ECE PhD Thesis Defense: Ruangrawee Kitichotkul

ECE PhD Thesis Defense: Ruangrawee Kitichotkul

Title: Single-Photon Lidar: Statistical Analysis, High-flux Imaging, and Velocimetry

Presenter: Ruangrawee Kitichotkul

Advisor: Professor Vivek Goyal

Chair: Professor Archana Venkataraman

Committee: Professor W. Clem Karl, Professor Vivek Goyal, Professor Prakash Ishwar, Professor David Lindell

Google Scholar Link: https://scholar.google.com/citations?user=SV4mQbYAAAAJ

Abstract: Single-Photon Lidar (SPL) systems leverage the sensitivity of single-photon avalanche diodes (SPADs) to achieve long-range, high-resolution 3D imaging. Despite these strengths, the technology faces three critical computational challenges that limit its real-world deployment: the reliance on knowing the ambient background flux, severe performance degradation in high-flux environments due to SPAD dead time, and the inability to measure velocity. This thesis addresses these limitations by developing probabilistic models and corresponding estimators. First, we introduce a joint ML estimator that simultaneously determines signal flux, background flux, and depth, enabling real-time adaptation to varying ambient light without requiring prior flux knowledge. Second, we develop computationally efficient joint ML estimators for high-flux operation under SPAD dead time, demonstrating the clear superiority of the free-running mode, which proves to be robustly depth-independent and outperforms the conventional synchronous mode even under extreme dead-time conditions. Finally, we pioneer Doppler SPL, a methodology that integrates target velocity into the probabilistic model as a Doppler shift in the pulsing repetition period. By employing Fourier analysis of Poisson processes and ML estimation, this approach jointly estimates velocity alongside all other scene parameters from absolute detection times. Collectively, these contributions significantly expand the operational envelope of SPL, transforming it into a robust, high-performance sensing modality capable of handling dynamic backgrounds, mitigating dead-time effects, and simultaneously measuring distance, velocity, and reflectivity.