title: Realization of a tilted reference wave for electron holography by means of a condenser biprism.
abstract: As proposed recently, a tilted reference wave in off-axis electron holography is expected to be useful for aberration measurement and correction. Furthermore, in dark-field electron holography, it is considered to replace the reference wave, which is conventionally diffracted in an unstrained object area, by a well-defined object-independent reference wave. Here, we first realize a tilted reference wave by employing a biprism placed in the condenser system above three condenser lenses producing a relative tilt magnitude up to 20/nm at the object plane (300kV). Paraxial ray-tracing predicts condenser settings for a parallel illumination at the object plane, where only one half of the round illumination disc is tilted relative to the optical axis without displacement. Holographic measurements verify the kink-like phase modulation of the incident beam and return the interference fringe contrast as a function of the relative tilt between both parts of the illumination. Contrast transfer theory including condenser aberrations and biprism instabilities was applied to explain the fringe contrast measurement. A first dark-field hologram with a tilted - object-free - reference wave was acquired and reconstructed. A new application for bright/dark-field imaging is presented.
authors.affiliation: Triebenberg Labor, Institut für Strukturphysik, Technische Universität Dresden, D-01062 Dresden, Germany; CEMES-CNRS and Université de Toulouse, 29 rue Jeanne Marvig, F-31055 Toulouse, France. Electronic address: Falk.Roeder@tu-dresden.de.
authors.forename: Falk
authors.initials: F
authors.lastname: Röder
authors.affiliation: CEMES-CNRS and Université de Toulouse, 29 rue Jeanne Marvig, F-31055 Toulouse, France.
authors.forename: Florent
authors.initials: F
authors.lastname: Houdellier
authors.affiliation: CEMES-CNRS and Université de Toulouse, 29 rue Jeanne Marvig, F-31055 Toulouse, France.
authors.forename: Thibaud
authors.initials: T
authors.lastname: Denneulin
authors.affiliation: CEMES-CNRS and Université de Toulouse, 29 rue Jeanne Marvig, F-31055 Toulouse, France.
authors.forename: Etienne
authors.initials: E
authors.lastname: Snoeck
authors.affiliation: CEMES-CNRS and Université de Toulouse, 29 rue Jeanne Marvig, F-31055 Toulouse, France.
authors.forename: Martin
authors.initials: M
authors.lastname: Hÿtch
keywords: Coherence; Condenser biprism; Dark-field electron holography; Off-axis electron holography; Tilted reference wave; Transmission cross-coefficient