SA-Based LiDAR System with Pulse Position Modulation Technique for Multi-user Interference Cancellation

Abstract

The demand for three-dimensional (3D) imaging technology is increasing, emphasizing its importance across various fields. This technology enhances user identification capabilities on mobile devices and contributes to improving immersive experiences in augmented reality (AR) and virtual reality (VR) applications. Furthermore, in the automotive sector, it enables advanced perception systems by accurately understanding the surrounding environment, preventing accidents, and providing convenience to users. Light detection and ranging (LiDAR) is a technology used to measure the distance from sensors to objects. direct Time-of-Flight (dToF) technology, suitable for long-range detection, employs high- sensitivity single-photon avalanche diode (SPAD) devices. While SPAD devices are highly sensitive, they can generate noise, potentially leading to errors in the sensor’s distance measurement. Generally, time correlated single photon counting (TCSPC) technology is used to accurately separate the reflected light signal from the inherent noise on SPAD and external noise from background light. This statistical solution enables precise distance measurement. However, there are noise components that even the TCSPC method cannot eliminate. One such component is interference from other light sources. In areas with heavy traffic or many devices, the likelihood of encountering multiple LiDAR systems is high. The infrared emission cycles of these other LiDAR systems are likely to correlate with the main user's system. Such interference signals act as critical noise to the LiDAR sensor, potentially disrupting its accurate functioning. This paper introduces a method to suppress interference signals using Pulse Position Modulation (PPM) and proposes a new LiDAR system that applies this technique to a Successive Approximation (SA)-based LiDAR system to eliminate interference signals from multiple users. This system allows for data conversion without a separate demodulation process. Even in situations with strong interference signals, selecting an appropriate number of PPM IDs ensures a frame rate of 30 FPS and a success rate of 99.9%. The proposed system's Up-Down cancellation effectively suppresses interference signals, achieving an interference suppression gain of 41.3 dB.