Noise and Interference Co-Suppression Technique in SPAD-Based Direct Time-of-Flight (d-ToF) Pulsed LiDAR Sensors

Single-photon avalanche diode (SPAD)-based direct time-of-flight (d-ToF) light detection and ranging (LiDAR) sensors are highly vulnerable to ambient noise, especially sunlight, and interference from nearby LiDAR systems. Simultaneously addressing both challenges remains difficult in real-world, densely populated environments. This paper presents a technique based on laser repetition frequency modulation for simultaneous suppression of background noise and strong interference. The method is analytically modeled for multi-target scenarios and experimentally validated on two platforms: a mechanicallyscanning LiDAR with linear-mode detection and a flash LiDAR using a custom-fabricated SPAD sensor chip. Measurements show interference suppression of 15.85 dB with 4-bit pseudo-random modulation with the SPAD-based sensor, demonstrating the method's effectiveness in mitigating both noise and interference. Additionally, depth image of the scene is captured at 87-fps frame rate with <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$2.34-\text{cm}$</tex> depth resolution.