Zernike Phase Contrast Electron Microscopy with a Spherically Corrected Foil Lens

2010 ◽  
Vol 16 (4) ◽  
pp. 441-444 ◽  
Author(s):  
Dieter Typke
Keyword(s):  
Electron Microscopy ◽  
Phase Shift ◽  
Phase Contrast ◽  
Thin Foil ◽  
Objective Lens ◽  
Lens System ◽  
Strong Phase ◽  
Spatial Frequencies ◽  
The Way

AbstractA lens system is proposed that not only provides spherical correction of the objective lens by charges that are induced on a thin foil, in the way proposed in a paper by Otto Scherzer [Optik56(2), 133–147, 1980], but also provides Zernike phase contrast by means of an appropriate phase shift of the scattered electrons within the foil. This system has the potential to provide strong phase contrast from very low spatial frequencies to frequencies above 1/(100 pm).

Fourier spectrum analysis of phase contrast of support film

1978 ◽  
Vol 36 (1) ◽  
pp. 170-171
Author(s):  
Tetsuo Oikawa ◽  
Fumiko Ishigaki ◽  
Kiichi Hojou ◽  
Koichi Kanaya
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Phase Shift ◽  
Phase Contrast ◽  
Fourier Transforms ◽  
Spherical Aberration ◽  
High Resolution Electron Microscopy ◽  
Spatial Frequencies ◽  
Resolution Electron ◽  
Atomic Phase

In high resolution electron microscopy, it is most important to determine the defocus of electron micrographs of amorphous support films. The variation of spatial frequencies of phase contrast of support films was obtained from the phase shift of the electron waves caused by defocus and spherical aberration as well as the atomic phase, which are demonstrated by use of optical Fourier transforms. The spatial frequencies of phase contrast of films of tungsten, prepared by ion bombardment, which are useful as support films for high resolution electron microscopy, has been discussed analytically.Taking account of atomic phase shift, the transfer function, which was originally presented by Thon (1966), was modified. Optical Fourier transforms are in similar to the calculated Fourier transforms of corre- sponding computed images. Accordingly, it turned out that the atomic phase shift should not be neglected. The thickness of tungsten film, in case of less than 2 nm thickness, can be determined by comparing the optical Fourier transforms with the calculated ones.

New challenges to image processing posed by cryo-Electron microscopy of single particles

1991 ◽  
Vol 49 ◽  
pp. 422-423
Author(s):  
Joachim Frank
Keyword(s):  
Electron Microscopy ◽  
Phase Contrast ◽  
Particle Orientation ◽  
Single Particles ◽  
Contrast Transfer Function ◽  
Virtual Absence ◽  
Cryo Electron Microscopy ◽  
Spatial Frequencies ◽  
New Challenges ◽  
Particle Images

Compared with images of negatively stained single particle specimens, those obtained by cryo-electron microscopy have the following new features: (a) higher “signal” variability due to a higher variability of particle orientation; (b) reduced signal/noise ratio (S/N); (c) virtual absence of low-spatial-frequency information related to elastic scattering, due to the properties of the phase contrast transfer function (PCTF); and (d) reduced resolution due to the efforts of the microscopist to boost the PCTF at low spatial frequencies, in his attempt to obtain recognizable particle images.

scholarly journals THE SUBMICROSCOPIC ORGANIZATION OF AXON MATERIAL ISOLATED FROM MYELIN NERVE FIBERS

1953 ◽  
Vol 98 (3) ◽  
pp. 269-276 ◽  
Author(s):  
E. De Robertis ◽  
C. M. Franchi
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Phase Contrast ◽  
Nerve Fibers ◽  
Myelinated Nerve ◽  
Myelinated Nerve Fibers ◽  
Dense Granules ◽  
Small Clusters ◽  
Membranous Material ◽  
The Way

A technique has been developed for the extrusion of axon material from myelinated nerve fibers. This material is then compressed and prepared for observation with the electron microscope. All the stages of preparation and purification of the axon material can be checked microscopically and in the present paper they are illustrated with phase contrast photomicrographs. Observation with the electron microscope of the compressed axons showed the presence of the following components: granules, fibrils, and a membranous material. Only the larger granules could be seen with the ordinary microscope. A considerable number of dense granules were observed. Of these the largest resemble typical mitochondria of 250 mµ by 900 mµ. In addition rows or small clusters of dense granules ranging in diameter from 250 to 90 mµ were present. In several specimens fragments of a membrane 120 to 140 A thick and intimately connected with the axon were found. The entire axon appeared to be constituted of a large bundle of parallel tightly packed fibrils among which the granules are interspersed. The fibrils are of indefinite length and generally smooth. They are rather labile structures, less resistant in the rat than in the toad nerve. They varied between 100 and 400 A in diameter and in some cases disintegrated into very fine filaments (less than 100 A thick). The significance is discussed of the submicroscopic structures revealed by electron microscopy of the material prepared in the way described.

