Résumé
Ultrasound-modulated optical tomography (UOT) is a technique that combines light and ultrasound able to image deep inside scattering media. A pulsed version of technique involving holography is proposed and discussed. Ultrasound-modulated optical tomography (UOT) [1] also called acousto-optic imaging [2] is a technique that combines light and ultrasound able to image deep inside scattering media. The ultimate goal of the technique is breast cancer imaging. Heterodyne holography combined with UOT is a powerful tool to detect the UOT tagged photons. Previous experiments are made with phantom samples. Since the sample does not move, the phase of the field remains correlated. Holographic detection is then efficient and shot noise sensitivity is reached [3]. To perform imaging with breast, a new setup with light and ultrasound pulses is proposed. Numerical simulations, that fits with the results of previous work, are made to extrapolate the phantom results to breast imaging with the new setup. They show that breast tumor imaging is possible. Fig. 1. Typical UOT setup (a) and pulsed modified setup to detect signal whose phase correlation is short (b). BS1, BS2: beam splitter; M: mirror; AOM1,AOM2: acousto optic modulator; PZT: piezoelectric transducer that generates the ultrasonic beam US; a: absorber imbedded in the diffusing sample; A: rectangular aperture; L: lens of focal d; C: camera; E LO , E T , E U : LO, tagged and untagged fields. Figure 1 (a) shows the heterodyne holography UOT setup of the phantom experiment [3]. The main laser beam L (frequency ω L) is split by the beam splitter BS1 into a local oscillator (LO), and a signal beam that is scattered by the diffusing sample. The sample is explored by an ultrasonic (US) beam of frequency ω US generated by a piezoelectric