We present a new method to acquire the 3D information from a 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 a 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