Optical holography allows to record tridimensionnal informations of a scene using only one 2D sensor. Physical optics allows to analyticaly modelise hologram formation according to objects parameters (position, size, shape...). In simple objects case (e.g. spherical particles), the model is reduced to few parameters (four per particles: x,y,z,radius). Using inverse problem approach, it is possible to determine these parameters resolving a global optimization problem. This new approach is more efficient than classical method : particle parameters estimation is far more precise and it is possible to localize particles outside of the camera field of view. The presented method achieves to detect particles in an area sixteenth times wider than the CCD field of view with equal precision on both simulated and real digital holograms. Moreover strong improvements in the precision of the localization of the particles were noticed, particularly along the depth dimension.