Computer-Assisted Microscope Alignment

1990 ◽  
Vol 48 (1) ◽  
pp. 152-153
Author(s):  
L.D. Marks
Keyword(s):  
Diffraction Pattern ◽  
Carbon Film ◽  
Numerical Procedure ◽  
Optical Diffraction ◽  
Computer Assisted ◽  
Astigmatism Correction ◽  
Film Image ◽  
Resolution Electron ◽  
High Resolution Electron Microscope ◽  
Diffraction Patterns

Full alignment of a high resolution electron microscope, including alignment of the beam tilt, is a very difficult process. Whereas astigmatism correction is relatively straightforward, correcting the beam tilt is by no means so simple and there is a strong interaction between astigmatism and tilt so that it is possible to apparently correct the two at one defocus. To overcome this problem, the method of applying a ± tilt oscillation to the beam has been introduced previously, the principle being to adjust the texture of an amorphous carbon film image so that it is symmetric with respect to the tilt oscillations. This procedure works, but in practice is not easy to use and there are additional experimental problems in terms of loss of intensity due to insufficiently corrected beam shift/tilt purity.As an extension of this process, and as a general extension of astigmatism correction as well, we have developed a procedure for providing a computer generated optical diffraction pattern to compliment the standard TV image. One critical problem was providing optical diffraction patterns at a sufficiently rapid speed to make the process experimentally viable; one optical diffraction pattern every 5 seconds for example is too slow. The numerical procedure can be broken down into a number of different steps:

Light Optical Diffraction Studies of Macromolecular Ultrastructure

1970 ◽  
Vol 28 ◽  
pp. 258-259
Author(s):  
Glen B. Haydon
Keyword(s):  
High Resolution ◽  
Diffraction Analysis ◽  
Diffraction Pattern ◽  
Electron Micrographs ◽  
Optical Diffraction ◽  
Electron Micrograph ◽  
Its Analysis ◽  
Resolution Electron ◽  
Diffraction Patterns

Analysis of light optical diffraction patterns produced by electron micrographs can easily lead to much nonsense. Such diffraction patterns are referred to as optical transforms and are compared with transforms produced by a variety of mathematical manipulations. In the use of light optical diffraction patterns to study periodicities in macromolecular ultrastructures, a number of potential pitfalls have been rediscovered. The limitations apply to the formation of the electron micrograph as well as its analysis.(1) The high resolution electron micrograph is itself a complex diffraction pattern resulting from the specimen, its stain, and its supporting substrate. Cowley and Moodie (Proc. Phys. Soc. B, LXX 497, 1957) demonstrated changing image patterns with changes in focus. Similar defocus images have been subjected to further light optical diffraction analysis.

Electron microscopy and diffraction studies of polyimides

1983 ◽  
Vol 41 ◽  
pp. 28-29
Author(s):  
O.C. de Hodgins ◽  
K. R. Lawless ◽  
R. Anderson
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Structural Features ◽  
Inert Atmosphere ◽  
Polyimide Films ◽  
Resolution Electron ◽  
The Matrix ◽  
High Resolution Electron Microscope ◽  
Diffraction Patterns ◽  
Polymeric Samples

Commercial polyimide films have shown to be homogeneous on a scale of 5 to 200 nm. The observation of Skybond (SKB) 705 and PI5878 was carried out by using a Philips 400, 120 KeV STEM. The objective was to elucidate the structural features of the polymeric samples. The specimens were spun and cured at stepped temperatures in an inert atmosphere and cooled slowly for eight hours. TEM micrographs showed heterogeneities (or nodular structures) generally on a scale of 100 nm for PI5878 and approximately 40 nm for SKB 705, present in large volume fractions of both specimens. See Figures 1 and 2. It is possible that the nodulus observed may be associated with surface effects and the structure of the polymers be regarded as random amorphous arrays. Diffraction patterns of the matrix and the nodular areas showed different amorphous ring patterns in both materials. The specimens were viewed in both bright and dark fields using a high resolution electron microscope which provided magnifications of 100,000X or more on the photographic plates if desired.

