Implementation of Image Inversion Microscopy by Using Digital Holography

Abstract

The resolution and the contrast of optical scanning microscopes can be enhanced by image field microscopy [1, 2, 3, 4]. The image of the sample is imaged by an image inverting interferometer onto the detectors positioned at both exits of that interferometer. There, the image is superposed with its spatially inverted copy (rotation by 180°). Image points distant from the inversion axis are superposed by points that are equally distant, but from the opposite site of the image. If the light coming from the probe is spatially incoherent, those image points far from the inversion axis are not correlated to each other. Thus the intensity values are added incoherently. In contrast, images of points close to the inversion axis are superposed (in part or fully) with their own copy, resulting in an interference structure. Integrating the full interference pattern gives a signal, which can be allocated with the point of the object on the inversion axis. The integration can be done numerically, if the detector does have spatial resolution. By using this method, it is possible to transfer small structures up to the cut-off frequency of the used microscope objective with a contrast of one. So far, an increased two point resolution of 26% could be realized experimentally [5].