Showing papers on "Contrast transfer function published in 1992"
TL;DR: In this paper, the development of the basic notions of electron microscope imaging and of contrast transfer theory are described and the effects of finite source size and chromatic instabilities (defocus fluctuations) can be represented by envelope functions which attenuate the oscillating contrast transfer function and which have significant effects on resolution.
151 citations
TL;DR: It is shown that compensation for the contrast transfer function is necessary and sufficient to convert the images into accurate representations of molecular density and in quantitative agreement with the atomic model derived from X-ray results.
112 citations
TL;DR: In this article, the positions of metallic atoms in crystal of K2O have been determined from a single high-resolution electron microscope image and from the combination of the image and the electron diffraction pattern.
65 citations
TL;DR: In this paper, a power spectral analysis of thin amorphous carbon film images is performed to determine the spherical aberration coefficient C s and to calibrate the defocus Δ f. Agreement with experiment provides evidence of the validity of a frozen phonon algorithm for simulation of energy-filtered convergent beam electron diffraction that is then extended to image simulation.
33 citations
TL;DR: It is shown that three-dimensional confocal imaging is strongly degraded if the amount of aberration is larger than a quarter wavelength and the compensation of the primary spherical aberration by introducing defocus is discussed.
Abstract: For both reflection- and transmission-mode confocal scanning microscope systems, three-dimensional coherent transfer functions are investigated by considering the effects of defocus and primary spherical aberration. We numerically calculate the three-dimensional coherent transfer functions for various amounts of aberration and show that three-dimensional confocal imaging is strongly degraded if the amount of aberration is larger than a quarter wavelength. The compensation of the primary spherical aberration by introducing defocus is also discussed.
29 citations
TL;DR: This is the first demonstration that cryo-electron microscopy images can be used to quantitate the absolute mass, mass per unit length and internal density distributions of proteins and nucleic acids.
26 citations
TL;DR: Energy-filtering transmission electron microscopy (EFTEM) with an imaging filter lens can combine the modes of electron spectroscopic imaging (ESI) and electron Spectroscopic Diffraction (ESD), and different modes can be used to record an electron energy-loss spectrum (EELS) as discussed by the authors.
Abstract: 2014 Energy-filtering transmission electron microscopy (EFTEM) with an imaging filter lens can combine the modes of electron spectroscopic imaging (ESI) and electron spectroscopic diffraction (ESD), and different modes can be used to record an electron energy-loss spectrum (EELS). Therefore, an EFTEM can make full use of the elastic and inelastic electron-specimen interactions. This review summarizes the possibilities of EFTEM for applications in materials science. Mic7wc. MicroanaL Microstruct. APRIIJJUNE 1992, PAGE 141 Classification Physics Abstracts 07.80 34.80 81.70
25 citations
TL;DR: In this paper, the authors define the contrast transfer function, which is a function of exposure and spatial frequency, and apply it to a commercially available asymmetric screen-film combination.
Abstract: The measurement of modulation transfer function for radiographic screen-film systems depends critically upon a proper linearization of the measured line spread function. This is normally done by photographic photometry (i.e., using the measured density versus log exposure relationship to transform the density line spread function into an exposure line spread function). It has been long appreciated that this procedure may fail for asymmetrical dual screen systems that use film with emulsion coated on both sides of the support. The advent of asymmetrical and near-zero crossover films that can be used with highly asymmetric screen pairs has prompted a reinvestigation of these concerns about the definition and measurement of modulation transfer function. For such cases, it is useful to define the contrast transfer function, which is a function of exposure and spatial frequency. When normalized by its zero frequency value the contrast transfer function can serve as the "effective MTF" for low-contrast input signals in such systems. In the limit of symmetrical systems this quantity approaches the conventionally measured MTF. The utility of this approach is demonstrated by applying it to a commercially available asymmetrical screen-film combination.
