5. Conclusion

Three types of system for passive depth estimation have been described: stereovision, defocus blurring (DFD) and plenoptic cameras. The aim of this paragraph is to summarize these approaches, and to give some points of comparison between the three.

What these three approaches have in common is the following. Firstly, they are passive approaches, exploiting the intensity contrasts emitted or reflected by the scene, and all three fail when these contrasts are too low, due to the scene itself (homogeneous walls, for example), the light propagation conditions (smoke, for example) and, of course, the illumination. All three combine a measurement device with parameters fixed at the design stage (baseline or geometry of the plenoptic device, characteristics of the DFD optics), adjustment parameters (focal length, aperture, focus) and digital processing stages with varying...