Long-range depth profiling based on time-correlated single-photon counting

Abstract

Single-photon detection technologies are of high relevance to light detection and ranging (LiDAR) applications for the range resolution and surface profiling of distant target objects. Modern single-photon detectors offer high quantum efficiencies and small timing jitters in the order of tens of ps, allowing for the rapid acquisition of high-resolution time-of-flight information with eye-safe illumination powers. In time-correlated single-photon counting (TCSPC), every detection event is treated as an independent measurement of time. The build-up of photon statistics over many measurement cycles allows for time-of-flight measurements with a precision that can be superior to the system’s single-shot timing uncertainty. This Thesis presents work on a scanning, long-range depth profiler based on TCSPC. Its design is discussed and a comprehensive set of performance metrics is evaluated, serving as the base for a theoretical performance model. Beside measurements at an illumination wavelength of 842 nm, the operation of the system at 1.56 m is also described. A special focus is made on the implementation and evaluation of different single-photon detection modules, including a novel, resonant-cavity-enhanced single-photon avalanche diode. A new data acquisition mode for TCSPC applications was developed to facilitate performance evaluation. Depth uncertainties of 250 m were achieved with the system at 320 m stand-off distance, and a pattern matching scheme was implemented to acquire unambiguous photon-counting depth images at a record-breaking target distance of 4.4 km while maintaining eye-safe illumination levels. Advanced return analysis algorithms were used to demonstrate the automatic resolution of multiple target surfaces.