Computational results are presented on micro-hologram diffraction for optical data storage using a finite element method. Retrieval of object light from a micro-hologram is formulated as an optical scattering problem in an infinite region. In order to overcome the difficulty of dealing with the infinite region a Dirichlet to Neumann (DtN) map is employed on an artificial boundary. By virtue of the DtN map reflection from the artificial boundary is effectively alleviated and non-reflecting boundary is obtained. Retrieval of the object light is computed for two different models.