PT Unknown
AU Henschke, A
TI Control Algorithm and Evaluation Strategies for Single-Photon Avalanche Diode-Based Direct Time of Flight Systems
PD 07
PY 2022
DI 10.17185/duepublico/78563
LA en
DE LiDAR, SPAD, Direct Time of Flight, Digital Signalprocessing, Multi Event, Signal-to-Noise Ratio
AB Single-Photon Avalanche Diode-based Direct Time of Flight systems are currently attracting much attention due to the need for optical systems with high temporal and spatial resolution, high frame rates, range, and high ambient light rejection for autonomous driving applications. Within the scope of this thesis, methods aiming to detect targets under high ambient light power are evaluated. Different pixel structures are considered, and the Signal-to-Noise Ratio derived as a measure of their performance. On this basis, a novel comparison between commercially available Avalanche Photodiode and Single-Photon Avalanche Diodes is conducted. It shows the latter’s advantages when only small return signals are present. The theoretical predictions are then investigated with numerical simulation and verified using available research prototype systems. With high frame rate and long range come small signal photon budgets. A rank-order filter-based signal processing chain for detecting faint return signal is investigated and compared to proven correlation-based approaches. It is shown that while the rank-order filters show excellent background light rejection, the signal is attenuated aggressively, limiting their usefulness in long-range ranging applications. Strong return signals distort the recorded pulse distribution and limit accuracy. An approach for computationally correcting this accuracy deterioration from the measurement result for a given temporal laser pulse form is designed with a view to hardware integration. It can be corrected for signal peak event rates of up to 0.2 GHz. The investigations result in a developed sensor control algorithm based on analysis of the recorded signal strength which yields high frame rates in low ambient light scenarios and high range in high ambient light scenarios. A range increase of up to 20% over systems without an active control algorithm can be shown, increasing to up to 700% for systems without active ambient light suppression.
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