Accession Number : ADP007066

Title :   Differential Phase Contrast Imaging in the Scanning Transmission X-Ray Micro scope,

Corporate Author : KING'S COLL LONDON (UNITED KINGDOM) DEPT OF PHYSICS

Personal Author(s) : Palmer, J. R. ; Morrison, G. R.

Report Date : 22 MAY 1992

Pagination or Media Count : 5

Abstract : Calculations of the contrast transfer functions for differential phase contrast imaging are presented and compared to those for absorption imaging in the x-ray microscope. In the scanning transmission x-ray microscope (STXM) the specimen is scanned in a raster by an x-ray probe formed with a Fresnel zone plate. To achieve near diffraction limited resolution it is necessary to have a coherent source, even when forming an incoherent brightfield image by measuring the x-ray intensity transmitted by the object. This has so far been the only imaging mode used in the STXM and for hydrated biological specimens is well suited to soft x-ray wavelengths within the water window (2.33 to 4.36 nm) where carbon absorbs much more strongly than water. However, by the use of phase contrast rather than amplitude contrast, it is possible to form images at wavelengths where the absorption is low, resulting in lower radiation dose for the same level of contrast. Calculations have demonstrated very clearly the advantages of phase contrast imaging at wavelengths outside the water window.

Descriptors :   *OPTICAL IMAGES, *X RAYS, *MICROSCOPES, COHERENT OPTICAL RADIATION, X RAY SCATTERING, SHORT WAVELENGTHS, COHERENT RADIATION, CONTRAST, FOURIER TRANSFORMATION, FRESNEL ZONES, SYMPOSIA.

Subject Categories : Optics
      Nuclear Physics & Elementary Particle Physics

Distribution Statement : APPROVED FOR PUBLIC RELEASE