Uses of multimodal ptychography

Session

Stream 1: EMAG - 4D-STEM

Authors

Professor John Rodenburg (1), Mr Yangyang Mu (1)

Affiliations

1. University of Sheffield

Keywords

ptychography, diffractive imaging, coherence, modal decomposition, X-ray microscopy, dose

Abstract text

Ptychography overcomes three long-standing limitations that arise in all forms of transmission microscopy [1]. First, its resolution is not limited by the numerical aperture of the lens - in fact, it can work without any lenses at all. Second, it provides a very clean phase image (as well as a modulus image), without any ringing or Fresnel effects, while at the same time preserving low frequency structure in the image. Third, the phase image is strong and has high contrast, meaning that counts (radiation dose, and hence specimen damage) can be much smaller than for conventional imaging modes. 

The ptychographic principle has slowly gained traction, mostly because of the increase in the size and power of computers, and the vastly improved quality of detectors. The data used in ptychography involves processing hundreds or even thousands of diffraction patterns: information that is nowadays sometimes called ‘4D STEM data’. Inversion strategies to obtain continuous, infinite images began the early 1990s, but the technique was only adopted widely after about 2007.

This talk will briefly present an elementary introduction to ptychography for those who may not be familiar with it, or its potential powers and applications. It will review progress over all wavelengths.

Recent results will be presented, showing how it is possible to increase the speed of data acquisition in ptychography by appropriate engineering of the coherent modes in the illumination function (‘multi-modal’ ptychography), and by the subsequent use of modal decomposition [2]. This is demonstrated experimentally using synchrotron radiation, although it has potential applications over all wavelengths.

References

[1] Rodenburg, J. and A. Maiden, Ptychography, in Springer Handbook of Microscopy, P.W. Hawkes and J.C.H. Spence, Editors. 2019, Springer International Publishing: Cham. p. 2-2.

[2]  Thibault, P. and Menzel, A., Nature, 494, (2013) p. 68–71