2D/3D lensless imaging: prototype and applications

Biological imaging has made tremendous progresses these last decades. The latest developments concern manipulating and imaging single cells with nanometer spatial resolutions. A recent category of imaging techniques, called lensless microscopy, are very promising because they combine very good spatial resolutions in a large field-of-view, simplicity of use and low cost, while operating on label free samples. In this thesis two different lensless approaches are considered: digital in-line holography (DILH) and Fourier transform holography (FTH). In lensless imaging, the usual optical system used to form the sample's image are remove and replace by numerical algorithms using the light spatial coherence properties.Two imaging prototypes, built on these principles, are presented. They offer (sub ) micrometer scale resolutions, and offer the possibility to retrieve both spatial amplitude and phase information of the optical field. This allows to achieve pseudo-3D reconstruction of volumetric objects from a single 2D hologram. Both devices were first characterized with reference samples. In a second step, real applications, relevant to selected biological problems, were performed to assess the devices' performances towards high resolution, real time imaging and 3D. This thesis objective is also to develop a new platform directly integrating in a single chip a microfluidics system for biological cell handling by dielectrophoresis and an optical mask for cell visualization by lensless microscopy. Its working principle is based on cell transport in a liquid media by microfluidics, cell separation in the microscope field of view by the electric field induced by specific electrodes, and simultaneous cell imaging by Fourier Transform Holography. The main advantage of such coupled electro-optical system for cell imaging and analysis are the improved control, the precision and sensitivity regarding cell morphology all together merged in a compact imaging platform. The capability of the platform can be extended to analysis of cells' behavior and morphologic deviation during the electrochemical processes of DEP.A major challenge in microscopy field is to reduce the production costs. The two types of lensless microscopy presented in this thesis aims to introduce new imaging tools that allows scientists to obtain low-cost high-resolution images in label-free conditions. Additionally, the microfluidics chip is a first demonstration of a new integrated platform for cell live analysis into a single Lab-on-a-chip device. (author)