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Contrast transfer function

About: Contrast transfer function is a research topic. Over the lifetime, 934 publications have been published within this topic receiving 26533 citations.


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Journal Article
01 Jan 1987-Optik
TL;DR: In this paper, the relativistic aberration theory for a combined electromagnetic foeusing-deflection system possessing a spherical cathode lens is studied by means of the variational principle.

4 citations

Journal ArticleDOI
TL;DR: In this paper, the authors show that instead of tuning out spherical aberration completely, there is an optimum value for the residual Cs that maximizes information transfer to the best possible resolution and depends only on the information limit of the microscope.
Abstract: With the advent of electron-optical systems able to generate negative spherical aberration (usually called ''Cs correctors''), it has now become feasible to zero-out objective lens Cs in the high-resolution transmission electron microscope. However, I show that - instead of tuning out spherical aberration completely - there is an optimum value for the residual Cs that maximizes information transfer to the best possible resolution and depends only on the information limit of the microscope.

4 citations

Journal ArticleDOI
TL;DR: It is proposed to use multiple wavelengths for phase retrieval using the contrast transfer function based formalism to retrieve the projected phase map of the object from the recorded intensity pattern.
Abstract: X-ray phase-contrast imaging has emerged as an important method for improving contrast and sensitivity in the field of X-ray imaging. This increase in the sensitivity is attributed to the fact that, in the hard X-ray regime, the phase shift is more prominent as compared with the attenuation for materials having a low X-ray absorption coefficient. Among all the methods using the X-ray phase-contrast technique, in-line phase-contrast imaging scores over the other methods in terms of ease of implementation and efficient use of available X-ray flux. In order to retrieve the projected phase map of the object from the recorded intensity pattern, a large number of algorithms have been proposed. These algorithms generally use either the transport of intensity or contrast transfer function based approach for phase retrieval. In this paper it is proposed to use multiple wavelengths for phase retrieval using the contrast transfer function based formalism.

4 citations

Journal ArticleDOI
TL;DR: In this article, a simple geometrical analysis suggests that the contrast is an artifact caused by spherical aberration in the microscope objective lens, which is explained by weak phase approximation.
Abstract: Iijima (1975) obtained a series of electron microscope images of crystallographic shear planes (CSPs) in tungsten trioxide, some of which showed light and dark bands accompanying the defect having a periodicity of approximately 20 A. This oscillatory contrast was interpreted, using the weak phase approximation (Cowley and Iijima 1972), as resulting from small displacement of cations from their original positions. We have obtained electron micrographs of CSPs in magnesium-doped rutile which show oscillatory contrast similar to that observed by Iijima. A simple geometrical analysis suggests that the contrast is an artifact caused by spherical aberration in the microscope objective lens. The many-beam dynamical theory of electron diffraction and the method of periodic continuation were used to calculate the image of widely-spaced, unstrained CSPs. The computer-simulated images showed light and dark bands adjacent to the CSP and a similar variation in spacing for changing objective lens defocus as di...

4 citations

Journal ArticleDOI
TL;DR: In this article, the aberration theory applied to co-axial optical systems is extended to offaxial systems, for which third-order aberration coefficients are considered, and derived aberrations are analyzed using three-dimensional ray bundles, spot diagrams, and image charts, and classified in relation to system symmetry.
Abstract: The aberration theory applied to co-axial optical systems is extended to off-axial systems, for which third-order aberration coefficients are considered. The derived aberrations are analyzed using three-dimensional ray bundles, spot diagrams, and image charts, and classified in relation to the system symmetry. This theory is very useful for optical designers, allowing them to clarify the relationship between the structures of off-axial optical systems and the corresponding off-axial aberrations.

4 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20235
202215
20218
20209
20199
20188