In this paper, we present the potentialities of the digital holography microscopy for 3D image reconstruction of transparent microscopic objects. A method for object volume reconstruction based on the capture of only one off-axis hologram is discussed. We show that this technique can be efficiently used for obtaining quantitative information from the intensity and the phase distributions of the reconstructed field at different locations along the propagation direction. The potential of the method has been exploited by applying the 3D image reconstruction procedure to etched nuclear tracks induced in the widely used polymer detector CR-39. Nowadays, confocal microscopy and atomic force microscopy are applied to study nuclear track morphology in CR-39 detectors. The micro-holographic method developed in this work, and applied to that particular study, constitutes a new alternative procedure that overcomes the previously described at least in technological simplicity.