Abstract
Light detection and ranging (LiDAR) sensors are promising for automated transportation to detect the surrounding environment. However, most LiDAR solutions are complex and bulky. By designing a MEMS-mirror-based LiDAR, we can improve the volume constraints, but MEMS mirrors could limit scanning angles. In this work, we simulated and demonstrated a MEMS LiDAR system to solve the current obstacles. Combining a MEMS mirror and a wide-angle lens into the system, small-volume and large field-of-view (FOV) LiDAR systems can be realized. We use ray tracing optical simulation software to design a pair of aspherical lenses to expand the scanning angle. After the laser beam passes through the wide-angle lens, the FOV can be increased to 104 degrees. The distortion of the wide-angle lens is controlled below 3%, making the scanned image precise to the actual situation. In order to experimentally demonstrate the small-volume MEMS scanning LiDAR, a modular laser rangefinder is used with a MEMS mirror. The entire system of the LiDAR scanner is around 15 cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times5$ </tex-math></inline-formula> cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times2.5$ </tex-math></inline-formula> cm. In the natural light environment for wide-angle LiDAR measurement, the maximum error is less than 2%. Finally, an image processing program is written to convert the scanned data into a 3D point cloud image, and the generated image proves the complete function of the proposed LiDAR.
Highlights
It is essential to acquire 3D images for autonomous driving
The light detection and ranging (LiDAR) system is composed of four parts: (1) laser diode collimator used to collimate the emitted light of the laser light source, (2) laser scanning system containing a MEMS mirror to deflect the laser light, (3) wide-angle scanning lens installed in front of the MEMS mirror to expand the scanning angle, and (4) a photodiode so that the reflected light signal at a larger angle can be detected
To demonstrate the scanning capabilities of our designed MEMS LiDAR and the effectiveness of the wide-angle lens, we modified the mechanical structure of the single-point laser rangefinder and added a MEMS mirror along with a wide-angle lens to successfully set up a LiDAR with a scanning angle of 104 degrees
Summary
It is essential to acquire 3D images for autonomous driving. The straightforward step is to use stereo cameras like human eyes. The rapid development of light detection and ranging (LiDAR) sensors could provide high image resolution, high range accuracy, and a high frame rate. We decided to use scanning LiDAR based on MEMS mirrors to scanning and ranging[1]. The mechanical tilt angle of a MEMS mirror is usually less than 20°. For a dual-axis MEMS mirror, the tilt angle could be even smaller. It is not enough for 3D imaging lidar systems. We design a wide-angle lens for a MEMS LiDAR transmitter to collimate the light to the entire scene to illuminate the object. We propose a system that uses a MEMS mirror as a LiDAR 3D scanning device, which successfully reduces the size and power. An in-house image processing program is used to convert the scanned data into a 3D point cloud image, and the generated image proves the complete function of a LiDAR system
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