Application of Vernier Principle to Photoelectric Autocollimator for Improvement of Accuracy, Angular Range and Speed

2021 ◽  
Author(s):  
Andrey V. Golitsyn ◽  
Alexandr A. Golitsyn ◽  
Alexander K. Dmitriev ◽  
Natalia A. Seyfi
Keyword(s):  
Angular Range

A linearity test for thick specimens imaged by HVEM over a 180° angular range

1991 ◽  
Vol 49 ◽  
pp. 552-553
Author(s):  
Yu Liu
Keyword(s):  
Phase Contrast ◽  
Three Dimensional ◽  
Angular Range ◽  
Two Dimensional ◽  
Back Projection ◽  
Line Integral ◽  
Exponential Law ◽  
Transmission Electron ◽  
Absorption Law ◽  
Linearity Test

The image obtained in a transmission electron microscope is the two-dimensional projection of a three-dimensional (3D) object. The 3D reconstruction of the object can be calculated from a series of projections by back-projection, but this algorithm assumes that the image is linearly related to a line integral of the object function. However, there are two kinds of contrast in electron microscopy, scattering and phase contrast, of which only the latter is linear with the optical density (OD) in the micrograph. Therefore the OD can be used as a measure of the projection only for thin specimens where phase contrast dominates the image. For thick specimens, where scattering contrast predominates, an exponential absorption law holds, and a logarithm of OD must be used. However, for large thicknesses, the simple exponential law might break down due to multiple and inelastic scattering.

Mosaic Mapping: A Means of Tiling Images to Shorten Acquisition Speed for Lower - Magnification SEM Images and Wavelength Dispersive Spectrometers (WDS) X-Ray Maps

1996 ◽  
Vol 54 ◽  
pp. 438-439
Author(s):  
J.D. Geller ◽  
C.R. Herrington
Keyword(s):  
Limiting Factors ◽  
X Rays ◽  
Angular Range ◽  
Acceptance Angle ◽  
Sem Images ◽  
Worst Case ◽  
X Ray ◽  
Focusing Distance ◽  
Layered Crystals ◽  
Working Distance

The minimum magnification for which an image can be acquired is determined by the design and implementation of the electron optical column and the scanning and display electronics. It is also a function of the working distance and, possibly, the accelerating voltage. For secondary and backscattered electron images there are usually no other limiting factors. However, for x-ray maps there are further considerations. The energy-dispersive x-ray spectrometers (EDS) have a much larger solid angle of detection that for WDS. They also do not suffer from Bragg’s Law focusing effects which limit the angular range and focusing distance from the diffracting crystal. In practical terms EDS maps can be acquired at the lowest magnification of the SEM, assuming the collimator does not cutoff the x-ray signal. For WDS the focusing properties of the crystal limits the angular range of acceptance of the incident x-radiation. The range is dependent upon the 2d spacing of the crystal, with the acceptance angle increasing with 2d spacing. The natural line width of the x-ray also plays a role. For the metal layered crystals used to diffract soft x-rays, such as Be - O, the minimum magnification is approximately 100X. In the worst case, for the LEF crystal which diffracts Ti - Zn, ˜1000X is the minimum.

A light-scattering photometer for the angular range 6–170°

1968 ◽  
Vol 6 (3) ◽  
pp. 207-212 ◽  
Author(s):  
G. Meyerhoff ◽  
U. Moritz ◽  
R. L. Darskus
Keyword(s):  
Light Scattering ◽  
Angular Range

scholarly journals Directional-TV Algorithm for Image Reconstruction from Limited-Angular-Range Data

2021 ◽  
pp. 102030
Author(s):  
Zheng Zhang ◽  
Buxin Chen ◽  
Dan Xia ◽  
Emil Y. Sidky ◽  
Xiaochuan Pan
Keyword(s):  
Image Reconstruction ◽  
Range Data ◽  
Angular Range

scholarly journals High-resolution characterization of the forbidden Si 200 and Si 222 reflections

2015 ◽  
Vol 48 (2) ◽  
pp. 528-532 ◽  
Author(s):  
Peter Zaumseil
Keyword(s):  
High Resolution ◽  
Angular Range ◽  
Angular Divergence ◽  
X Ray Diffraction ◽  
Multiple Diffraction ◽  
Diffraction Plane ◽  
X Ray ◽  
Sample Orientation ◽  
Plane Sample

The occurrence of the basis-forbidden Si 200 and Si 222 reflections in specular X-ray diffraction ω–2Θ scans is investigated in detail as a function of the in-plane sample orientation Φ. This is done for two different diffractometer types with low and high angular divergence perpendicular to the diffraction plane. It is shown that the reflections appear for well defined conditions as a result of multiple diffraction, and not only do the obtained peaks vary in intensity but additional features like shoulders or even subpeaks may occur within a 2Θ range of about ±2.5°. This has important consequences for the detection and verification of layer peaks in the corresponding angular range.

