Image Width Research Articles

Microvascular measurements by video image shearing and splitting

A method is described for the measurement of dimensions from video displays by image splitting and shearing by electronic means only. Accuracy and repeatability are of the order of 0.5% of the video image width. The technique has the advantage that it can be adapted to provide multiple simultaneous measurements.

Shifts of Light Beams Due to Total Internal Reflection

A method for treatment of the transverse or longitudinal shifts of multiply internally reflected light beams is developed in terms of eigenfunctions for the reflection processes. Localized wave packets composed of plane-wave eigenfunctions are used to discuss the detailed structure of the shifted intensity distributions for several experimental conditions. With this approach image widths and over-all shifts, as well as splittings between images, can be calculated. The predictions are compared with the experimental results of Imbert and are found to agree with the observed transverse splitting between left and right circularly polarized light beams. Since the theory presented here disagrees with that proposed by Imbert in several respects, experiments are suggested which would distinguish between alternative theories.

A Study for Positions and Widths of Image Lines in Ion Optical Systems. I. The First-Order Theory with Ideal Magnetic Fields

In ion optical systems which contain ideal uniform sector-shaped magnetic fields, the expressions for positions X and widths W of image lines for arbitrary configurations of a magnet and an ion trajectory are derived using six (or eight) independent variables V i . When an ion optical system is set in some configuration and if one regards the ideal configuration as the origin for measurements, the differential changes of positions or widths of images can be obtained by the linear combinations of the partial differential coefficients ∂ X /∂ V i or ∂ W /∂ V i . Comparing calculations of these changes with experiments following the methods described in this paper, one can estimate the order of magnitude of the effect due to, such as, higher order aberrations, fringing fields, or room temperature fluctuations, which influences to positions and widths of images.

X-ray topographical study of dislocations in pure and HF-doped ice

Abstract Dislocations in ice have been studied by X-ray transmission topography, and dislocation densities in various types of ice have been determined. The Burgers vector, b, of the vast majority of basal (0001) dislocations is ⅓ 〈1120〉 confirming results of previous workers. Experimental image widths of the dislocations agree with theoretical calculations, and a bimodal intensity profile is observed in some reflections. In successive topographs taken at—10°C, dislocations are shown to have moved. Within approximately 100 μm of the surface, the dislocation density is much lower than in the bulk of the crystal and those dislocations that are present are usually perpendicular to the surface. At—18°C, when HF is diffused into a crystal, the total dislocation density is increased by a factor of about five, and many prismatic loops appear, grow, and then shrink. The rate of shrinkage is governed by the diffusion coefficient of HF in ice, rather than the vacancy diffusion coefficient. The increase in the numbe...

Characteristics and Measurements of an Aperture-Limited In-Line Hologram Image

The intensity distribution in the neighborhood of the real image reconstructed from an in-line Fraunhofer hologram was investigated. Assuming a finite amount of information recorded on the hologram in terms of a limiting aperture, the image is shown to possess intensity variations that are dependent on the argument of a first-order Bessel function recorded on the hologram. The theoretical results are presented on isophote diagrams and are verified experimentally. Three measurements of the image width are presented, and the inherent errors are found. The focal tolerance of the aperture-limited image relative to the recording parameters is discussed.

Investigations of Images of a Superdislocation and a Dislocation Dipole Using the Systematic Reflections

A study is made on the resolution of images of pairs of closely spaced dislocations in the bright-field electron microscopy when the foil is tilted to give the systematic reflections. Experiments are carried out on a superdislocation in an ordered Cu3Au alloy and on a dislocation dipole in stainless-steel, using electron microscopes operated at 125 kV and 500 kV. The image width of dislocation becomes narrow and the resolution is improved by tilting a specimen to give the systematic reflections and to satisfy the Bragg condition at higher-order reflections. A superdislocation with a separation of 50 Å between a pair of dislocations is observed as a two-line image. It is shown that this technique gives as good a resolution of closely spaced dislocations as the weak-beam technique.

Ray tracing of charged-particle trajectories in a prismatic uniform-field astigmatic spectrometer

An analytical ray-tracing method is discussed to describe the path of charged particles on the basis of simple mathematical concepts derived from the stereogoomotry of the trajectories, obeying Barber’s rule, within the uniform magnetic field of a prismatic spectrometer. Formulae accurate to first-order terms are computed to estimate image width, momentum spread, velocity dispersion and resolving power for particles emanated from a point source. The effect of the fringing field is also taken into account.

