title: Shadow effects in spiral phase contrast microscopy.
abstract: Recently it has been demonstrated that spatial filtering of images in microscopy with a spiral phase element in a Fourier plane of the optical path results in a strong edge enhancement of object structures. In principle the operation is isotropic, i.e., all phase edges of a sample object are highlighted simultaneously, independent of their local direction. However, here we demonstrate that the symmetry can be broken intentionally by controlling the phase of the central area of a spiral phase hologram, which is displayed at a computer controlled spatial light modulator. This produces an apparent shadow effect which can be rotated at video rate. The resulting relieflike impression of the sample topography with a longitudinal resolution in the subwavelength regime is demonstrated by imaging a standard low contrast test sample consisting of a human cheek cell.
authors.affiliation: Division of Biomedical Physics, Medical University of Innsbruck, Müllerstr. 44, A-6020 Innsbruck, Austria.
authors.forename: Alexander
authors.initials: A
authors.lastname: Jesacher
authors.forename: Severin
authors.initials: S
authors.lastname: Fürhapter
authors.forename: Stefan
authors.initials: S
authors.lastname: Bernet
authors.forename: Monika
authors.initials: M
authors.lastname: Ritsch-Marte