Design of an analytical TEM with integrated imaging ω spectrometer

1991 ◽  
Vol 49 ◽  
pp. 354-355
Author(s):  
J. Bihr ◽  
G. Benner ◽  
D. Krahl ◽  
A. Rilk ◽  
E. Weimer
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Objective Lens ◽  
High Resolution Imaging ◽  
Lens System ◽  
Transmission Electron ◽  
Electron Energy Loss Spectrometer ◽  
Resolution Imaging ◽  
Koehler Illumination ◽  
Electron Energy Loss

Conventional transmission electron microscopy (CTEM) can be used for high resolution imaging of specimens and for the analysis of minute specimen areas. The capabilities of such an instrument are strongly improved by the integration of an imaging electron energy loss spectrometer. All imaging and diffraction techmques are provided in such an energy filtered transmission electron microscope (EFTEM).In addition to the well-known objective lens for Koehler illumination, the new Zeiss EFTEM features a projective lens system which integrates a new imaging ω-spectrometer comprising four individual magnets and one hexapole corrector Fig.l and Fig. 3 show the design of this microscope.

Quantification of micromagnetic structure from Lorentz micrographs

1994 ◽  
Vol 52 ◽  
pp. 894-895
Author(s):  
J. Zweck ◽  
M. Herrmann ◽  
H. Hoffmann
Keyword(s):  
Phase Shift ◽  
Quantitative Evaluation ◽  
Magnetic Induction ◽  
Phase Contrast ◽  
Magnetic Domain ◽  
Contrast Transfer Function ◽  
Lorentz Microscopy ◽  
Domain Structures ◽  
Spatial Frequencies ◽  
Microscopy Images

Defocused imaging of magnetic domain structures is a well-known technique to observe the micromagnetic structures in ferromagnetic thin films. Nevertheless, Lorentz microscopy images are rarely subject to a quantitative evaluation of micromagnetic parameters. In this paper, we offer a new method for quantitative evaluation of ripple wavelengths and ripple angle from Lorentz microscopy images carried out on soft magnetic Ni81Fe19 films. The work was carried out using a Philips CM30 electron microscope with a combined Twin/Lorentz lens.The experiments were performed on thin ferromagnetic films of a Ni81Fe19 alloy. Due to the internal magnetic induction within the specimens, the partial electron waves experience a phase shift proportional to the local in-plane magnetic induction , the specimen's thickness t and the lateral distance x from an arbitrarily chosen point of zero phase shift on the specimen. This phase shift can then be imaged using phase contrast methods similar to HREM. Since the phase shifts and the corresponding deflection angles can be very small, a large defocus is necessary to obtain contrast. This large defocus gives rise to an oscillating phase contrast transfer function for the spatial frequencies under observation as well as to a damping envelope for higher spatial frequencies.

Image resolution in conventional transmission electron microscopy

1991 ◽  
Vol 49 ◽  
pp. 468-469
Author(s):  
Mehmet Sarikaya ◽  
James M. Howe
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Phase Contrast ◽  
Spherical Aberration ◽  
Dark Field ◽  
Image Resolution ◽  
Objective Lens ◽  
Contrast Imaging ◽  
Conventional Transmission Electron Microscopy ◽  
Transmission Electron

The image resolution in bright-field (BF) and dark-field (DF) conventional transmission electron microscopy (TEM) is given by: r = 0.66 CS¼¾¾, where Cs and ¾ are the spherical aberration coefficient of the objective lens and electron wavelength, respectively. Based on this formula, it should be possible to resolve single atoms or clusters of atoms by phase contrast imaging with a highly coherent electron beam and a properly defocused objective lens; this has been demonstrated for both BF and DF imaging. However, for most situations encountered in conventional TEM, the type of information that can be obtained about the specimen is the most important, rather than the instrumental resolution. Atomicresolution microscopy of crystalline specimens relies on phase contrast produced when two or more beams interfere to form an image and this is discussed elsewhere in this symposium. This paper discusses the contrast and resolution when either a single beam or diffuse scattering is used to form an image.

scholarly journals Improving on Phase Contrast by Extending the Range of Captured Spatial Frequencies in Transmission Electron Microscopy

2010 ◽  
Vol 16 (S2) ◽  
pp. 522-523
Author(s):  
C Kisielowski
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Phase Contrast ◽  
Spatial Frequencies ◽  
Transmission Electron

Extended abstract of a paper presented at Microscopy and Microanalysis 2010 in Portland, Oregon, USA, August 1 – August 5, 2010.