24 citations
TL;DR: In this article, state-of-the-art deep ultraviolet steppers and some i-line steppers were compared by measuring the contrast transfer function, i.e., contrast versus linewidth.
Abstract: The aerial image contrast is a key parameter for the evaluation of the performance of optical projection systems. State‐of‐the‐art deep ultraviolet steppers and some i‐line steppers were investigated for comparison by measuring the contrast transfer function, i.e., contrast versus linewidth. Examples are shown how specific weaknesses of an imaging system like astigmatism and sensitivity from internal reflections can be quantified with this technique. For comparison the contrast transfer functions were also calculated, assuming ideal, purely diffraction limited image transfer of the optics, and with the numerical aperture and partial coherence as parameters. Interestingly none of the steppers meet the imaging performance which can be expected from theory.
23 citations
TL;DR: In this article, defocus-modulation image processing has been applied in order to correct the spherical aberration in transmission electron microscope images and the usefulness of this method was confirmed experimentally by the off-line image integration of the through-focus images recorded on a video tape.
Abstract: The defocus-modulation image processing has been applied in order to correct the spherical aberration in transmission electron microscope images. The usefulness of this method was confirmed experimentally by the off-line image integration of the through-focus images recorded on a video tape. The diffractograms in which power spectra were plotted as a function of defocus value, often called Thon diagram, constructed by the processed images demonstrated the correction of spherical aberration and the considerable improvement of the resolution from 2.9 nm -1 to 3.3 nm -1
19 citations
25 Oct 1992
TL;DR: The authors present the first images of submillimeter high-contrast phantoms obtained with an X-ray mammography tube operating at high flux density.
Abstract: Double-sided microstrip silicon crystals are being tested as detectors for X-rays in the diagnostic energy range (10-100 keV) for digital radiology. An analog-to-digital-converter and CAMAC based acquisition system has been developed to study the imaging capabilities of a silicon microstrip detector with 100 and 200 mu m read-out pitch. The authors present the first images of submillimeter high-contrast phantoms obtained with an X-ray mammography tube operating at high flux density. A preliminary contrast transfer function study was performed; a low frequency contrast of about 0.97 for a high-contrast phantom and a decrease of contrast at a frequency of 5 1p/mm corresponding to the detector intrinsic spatial resolution (100 mu m) were measured. >
TL;DR: In this paper, the object plane resolution of a microscope was analyzed as a function of the object height and numerical aperture (NA) of the primary for several spherical Schwarzschild, conic, and aspherical Head reflecting two-mirror microscope configurations.
Abstract: The spherical Schwarzschild microscope for soft X-ray applications in microscopy and projection lithography consists of two concentric spherical mirrors configured such that the third-order spherical aberration and coma are zero. Since multilayers are used on the mirror substrates for X-ray applications, it is desirable to have only two reflecting surfaces in a microscope. To reduce microscope aberrations and increase the field of view, generalized mirror surface profiles are here considered. Based on incoherent and sine wave modulation transfer function calculations, the object plane resolution of a microscope has been analyzed as a function of the object height and numerical aperture (NA) of the primary for several spherical Schwarzschild, conic, and aspherical Head reflecting two-mirror microscope configurations. The Head microscope with a NA of 0.4 achieves diffraction limited performance for objects with a diameter of 40 microns. Thus, it seems possible to record images with a feature size less than 100 A with a 40x microscope when using 40 A radiation.
TL;DR: In this paper, the compositional contrast in the scanning electron microscope image is calculated for Al-Cu, Si-Cu and Al-Si contacts, and an electron scattering phenomenon in the specimen is simulated in a direct manner.
Abstract: The compositional contrast in the scanning electron microscope image is calculated for Al-Cu, Si-Cu and Al-Si contacts. An electron scattering phenomenon in the specimen is simulated in a direct manner. Electron refraction at the boundary, because of the agreement of each Fermi energy at the boundary, is precisely taken into account. The backscattered electron image shows better resolution than the secondary electron image in terms of the boundary contrast when the primary electron energy is 1 keV. The signal intensity varies depending on materials adjacent to the location observed. The ultimate resolution of the compositional contrast of the scanning electron microscope can be below 1 nm.
