Passive Micron-scale Time-of-Flight with Sunlight Interferometry
This enables passive, high-resolution depth sensing in outdoor environments, addressing challenges in imaging through adverse conditions, though it appears incremental as it builds on existing interferometric methods.
The paper tackles the problem of passive time-of-flight imaging and depth sensing by introducing an interferometric technique using sunlight, achieving micrometer axial resolutions and robustness to indirect illumination effects like interreflections and subsurface scattering.
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.