Non-Line-of-Sight Ranging and 3D Imaging Using Vector Enhanced Sensitive FMCW LiDAR

Non-line-of-sight (NLOS) detection technology enables high-precision target detection and reconstruction even in environments with limited visibility. It has been widely used in areas such as military reconnaissance and defect detection in advanced equipment. However, current NLOS techniques face significant limitations when challenged by wide field-of-view scenarios with strong interference or when required to meet the demands of multidimensional sensing. Frequency-modulated continuous-wave (FMCW) laser measurement technology offers advantages such as high precision, strong anti-interference capabilities, and a large unambiguous range. In this paper, we propose and demonstrate a vector-enhanced sensitive FMCW LiDAR (VES-FMCW) for NLOS ranging and 3D imaging. By leveraging laser feedback interferometry (LFI), we achieve sensitive multidimensional sensing of low-reflectivity targets. A distributed feedback (DFB) fast-tuning laser source is employed to enhance the polarization vector characteristics of the measurement beam, boosting detection efficiency. Additionally, a K-domain triggering resampling method is used to eliminate laser modulation nonlinearity and phase shift errors, improving measurement accuracy and simplifying the system design. In our demonstration experiment, we measured a diffuse reflection plate placed on a linear precision guide rail at an NLOS distance of approximately 2.8 m. We achieved absolute distance measurement accuracy better than 32 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i>m, with a minimum Allen deviation of [email protected]. In an NLOS scenario, we conducted a real-world imaging experiment using a cardboard with a “THL” depth pattern and a step-like structure built with toy blocks as the target. The results showed millimeter-level imaging accuracy with high reliability. Overall, the proposed vector-enhanced sensitive FMCW LiDAR features a simple structure, high measurement efficiency, and strong robustness, offering a novel approach for high-precision NLOS detection of concealed targets under extreme conditions. This technology holds promising application potential.