Weak beam observation of dislocation loops in silicon

SUMMARY Weak-beam microscopy has been used to examine the dislocation loops formed when ion implanted silicon is annealed in the temperature range 900–1300 K. The extinction distances of about 10 nm, resulting from the use of large deviation parameters S' enable stacking fault fringes of 4nm spacing to be resolved in faulted loops. The projected shape of the dislocation loops and the variable contrast along the perimeter of the bounding partial dislocation enables the habit planes of the dislocation loops to be determined from inspection. These together with the width of the dislocation image, which is about 3 nm enables the type of loop to be characterized completely from a single micrograph.

Enhanced Resolution of Dislocation Imaging at High Voltages

Some results of up to 12 beam contrast calculations for systematic orientations have indicated that high order reflections at high voltages may provide improved dislocation resolution. For example the contrast profiles for dislocations show a decrease in image width for increasing order of reflection (i.e. increasing ḡ·), thus enabling improved resolution of narrow dislocation dissociations and closely spaced dipoles or superdislocations.This paper provides experimental confirmation that high order systematic reflections do indeed result in an improvement in bright field image resolution, e.g. image widths of dislocations can be reduced by a factor of ~3. The results have been obtained from [001] foils of GaAs semiconducting devices in which dislocations are associated with surface and interfacial defects. In each case the crystal is set at the exact Bragg condition for each reflection along the systematic row being used. The work was done on the Berkeley Hitachi microscope operated at 650 kV.

A densitometer for analytical ultracentrifuge films utilizing the Gilford linear transport

A scanning densitometer for ultracentrifuge films, based on the Gilford linear transport and recording spectrophotometer, is described. The width of the slit image formed on the plane of the film can be made as small as 15 μ The transport and photometric systems are sufficiently accurate that repeated tracings of the same film agree within the thickness of the pen line. Three scanning speeds are provided. The spectrophotometer remains available for its ordinary uses, as does the linear transport without dismounting the components from the optical bench rods. The cost is very moderate.

The energy flow of X-rays in silicon single crystals

The angular divergence of the energy flow of anomalously transmitted X-rays in nearly perfect silicon crystals has been determined experimentally from image widths of dislocations on X-ray topographs. Anomalous transmission of copper, iron, and chromium radiation has been used. The result is compared with calculations using the dynamical theory of diffraction. It is shown that the angular divergence is almost constant regardless of the X-ray wavelength and that it can be made to decrease only by increasing the crystal thickness.

Television: Some viewer-display considerations

There has been much ambiguity and confusion on the subject of viewing distances. This was clearly pointed out in an article by Patrie (1966), How Does It Look From Where You Sit? published in the March 1966, issue of Audiovisual Instruction. Indeed, there has been little agreement among the experts as to what are the optimum and acceptable minimum and maximum distances for viewing film and television. For example, the University (Wisconsin) Facilities Research Center (1963) suggested 2W and 8W as the minimum and maximum viewing distances for film (where W = width of image) and 5W and 14W the minimum and maximum viewing distances for television viewing. Ash and Jaspen (1953), on the other hand, found a viewing distance of 12W not unsatisfactory for film viewing (rear screen). Wadsworth (1968) shared a position common to a number of other audiovisual specialists, recommending that 2W and 6W be the minimum and maximum viewing distance. Chapman (1960), on the other hand, recommended the 6W figure (maximum) for film and 12W (maximum) for television where legibility standards common to education are observed.

Third Order Aberration in a Sector Type Electromagnetic Analyzing Field with Straight Edges(I)Discussion from View-point of Geometrical Optics

In order to study behaviour of ion beams precisely in a electromagnetic sector type mass analyzer, characteristics of the 3 rd order aberration of the aperture angle are discussed from the view-point of geometrical optics. It is proved that the position of the minimum image is affected mainly by the 3 rd order aberration, while the1st and the 2 nd have affects on the angle of tilt of the beam trajectory and the width of the minimum image, respectively. The effect of the 2 nd order aberration is compensated by that of the 3 rd and the resolving power may increase considerably, if the central beam enters into the uniform field with a small angle to the normal of the field boundary. The critical small angle should be determined from the coefficient of the 3 rd order aberration. This effect was verified by some experimental results.