scholarly journals Optimising the AR Engraved Structure on Light-Guide Facets for a Wide Range of Wavelengths

Optics ◽  
2020 ◽  
Vol 2 (1) ◽  
pp. 25-42
Author(s):  
Ioseph Gurwich ◽  
Yakov Greenberg ◽  
Kobi Harush ◽  
Yarden Tzabari
Keyword(s):  
Theoretical Analysis ◽  
Light Guide ◽  
Spectral Band ◽  
Angular Range ◽  
The Past ◽  
Input And Output ◽  
Wide Range ◽  
The Given ◽  
Theoretical Results ◽  
Shape And Size

The present study is aimed at designing anti-reflective (AR) engraving on the input–output surfaces of a rectangular light-guide. We estimate AR efficiency, by the transmittance level in the angular range, determined by the light-guide. Using nano-engraving, we achieve a uniform high transmission over a wide range of wavelengths. In the past, we used smoothed conical pins or indentations on the faces of light-guide crystal as the engraved structure. Here, we widen the class of pins under consideration, following the physical model developed in the previous paper. We analyze the smoothed pyramidal pins with different base shapes. The possible effect of randomization of the pins parameters is also examined. The results obtained demonstrate optimized engraved structure with parameters depending on the required spectral range and facet format. The predicted level of transmittance is close to 99%, and its flatness (estimated by the standard deviation) in the required wavelengths range is 0.2%. The theoretical analysis and numerical calculations indicate that the obtained results demonstrate the best transmission (reflection) we can expect for a facet with the given shape and size for the required spectral band. The approach is equally useful for any other form and of the facet. We also discuss a simple way of comparing experimental and theoretical results for a light-guide with the designed input and output features. In this study, as well as in our previous work, we restrict ourselves to rectangular facets. We also consider the limitations on maximal transmission produced by the size and shape of the light-guide facets. The theoretical analysis is performed for an infinite structure and serves as an upper bound on the transmittance for smaller-size apertures.

scholarly journals A Study of The Alpha – Nucleus Scattering

2014 ◽  
Vol 40 (2) ◽  
pp. 249-258
Author(s):  
DR Sarker ◽  
Ain Ul Huda ◽  
SK Das ◽  
Md K Hasan ◽  
Md M Parvej ◽  
...  
Keyword(s):  
Angular Distribution ◽  
Alpha Particles ◽  
Strong Absorption ◽  
Distribution Data ◽  
Absorption Model ◽  
Angular Range ◽  
Deformation Parameters ◽  
Nucleus Scattering ◽  
Best Fit ◽  
Collective States

Angular distribution data for the elastic scattering of 1.37 GeV alpha particles from several nuclei are analyzed in terms of the three parameter strong absorption model of Frahn and Venter. The fits are quite satisfactory over practically the entire angular range and the best fit parameters are obtained. These are used for the study of the inelastic scattering of alpha particles leading to the collective states in nuclei. A reasonably good fit is obtained without any adjustment of the parameters suggesting thereby the success of the strong absorption model. Deformation parameters are extracted for the collective states in nuclei. Asiat. Soc. Bangladesh, Sci. 40(2): 249-258, December 2014

scholarly journals An Analytical Method for the Quantitative Determination of the Volume Fractions in Fiber Textures

1979 ◽  
Vol 3 (2) ◽  
pp. 73-83 ◽  
Author(s):  
Ivan Tomov ◽  
H. J. Bunge
Keyword(s):  
Quantitative Determination ◽  
Pole Figure ◽  
Angular Range ◽  
Asymmetric Unit ◽  
Normalization Factor ◽  
Measured Intensity ◽  
Volume Fractions ◽  
Pole Figures ◽  
Axis Of Symmetry

In order to evaluate pole-figure measurements quantitatively, one needs the normalization factor which reduces measured intensity values to multiples of the random density. This factor may be determined experimentally by measuring the intensities of a random sample or it may be calculated by integrating over the whole pole-figure or its asymmetric unit. If pole-figure values are not available in the whole angular range 0≤φ≤90° (incomplete pole-figures), then the calculation is in general much more difficult and it usually presumes the knowledge of several pole-figures.In the case of fiber textures (axial symmetry), consisting of only a few strongly preferred orientations with the crystal directions 〈uvw〉i parallel to the axis of symmetry, the normalization factor and hence the volume fractions of the components i may be calculated in a rather simple way requiring only one, possibly incomplete, pole figure.

Acceptable Angular Range of Beam Pointing in Free-Space Optical Communications

2021 ◽  
Author(s):  
Tomoko Nakayama ◽  
Yoshihisa Takayama ◽  
Chiemi Fujikawa ◽  
Kashiko Kodate
Keyword(s):  
Optical Communications ◽  
Free Space ◽  
Angular Range ◽  
Free Space Optical
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