Figure 3: 3D structure and reflectivity reconstructions.

(a–d) Results of imaging 3D structure and reflectivity using the filtered histogram method, the state-of-the-art pseudo-array imaging method, our proposed framework and the ground-truth proxy obtained from detecting 550 signal photons per pixel. For visualization, the reflectivity estimates are overlaid on the reconstructed depth maps for each method. The frontal views, shown here, provide the best visualizations of the reflectivity estimates. (e–h) Results of imaging 3D structure and reflectivity from a–d rotated to reveal the side view, which makes the reconstructed depth clearly visible. The filtered histogram image is too noisy to show any useful depth features. The pseudo-array imaging method successfully recovers gross depth features, but in comparison with the ground-truth estimate in h, it overestimates the dimensions of the mannequin’s face by several cm and oversmooths the facial features. Our SPAD-array-specific method in g, however, gives high-resolution depth and reflectivity reconstruction at low flux. (i–k) The depth error maps obtained by taking the absolute difference between estimated depth and ground-truth depth show that our method successfully recovers the scene structure with mean absolute error of 2 cm, which is sub-bin-duration resolution as cΔ/2≈6 cm, while existing methods fail to do so. (l) Vertical cross section plot of the middle of 3D reconstructions from pseudo-array imaging (red line), pixelwise ground truth (black line) and our proposed method (blue line). Note that our framework recovers fine facial features, such as the nose, while the pseudo-array imaging method oversmoothes them.