A Multi-Mode SPAD-Based Ranging System Integrated Nonlinear Histogram and FIR With Adaptive Coefficient Adjustment

This paper proposed a fully integrate single photon ranging system (ISPRS), which mainly consists of a laser pulse driver circuit with adaptive power adjustment, bias voltage generation circuit, 512 independently enabled single photon avalanche diodes (SPADs) used as Reference SPAD array and Return SPAD array respectively, two multi-event time-to-digital converters (TDCs) based on multi-phase sampling, and the ranging extraction circuit. The ranging extraction circuit mainly consists of nonlinear histogram, the FIR with adaptively coefficient adjustment algorithm, and receiving photon adaptive conditioning circuit. The nonlinear histogram is proposed to collect the distribution characteristics of the photons received by the Reference SPAD array and Return SPAD array, which can enhance the equivalent trigger probability of the SPAD array for laser echo. The coefficients of the FIR filter are obtained by normalizing the histogram collected by the Reference SPAD array. By adjusting the number of the enabled SPADs of Reference SPAD array, the envelope of the histogram collected by Reference SPAD array will be changed to match different measurement signal-to-background noise ratio (SBR) for Return SPAD array, which can improve the measurement precision of the ISPRS. The laser power meets the safety of the human eye while effectively improving the measurement range based on the proposed ranging extraction circuit and receiving photon adaptive conditioning circuit. The experimental results show that the measurement range and precision can reach 4.7 m and ±0.5 cm respectively of the ISPRS when the measurement rate is set 30 Hz.