3D imaging sensors are crucial components for modern intelligent machines to detect and perceive the surrounding world. Among different 3D sensing technologies, light detection and ranging (LiDAR) systems offer high distance and lateral resolutions and are able to work in darkness, therefore have applications that span several industries and markets, from metrology, robotic control, autonomous vehicles, to consumer electronics.

Compared with other LiDAR principles such as the pulsed time-of-flight, frequency-modulated continuous wave (FMCW) LiDAR can achieve high-resolution distance and velocity measurements without fast electronics or high peak optical power thanks to the coherent detection advantages, but it typically requires narrow-linewidth lasers with complex feedback circuits to generate linear chirps. In this dissertation, we will summarize our research on linearizing the laser chirp by iterative learning pre-distortion of the drive waveform and compensating for the laser phase noise in post-processing. With these two methods, high-performance FMCW LiDAR can be achieved with commercial semiconductor lasers and a simple setup.

Besides the laser ranging system, the optical beam scanner is an essential component in scanning LiDAR. An integrated optical beam scanner with fast speed, large field-of-view, high resolution, and low power consumption is an essential element for solid-state LiDAR. In this dissertation, we will introduce two integrated beam scanner architectures based on microelectromechanical system (MEMS), (1) grating-based 2D optical phased array (OPA), and (2) 2D focal plane switch array (FPSA) with MEMS optical switches. We will discuss their operation principles as well as the advantages and challenges, and we will show the design, fabrication, and characterization of a 160x160-element OPA, a 20x20-element FPSA, and a 128x128-element FPSA. We will also demonstrate the implementation of the 128x128-element FPSA beam scanner on an FMCW LiDAR for 3D imaging. We believe these highly scalable integrated beam scanners are very promising candidates for chip-scale solid-state LiDAR sensors.




Download Full History