scholarly journals VOLUMETRIC EFFECTS FOR IMAGE FORMATION OF 3D ASYMMETRIC EDGE

2020 ◽  
Vol 8 (1) ◽  
pp. 65-81
Author(s):  
Yuri V. Chugui
Keyword(s):  
Optical System ◽  
Fresnel Zone ◽  
Analytical Form ◽  
Constant Thickness ◽  
Back Side ◽  
Edge Image ◽  
Angular Aperture ◽  
Projection System ◽  
Dimensional Inspection ◽  
Main Fragment

The peculiarities for formation of the image of volumetric asymmetric absolutely absorbing edge (the main fragment of constant thickness thick plates) in a diffraction-limited projection system are investigated in analytical form applied to 3D-objects dimensional inspection. Structures and profiles of image intensities for front and back object sides are studied respectively at small and big apertures of the 3D-object optical system for various ratios of object bevel c , the Fresnel zone size d ~ ( l - the light wavelength, d - object thickness) and an angular aperture of the optical system. It is shown that in case when the bevel с << d , the shift of intensity profile of the 3D-edge image, proportional to Fresnel's zone and bevel size, takes place. Formulas for the image profile of the back side are obtained and investigated in case of strong volumetric effects, when the focus-row depth of the system is much less than the object thickness. The obtained results are in good agreement with results of computer simulations.

scholarly journals THE CONSTRUCTIVE METHOD FOR CALCULATING OF FRAUNHOFER'S DIFFRACTION PICTURES AND IMAGES OF 3D-OBJECT REFLECTIVE VOLUMETRIC EDGE

2021 ◽  
Vol 8 ◽  
pp. 64-73
Author(s):  
Yuri V. Chugui
Keyword(s):  
Fresnel Zone ◽  
Internal Surface ◽  
Analytical Form ◽  
Constructive Method ◽  
Front Face ◽  
Depth Of Focus ◽  
Angular Aperture ◽  
Dimensional Inspection ◽  
3D Object ◽  
Diffraction Patterns

In analytical form, the peculiarities of forming Fraunhofer diffraction patterns and images of faces of a volumetric asymmetric edge of an object with an absolutely reflective internal surface in relation to dimensional inspection were investigated. Formulas were obtained for calculating fields in diffraction-limited systems depending on the magnitude of the bevel of the object c , the phase shift j of the wave reflected from the inner surface of the object, and the angular aperture of the coherent optical system for forming and filtering images. It has been established that for metal 3D-objects (j = p), the value of the field in the image of the back face at a point, corresponding to the position of its border is negligible with the depth of focus of the system much less than the thickness of the object. It is shown that when bevels of an object, much less than the size of the Fresnel zone d ~ ( l - wavelength of light, d - thickness of the object) and more than the depth of focus, the displacement of the intensity profile in the image of the front face is proportional and depends on the angle j. With large bevels, when and, the displacement of the front face boundary is inversely proportional to the value. These displacements can lead to systematic errors in measuring the position of the boundaries of the faces of a 3D-object and should be taken into account in precision dimensional inspection.

Electromagnetic diffraction in optical systems - I. An integral representation of the image field

1959 ◽  
Vol 253 (1274) ◽  
pp. 349-357 ◽  
Keyword(s):  
Electromagnetic Field ◽  
Integral Representation ◽  
Optical System ◽  
Plane Waves ◽  
Angular Spectrum ◽  
Optical Systems ◽  
Angular Aperture ◽  
Spherical Waves ◽  
Simple Physical Interpretation ◽  
Electromagnetic Diffraction

An integral representation is obtained for the electromagnetic field in the image space of an optical system . This representation, which is not restricted to systems of low angular aperture, is in the form of an angular spectrum of plane waves, and is closely related to that introduced by Luneberg (1944) as a vector generalization of well-known formulae of Debye (1909) and Picht (1925). It is shown that the representation has a simple physical interpretation in terms of a modified Huygens—Fresnel principle which operates with secondary plane waves rather than with secondary spherical waves.

