Amplitude and Phase Contrast in X-Ray Microscopy

Abstract

When a material object is placed in the path of an electromagnetic wave, the latter undergoes a change in both its amplitude and its phase. In particular, calculations have been performed previously for two extremes⁽¹⁾ to obtain the contrast caused purely by the change in amplitude produced when an object is imaged by soft X rays (an amplitude object) or, alternatively, by the change in phase (a phase object) when imaged in a phase-contrast microscope with coherent illumination. These calculations show that phase contrast exceeded amplitude contrast. In fact, phase-contrast microradiography⁽²⁾ and phase-contrast topography using x-ray interferometers⁽³⁾ had already been suggested several years prior to the work reported here. To confirm these calculations, preliminary phase-contrast x-ray microscopy experiments were performed with the x-ray microscope at the BESSY electron storage ring.^(4.5)