The ultrastructure of coccoliths from the marine alga Emiliania huxleyi (Lohmann) Hay and Mohler: an ultra-high resolution electron microscope study

1983 ◽  
Vol 219 (1215) ◽  
pp. 111-117 ◽  
Keyword(s):  
High Resolution ◽  
High Resolution Electron Microscopy ◽  
Emiliania Huxleyi ◽  
Growth Patterns ◽  
Lattice Image ◽  
Nucleation Sites ◽  
Resolution Electron ◽  
Lattice Images ◽  
High Resolution Electron Microscope ◽  
Diffraction Patterns

The calcite coccoliths from the alga Emiliania huxleyi (Lohmann) Hay and Mohler have been studied by ultra-high resolution electron microscopy. This paper describes the two different types of structure observed, one in the upper elements, the other in the basal plate, or lower element. The former consisted of small, microdomain structures of 300-500 Å (1 Å = 10 -10 m) in length with no strong orientation. At places along these elements, and particularly in the junction between stem and head pieces, triangular patterns of lattice fringes were observed indicating multiple nucleation sites in the structure. In contrast, the lower element consisted of a very thin single crystalline sheet of calcite which could be resolved into a two dimensional lattice image, shown by a computer program that is capable of simulating electron diffraction patterns and lattice images to be a [421] zone of calcite. A possible mechanism for these growth patterns in the formation of coccoliths is discussed, together with the relevance of such mechanisms to biomineralization generally.

scholarly journals Electron Microscopy for Atomic/Electronic Structure of Quasicrystals

2014 ◽  
Vol 70 (a1) ◽  
pp. C1193-C1193
Author(s):  
Eiji Abe
Keyword(s):  
Electron Microscopy ◽  
Electronic Structure ◽  
Scanning Transmission Electron Microscopy ◽  
Transmission Electron ◽  
Resolution Electron ◽  
Aperiodic Order ◽  
Scanning Transmission ◽  
High Resolution Electron Microscope ◽  
Diffraction Patterns ◽  
Key Questions

As stated with special emphasis in the Noble Lecture by Dr. Shechtman, the quasicrystal discovery is definitely the victory of electron microscopy – the first icosahedral stereogram was constructed by a series of electron diffraction patterns from a tiny quasicrystalline grain, and the following high-resolution electron microscope images indeed confirmed a unique aperiodic order that can never be consistent with twinning of normal crystals. Almost thirty years after these early electron microscopy studies, we are now in the era of aberration-corrected electron microscopy which realizes a remarkable resolution beyond an Ångstrom scale [1, 2]. In the talk, I will describe the local atomic/electronic structure of quasicrystals using state-of-the-art scanning transmission electron microscopy, providing several striking insights that may lead to the answers for the longstanding key questions; "Where are the atoms? And why do quasicrystals form?"

Real-time computer simulation of electron microscope images via a digital television frame store system

1986 ◽  
Vol 44 ◽  
pp. 542-543
Author(s):  
W. Krakow
Keyword(s):  
Electron Microscope ◽  
Real Time ◽  
Optical Diffraction ◽  
Digital Television ◽  
Software Packages ◽  
Resolution Electron ◽  
Computational Speed ◽  
Microscope Images ◽  
High Resolution Electron Microscope ◽  
Electron Microscopes

Digital television frame store devices and software packages have made it possible to obtain images directly from electron microscopes, photographic prints and transparencies in real time and obtain the power spectrum (optical diffraction pattern) and filtered image of various electron micrographs. Enhancements have been added to the Fourier analysis program package which include the use of offset filter functions and the computation of high resolution electron microscope images by including the microscope lens aberration phase shifts and illumination conditions. Because of the use of the frame store and a large mainframe computer, it is possible to have several orders of magnitude gain in image computational speed which makes real-time interactive computations possible.

Computer Modeling of High Resolution Electron Microscope Images Using 65,536 Beams

1980 ◽  
Vol 38 ◽  
pp. 178-179
Author(s):  
William Krakow
Keyword(s):  
Strain Field ◽  
Dynamical Theory ◽  
Sample Thickness ◽  
Computational Time ◽  
Scattering Approximation ◽  
Resolution Electron ◽  
Interstitial Defects ◽  
Microscope Images ◽  
High Resolution Electron Microscope ◽  
Diffraction Patterns

A system of computer programs which calculates both diffraction patterns and images of generalized objects using the kinematical scattering approximation has now been extended to include multislice dynamical theory. Calculations of this type have been obtained by other authors for interstitial defects where several approximations were necessary to save computational time such as considering the defect strain field to be confined to one slice or reducing the number of beams and sample thickness (e.g. 3999 beams at 7 min./slice).

