Showing papers on "Contrast transfer function published in 1986"
TL;DR: In this article, the strength of the very weak high-resolution Fourier components of the image of a two-dimensional crystal was determined using real space correlation analysis, and the amplitude and phase information was extracted from the distortion-corrected image of the crystal.
694 citations
TL;DR: In this paper, the interference fringes, or electron Ronchigrams, appearing in the shadow images of thin periodic objects were used for calibration of the operating parameters of a scanning transmission electron microscopy (STEM) instrument.
82 citations
TL;DR: In this paper, optical transforms from a through focal series of images of amorphous films of Ge were used to measure the spatial frequencies of maximum and minimum phase contrast of a specific 200 kV lEOL electron microscope.
Abstract: Optical transforms from a through focal series of images of amorphous films of Ge were used to measure the spatial frequencies of maximum and minimum phase contrast of a specific 200 kV lEOL electron microscope. This information was used to determine precise values for the spherical aberration coefficient and defect of focus. Under the appropriate conditions of lens excitation the spherical aberration coefficient was found to be as low as 0·94 mm. Other image defects revealed with great precision were associated with astigmatism, beam divergence and specimen drift in the microscope stage. Quantitative examples illustrating these effects are discussed.
9 citations
TL;DR: Frozen-hydrated microtubules have been studied by cryoelectron microscopy and their relationship with the computed or X ray diffraction patterns, and the influence of the contrast transfer function are described.
Abstract: Frozen-hydrated microtubules have been studied by cryoelectron microscopy We have described some structural features of microtubules, their relationship with the computed or X ray diffraction patterns, and the influence of the contrast transfer function
3 citations
01 Jan 1986
TL;DR: In this article, the Fermat-Hamilton formulation of Gaussian beams is used to model optical fibers and to describe the output of laser devices, and the behavior of the center of the beam, its width and the way in which the initial uncorrelation of position and momentum is lost.
Abstract: Gaussian beams include a number of field or wavefunctions which have a clear quantum mechanical analogue: coherent states, correlated coherent states and discrete modes for quantum oscillators. These are used to model optical fibers and to describe the output of laser devices. When these beams leave their source and travel freely through space, they loose their coherence and aberrate. The source of this aberration is purely geometrical, and is termed spherical aberration. We describe this process in the framework of the Fermat-Hamilton formulation of optics, studying the behaviour of the center of the beam, its width, and the way in which the initial uncorrelation of position and momentum is lost.
3 citations
TL;DR: In this article, the spatial resolution and contrast resolution required of a multiformat camera (MFC) for medical imaging are discussed, and a typical cathode-ray tube (CRT) MFC and a prototype laser MFC are compared based on the following measured quantities: line spread function and associated contrast transfer function, noise characteristics, intensity transfer function (dynamic range), large-area contrast, and film irradiance.
Abstract: The spatial resolution and contrast resolution required of a multiformat camera (MFC) for medical imaging are discussed. A typical cathode-ray tube (CRT) MFC and a prototype laser MFC are compared based on the following measured quantities: line spread function and associated contrast transfer function, noise characteristics, intensity transfer function (dynamic range), large-area contrast, and film irradiance. The laser MFC is found to provide significantly better performance than the CRT MFC in all of these areas.
2 citations
TL;DR: In this paper, a shadow image of fine particles was used for stigmation and the measurement of spherical aberration of the probe-forming lens, and the error of measurement is within several percent for the spherical aberrations coefficient and is less than 30 nm for the coefficient of two-fold astigmatism.
1 citations
30 Jan 1986
TL;DR: In this paper, the theory of image formation by a high-resolution electron microscope is reviewed based on the wave-optics, which is characterized by strong interaction of electrons as well as a large spherical aberration of an objective lens.
Abstract: The theory of image formation by a high-resolution electron microscope is reviewed based on the wave-optics. The image formation in an electron microscope is characterized by strong interaction of electrons as well as a large spherical aberration of an objective lens. Thus the interference between scattered waves at recording an image becomes important. Ananalvtical expression of the transmission-cross-coefficient is derived, which describes the degree of coherence between each two scattered waves due to the aberrations. The transmission-cross-coefficients control the information transfer through the electron microscope, and thus limit the attainable resolution of the microscope. The characteristics of high-resolution electron microscopy will be made clear by comparison with optical microscopy.
1 citations
TL;DR: In this paper, the effect of the higher-order spherical aberration coefficient on the transfer function in transmission electron microscopy was calculated, where the optical illumination system was assumed to be perfectly coherent and axially symmetric.
Abstract: The effect of the higher-order spherical aberration coefficient on the transfer function in transmission electron microscopy was calculated. In order to simplify the system, the optical illumination system was assumed to be perfectly coherent and axially symmetric. The result shows that the effect of the fifth-order spherical aberration coefficient, C5, on the usual transfer function with the third-order spherical aberration coefficient C5≡C3=0.5 mm for 100 keV electrons cannot be neglected, if high-order Bragg reflections from net planes with smaller lattice spacings than 0.1 nm are utilized for lattice imaging. The effect of the higher-order term due to the defocussing on the transfer function is also discussed.
1 citations
10 May 1986
TL;DR: For points on and near the optical axis, asymptotic solutions to the Rayleigh-Sommerfeld diffraction integral are possible for annular apertures illuminated by plane waves of uniform intensity distribution containing rotationally symmetric Seidel aberrations (defocus and spherical aberration).
Abstract: For points on and near the optical axis, asymptotic solutions to the Rayleigh-Sommerfeld diffraction integral are possible for annular apertures illuminated by plane waves of uniform intensity distribution containing rotationally symmetric Seidel aberrations (defocus and spherical aberration). Computer studies of these cases show excellent agreement with experiment. The amount of defocus and spherical aberration can be determined from shifts in positions of on-axis intensity extrema. An empirical study of the non-rotationally symmetric Seidel aberration astigmatism reveals a predictable change in the diffraction pattern allowing for the verification of the aberration to within .05 wavelengths.