Dissertation Defense: Jeff Ching-wen Chan, "Diffractive MPPC-Lidar System with Image Steering and FOV Expansion by Digital Micromirror Device"

Title: Diffractive MPPC-Lidar System with Image Steering and FOV Expansion by Digital Micromirror Device

Abstract:

In this work, we propose a novel hybrid optical architecture that employs a high diffraction efficiency Digital Micromirror Device (DMD) for beam steering in a Time-of-Flight (ToF) LIDAR. By synchronizing the laser pulse to the dynamic tilt movement of the micromirrors, light can be diffracted and steered into one of the multiple diffraction orders with high diffraction efficiency. The proposed lidar architecture utilizes two synchronized DMDs with a two-dimensional Multi-Pixel Photon Counter (MPPC) to diffractively steer and transmit the laser beam as well as to steer the lidar receiver's Field of View (FOV) over the diffraction orders of the blazed grating formed by the micromirrors of DMD. The experimental results demonstrate that the proposed lidar architecture expands the FOV 7 times larger than the original FOV, achieving a FOV of 35 degrees in the horizontal direction and 5 degrees in the vertical direction while retaining an angular resolution of 0.22 degrees which corresponds to the instantaneous FOV of the MPPC detector. The system can capture up to 7 diffraction orders of LIDAR images without sacrificing image resolution, and the Arduino Due microcontroller used in the system enables a high frame rate of 10kHz.

The diffractive lidar image quality and lidar system crosstalk tests demonstrate the system's ability to accurately capture lidar images without being impacted by ambient light. Additionally, this work proposes a diffractive image steering method to expand the FOV of the lidar system by sequentially steering the receiver FOV over multiple diffraction orders and employing an image stitching process to create a real-time wide FOV lidar image. The proposed hybrid optical architecture offers a solution for expanding the FOV of a lidar system, which has significant applications in autonomous driving, robotics, and 3D imaging.

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