Anamorphic Condensing Optics for a Slitless Spectrograph

The use of a slitless spectrograph to obtain the spectra of wakes of hypervelocity projectiles launched in a free flight ballistic range has several advantages. The use of this instrument as a general spectroscopic tool is, however, especially limited for large objects. This is because resolution is determined by final trajectory image size as well as dispersion. The spectral resolution can be improved without altering the desirable properties of the instrument by using an anamorphic system to demagnify the wake image width only. Requirements are given for anamorphic optics used to focus the luminous wakes of hypervelocity projectiles onto the entrance focal plane of a slitless spectrograph. A system currently in use that meets these requirements is described. A comparison of spectra taken with anamorphic and spherical condensing systems is made.

Développements d'une technique de topographie en réflexion des rayons X

An X-ray reflexion topography camera has been designed to study structural defects near the surface of monocrystalline semiconductors. Large surfaces can be covered by means of successive fixed exposures. A surface of 30 mm x 10 mm for example can be studied in less than ten minutes on nuclear emulsions. The conditions for the observations of dislocations in gallium arsenide have been examined: the choice of reflecting planes is limited by the depth of penetration of X-rays, so that the effective crystal thickness must be of the order of the width of a dislocation image (2-5 microns). Studies to which these observations can be applied are numerous: structural defects induced by diffusion, lattice strains, orientation of dislocations near the surface, structural evolution of silicon during integrated circuits elaboration, structure of cleavage surfaces, lapping and polishing defects, structural defects of epitaxic layers.

Optimization of a 4-m Asymmetric Czerny–Turner Spectrograph*

The properties of a 4-m plane-grating Czerny–Turner spectrograph have been analyzed by tracing rays through the spectrograph. Contrary to results recently reported by Chandler in this journal, it was found that the optimum position of the grating is near that predicted by the Fastie–Rosendahl analytical expression. It is also shown that the image width can be made small all the way across a 50-cm plate, that the focal curve can be made straight, and that a position of the entrance slit can be found that makes it unnecessary to refocus the spectrograph when the grating is rotated.

Optimization of a 4-m Asymmetric Czerny–Turner Spectrograph

Methods are discussed for finding the optimum configuration of an inplane Czerny–Turner-type spectrograph. An asymmetry parameter is used which involves a lateral movement of the grating, perpendicular to the rulings. This displacement improves image quality at the center of a fixed photographic plate, and we find that the grating position for best imaging varies with angle. The optimum relationship between grating angle and position is derived by ray tracing for a specific 4-m instrument and the image widths are found to be superior to those calculated for configurations based on analytical expressions. Ray tracing is used to derive a compromise configuration with a fixed plate and a fixed grating for which the image quality is maximized at the photographic plate-center for all useful grating angles, and falls off symmetrically toward each end of the plate. For this configuration, it is necessary only to refocus the entrance slit as the grating is rotated to scan wavelengths.

Experimental study of the magnetic prism of an electromagnetic isotope separator

Two experimental methods are described. One, using a floating wire, leads to the knowledge of the “optical axis” of the prism. The other, using an ion beam, leads to the determination of correcting profiles which, when put on the entrance face of the prism, reduce the image width to an acceptable value.

Contrast of Dislocation Images in X-Ray Transmission Topography

AbstractA brief review of the different topographic methods is given in order to attempt a classification of the various types of contrast observed. Depending on whether the image is obtained by a reflection or transmission method, is simple or integrated, dynamic, direct, or intermediary, the contrast and image width vary greatly. A detailed analysis is given in the case of transmission section topographs.

Spherical aberration of compound quadrupole lenses and systems

Abstract In the paper are given equations of third-order trajectories for a compound quadrupole lens which are used to deduce expressions for the spherical aberration in the form of integrals. Coefficients of spherical aberration are given in the short lens approximation. Analytical expressions were obtained for the coefficients of spherical aberration for a bell-shaped field distribution. In the case of a doublet consisting of two compound lenses with a bell-shaped field distribution it is possible to compensate the spherical aberration of the width of a linear image over all its length.