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Simulation of partially coherent image formation in x-ray microscopy - art. no. 67050I
KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.ORCID iD: 0000-0002-4394-0591
2007 (English)In: Advances in X-Ray/EUV Optics and Components II, SPIE - International Society for Optical Engineering, 2007, Vol. 6705, I7050-I7050 p.Conference paper, Published paper (Refereed)
Abstract [en]

We present the theory and implementation of a numerical model capable of simulating two-dimensional images for an x-ray microscope using partially coherent illumination considerations. Partially coherent illumination is found in all x-ray microscopes and particularly in the latest generation of our in-house compact soft x-ray microscope. This is due to an introduced mismatch in numerical aperture of the condenser and objective zone plate, and will yield diffraction-like artifacts in phase-shifting objects. The numerical model approximates the condenser zone plate as a secondary incoherent source represented by individually coherent but mutually incoherent source emitters, each giving rise to a separate image. A final image is obtained by adding up the image intensities of the individual contributions. The simulation has been a useful tool for investigating the influence of coherence on images in both the mirror and zone plate condenser arrangement of the in-house compact soft x-ray microscope. The latest development included in the program is the effect of astigmatism and partial coherence, where the calculated results show good qualitative agreement with respect to the microscope images.

Place, publisher, year, edition, pages
SPIE - International Society for Optical Engineering, 2007. Vol. 6705, I7050-I7050 p.
Series
Proceedings of the society of photo-optical instrumentation engineers (spie), ISSN 0277-786X ; 6705
Keyword [en]
x-ray microscopy, zone plates, partial coherence, image formation
National Category
Atom and Molecular Physics and Optics
Identifiers
URN: urn:nbn:se:kth:diva-29734DOI: 10.1117/12.734003ISI: 000252146700015Scopus ID: 2-s2.0-42149185208ISBN: 978-0-8194-6853-6 (print)OAI: oai:DiVA.org:kth-29734DiVA: diva2:397355
Conference
Advances in X-Ray/EUV Optics and Components II; San Diego, CA; United States; 27 August 2007 through 28 August 2007
Note

QC 20110214

Available from: 2011-02-14 Created: 2011-02-14 Last updated: 2014-11-07Bibliographically approved
In thesis
1. Laboratory soft x-ray microscopy and tomography
Open this publication in new window or tab >>Laboratory soft x-ray microscopy and tomography
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Soft x-ray microscopy in the water-window (λ = 2.28 nm – 4.36 nm) is based on zone-plate optics and allows high-resolution imaging of, e.g., cells and soils in their natural or near-natural environment. Three-dimensional imaging is provided via tomographic techniques, soft x-ray cryo tomography. However, soft x-ray microscopes with such capabilities have been based on large-scale synchrotron x‑ray facilities, thereby limiting their accessibility for a wider scientific community.

This Thesis describes the development of the Stockholm laboratory soft x-ray microscope to three-dimensional cryo tomography and to new optics-based contrast mechanisms. The microscope relies on a methanol or nitrogen liquid-jet laser-plasma source, normal-incidence multilayer or zone-plate condenser optics, in-house fabricated zone-plate objectives, and allows operation at two wavelengths in the water-window, λ = 2.48 nm and λ = 2.48 nm. With the implementation of a new state-of-the-art normal-incidence multilayer condenser for operation at λ = 2.48 nm and a tiltable cryogenic sample stage the microscope now allows imaging of dry, wet or cryo-fixed samples. This arrangement was used for the first demonstration of laboratory soft x-ray cryo microscopy and tomography. The performance of the microscope has been demonstrated in a number of experiments described in this Thesis, including, tomographic imaging with a resolution of 140 nm, cryo microscopy and tomography of various cells and parasites, and for studies of aqueous soils and clays. The Thesis also describes the development and implementation of single-element differential-interference and Zernike phase-contrast zone-plate objectives. The enhanced contrast provided by these optics reduce exposure times or lowers the dose in samples and are of major importance for harder x-ray microscopy. The implementation of a high-resolution 50 nm compound zone-plate objective for sub-25-nm resolution imaging is also described. All experiments are supported by extensive numerical modelling for improved understanding of partially coherent image formation and stray light in soft x-ray microscopes. The models are useful tools for studying effects of zone plate optics or optical design of the microscope on image formation and quantitative accuracy in soft x-ray tomography.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2011. x, 76 p.
Series
Trita-FYS, ISSN 0280-316X ; 2011:03
Keyword
Microscopy, X-ray optics, Diffractive optics, Zone plates, X-ray microscopy, Soft X-ray physics, Tomography
National Category
Atom and Molecular Physics and Optics Physical Sciences
Identifiers
urn:nbn:se:kth:diva-29950 (URN)978-91-7415-874-8 (ISBN)
Public defence
2011-02-25, FB42, AlbaNova Universitetscentrum, Roslagstullsbacken 21, Stockholm, 13:00 (English)
Opponent
Supervisors
Note
QC 20110221Available from: 2011-02-21 Created: 2011-02-18 Last updated: 2011-02-21Bibliographically approved

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