Ref HAL: hal-01927266_v1
DOI: 10.1109/cleoe-eqec.2017.8087768
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From the session Tomography and Computational Imaging (JSII_1) (invited) 4D Digital Holographic Microscopy (4D-DHM) is a new technique capable of performing 3D imaging of moving objects. 3D reconstruction is made from a single hologram, but is restricted to sparse objects that occupy only small part of the volume. For a sequence of holograms, 4D-DHM therefore performs 4D (x; y; z and t) imaging. 4D-DHM is well suited to image micro circulation, and has been validated imaging red blood cells circulating in a zebrafish embryo in vivo [1-3]. Fig. 1 (a) Holographic setup. (b, c and d) Images of blood flow within a zebrafish embryo: blood vessel (purple) and RBCs (green). The displayed 2D images correspond to the projections along z of the 3D images rotated along the y direction by-30° (b), 0° (c) and +30° (d). Bar is 50 m, The principle of the 4D DHM is illustrated by Fig. 1 (a). The setup is an upright microscope, which has been modified to perform Digital Holographic Microscopy (DHM) in transmission. The white light illumination is replaced by a laser, which is split in two beams of different directions. To perform holographic detection a reference arm (ELO field) is added on the detection side. The field E scattered by the object interferes with ELO , and a camera records sequences of frames. These frames are used to calculate the holograms, and to reconstruct in 3D the field scattered by the sample. By a proper analysis of this information, 3D images of the blood vessels, and 4D images of the moving red blood cells (RBCs) can be obtained see Fig,1 (b) to (d). To get these images, we have proceeded by the following way [2,3]. First, we calculate the holograms which differences of frames, and select by the way the signal from the moving components of the object (i.e.) the RBCs signal. We have then extract from the data, the holograms corresponding to the two illumination. For each RBC, and each illumination, the field that can be reconstructed by holography as a narrow cone of light (narrow because RCBs are much larger than the wavelength), which is angularly tilted like the illumination. The location of RBCs is then obtained by considering the intersection of the two cones. To prevent the signals of the different RBCs to mix together, the positions of the RBCs that give the largest signals are calculated first. The contributions of these RBCs are then removed from the hologram, and the positions of the following RBCs are calculated from the hologram thus cleaned. The reconstruction by cleaning is highly non-linear (unlike conventional holographic reconstructions), since it is the algorithm that decides to place a RBC in a plane and to remove the field diffused by this RBC from the other planes. In order to converge successively it requires to image sparses objects, that occupy only small part of the holographic reconstructed volume. 4D-DHM is thus capable of performing 3D reconstruction is made from a single hologram, but is restricted to sparse objects that occupy only small part of the volume.

Ref HAL: hal-01927223_v1
DOI: 10.1109/cleoe-eqec.2017.8087591
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Open channels are peculiar incidents modes of the optical field that are transmitted by a highly diffusing medium with high efficiency (100 % in the ideal case). The existence of these modes has been predicted by Dorokhov et al. [1] more than 25 years ago. Although many experiments were made to prepare these modes [2,3], the maxima of transmission obtained in experiments, are ever much lower than 100 %. To test the theory, we have considered here another Dorokhov's prediction: the average transmission of the modes that sustain the transmitted field must be TT=66%, where TT is defined by N2 TT= N1 T (where T is the averaged transmission of energy, and N1 and N2 the number of incident and transmitted modes i.e. the size of the incident and transmitted mode basis). Fig.1 (a) Holographic experimental setup. (b) Residual correlation of the transmitted field. The horizonal axis is SQ'. The sample transverse size is L=70 µm red, 50 µm green, 35 µm blue.... The horizontal grey line is the residual correlation expected for N1=N2. To verify this prediction, we have measured N2 on a slab sample of ZNO powder (transverse size L<=70 µm, thickness 20 µm) [4], by assuming that N1 is given by the sample geometry. The experimental setup is seen in Fig. 1(a). The incident fields are random (there are scrambled by a diffusing liquid DL) and digital holography is used to measure the complex transmitted field E(x,y) for the two polarisations. N2 is measured by analysing the residual correlations of the transmitted field measured for uncorrelated incident fields. Since the average transmission is T=1/25, we expect N2=N1/16. To get this optimal result, the transverse size of sample L must be infinite and the defocusing SQ' of the microscope objective MO2 must be zero (where S is the sample outgoing surface and Q' the plane imaged by MO2). Figure 1 (b) shows the residual correlation (which is proportional to 1/N2) as a function these two parameters. We get N2=N1/12 without extrapolation, and N2=N1/16 with extrapolation to L infinite. Here, the open channel effect is huge (factor 16) and the aggreement with the Dorokhov's prediction is excellent. We acknowledge Labex Numev (convention ANR-10-LABX-20) for funding. References 1. O.N. Dorokhov. On the coexistence of localized and extended electronic states in the metallic phase. Solid state communications, 51(6): 381-384, (1984).

Ref HAL: hal-01927511_v1
DOI: 10.1364/dh.2016.dth1e.1
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An holographic microscopy setup using two illumination beams is proposed to image blood microcirculation in preclinical models. Greedy algorithm reconstruction of the two resulting holograms leads to a 3D reconstruction of the sample over time.

Ref HAL: hal-01927378_v1
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A holographic microscopy algorithm is proposed enabling to deal with high numerical aperture holograms. Hologram reconstruction kernel performs under afocal conditions , which allows keeping the full NA over wide defocus range.

Ref HAL: hal-01927325_v1
DOI: 10.1364/dh.2016.dt1e.3
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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

Ref HAL: hal-01927313_v1
DOI: 10.1364/dh.2016.dth4c.2
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Open channels are peculiar incidents modes that are transmitted by a diffusing medium with high efficiency (up to 100%). Digital holography is used to analyze the correlations of the transmitted field, and to test open channel theory. Quantitative agreement is obtained.

Ref HAL: hal-01474043_v1
Ref Arxiv: 1702.07378
DOI: 10.1364/AO.56.001846
WoS: 000395668400007
Ref. & Cit.: NASA ADS
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3 Citations
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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.