  The structured illumination (SI) architecture can be adopted in a digital
holographic (DH) microscope to enhance the spatial resolution. In this paper,
we propose and demonstrate a compact and simple SI method in a self-referencing
common-path configuration of DH microscopy. The combination of SI pattern
generated by a compact disk and common-path off-axis geometry formed by Fresnel
biprism introduces a low-cost and highly stable system to image both amplitude
and phase objects with a twofold improvement of the spatial resolution.
Experimental results for the case of a standard test sample validate the
predicted resolution enhancement compared to that of the conventional imager.
The presented DH method allows for imaging living cells with strikingly
improved clarity compared to the conventional DH microscopes.
