  We introduce an interferometric technique for passive time-of-flight imaging
and depth sensing at micrometer axial resolutions. Our technique uses a
full-field Michelson interferometer, modified to use sunlight as the only light
source. The large spectral bandwidth of sunlight makes it possible to acquire
micrometer-resolution time-resolved scene responses, through a simple axial
scanning operation. Additionally, the angular bandwidth of sunlight makes it
possible to capture time-of-flight measurements insensitive to indirect
illumination effects, such as interreflections and subsurface scattering. We
build an experimental prototype that we operate outdoors, under direct
sunlight, and in adverse environment conditions such as machine vibrations and
vehicle traffic. We use this prototype to demonstrate, for the first time,
passive imaging capabilities such as micrometer-scale depth sensing robust to
indirect illumination, direct-only imaging, and imaging through diffusers.
