  Hong-Ou-Mandel (HOM) interference, the bunching of indistinguishable photons
at a beam splitter, is a staple of quantum optics and lies at the heart of many
quantum sensing approaches and recent optical quantum computers. Here, we
report a full-field, scan-free, quantum imaging technique that exploits HOM
interference to reconstruct the surface depth profile of transparent samples.
We demonstrate the ability to retrieve images with micrometre-scale depth
features with a photon flux as small as 7 photon pairs per frame. Using a
single photon avalanche diode camera we measure both the bunched and
anti-bunched photon-pair distributions at the HOM interferometer output which
are combined to provide a lower-noise image of the sample. This approach
demonstrates the possibility of HOM microscopy as a tool for label-free imaging
of transparent samples in the very low photon regime.
