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

## TL;DR

This paper presents a theoretical analysis of heterodyne holography for ultrasound-modulated optical tomography, demonstrating optimal detection sensitivity by matching camera exposure time to speckle decorrelation time.

## Contribution

It introduces a method to filter tagged photons in heterodyne holography UOT and analyzes the impact of shot noise and speckle decorrelation on detection sensitivity.

## Key findings

- Optimal detection sensitivity is achieved when camera exposure time matches decorrelation time.
- Theoretical framework for filtering untagged photons in heterodyne holography UOT.
- Analysis of shot noise effects on tagged photon detection.

## Abstract

Ultrasound-modulated optical tomography (UOT) is a technique that images optical contrast deep inside scattering media. Heterodyne holography is a promising tool able to detect the 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 considers also 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 of the order of the decorrelation time.