Numerical Reconstruction of Hi-Resolution Microscopic Images for Lens-Less Holographic Microscopy

Abstract

A new method numerically reconstructing ahigh-resolution microscopic image is developed for lens-less holographic microscopy. Acomplex-amplitude in-line hologram with a large numerical aperture (NA) is extracted from one off-axis hologram recorded with a CCD or CMOS camera by applied one-shot digital holography. The large hologram is divided into a number of small sections, and these sections are superimposed to generate a small complex-amplitude in-line hologram. Focus-free images with high resolving power and no distortion are numerically reconstructed from the generated small hologram using Fast-Fourier-Transforms (FFTs). A resolution higher than 1μm is obtained in the optical experiment, which can be improved up to the wave length. High-resolution microscopic images can also be observed for three-dimensional (3-D) objects with a large depth immersed in dielectric media by using the lens-less holographic microscopy.