Sensing three-dimensional index-of-refraction variations by means of optical wavefront sensor measurements and tomographic reconstruction

1995 ◽  
Vol 34 (5) ◽  
pp. 1374 ◽  
Author(s):  
Michael C. Roggemann
Keyword(s):  
Tomographic Reconstruction ◽  
Three Dimensional ◽  
Index Of Refraction ◽  
Wavefront Sensor

Design and calibration of an IVEM for general 3-dimensional imaging of non-diffracting materials

1992 ◽  
Vol 50 (2) ◽  
pp. 1040-1041
Author(s):  
Neil Rowlands ◽  
Jeff Price ◽  
Michael Kersker ◽  
Seichi Suzuki ◽  
Steve Young ◽  
...  
Keyword(s):  
3D Imaging ◽  
Tomographic Reconstruction ◽  
Three Dimensional ◽  
3 Dimensional ◽  
3D Microstructure ◽  
Image Translation ◽  
Digital Correlation ◽  
On Line ◽  
Mechanical Stage ◽  
Projection Angle

Three-dimensional (3D) microstructure visualization on the electron microscope requires that the sample be tilted to different positions to collect a series of projections. This tilting should be performed rapidly for on-line stereo viewing and precisely for off-line tomographic reconstruction. Usually a projection series is collected using mechanical stage tilt alone. The stereo pairs must be viewed off-line and the 60 to 120 tomographic projections must be aligned with fiduciary markers or digital correlation methods. The delay in viewing stereo pairs and the alignment problems in tomographic reconstruction could be eliminated or improved by tilting the beam if such tilt could be accomplished without image translation.A microscope capable of beam tilt with simultaneous image shift to eliminate tilt-induced translation has been investigated for 3D imaging of thick (1 μm) biologic specimens. By tilting the beam above and through the specimen and bringing it back below the specimen, a brightfield image with a projection angle corresponding to the beam tilt angle can be recorded (Fig. 1a).

Methods for three-dimensional reconstruction of cellular components within a thick section

1986 ◽  
Vol 44 ◽  
pp. 18-21
Author(s):  
J. Frank ◽  
B. F. McEwen ◽  
M. Radermacher ◽  
C. L. Rieder
Keyword(s):  
Tilt Angle ◽  
Tomographic Reconstruction ◽  
3D Structure ◽  
Three Dimensional ◽  
Thick Section ◽  
Three Dimensional Reconstruction ◽  
Axis Ratio ◽  
Dimensional Reconstruction ◽  
Cellular Components

The tomographic reconstruction from multiple projections of cellular components, within a thick section, offers a way of visualizing and quantifying their three-dimensional (3D) structure. However, asymmetric objects require as many views from the widest tilt range as possible; otherwise the reconstruction may be uninterpretable. Even if not for geometric obstructions, the increasing pathway of electrons, as the tilt angle is increased, poses the ultimate upper limitation to the projection range. With the maximum tilt angle being fixed, the only way to improve the faithfulness of the reconstruction is by changing the mode of the tilting from single-axis to conical; a point within the object projected with a tilt angle of 60° and a full 360° azimuthal range is then reconstructed as a slightly elliptic (axis ratio 1.2 : 1) sphere.

Practical electron tomography

1995 ◽  
Vol 53 ◽  
pp. 742-743
Author(s):  
C.L. Woodcock
Keyword(s):  
Electron Tomography ◽  
Tomographic Reconstruction ◽  
Three Dimensional ◽  
3D Shape ◽  
Computational Resources ◽  
Shape Of Particles

Despite the potential of the technique, electron tomography has yet to be widely used by biologists. This is in part related to the rather daunting list of equipment and expertise that are required. Thanks to continuing advances in theory and instrumentation, tomography is now more feasible for the non-specialist. One barrier that has essentially disappeared is the expense of computational resources. In view of this progress, it is time to give more attention to practical issues that need to be considered when embarking on a tomographic project. The following recommendations and comments are derived from experience gained during two long-term collaborative projects.Tomographic reconstruction results in a three dimensional description of an individual EM specimen, most commonly a section, and is therefore applicable to problems in which ultrastructural details within the thickness of the specimen are obscured in single micrographs. Information that can be recovered using tomography includes the 3D shape of particles, and the arrangement and dispostion of overlapping fibrous and membranous structures.

Three-dimensional tomographically reconstructed optical emission profiles of Hall thruster plasmas

2021 ◽  
Author(s):  
jinwoo kim ◽  
Dongho Lee ◽  
Guentae Doh ◽  
Sanghoo Park ◽  
Holak Kim ◽  
...  
Keyword(s):  
Radiative Decay ◽  
Tomographic Reconstruction ◽  
Gaussian White Noise ◽  
Three Dimensional ◽  
Diagnostic System ◽  
Optical Emission ◽  
Ccd Camera ◽  
Hall Thruster ◽  
Plume Region ◽  
Reconstruction Performance

