Fig. 1. Schematic diagram of the underwater depth imaging system.

Fig. 2. IRF fitting plot. (a) The IRF without polarization module. (b) The IRF with a polarization module added.

Fig. 3. Acquired detection histogram. The attenuation length between the system and the target is 3.6. Collected data of the target to plot timing histograms under different conditions: (a) polarization module is not added to the system; (b) polarization module is added to the system.

Fig. 4. The depth and intensity of a flange target at 3.6 AL between the system and the target under different conditions: (a) reference images; (b) polarization module is not added to the system; (c) polarization module is added to the system.

Fig. 5. Photographs of the object and its dimensions used in the experiment. (a) Plastic flange, side shown by (b). (c) Depth-resolution object with nine square columns providing ten planes of different heights, shown from the side (d).

Fig. 6. Intensity (top row) and depth (bottom row) profiles of the flange target at 1.9, 3.6, 4.4, 6.7, 7.4, and 8.5 attenuation lengths between the system and the target. The acquisition time per pixel is 20 ms.

Fig. 7. Intensity (first row), depth (second row), 3D (third row), and MAE (fourth row) profiles of the flange target at 3.6 AL between the system and the target. The acquisition time per pixel was varied by software from 20 to 0.02 ms.

Fig. 8. Depth profiles of the deep target at 1.9, 3.1, 4.6, 5.3, 6.7, 7.2, and 8.2 attenuation lengths between the system and the target.