Etude d’opportunité pour le développement d’une application permettant d’aider une personne à choisir un vin

GWS - Aux Services du Vin SA, entreprise mandante de cette étude, a pour activité principale l’organisation de dégustations professionnelles de vin. Cette société souhaite élargir ses activités et s’intéresse au potentiel d’une application mobile qui permettrait de recommander des vins suisses aux clients de restaurants et de supermarchés. Les objectifs de cette recherche consistaient à déterminer s’il existe un marché pour une application de ce type et, si tel était le cas, identifier le public cible et ses besoins. Le mandant souhaitait également que la solution recommandée s’intègre dans l’infrastructure existante pour l’organisation des concours de vin. Pour terminer, l’étude d’opportunité devait proposer un Business Model et contenir un Product Backlog

Coherent transfer functions and extended depth of field

To preserve the speed advantage of Fourier Domain detection in Optical Coherence Microscopy (OCM), extended depth of field is needed. With a narrow probing volume that extends over a long axial range, tissue could be measured in vivo and at cellular resolution. To assess and improve the DOF and the lateral resolution, we analyzed the coherent transfer function (CTF) of OCM. Both the illumination and detection optics contribute equally to the overall imaging performance. In the Fourier domain detection, each pixel of the spectrometer has its specific CTF, sampling a different region of the object’s spatial frequency spectrum. For classical optics and increasing numerical apertures these regions start to overlap and bend, which limits the depth of field. Annular apertures, created with Bessel-like beams produced by axicon lenses or phase filters, circumvent these detrimental effects, but introduce strong side lobes. Decoupling the detection and the illumination apertures is needed to provide the flexibility in engineering a CTF that optimizes the lateral resolution and the DOF at the same time all while reducing these side lobes. We evaluated different combinations of Gaussian and Bessel-like illumination and detection optics, both theoretically and experimentally. Using Bessel-like beams as well in the illumination as in the detection paths, but with annular apertures of different lobe radii, we obtained a lateral resolution of 1.3 μm and an extended depth of field of more than 300 μm, which was completely decoupled from the numerical aperture and scalable to high lateral resolution

Optical Coherence Correlation Spectroscopy (OCCS)

A classical technique to monitor dynamical processes at the molecular level is fluorescence correlation spectroscopy (FCS). FCS requires fluorescent labels that are typically limited by photobleaching and saturation. We present a new method that uses noble-metal nanoparticles instead of fluorophores: optical coherence correlation spectroscopy (OCCS). OCCS is a correlation spectroscopy technique based on dark-field optical coherence microscopy, a Fourier domain optical coherence tomography technique. In OCCS, several sampling volumes are measured simultaneously with high detection sensitivity. OCCS measures the time correlation function of the light back-scattered by the nanoparticles. Using a mode-locked Ti:Sapphire laser (780nm central wavelength) we performed first experiments with different nanoparticles down to 30nm in diameter. We present experimental results and a preliminary model to fit the correlation curves and extract the particles’ concentrations and diffusion coefficients. The experimental determination of the diffusion times of gold nanoparticles using this model is presented, showing the potential of our method. In the near future, we aim at investigating smaller gold nanoparticles that interfere less with the biological phenomena under study

Optical Coherence Correlation Spectroscopy (OCCS)

A classical technique to monitor dynamical processes at the single-molecule level is fluorescence correlation spectroscopy (FCS). However, FCS requires fluorescent labels that are typically limited by photobleaching and saturation. We present a new method, optical coherence correlation spectroscopy (OCCS), based on noble-metal nanoparticles that overcome those photobleaching and saturation limitations. OCCS is a correlation spectroscopy technique based on dark-field optical coherence microscopy (dfOCM), a Fourier domain optical coherence microscopy technique. OCCS is based on the amplified backscattered light caused by diffusing nanoparticles. Due to the interferometric principle of OCCS, several sampling volumes along the optical axis are measured simultaneously with high detection sensitivity. This adds the possibility to assess axial flow, which is similar to a lateral flow measurement in dual-focus fluorescence correlation. Using a mode-locked Ti:Sapphire laser (780nm central wavelength) we performed experiments with nanoparticles down to 30nm in diameter. We present these first experimental results and an associated theoretical fit model allowing the extraction of the particles’ concentrations and diffusion parameters. The experimental determination of the diffusion time and concentration of gold nanoparticles based on this method is presented as a proof of principle and shows the potential of this technique. In the near future, we aim at investigating smaller gold nanoparticles assessing biological phenomena. As a first application we apply this method to membrane receptor interaction using functionalized nanoparticles

