Fig. 1. (a) Schematic diagram for realizing polarization splitting; (b) Flow chart of program

Fig. 2. Schematic diagram of the double Gm-APDs polarization lidar system(FDC, Frequency doubling crystal; PIN, High-speed PIN detector; BS, Beam splitter; HWP, Half wave plate; Polarizer, Glan-Taylor prism; PBS, Polarization beam splitting prism; NBPF, Narrow band pass filter; Gm-APD, Gm-APD detecting module)

Fig. 3. (a) Double Gm-APD polarization lidar system in the laboratory; (b) Shallow water layer designed in the laboratory

Fig. 4. Photon counting distributions of the two Gm-APDs with different line polarized light on a pixel. (a) Horizontal line polarized light; (b) Vertical line polarized light

Fig. 5. Depth image of the shallow water layer obtained in the experiment. (a) Before the restraint of range walk error; (b) Depth image under another view of (a); (c) After the restraint of range walk error; (d) Depth image under another view of (c)

Fig. 6. Histogram of range error distribution of experimental data points. (a) Pixels of the shallow water surface in Fig.5(a); (b) Pixels of the bottom surface in Fig.5(a); (c) Pixels of the shallow water surface in Fig.5(c); (d) Pixels of the bottom surface in Fig.5(c)