In-Focus Electrostatic Zach Phase Plate Imaging for Transmission Electron Microscopy with Tunable Phase Contrast of Frozen Hydrated Biological Samples

2014 ◽  
Vol 20 (1) ◽  
pp. 175-183 ◽  
Author(s):  
Nicole Frindt ◽  
Marco Oster ◽  
Simon Hettler ◽  
Björn Gamm ◽  
Levin Dieterle ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Phase Contrast ◽  
Structural Information ◽  
Signal To Noise Ratio ◽  
Phase Plate ◽  
Spatial Frequencies ◽  
Transmission Electron ◽  
Sample Orientation ◽  
Phase Plates

AbstractTransmission electron microscopy (TEM) images of beam sensitive weak-phase objects such as biological cryo samples usually show a very low signal-to-noise ratio. These samples have almost no amplitude contrast and instead structural information is mainly encoded in the phase contrast. To increase the sample contrast in the image, especially for low spatial frequencies, the use of phase plates for close to focus phase contrast enhancement in TEM has long been discussed. Electrostatic phase plates are favorable in particular, as their tunable potential will allow an optimal phase shift adjustment and higher resolution than film phase plates as they avoid additional scattering events in matter. Here we show the first realization of close to focus phase contrast images of actin filament cryo samples acquired using an electrostatic Zach phase plate. Both positive and negative phase contrast is shown, which is obtained by applying appropriate potentials to the phase plate. The dependence of phase contrast improvement on sample orientation with respect to the phase plate is demonstrated and single-sideband artifacts are discussed. Additionally, possibilities to reduce contamination and charging effects of the phase plate are shown.

High Resolution Electron Microscopy Using Phase Plates

1971 ◽  
Vol 29 ◽  
pp. 38-39
Author(s):  
F. Thon ◽  
D. Willasch
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Focal Plane ◽  
Phase Contrast ◽  
High Resolution Electron Microscopy ◽  
Dominant Factor ◽  
Objective Lens ◽  
Resolution Electron ◽  
Optical Reconstruction ◽  
Transfer Properties

The phase contrast transfer properties of objective lenses used in electron microscopy are not at all satisfactory and therefore the interpretation of phase contrast images is quite limited in the high resolution field. Phase contrast, however, is the dominant factor in creating contrast in high resolution electron microscopy. This is why methods which promise to improve the transfer conditions are of great importance.A series of experiments has been reported to improve the contrast transfer conditions by zonal or semicircular filtering in the back focal plane of the objective lens or in subsequent light optical reconstruction. By these methods the transfer properties can be improved only to a certain degree.For ideal imaging a transfer function would be desirable that is of constant value for the whole spatial frequency spectrum relevant to high resolution microscopy. This should in principle be attainable by inserting a phase shifting foil of varying thickness into the back focal plane.

Correlation of cryo-electron microscopic and x-ray data and compensation of the contrast transfer function

1992 ◽  
Vol 50 (2) ◽  
pp. 996-997
Author(s):  
R. Holland Cheng
Keyword(s):  
Transfer Function ◽  
Phase Contrast ◽  
Objective Lens ◽  
Biological Macromolecules ◽  
Electron Microscopic ◽  
Contrast Transfer Function ◽  
Image Reconstruction Techniques ◽  
X Ray ◽  
Mass Distributions ◽  
Spatial Frequencies

Cryo-electron microscopy (cryoEM) along with image reconstruction techniques can produce vivid images of biological macromolecules in their “native” state, although objective interpretation of these images is influenced by the fact that the contribution of phase contrast greatly exceeds that of amplitude contrast in such weakly scattering objects. The microscope contrast transfer function (CTF), which is strongly dependent on the defocus level of objective lens, modulates images of the object density distribution as a function of spatial frequency. Compensation for the effects of phase contrast transfer is important because underweighting of the low spatial frequencies usually causes difficulties in evaluating absolute mass distributions in objects.Correct compensation for the CTF is difficult to achieve. This is due, in part, to ambiguities in measuring the exact defocus level in noisy micrographs, and in knowing the relative contributions of amplitude and phase contrast, beam coherence, and inelastic scattering. The availability of atomic resolution determinations for a few viruses allows one to determine empirically how to correct the cryoEM images to best fit the x-ray data.

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