  Holography is an established technique for measuring the wavefront of optical
signals through interferometric combination with a reference wave.
Conventionally the integration time of a hologram is limited by the
interferometer coherence time, thus making it challenging to prepare holograms
of remote objects, especially using weak illumination. Here, we circumvent this
limitation by using intensity correlation interferometry. Although the exposure
time of individual holograms must be shorter than the interferometer coherence
time, we show that any number of randomly phase-shifted holograms can be
combined into a single intensity-correlation hologram. In a proof-of-principle
experiment, we use this technique to perform phase imaging and 3D
reconstruction of an object at a ~3m distance using weak illumination and
without active phase stabilization.
