Emeric Mudry

Structured illumination fluorescence microscopy with distorted excitations using a filtered blind-SIM algorithm.

Structured illumination microscopy (SIM) is a powerful technique for obtaining super-resolved fluorescence maps of samples, but it is very sensitive to aberrations or misalignments affecting the excitation patterns. Here, we present a reconstruction algorithm that is able to process SIM data even if the illuminations are strongly distorted. The approach is an extension of the recent blind-SIM technique, which reconstructs simultaneously the sample and the excitation patterns without a priori information on the latter. Our algorithm was checked on synthetic and experimental data using distorted and nondistorted illuminations. The reconstructions were similar to that obtained by up-to-date SIM methods when the illuminations were periodic and remained artifact-free when the illuminations were strongly distorted.

Electromagnetic wave imaging of three-dimensional targets using a hybrid iterative inversion method

In microwave or optical wave imaging set-ups, the measured scattered field is usually not linearly linked to the target parameter of interest. To reconstruct the latter, nonlinearized or linearized iterative inversion techniques, such as the contrast source inversion method (CSI) or the conjugate gradient method (CGM) have been proposed (Litman and Crocco 2009 Inverse Problems 25 020201–5). In this paper, we adapt to the three-dimensional vectorial case, a hybrid method (HM) that combines the advantages of the CSI and CGM, and compare the performances of the different approaches using microwave experimental data. The HM appears to be the best compromise in terms of reconstruction accuracy, computation time and robustness to noise. (Some figures may appear in colour only in the online journal)

Mirror-assisted tomographic diffractive microscopy with isotropic resolution

We demonstrate that the axial resolution of a reflection tomographic diffractive microscope is drastically improved when the sample is placed in front of a perfect mirror. We show analytically and with rigorous simulations that this approach permits us to obtain images with the same isotropic resolution as that obtained when the sample is illuminated and observed from every possible angle. The main difficulty lies in accounting properly for the mirror in the inversion algorithm.

Electromagnetic wave imaging of targets buried in a cluttered medium using a hybrid inversion-DORT method

The detection and the characterization of targets buried in a natural medium using an array of monochromatic micro-wave antennas are difficult tasks as medium heterogeneities blur the signature of the objects of interest. In this paper, we propose to couple a nonlinear inversion method to an eigenvector analysis of the time reversal operator (D´ ecomposition de l’Op´ erateur de Retournement temporel (DORT) technique) for imaging the targets. We show that this combined approach yields much better results than those of the inversion or DORT approaches alone. In particular, it enables us to characterize targets in highly cluttered environments supporting multiple scattering. The efficiency of the technique is illustrated throughout many examples with varying clutter statistics. (Some figures may appear in colour only in the online journal)

Isotropic single-objective microscopy: theory and experiment.

Isotropic single-objective (ISO) microscopy is a recently proposed imaging technique that can theoretically exhibit the same axial and transverse resolutions as 4Pi microscopy while using a classical single-objective confocal microscope. This achievement is obtained by placing the sample on a mirror and shaping the illumination beam so that the interference of the incident and mirror-reflected fields yields a quasi-spherical spot. In this work, we model the image formation in the ISO fluorescence microscope and simulate its point spread function. Then, we describe the experimental implementation and discuss its practical difficulties.

Tomographic diffractive microscopy with a wavefront sensor

Tomographic diffractive microscopy is a recent imaging technique that reconstructs quantitatively the three-dimensional permittivity map of a sample with a resolution better than that of conventional wide-field microscopy. Its main drawbacks lie in the complexity of the setup and in the slowness of the image recording as both the amplitude and the phase of the field scattered by the sample need to be measured for hundreds of successive illumination angles. In this Letter, we show that, using a wavefront sensor, tomographic diffractive microscopy can be implemented easily on a conventional microscope. Moreover, the number of illuminations can be dramatically decreased if a constrained reconstruction algorithm is used to recover the sample map of permittivity.

Two-photon fluorescence isotropic-single-objective microscopy

Two-photon excitation provides efficient optical sectioning in three-dimensional fluorescence microscopy, independently of a confocal detection. In two-photon laser-scanning microscopy, the image resolution is governed by the volume of the excitation light spot, which is obtained by focusing the incident laser beam through the objective lens of the microscope. The light spot being strongly elongated along the optical axis, the axial resolution is much lower than the transverse one. In this Letter we show that it is possible to strongly reduce the axial size of the excitation spot by shaping the incident beam and using a mirror in place of a standard glass slide to support the sample. Provided that the contribution of sidelobes can be removed through deconvolution procedures, this approach should allow us to achieve similar axial and lateral resolution.

Tomographic Diffraction Microscopy : Improving Marker-free Microscopy Resolution Using Holograms and Numerical Reconstructions

While the resolution of fluorescence microscopy has undergone a significant improvement in the recent years, reaching a few tens of nanometers, that of marker-free microscopes remains stuck at several hundreds of nanometers.

Isotropic diffraction-limited focusing using a single lens

Using the time reversal concept, we show that isotropic focusing can be realized by placing a mirror after the focal point and shaping the incident beam. This idea is applied to axial resolution improvement in confocal microscopy.

High-resolution total-internal-reflection fluorescence microscopy using periodically nano-structured glass slides

Resolution of the Optical fluorescence microscopy is improved up to fourfold thanks to a standing-wave structured-illumination, whose illumination field is created by a nano-structured glass slides.