scholarly journals Investigations on Practical Issues in Solid Immersion Lens Based Sub-Wavelength Terahertz Imaging Technique: System Stability Verification and Interference Pattern Removal

Sensors ◽  
2021 ◽  
Vol 21 (21) ◽  
pp. 6990
Author(s):  
Da-Hye Choi ◽  
Jun-Hwan Shin ◽  
Il-Min Lee ◽  
Kyung Hyun Park
Keyword(s):  
Imaging Techniques ◽  
Imaging Systems ◽  
System Stability ◽  
Objective Lens ◽  
Solid Immersion Lens ◽  
Thz Imaging ◽  
Destructive Testing ◽  
Wide Range ◽  
Surface Profiles ◽  
Sub Wavelength

Terahertz (THz) imaging techniques are attractive for a wide range of applications, such as non-destructive testing, biological sensing, and security imaging. We investigate practical issues in THz imaging systems based on a solid immersion lens (SIL). The system stability in terms of longitudinal misalignment of the SIL is experimentally verified by showing that the diffraction-limited sub-wavelength beam size (0.7 λ) is maintained as long as the SIL is axially located within the depth-of-focus (~13 λ) of the objective lens. The origin of the fringe patterns, which are undesirable but inevitable in THz imaging systems that use continuous waves, is analytically studied, and a method for minimizing the interference patterns is proposed. By combining two THz images obtained at different axial positions of the object and separated by λ/4, the interference patterns are significantly reduced, and the information hidden under the interference patterns is unveiled. The broad applicability of the proposed method is demonstrated by imaging objects with different surface profiles. Our work proves that the resolution of conventional THz imaging systems can easily be enhanced by simply inserting a SIL in front of the object with high tolerance in the longitudinal misalignment and provides a method enabling THz imaging for objects with different surface profiles.

scholarly journals Mid infrared digital holography and terahertz imaging

2015 ◽  
Author(s):  
Massimiliano Locatelli
Keyword(s):  
Digital Holography ◽  
Imaging Technique ◽  
Imaging Techniques ◽  
Imaging Systems ◽  
Thz Radiation ◽  
Interferometric Imaging ◽  
Thz Imaging ◽  
Spectroscopic Information ◽  
Military Security ◽  
The Military

Mid IR and Far IR (THz) regions have been attracting a continuously growing interest, especially for imaging applications. Mid IR imaging systems are widespread in the military, security and medical fields and are, consequently, in continuous development. Even greater expectation is placed on THz imaging techniques, because of the well-known capacity of THz radiation to penetrate many common materials and to provide important spectroscopic information about various strategic stuffs. In this scenario Digital Holography, a quite recent interferometric imaging technique, is proving to be mature enough to play a key role among the other imaging techniques, both in the Mid IR and in the Far IR.

Comparison of Deterministic and Linear Cosine Spatial Filtering of Transmission Electron Micrographs

1972 ◽  
Vol 30 ◽  
pp. 596-597
Author(s):  
David A. Ansley
Keyword(s):  
Spherical Aberration ◽  
Focal Length ◽  
Chromatic Aberration ◽  
Spatial Filter ◽  
Operating Conditions ◽  
Objective Lens ◽  
List Type ◽  
Spatial Filters ◽  
Transmission Electron ◽  
Wide Range

The coherence of the electron flux of a transmission electron microscope (TEM) limits the direct application of deconvolution techniques which have been used successfully on unmanned spacecraft programs. The theory assumes noncoherent illumination. Deconvolution of a TEM micrograph will, therefore, in general produce spurious detail rather than improved resolution.A primary goal of our research is to study the performance of several types of linear spatial filters as a function of specimen contrast, phase, and coherence. We have, therefore, developed a one-dimensional analysis and plotting program to simulate a wide 'range of operating conditions of the TEM, including adjustment of the:(1) Specimen amplitude, phase, and separation(2) Illumination wavelength, half-angle, and tilt(3) Objective lens focal length and aperture width(4) Spherical aberration, defocus, and chromatic aberration focus shift(5) Detector gamma, additive, and multiplicative noise constants(6) Type of spatial filter: linear cosine, linear sine, or deterministic