3D Image Formation in Transmitted Partially Coherent and Incoherent Light Applied to Dimensional Inspection

2015 ◽  
Vol 9 (5) ◽  
pp. 508-514 ◽  
Author(s):  
Yuri V. Chugui ◽  
◽  
Elena S. Senchenko ◽  
◽  
Keyword(s):  
Measurement Accuracy ◽  
Image Formation ◽  
Constructive Theory ◽  
Incoherent Light ◽  
Projection System ◽  
Dimensional Inspection ◽  
3D Objects ◽  
Partially Coherent ◽  
Threshold Algorithms ◽  
Shadow Projection

The peculiarities of 3D objects image formation with clear shadow projection based on the constructive theory of 3D objects formation under illumination by partially coherent and perfectly incoherent light are investigated. Threshold algorithms for determining the position of boundaries of geometric 3D objects are developed, algorithms taking into account object thickness, light source angular sizes, and projection system angular apertures. These algorithms are based on the application of a true (calculated) threshold or a standard one using the corrective component for thresholds. Cases of weak and strong 3D object volumetricity for partially coherent and incoherent illumination are studied. The analytical equations for these algorithms are given. It is shown that the use of algorithms can significantly improve the measurement accuracy of the extended objects.

Characterization of resolution and uniqueness in crosswell direct‐arrival traveltime tomography using the Fourier projection slice theorem

Geophysics ◽  
1994 ◽  
Vol 59 (11) ◽  
pp. 1642-1649 ◽  
Author(s):  
James W. Rector ◽  
John K. Washbourne
Keyword(s):  
Plane Wave ◽  
Oil And Gas ◽  
Fresnel Zone ◽  
Spatial Spectrum ◽  
Limiting Factor ◽  
Angular Aperture ◽  
Data Set ◽  
Traveltime Tomography ◽  
Slice Theorem ◽  
Well Spacing

The process of acquiring a crosswell seismic direct‐arrival traveltime data set can be approximated by a series of truncated plane‐wave projections through an interwell slowness field. Using this approximation, the resolution and uniqueness of crosswell direct‐arrival traveltime tomograms can be characterized by invoking the Fourier projection slice theorem, which states that a plane‐wave projection through an object constitutes a slice of the object’s spatial spectrum. The limited vertical aperture of a crosswell survey introduces a small amount of nonuniqueness into the reconstructed tomogram by truncating the plane‐wave projection. By contrast, the limitations on angular aperture have a significant effect on resolution. The reconstructed tomogram is smeared primarily along the limiting projection angles, with the amount of smearing dependent upon the well spacing and the angular aperture. The amount of smearing was found to be inversely proportional to tan Δϕ, where Δϕ is the angular aperture illuminating a sector of the interwell plane. Consequently, the amount of smearing can be large where the angular aperture becomes small, such as at the top and bottom of the tomogram. For interwell sectors illuminated by large angular apertures, Fresnel zone effects will generally be the limiting factor in crosswell tomogram resolution. However, in some circumstances, angular aperture effects may control the tomogram resolution. The effects of angular aperture and direct‐arrival Fresnel zones produce tomograms with spatial resolution that is dependent upon the well spacing. This study indicates that direct‐arrival traveltime tomography will not usually produce tomograms with substantially greater resolution than surface seismic techniques for normal oil and gas well spacings.

Optimum Shape of Constant Stress Toroidal Shells

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
Vu Truong Vu
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Thickness Distribution ◽  
Analytical Form ◽  
Optimum Shape ◽  
Constant Thickness ◽  
Toroidal Shell ◽  
Volume Increase ◽  
Material Saving ◽  
Better Than

The paper presents the optimization of toroidal shell cross-sections under internal pressure. The wall thickness distribution along a circular centerline is derived in an analytical form. In membrane solution, this cross-section gives a constant Mises stress all over the shell. Therefore, it leads to material saving and contained volume increase in comparison with the traditional cross-section of circular constant thickness. The optimum shapes are designed for two states of shell, one is elasticity and the other is up to destruction. The maximum material saving can reach 70% in some configurations of toroid. Results of the proposed method are as good as or better than those found in literature.

