Fig. 1. Schematic diagram of a conventional range-gated imaging system. BE represents beam expansion. TL represents telescopic lens. The imaging distance is ct₀/2 and the imaging DOF is ct_g/2, where c is the speed of light.

Fig. 2. The RIPs of different imaging modes.

Fig. 3. The RIPs of different pixels. (a) The influence of surface reflectivity. (b) After the gray normalization.

Fig. 4. Schematic diagram of the DP-RGI system. HWP is a half-wave plate. PBS denotes the polarizing beam splitter. APD is an avalanche photo-diode. HE represents the beam homogenization and expansion device. MR is a mirror. BF is a band-pass filter. TL is a telescopic lens. DG645 is a digital signal generator.

Fig. 5. Imaging target and experimental data. (a) The diffuse plate. (b) The DP-RIP of one pixel.

Fig. 6. The results of different imaging modes. The objects are three cardboard boxes. (a)–(c) are captured by the ICMOS camera. (a) Works in the DP-RGI mode and (b), (c) works in the SP-RGI mode with the same parameters but different pulse emitting times. The color in the pink rectangle is the pseudo-color of depth. The corresponding depths of red, green, and blue are approximately 21.2, 22.7, and 24.2 m, respectively. The black area in the pink rectangle is out of DOF. The curves in (d)–(f) are the distributions of gray values corresponding to the white line in (a)–(c), respectively.

Fig. 7. Depth estimation of static objects with different reflectivities. (a) is taken by the ICMOS camera in the DP-RGI mode. (c) is the normalized image. (b) and (d) are the corresponding depth distributions. Curve 1 and Curve 2 are plotted in (e).

Fig. 8. The depth estimation of the forward-moving target. (a)–(g) are original images captured in DP-RGI mode, which correspond to sub-intervals (1)–(7) in Fig. 5(b). (h)–(n) and (o)–(u) are the depth distributions without and with post-processing.

Fig. 9. The depth estimation of a person walking forward and afterward. (a)–(h) are the original images, whose depth estimations correspond to (i)–(p). fps represents frame/s.