Digital imaging and quantitative image analysis of polymer blends

1996 ◽  
Vol 54 ◽  
pp. 170-171
Author(s):  
Xiao Zhang
Keyword(s):  
Digital Imaging ◽  
Imaging Techniques ◽  
Imaging Systems ◽  
Polymer Science ◽  
Key Factors ◽  
Multiple Imaging ◽  
Quantitative Image ◽  
Digital Imaging Systems ◽  
Multi Phase ◽  
Network Technologies

Polymer microscopy involves multiple imaging techniques. Speed, simplicity, and productivity are key factors in running an industrial polymer microscopy lab. In polymer science, the morphology of a multi-phase blend is often the link between process and properties. The extent to which the researcher can quantify the morphology determines the strength of the link. To aid the polymer microscopist in these tasks, digital imaging systems are becoming more prevalent. Advances in computers, digital imaging hardware and software, and network technologies have made it possible to implement digital imaging systems in industrial microscopy labs.

Recent Progress and Plans in Computer-Controlled High Resolution Electron Microscopy

1990 ◽  
Vol 48 (1) ◽  
pp. 154-155
Author(s):  
W.J. de Ruijter ◽  
Peter Rez ◽  
David J. Smith
Keyword(s):  
Electron Microscopy ◽  
Digital Processing ◽  
High Resolution Electron Microscopy ◽  
Objective Lens ◽  
Linear Filter ◽  
Contrast Transfer Function ◽  
Image Displacement ◽  
Spatially Resolved ◽  
Wide Range ◽  
On Line

Digital computers are becoming widely recognized as standard accessories for electron microscopy. Due to instrumental innovations the emphasis in digital processing is shifting from off-line manipulation of electron micrographs to on-line image acquisition, analysis and microscope control. An on-line computer leads to better utilization of the instrument and, moreover, the flexibility of software control creates the possibility of a wide range of novel experiments, for example, based on temporal and spatially resolved acquisition of images or microdiffraction patterns. The instrumental resolution in electron microscopy is often restricted by a combination of specimen movement, radiation damage and improper microscope adjustment (where the settings of focus, objective lens stigmatism and especially beam alignment are most critical). We are investigating the possibility of proper microscope alignment based on computer induced tilt of the electron beam. Image details corresponding to specimen spacings larger than ∼20Å are produced mainly through amplitude contrast; an analysis based on geometric optics indicates that beam tilt causes a simple image displacement. Higher resolution detail is characterized by wave propagation through the optical system of the microscope and we find that beam tilt results in a dispersive image displacement, i.e. the displacement varies with spacing. This approach is valid for weak phase objects (such as amorphous thin films), where transfer is simply described by a linear filter (phase contrast transfer function) and for crystalline materials, where imaging is described in terms of dynamical scattering and non-linear imaging theory. In both cases beam tilt introduces image artefacts.

Leakage characteristics of flanged pipe joints

1977 ◽  
Vol 12 (1) ◽  
pp. 29-36 ◽  
Author(s):  
H Fessler ◽  
D A Perry
Keyword(s):  
Surface Finish ◽  
Joint Surface ◽  
Clamping Force ◽  
Face Surface ◽  
Joint Efficiency ◽  
Wide Range ◽  
Pipe Joints ◽  
Surface Profiles ◽  
Leakage Characteristics ◽  
Gasket Material

Standard flanges for five widely differing pressure ratings, having a wide range of different joint surface profiles, were sealed by flat rubber or asbestos gaskets. Different initial bolt tensions were applied and the variation of clamping force with internal pressure was measured up to leakage of the joint. The joint efficiency, defined as: (end thrust due to leakage pressure on bore area of pipe)/(total initial bolting force), is not affected by variations in joint-face surface finish if machining grooves across the joint surface are avoided. Minimum values of joint efficiency are given. The effects of gasket material, width and thickness and number of bolts on joint efficiency are considered.

scholarly journals Design of a high-stability heterogeneous clock system for small satellites in LEO

GPS Solutions ◽  
2021 ◽  
Vol 25 (3) ◽  
Author(s):  
Damon Van Buren ◽  
Penina Axelrad ◽  
Scott Palo
Keyword(s):  
Low Power ◽  
High Stability ◽  
Time Frame ◽  
System Stability ◽  
Small Satellite ◽  
Crystal Oscillator ◽  
Small Satellites ◽  
Clock System ◽  
Wide Range