Contrast Enhancement in Optical Coherence Microscopy

Optical Coherence Microscopy (OCM) is a three-dimensional imaging technique that provides cross-sectional views of the subsurface microstructure of biological tissue, with a high axial and lateral resolution. In OCM, a low time coherence light source is split into two beams, propagating along the reference and object arms. Light backscattered by variation of the index of refraction in the sample is then recombined with the strong reference field. The high intensity of the reference beam provides a coherent amplification of the weak sample field, resulting in a high sensitivity. By detecting in the Fourier domain, only a two-dimensional scan is required, as the whole depth structure is extracted from a single spectrum acquisition. For volumetric imaging, this parallel acquisition confers a tremendous speed advantage over classical techniques, such as confocal fuorescence microscopy. In addition, the contrast in OCM relies on fundamental properties of the object, namely scattering and absorption. This intrinsic contrast offers the advantage of not requiring any staining process of the sample. Above all, relying on the sensitive phase information, motions on a nanometer scale can be revealed in a non-contact and non-invasive manner. However, depending on the application, this asset may become a drawback as the signal lacks specificity, in comparison to exogenous labels. The aim of this thesis work was to evaluate and implement contrast enhancement mechanisms in OCM for 3D cell imaging. In brief, an improvement of the sensitivity to weakly scattering objects, such as single cells combined with the molecular specificity of nanolabels were investigated. The developed technique was then employed for the imaging of dynamic cellular processes. First, we realized a dark-field illumination scheme for OCM (dfOCM). This design efficiently filters scattered light and suppresses specular reflections arising from glass interfaces, almost compulsory in cell preparation. The sensitivity to backscattered light was drastically enhanced in comparison to the classical approach. After a careful analysis of the imaging performances, tomograms of living cells were acquired, where even subcellular structures could be identified. Second, we implemented photothermal optical lock-in OCM (poli-OCM), which uses the photothermal contrast to exclusively localize gold nanoparticles within scattering medium. We provided a theoretical analysis of the signal-to-noise ratio and explained thoroughly the lock-in detection effect. Significant parameters such as resolution and depth of field were measured experimentally and we applied the combined dfOCM/poli-OCM technique for the 3D imaging of gold nanoparticles in living cells. Finally, dfOCM has been successfully applied to the monitoring of dynamic cellular processes, opening new horizons for further investigations

Measurement of the coherent transfer function

It is important to characterize and quantify the imaging performance of optical coherence tomography (OCT) and especially optical coherence microscopy (OCM) systems for validation and calibration of the setup. We suggest using a simple rubber surface, presented to the setup at different focal positions, to measure the system’s lateral resolution and depth of field. Rubber is a nearly perfect scatterer and produces a fully developed speckle pattern. The speckle size and shape are directly defined by the optical system and its illumination and detection apertures. Analysis of the speckle pattern reveals the system’s coherent transfer function (CTF) and hence the point spread function (PSF) in a straightforward computation

Dark-field optical coherence microscopy

Dark-field illumination is known to enhance scattering contrast in optical microscopy. We combined this concept with Fourier domain optical coherence microscopy (OCM). The detection and illumination paths are decoupled, and only the scattered light originating from the sample generates the tomogram signal, whereas any specular reflection is highly suppressed. We analyze and discuss this dark-field OCM concept and present its superior imaging quality on live cell samples

Dark-field optical coherence microscopy

Dark-field illumination is known to enhance scattering contrast in optical microscopy. We combined this concept with Fourier domain optical coherence microscopy (OCM). The detection and illumination paths are decoupled, and only the scattered light originating from the sample generates the tomogram signal, whereas any specular reflection is highly suppressed. We analyze and discuss this dark-field OCM concept and present its superior imaging quality on live cell samples. © 2010 Optical Society of America OCIS codes: 180.1655, 170.1530, 120.5820. The imaging of label-free cell samples has long since propelled the development of novel imaging techniques. Because of the high transparence of the cell, imaging in the transmission mode has received the most attention. Many recent approaches aim at a quantitative evaluation of the spatially resolved susceptibility of the cell [1,2]. In contrast, spectral domain optical coherence phase microscopy [3,4] works in the reflection mode. It uses the high NA of optical coherence microscopy (OCM

Engineering of Extended Focii for Optical Coherence Microscopy

Based on a Debye integral approach, we engineered an extended focal field distribution for Fourier domain optical coherence microscopy. This simulation optimizes beam con- figurations for high lateral resolution combined with extended depth of field