  Depth imaging is vital for many emerging technologies with applications in
augmented reality, robotics, gesture detection, and facial recognition. These
applications, however, demand compact and low-power systems beyond the
capabilities of state-of-the-art depth cameras. Here, we leverage ultrathin
dielectric metasurfaces to demonstrate a solution that, with a single surface,
replicates the functionality of a high-performance depth camera typically
comprising a spatial light modulator, polarizer, and three lenses. Using
cylindrical nano-scatterers that can arbitrarily modify the phase of an
incident wavefront, our metasurface passively encodes two complementary optical
responses to depth information in a scene with a single camera snapshot. By
decoding the captured data in software, our system produces a fully
reconstructed image and transverse depth map of three-dimensional scenes with a
fractional ranging error of 1.7%. We demonstrate the first visible wavelength
and polarization-insensitive metasurface depth camera, representing a
significant form factor reduction for such systems.