Abstract A diagnostic system was developed for spectrally resolved, three-dimensional tomographic reconstruction of Hall thruster plasmas, and local intensity profiles of Xe I and Xe II emissions were reconstructed. In this diagnostic system, 28 virtual cameras were generated using a single, fixed charge-coupled device (CCD) camera by rotating the Hall thruster to form a sufficient number of lines of sight. The Phillips-Tikhonov regularization algorithm was used to reconstruct local emission profiles from the line-integrated emission signals. The reconstruction performance was evaluated using both azimuthally symmetric and asymmetric synthetic phantom images including 5% Gaussian white noise, which resulted in a root-mean-square error of the reconstruction within an order of 10-3 even for a 1% difference in the azimuthal intensity distribution. Using the developed system, three-dimensional local profiles of Xe II emission (541.9 nm) from radiative decay of the excited state 5p4(3P2)6p2[3]˚5/2 and Xe I emission (881.9 nm) from 5p5(2P˚3/2)6p2[5/2]3 were obtained, and two different shapes were found depending on the wavelength and the distance from the thruster exit plane. In particular, a stretched central jet structure was distinctively observed in the Xe II emission profile beyond 10 mm from the thruster exit, while gradual broadening was found in the Xe I emission. Approximately 10% azimuthal nonuniformities were observed in the local Xe I and Xe II intensity profiles in the near-plume region (< 10 mm), which could not be quantitatively distinguished by analysis of the frontal photographic image. Three-dimensional Xe I and Xe II intensity profiles were also obtained in the plume region, and the differences in the structures of both emissions were visually confirmed.

scholarly journals Three-dimensional imaging of hold baggage for airport security

2014 ◽  
Vol XL-5 ◽  
pp. 331-336
Author(s):  
S. Kolokytha ◽  
R. Speller ◽  
S. Robson
Keyword(s):  
3D Imaging ◽  
Imaging System ◽  
Tomographic Reconstruction ◽  
Three Dimensional ◽  
Handling Time ◽  
Cost Effective ◽  
Airport Security ◽  
X Ray ◽  
Common System ◽  
Close Range

This study describes a cost-effective check-in baggage screening system, based on "on-belt tomosynthesis" (ObT) and close-range photogrammetry, that is designed to address the limitations of the most common system used, conventional projection radiography. The latter's limitations can lead to loss of information and an increase in baggage handling time, as baggage is manually searched or screened with more advanced systems. This project proposes a system that overcomes such limitations creating a cost-effective automated pseudo-3D imaging system, by combining x-ray and optical imaging to form digital tomograms. Tomographic reconstruction requires a knowledge of the change in geometry between multiple x-ray views of a common object. This is uniquely achieved using a close range photogrammetric system based on a small network of web-cameras. This paper presents the recent developments of the ObT system and describes recent findings of the photogrammetric system implementation. Based on these positive results, future work on the advancement of the ObT system as a cost-effective pseudo-3D imaging of hold baggage for airport security is proposed.

scholarly journals A Survey of the Use of Iterative Reconstruction Algorithms in Electron Microscopy

2017 ◽  
Vol 2017 ◽  
pp. 1-17 ◽  
Author(s):  
C. O. S. Sorzano ◽  
J. Vargas ◽  
J. Otón ◽  
J. M. de la Rosa-Trevín ◽  
J. L. Vilas ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Electron Tomography ◽  
Tomographic Reconstruction ◽  
Three Dimensional ◽  
Iterative Algorithms ◽  
Projection Methods ◽  
Particle Analysis ◽  
Reconstruction Algorithms ◽  
Large Families ◽  
Key Steps

One of the key steps in Electron Microscopy is the tomographic reconstruction of a three-dimensional (3D) map of the specimen being studied from a set of two-dimensional (2D) projections acquired at the microscope. This tomographic reconstruction may be performed with different reconstruction algorithms that can be grouped into several large families: direct Fourier inversion methods, back-projection methods, Radon methods, or iterative algorithms. In this review, we focus on the latter family of algorithms, explaining the mathematical rationale behind the different algorithms in this family as they have been introduced in the field of Electron Microscopy. We cover their use in Single Particle Analysis (SPA) as well as in Electron Tomography (ET).

Kinematics and Dynamics of Nanostructured Origami™

2005 ◽  
Author(s):  
P. Stellman ◽  
W. Arora ◽  
S. Takahashi ◽  
E. D. Demaine ◽  
G. Barbastathis
Keyword(s):  
Dynamic Modeling ◽  
Periodic Structures ◽  
Metal Layer ◽  
Three Dimensional ◽  
Spatial Dimension ◽  
Index Of Refraction ◽  
Coulomb Energy ◽  
Single Vertex ◽  
Revolute Joints ◽  
Final Design

Two-dimensional (2D) nanofabrication processes such as lithography are the primary tools for building functional nanostructures. The third spatial dimension enables completely new devices to be realized, such as photonic crystals with arbitrary defect structures and materials with negative index of refraction [1]. Presently, available methods for three-dimensional (3D) nanopatterning tend to be either cost inefficient or limited to periodic structures. The Nanostructured Origami method fabricates 3D devices by first patterning nanostructures (electronic, optical, mechanical, etc) onto a 2D substrate and subsequently folding segments along predefined creases until the final design is obtained [2]. This approach allows almost arbitrary 3D nanostructured systems to be fabricated using exclusively 2D nanopatterning tools. In this paper, we present two approaches to the kinematic and dynamic modeling of folding origami structures. The first approach deals with the kinematics of unfolding single-vertex origami. This work is based on research conducted in the origami mathematics community, which is making rapid progress in understanding the geometry of origami and folding in general [3]. First, a unit positive “charge” is assigned to the creases of the structure in its folded state. Thus, each configuration of the structure as it unfolds can be assigned a value of electrostatic (Coulomb) energy. Because of repulsion between the positive charges, the structure will unfold if allowed to decrease its energy. If the energy minimization can be carried out all the way to the completely unfolded state, we are simultaneously guaranteed of the absence of collisions for the determined path. The second method deals with dynamic modeling of folding multi-segment (accordion style) origamis. The actuation method for folding the segments uses a thin, stressed metal layer that is deposited as a hinge on a relatively stress free structural layer. Through the use of robotics routines, the hinges are modeled as revolute joints, and the system dynamics are calculated.

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