Fast SPAD-array timing-error correction with time-referencing for non-line-of-sight imaging

We present a fast calibration and correction algorithm to compensate for timing errors in time-correlated single-photon counting (TCSPC) with single-photon avalanche diode (SPAD) array detectors. Manufacturing tolerances cause pixel-dependent variations in mean time-bin width (≈6%) and bin-to-bin fluctuation (≈0.6%), leading to temporal broadening when signals are combined. Our method addresses these errors with a pre-computed lookup table that equalises pixel-dependent time-bin widths. A second stage then establishes an absolute time reference for non-line-of-sight (NLOS) reconstruction by exploiting intrinsic line-of-sight (LOS) signal features, eliminating the need for external calibration. The approach improves temporal alignment and facilitates more accurate NLOS reconstructions, as demonstrated in two non-confocal experimental setups and with simulated confocal data.