Selection of the tagged photons by off axis heterodyne holography in ultrasound-modulated optical tomography.

Ultrasound-modulated optical tomography (UOT) is a technique that images optical contrast deep inside scattering media. Heterodyne holography is a promising tool that is able to detect UOT-tagged photons with high efficiency. In this work, we describe theoretically the detection of the tagged photon in heterodyne holography-based UOT, show how to filter the untagged photon, and discuss the effect of shot noise. The discussion also considers speckle decorrelation. We show that optimal detection sensitivity can be reached, if the frame exposure time of the camera used to perform the holographic detection is on the order of the decorrelation time.