title: Nonlinear phase retrieval from single-distance radiograph.
abstract: Phase contrast in the object plane of a phase object is retrieved from intensity contrast at a {\sl single} object-detector distance. Expanding intensity contrast and phase shift in the detector plane in powers of object-detector distance, phase retrieval is performed beyond the solution to the linearized transport-of-intensity equation. The expansion coefficients are determined by the entire paraxial wave equation. The Laplacian of the phase shift in the object plane thus is written as a local expression linear in the intensity contrast and nonlinear in the phase shift in the object plane. A perturbative approach to this expression is proposed and tested with simulated phantom data.
authors.affiliation: Laboratorium f¨ur Applikationen der Synchrotronstrahlung Karlsruher Institut für Technologie, Postfach 6980, D-76128 Karlsruhe, Germany.
authors.forename: Julian
authors.initials: J
authors.lastname: Moosmann
authors.forename: Ralf
authors.initials: R
authors.lastname: Hofmann
authors.forename: Andrei
authors.initials: A
authors.lastname: Bronnikov
authors.forename: Tilo
authors.initials: T
authors.lastname: Baumbach
mesh_terms: D000465:Algorithms; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008858:Microscopy, Phase-Contrast / Q000379:methods*; D017711:Nonlinear Dynamics; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity