because it offers high speeds, small sizes, and high resolution in one package.
MEMS LiDAR is a quasi-mechanical form of LiDAR, where the laser itself does not physically move, but instead, MEMS mirrors are moved in such a way to steer and modulate the laser while the remainder of the system is stationary.
How Do MEMS Mirrors Work?
The press release for the Intel RealSense LiDAR camera L515 nods to ST's micro-mirror technology as a key factor in its success. How exactly do these devices work on a system level?
MEMS mirrors are very compact, which allows for smaller form-factor systems, faster control speeds, and more precise light steering compared to other mechanical-scanning LiDAR methods.
These devices often require a high-voltage driver for voltages (ranging from 200 V to 300 V) to move the mirror's position. An MCU or FPGA can determine the specific drive voltages while also controlling the laser diode driver to coordinate the tandem operation of the mirror and laser diode.
Block diagram of a typical MEMs mirror system. Image used courtesy of Microchip
A MEMs micro-mirror system will also typically include a digital-to-analog converter (DAC) to bridge controller and amplifier operations as well as a photodiode to provide feedback on closed-loop systems.
STMicroelectronics and Intel Link Up
After six years of collaboration, STMicroelectronics and Intel have released a MEMS LiDAR depth camera with micro-mirror scanning as a technology highlight.
The Intel RealSense L515 animated by ST's MEMs micro-mirror. Image used courtesy of STMicroelectronics
Coming in a hockey-puck shape with a 61 mm diameter and a 26 mm height, the Intel RealSense L515 LiDAR camera is being touted as the world’s smallest high-resolution LiDAR depth camera by both companies. A major factor in achieving this low size was the MEMS mirror approach, which allowed for a desirably wide FOV while also keeping the form factor to a minimum.
As for technical specs, the camera claims 30 frames per second while offering 70° x 55° FOV. According to the datasheet (PDF), the camera can achieve a range of up to 9 meters and a depth accuracy of < 14 mm while still measuring 2.3 million depth points.
MEMs micro-mirrors open many doors for LiDAR, but they undoubtedly have some design-level challenges related to their compact size as well. Have you worked with these devices? Share your experiences in the comments below.