Histogram-Less LiDAR Through SPAD Response Linearization

We present a new method to acquire the 3-D information from a Single-photon avalanche diode (SPAD)-based direct-Time-of-Flight (d-ToF) imaging system which does not require the construction of a histogram of timestamps and can withstand high-flux operation regime. The proposed acquisition scheme emulates the behavior of an SPAD detector with no distortion due to dead time, and extracts the ToF information by a simple average operation on the photon timestamps ensuring ease of integration in a dedicated sensor and scalability to large arrays. The method is validated through a comprehensive mathematical analysis, whose predictions are in agreement with a numerical Monte Carlo model of the problem. Finally, we show the validity of the predictions in a real d-ToF measurement setup under challenging background conditions well beyond the typical pile-up limit of 5% detection rate up to a distance of 3.8 m.