Coherent X-ray Imaging

Abstract

AbstractThis chapter briefly summarizes some main concepts of coherent X-ray imaging. More specifically, we consider lensless X-ray imaging based on free-space propagation. It is meant as primer and tutorial which should help to understand later chapters of this book devoted to X-ray imaging, phase contrast methods, and optical inverse problems. We start by an introduction to scalar wave propagation, first in free space, followed by propagation of short wavelength radiation within matter. This provides the basic tools to consider the mechanisms of coherent image formation in a lensless X-ray microscope. The recorded intensities are inline holograms created by self-interference behind the object. We then present single-step and iterative fixed-point techniques based on alternating projections onto constraint sets as tools to decode the measured intensities (phase retrieval). The chapter closes with a brief generalization of two dimensional coherent imaging to three dimensional imaging by tomography.