Digital in-line holographic microscopy with partially coherent light: micrometer resolution

Using a blue light-emitting diode (LED) it is shown that lensless Digital In-line Holography Microscopy (DIHM) with spherical waves can yield micrometer resolution, even when large objects, such as the head of a fruit fly (Drosophila melanogaster), are imaged. By changing the size of the pinhole, the influence of spatial coherence of the spherical wave at the plane of the sample on the resolution is analysed. Although the achieved resolution is less than that ultimately obtained with a fully coherent laser and a numerical aperture of over 0.5, the use of a LED allows for a very compact and low cost implementation of DIHM. Experiments with micrometer-size beads support the claim of micrometer resolution.