Gradient-flipping-assisted Flux-preserving Wave Reconstruction for Improved Lowspatial- Frequency Recovery and High-contrast Imaging Using in-line Holography

Abstract

In-line holography in the transmission electron microscope is a versatile technique, which provides real-space phase information that can be used for the correction of imaging aberrations, as well as for measuring electric and magnetic fields and strain distributions. It is able to recover high-spatial-frequency contributions to the phase effectively but suffers from the weak transfer of low-spatial-frequency information, as well as from incoherent scattering. Here, we combine gradient flipping and phase prediction in an iterative flux-preserving focal series reconstruction algorithm with incoherent background subtraction that gives extensive access to the missing low spatial frequencies. A procedure for optimizing the reconstruction parameters is presented, and results from MgO cubes, and Fe-filled C nanospheres are compared with phase images obtained using off-axis holography.