In this thesis, we have developed a novel heterodyne digital holographic microscope combining the off -axis geometry and phase-shifting interferometry to detect and localize in three dimensions nanometric-sized colloidal gold particles used as biological markers in live cells environments. Genuine aliasing-free holograms are obtained using the phase-shifting technique that is performed using two accurately synchronized Acousto-Optic modulators, and since a heterodyne detection is performed, holograms are only shot-noise limited. We have also elaborated an ingenious numerical reconstruction method that o ffers striking advantages : reconstructed images do not su ffer from longitudinal distortions, reconstruction parameters are obtained without an additional experimental calibration, aberrations compensation as well as lens curvature corrections are automatically obtained. Using the developed optical apparatus and numerical processing procedure, we have been able to image and localize for the first time in the context of digital holographic microscopy, 40 nm gold particles attached to the integrin surface receptors of live 3T3 fibroblasts with a localization precision of 5 nm laterally and 100 nm in depth, when 32 images averaging is performed. Additionally, 3D mapping of the entire scattered eld was achieved where the 3D exploration was performed within a relatively big volume (90 x90x 90) microm. Finally, we have been able to characterize the scattering regimes of the gold markers and cellular structures by analyzing the 3D shape of the corresponding scattering patterns that are easily accessible by digital holography.
