Laser Feedback Frequency-Modulated Continuous-Wave LiDAR and 3-D Imaging

We propose and demonstrate a novel light detection and ranging (LiDAR) system for 3-D imaging, combined with laser feedback interferometry (LFI) and frequency-modulated continuous-wave (FMCW). Compared with the conventional FMCW method, the intracavity interference between the echo signal and local oscillator enhances the amplitude of the generated beat signal effectively, which improves the sensitivity in weak-signal detection with low photon consumption. The improvement is still effective even with frequency modulation nonlinearity. Besides, the system inherits the advantages of FMCW, possessing the capacity to measure position and velocity simultaneously. In experiments, the validity of distance and velocity measurement is demonstrated, and 3-D imaging is realized by employing a pair of beam scanners. With a less than $200 \mu \text{W}$ probe beam, the system achieves imaging over 65 m away in various scenes with good fidelity, and the distance resolution is better than 1 mm. A portable prototype is also designed and fabricated. Overall, the proposed system possesses high echo-signal sensitivity, simple structure, and dynamic information availability, which provides a new idea for FMCW-LiDAR optimization for practical applications.