Concurrent Ranging and Velocimetry with Amplitude-modulated Continuous-wave Laser by Dual-frequency Source

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 employs 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 reflected signals. Subsequently, the obtained Doppler shift from the low-frequency signal is then employed to compensate for this phase difference, allowing precise distance calculation from the compensated phase. The experimental results demonstrate that this method not only achieves highly precision velocity measurements with a precision consistently within 5 mm/s but also maintains ranging precision comparable to that of static targets under identical conditions. All experimental findings validate the feasibility of the proposed approach. We believe this method provides a new perspective for LiDAR systems to realize simultaneous and high-precision ranging and velocimetry for dynamic target characterization.