A digital micro-holographic optical system based on magnified hologram is designed. Compared with the typical pre-magnification system

the proposed system directly eliminates the main phase error introduced by spherical wave before record. In the post-magnification system

the object beam interferes with the parallel reference beam to generate hologram. A microscope is used to magnify the hologram and then recorded by a CCD camera. This method intends to be more useful to the post numerical reconstruc-tion and real-time operation because of no quadratic phase aberration. The system is studied by the experiments with the phase grating (30 lines/mm

about 0.3 m depth). Besides

Fresnel approximation and convolution algorithm are respectively used to reconstruct amplitude and phase information of the micro sample. Phase depth is about 0.27 m. The results show that the present system is greatly helpful to restrain the quadratic phase error.