On the interpretation of electron diffraction patterns from materials containing planar boundaries: the intergrowth tungsten bronzes

1990 ◽  
Vol 429 (1876) ◽  
pp. 91-117 ◽  
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Electron Diffraction ◽  
High Resolution Electron Microscopy ◽  
Optical Diffraction ◽  
General Interest ◽  
Transmission Electron ◽  
Resolution Electron ◽  
Resolution Imaging ◽  
Diffraction Patterns

Materials containing planar boundaries are of general interest and complete understanding of their structures is important. When direct imaging of the boundaries by, for instance, high-resolution electron microscopy, is impracticable, details of their structure and arrangement may be obtained from electron diffraction patterns. Such patterns are discussed in terms of those from intergrowth tungsten bronzes as specific examples. Fourier-transform calculations for proposed structures have been made to establish, in conjunction with optical-diffraction analogues, the features of the far-field diffraction patterns. These results have been compared with diffraction patterns obtained experimentally by transmission electron microscopy. The aim of the study, to show that the arrangement of the boundaries in these complicated phases can be deduced from their diffraction patterns without the need for high-resolution imaging, has been achieved. The steps to be taken to make these deductions are set out.

scholarly journals Arrangement of subunits in microtubules with 14 profilaments.

1980 ◽  
Vol 87 (2) ◽  
pp. 521-526 ◽  
Author(s):  
G M Langford
Keyword(s):  
High Resolution Electron Microscopy ◽  
Optical Diffraction ◽  
Beta Subunit ◽  
Simultaneous Imaging ◽  
Left Handed ◽  
Resolution Electron ◽  
Dogfish Shark ◽  
Diffraction Patterns ◽  
Two Sides ◽  
Brain Tubulin

The structure of 14-protofilament microtubules reassembled from dogfish shark brain tubulin was analyzed by high resolution electron microscopy and optical diffraction. The simultaneous imaging of the protofilaments from near and far sides of these tubules produces a moiré pattern with a period of approximately 96 nm. Optical diffraction patterns show that the 5-nm spots that arise from the protofilaments for the two sides of the tubule are not coincident but lie off the equator by a distance of 1/192 nm-1. These data provide evidence that in reassembled microtubules containing 14 protofilaments, the protofilaments are tilted 1.5 degrees with respect to the long axis of the tubule, giving a left-handed superhelix with a pitch of 2.7 micron. The hypothesis is that the tilt of the protofilaments occurs to accommodate the 14th protofilament. It is determined that when the 14th protofilament is incorporated, the 3-start helix is maintained, but the pitch angle changes from 10.5 degrees to 11.2 degrees, the angle between protofilaments measured from the center of the microtubule changes by 2 degrees, and the dimer lattice is discontinuous. These observations show that the tubulin molecule is sufficiently flexible to accomodate slight distortions at the lateral bonding sites and that the lateral bonding regions of the alpha and beta monomers are sufficiently similar to allow either alpha-alpha and beta-beta subunit pairing or alpha-beta subunit pairing.

A direct investigation of lattice relaxation at a crystal surface by optical transforms of surface profile images

1989 ◽  
Vol 22 (6) ◽  
pp. 592-600 ◽  
Author(s):  
J. Harada ◽  
M. Takata ◽  
H. Miyatake ◽  
H. Koyama
Keyword(s):  
Crystal Surface ◽  
Surface Profile ◽  
Lattice Relaxation ◽  
Optical Diffraction ◽  
Wafer Surface ◽  
X Ray Diffraction ◽  
X Ray ◽  
Resolution Electron ◽  
Surface Modulation ◽  
Diffraction Patterns

Rod-shaped scattering, referred to as crystal truncation rod (CTR) scattering in X-ray diffraction, can also be observed in optical diffraction patterns obtained from the surface profile image of high-resolution electron micrographs. The characteristics of the CTR scattering are shown to be in agreement with those observed by X-ray scattering. With this technique, information about the lattice relaxation of the image of surfaces or interface boundaries observed in the electron microscope (EM) can be easily obtained and the lattice spacing of a GaAs crystal is shown to be shrunk at the interface boundary between the (001) surface and the amorphous oxide layer. This is precisely opposite to the effect observed for an Si (001) wafer surface. Several effects of surface modulation on CTR scattering are demonstrated using an optical diffractometer and masks of the f.c.c. lattice.

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