Engineering illumination modes in X-ray ptychography

Session

PST.5 - Diffraction techniques and structural analysis

Authors

Mr. yangyang mu (1), Professor John Rodenburg (1)

Affiliations

1. The University of Sheffield

Keywords

Ptychography, Partial Coherence

Abstract text

Ptychography is a type of computational imaging method that is used to overcome the limitation of finite numerical aperture (NA) of lenses and to solve the image phase problem. Its transfer function is, in theory, perfect [1]. Like any method that depends on coherent interference, partial coherence significantly affects the performance of ptychography. Thibault and Menzel [2] showed that the inversion algorithms used in ptychography are amenable to modal decomposition of partial coherence in the illumination. In this work, we present initial results from a hard X-ray imaging experiment where we have deliberately engineered orthogonal modes in the illumination. The field of illumination is interrupted by horizontal and vertical stops. We see that although the total flux used in the experiment is reduced, the proportion of coherent flux (residing in low-order modes) is increased, thereby reducing the number of modes required in the reconstruction. The quality of the reconstruction can also be increased according to the power in the low-order modes. The work suggests that manipulating the illumination optics can enhance the usable coherent flux even when the source is substantially incoherent.

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 A. Menzel, Reconstructing state mixtures from diffraction measurements. Nature, 2013. 494(7435): p. 68-71.