A Flash LiDAR with SA-Based Pulse Position Modulation for Multi-user Interference Cancellation

This paper presents a flash LiDAR system based on successive approximation (SA) in-pixel histogramming time-to-digital converter (hTDC) featuring pulse position modulation (PPM) to suppress interference from other light sources. The pulse position is randomly shifted with the start time of the hTDC, spreading out interference equally to both bins and canceling it by the up-down counting with no demodulation process. The PPM modulator is implemented in an FPGA with a flash LiDAR sensor and is fully characterized. The proposed SA-based PPM successfully attenuates 16-fold larger interference than the user’s optical power, achieving a frame rate of 30 fps and a success rate of 99.9% at the same time.