High Precision Algorithms for 3D Objects Shadow Inspection in Partially Coherent Light

2014 ◽  
Vol 613 ◽  
pp. 151-156 ◽  
Author(s):  
Yuri V. Chuguy ◽  
Elena S. Senchenko
Keyword(s):  
Angular Size ◽  
Coherent Light ◽  
Measuring Systems ◽  
Projection System ◽  
Dimensional Inspection ◽  
3D Objects ◽  
Partially Coherent ◽  
Partially Coherent Light ◽  
Threshold Algorithms ◽  
Shadow Projection

As applied to the dimensional inspection the peculiarities of 3D objects image formation with clear shadow projection under their illumination by quasi-monochromatic partially coherent light based on the constructive theory of 3D objects formation using a model of equivalent diaphragms are studied. Two threshold algorithms for determining the position of 3D objects geometric boundaries under their inspection by optical shadow method according to their thickness as well as the light source angular size and the projection system aperture diaphragm are developed. These algorithms are based on the application of true (calculated) threshold or standard one using the corrective component to threshold. It has been shown theoretically and experimentally that their use can significantly improve the measurement accuracy of extended objects. The obtained results under the development of measuring systems for industrial inspection of ceramic details allowed us to reduce the measurement error.

scholarly journals Measurement and compensation of misalignment in double-sided hard X-ray Fresnel zone plates

2020 ◽  
Vol 27 (3) ◽  
pp. 583-589
Author(s):  
Viktoria Yurgens ◽  
Frieder Koch ◽  
Mario Scheel ◽  
Timm Weitkamp ◽  
Christian David
Keyword(s):  
Fresnel Zone ◽  
Back Side ◽  
Fresnel Zone Plates ◽  
X Ray ◽  
Zone Plates ◽  
Recording Efficiency ◽  
Aspect Ratios ◽  
Diffractive Lenses ◽  
Tilting Angle ◽  
Tungsten Anode

Double-sided Fresnel zone plates are diffractive lenses used for high-resolution hard X-ray microscopy. The double-sided structures have significantly higher aspect ratios compared with single-sided components and hence enable more efficient imaging. The zone plates discussed in this paper are fabricated on each side of a thin support membrane, and the alignment of the zone plates with respect to each other is critical. Here, a simple and reliable way of quantifying misalignments by recording efficiency maps and measuring the absolute diffraction efficiency of the zone plates as a function of tilting angle in two directions is presented. The measurements are performed in a setup based on a tungsten-anode microfocus X-ray tube, providing an X-ray energy of 8.4 keV through differential measurements with a Cu and an Ni filter. This study investigates the sources of the misalignments and concludes that they can be avoided by decreasing the structure heights on both sides of the membrane and by pre-programming size differences between the front- and back-side zone plates.

Ray-Tracing Analysis of Fresnel-Zone-Plate Optical System as an Electron Beam Profile Monitor

2007 ◽  
Author(s):  
Masami Fujisawa ◽  
Hiroshi Sakai ◽  
Norio Nakamura ◽  
Hitoshi Hayano ◽  
Toshiya Muto
Keyword(s):  
Electron Beam ◽  
Ray Tracing ◽  
Optical System ◽  
Fresnel Zone ◽  
Beam Profile ◽  
Zone Plate ◽  
Fresnel Zone Plate ◽  
Beam Profile Monitor

A Field Emission System For Transmission Electron Microscopy

1973 ◽  
Vol 31 ◽  
pp. 298-299
Author(s):  
Michel Troyonal ◽  
Huei Pei Kuoal ◽  
Benjamin M. Siegelal
Keyword(s):  
Electron Microscope ◽  
Field Emission ◽  
Optical System ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Objective Lens ◽  
Electron Optical System ◽  
Cross Sectional ◽  
Transmission Electron ◽  
Emission System

A field emission system for our experimental ultra high vacuum electron microscope has been designed, constructed and tested. The electron optical system is based on the prototype whose performance has already been reported. A cross-sectional schematic illustrating the field emission source, preaccelerator lens and accelerator is given in Fig. 1. This field emission system is designed to be used with an electron microscope operated at 100-150kV in the conventional transmission mode. The electron optical system used to control the imaging of the field emission beam on the specimen consists of a weak condenser lens and the pre-field of a strong objective lens. The pre-accelerator lens is an einzel lens and is operated together with the accelerator in the constant angular magnification mode (CAM).

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