Topic
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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TL;DR: In this article, a fast and accurate matrix method is used for calculating and mapping electron microscopy contrast around lattice defects, which can be used for defects of any geometry of any dimension.
Abstract: A fast and accurate matrix method is used for calculating and mapping electron microscopy contrast around lattice defects. As each contrast point is calculated separately the method can be used for defects of any geometry.
43 citations
01 Jan 1997
TL;DR: In this article, a method of threedimensional (3D) reconstruction that combines an algebraic, iterative 3D reconstruction technique with CTF correction is proposed, and the potential to incorporate a priori knowledge into the reconstruction process is discussed.
Abstract: Cryo-electron microscopy provides the means to quantitatively study macromolecules in their native state. However, the original mass distribution of the macromolecule is distorted by the contrast transfer function (CTF) of the electron microscope. In addition, the zeros of the CTF put a practical limit on the resolution that can be achieved. Substantial improvement to the quality of the results can be accomplished by collecting the data using a series of defocus settings. Such data sets can be combined and the resolution can be extended beyond the first zero of the CTF. This procedure can be applied either at the stage of raw data, or more effectively at the stage of reconstructed volumes which have a high signal-to-noise ratio as a result of averaging over many projections. A method of threedimensional (3D) reconstruction that combines an algebraic, iterative 3D reconstruction technique with CTF correction is proposed. The potential to incorporate a priori knowledge into the reconstruction process is discussed. This approach was used to obtain a 3D reconstruction of the E. coli 70S ribosome from energy filtered cryo-images.
42 citations
TL;DR: In this article, a least squares technique applied to the experimental zeros of the microscope's transfer function with a parabola instead of a straight line as fitting curve represents the major key to improved determination of the spherical aberration coefficient.
42 citations
Patent•
01 Jul 1974TL;DR: In this paper, a phase contrast signal for a scanning transmission electron microscope was developed. But the phase contrast was not used to measure the number of electrons incident thereon and the signal developed by the first detector was subtracted from the signal derived by the record detector to provide a phase-contrast signal.
Abstract: A device is provided for developing a phase contrast signal for a scanning transmission electron microscope. The lens system of the microscope is operated in a condition of defocus so that predictable alternate concentric regions of high and low electron density exist in the cone of illumination. Two phase detectors are placed beneath the object inside the cone of illumination, with the first detector having the form of a zone plate, each of its rings covering alternate regions of either higher or lower electron density. The second detector is so configured that it covers the regions of electron density not covered by the first detector. Each detector measures the number of electrons incident thereon and the signal developed by the first detector is subtracted from the signal developed by the record detector to provide a phase contrast signal.
42 citations
TL;DR: In this article, a theoretical ansatz for correction of the chromatic and spherical aberration of round-lens systems in photoemission and low-energy electron microscopy (PEEM/LEEM) is presented.
Abstract: A theoretical ansatz for correction of the chromatic and spherical aberration of round-lens systems in photoemission and low-energy electron microscopy (PEEM/LEEM) is presented. The method is based on fast switching of electrical acceleration or lens fields. It exploits the highly precise time structure of pulsed photon sources like electron storage rings for synchrotron radiation or pulsed lasers as well as pulsed photocathodes of a LEEM. The initial results indicate that the approach is a promising alternative to the implementation of multipole or mirror correctors in the electron optical column of a microscope.
42 citations