TL;DR: Several methods of avoiding errors arising from chromatic aberration are discussed, including selection of a suitable optical mode (dependent on the desired spatial resolution), adjustment of the TEM imaging system so as to focus the system for a chosen energy loss, and analysis of a large area of a uniform specimen.
Abstract: An investigation has been made into the effect of chromatic aberrations of a pre-spectrometer lens system on quantitative elemental analysis by electron energy loss spectroscopy (EELS). In transmission electron microscopy (TEM) diffraction mode, the measured effects are typically 150–330 times larger than if only objectiv-lens chromatic aberration were important. We discuss several methods of avoiding errors arising from chromatic aberration, including selection of a suitable optical mode (dependent on the desired spatial resolution), adjustment of the TEM imaging system so as to focus the system for a chosen energy loss, and analysis of a large area of a uniform specimen. © 1992 Wiley-Liss, Inc.
TL;DR: In this article, the power spectra of the processed images were constructed as a function of virtual defocus value to assess the information limit more accurately, and represented the Thon diagrams for the amplitude and phase components separately.
01 Aug 1992
01 Dec 1992-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this article, a prototype X-ray imaging system was investigated in which scintillating fiber-optic glass plates are fiberoptically coupled to an intensified CCD camera.
Abstract: We are investigating a prototype X-ray imaging system in which scintillating fiber-optic glass plates are fiber-optically coupled to an intensified CCD camera. Scintillating fiber optics combine scintillating material with a waveguide permitting an increase in the thickness of the scintillating material and therefore preserving the spatial resolution with increased detection efficiency for high-energy X-rays. Experimental evaluation of the spatial resolution, by measurement of the contrast transfer function (CTF), is reported for the whole system.
Journal Article•
01 Mar 1992
TL;DR: In this paper, a high-angle annular detector was used to obtain a direct image of the crystal projection, revealing the location of the atomic columns and their relative high-angles scattering power.
Abstract: Z-contrast scanning transmission electron microscopy (STEM) with a high-angle annular detector breaks the coherence of the imaging process, and provides an incoherent image of a crystal projection Even in the presence of strong dynamical diffraction, the image can be accurately described as a convolution between an object function, sharply peaked at the projected atomic sites, and the probe intensity profile Such an image can be inverted intuitively without the need for model structures, and therefore provides the important capability to reveal unanticipated interfacial arrangements It represents a direct image of the crystal projection, revealing the location of the atomic columns and their relative high-angle scattering power Since no phase is associated with a peak in the object function or the contrast transfer function, extension to higher resolution is also straightforward Image restoration techniques such as maximum entropy, in conjunction with the 13 {Angstrom} probe anticipated for a 300 kV STEM, appear to provide a simple and robust route to the achievement of sub-{Angstrom} resolution electron microscopy
TL;DR: In this paper, a simple method is presented by which experimentally determined curves of the lens throughput as a function of lens potentials can be analyzed using electron trajectory calculations which include spherical aberration.
TL;DR: In this paper, the performance of an off-axis holographic lens afflicted with third-order spherical aberration and coma using a numerical ray-tracing procedure was evaluated for both an extended coherent and an incoherent edge as well as bar objects.
Abstract: The aim of this paper is to evaluate the performance of an off-axis holographic lens afflicted with third-order spherical aberration and coma using a numerical ray-tracing procedure. The light intensity distribution in the aberration spot observed at the Gaussian image plane has been evaluated for different amounts of coma and for a fixed value of spherical aberration. The images of both an extended coherent and an incoherent edge as well as bar objects have been computed and the results compared with the aberration-free case. All the results are illustrated in graphical form.