Dual-frequency AMCW concurrent ranging and velocimetry for LiDAR imaging

Ranging and velocimetry constitute fundamental operational capabilities in light detection and ranging (LiDAR) systems. However, the presence of Doppler shift during moving targets imposes severe interference on the ranging accuracy of continuous-wave (CW) LiDAR systems. In order to overcome these inherent constraints in conventional amplitude-modulated continuous-wave (AMCW) systems, we propose a dual-frequency source amplitude modulation (DFAM) scheme that enables concurrent laser ranging and velocimetry. This method utilizes two modulation components: a low-frequency signal for Doppler shift quantification throughout the velocity measurement, along with a higher-frequency signal that facilitates phase-difference measurements between transmitted and echo signals. The obtained Doppler shift from the low-frequency signal is subsequently employed to compensate for this phase difference, allowing precise distance calculation from the compensated phase. Experimental results demonstrate that this approach not only achieves highly precise velocimetry with consistency within a few millimeters per second but also maintains ranging accuracy comparable to that under static target conditions. Furthermore, the system has been successfully implemented in LiDAR imaging, enabling multi-dimensional object reconstruction and analysis.