Fig. 1. Schematic of optical path received by optical fiber collimator in defocus mode

Fig. 2. Simulation results of one-dimensional beam broadening in defocus mode

Fig. 3. Receiving beam broadening experiment in defocus mode

Fig. 4. Schematic of overlapping field-of-view (FOV) receiving optical path in defocus mode

Fig. 5. Receiving beam broadening results based on cylindrical lens. (a) Simulation beam diagram of azimuth direction; (b) simulation beam diagram of elevation direction

Fig. 6. Transmission beam broadening results based on cylindrical lens. (a) Linear spot formed by beam expansion; (b) simulation beam diagram of azimuth direction; (c) simulation beam diagram of elevation direction

Fig. 7. Simulation results of beam broadening. (a) 1550.0 nm; (b) 1549.6 nm; (c) 1549.2 nm

Fig. 8. Experimental results of beam broadening. (a) 1550.0 nm; (b) 1549.6 nm; (c) 1549.2 nm

Fig. 9. Simulation results of beam scanning based on wavelength change

Fig. 10. System schematic of LiDAR

Fig. 11. AD sampling results. (a) Signal spectrum before sampling; (b) signal spectrum after sampling

Fig. 12. Detection results of chimney at the distance of 1.1 km. (a) Photograph of chimney; (b) range-Doppler domain imaging result; (c) range-Doppler domain imaging result after PGA processing; (d) Doppler domain profile of imaging result; (e) Doppler domain profile of imaging result after PGA processing; (f) time domain waveform of signal; (g) time domain waveform of signal after PGA processing and low-pass filtering

Fig. 13. Detection results of high reflectivity target at a distance of 5.4 km. (a) Photograph of high reflectivity target; (b) range-Doppler domain imaging result; (c) range-Doppler domain imaging result after PGA processing; (d) Doppler domain profile of imaging result; (e) Doppler domain profile of imaging result after PGA processing; (f) time domain waveform of signal; (g) time domain waveform of signal after PGA processing and low-pass filtering