AbstractWe describe our investigation into the performance of low-power heterogeneous timing systems for small satellites, using real GPS observables from the GRACE Follow-On mission. Small satellites have become capable platforms for a wide range of commercial, scientific and defense missions, but they are still unable to meet the needs of missions that require precise timing, on the order of a few nanoseconds. Improved low-power onboard clocks would make small satellites a viable option for even more missions, enabling radio aperture interferometry, improved radio occultation measurements, high altitude GPS navigation, and GPS augmentation missions, among others. One approach for providing improved small satellite timekeeping is to combine a heterogeneous group of oscillators, each of which provides the best stability over a different time frame. A hardware architecture that uses a single-crystal oscillator, one or more Chip Scale Atomic Clocks (CSACs) and the reference time from a GPS receiver is presented. The clocks each contribute stability over a subset of timeframes, resulting in excellent overall system stability for timeframes ranging from less than a second to several days. A Kalman filter is used to estimate the long-term errors of the CSACs based on the CSAC-GPS time difference, and the improved CSAC time is used to discipline the crystal oscillator, which provides the high-stability reference clock for the small satellite. Simulations using GRACE-FO observations show time error standard deviations for the system range from 2.3 ns down to 1.3 ns for the clock system, depending on how many CSACs are used. The results provide insight into the timing performance which could be achieved on small LEO spacecraft by a low power timing system.

scholarly journals Potential predictors of severe cardiovascular involvement in Marfan syndrome: the emphasized role of genotype–phenotype correlations in improving risk stratification—a literature review

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Roland Stengl ◽  
Bence Ágg ◽  
Miklós Pólos ◽  
Gábor Mátyás ◽  
Gábor Szabó ◽  
...  
Keyword(s):  
Risk Stratification ◽  
Marfan Syndrome ◽  
Current Knowledge ◽  
Imaging Techniques ◽  
Connective Tissue Disorder ◽  
Main Body ◽  
Wide Range ◽  
Stratification System ◽  
Genetically Determined ◽  
Aortic Dissections

Abstract Background Marfan syndrome (MFS) is a genetically determined systemic connective tissue disorder, caused by a mutation in the FBN1 gene. In MFS mainly the cardiovascular, musculoskeletal and ocular systems are affected. The most dangerous manifestation of MFS is aortic dissection, which needs to be prevented by a prophylactic aortic root replacement. Main body The indication criteria for the prophylactic procedure is currently based on aortic diameter, however aortic dissections below the threshold defined in the guidelines have been reported, highlighting the need for a more accurate risk stratification system to predict the occurrence of aortic complications. The aim of this review is to present the current knowledge on the possible predictors of severe cardiovascular manifestations in MFS patients, demonstrating the wide range of molecular and radiological differences between people with MFS and healthy individuals, and more importantly between MFS patients with and without advanced aortic manifestations. These differences originating from the underlying common molecular pathological processes can be assessed by laboratory (e.g. genetic testing) and imaging techniques to serve as biomarkers of severe aortic involvement. In this review we paid special attention to the rapidly expanding field of genotype–phenotype correlations for aortic features as by collecting and presenting the ever growing number of correlations, future perspectives for risk stratification can be outlined. Conclusions Data on promising biomarkers of severe aortic complications of MFS have been accumulating steadily. However, more unifying studies are required to further evaluate the applicability of the discussed predictors with the aim of improving the risk stratification and therefore the life expectancy and quality of life of MFS patients.

scholarly journals Roadmap of Terahertz Imaging 2021

Sensors ◽  
2021 ◽  
Vol 21 (12) ◽  
pp. 4092
Author(s):  
Gintaras Valušis ◽  
Alvydas Lisauskas ◽  
Hui Yuan ◽  
Wojciech Knap ◽  
Hartmut G. Roskos
Keyword(s):  
Room Temperature ◽  
Continuous Wave ◽  
Computational Imaging ◽  
Imaging Systems ◽  
Thz Imaging ◽  
Operational Conditions ◽  
Frequency Combs ◽  
Wave Imaging ◽  
On Chip ◽  
Nano Imaging

In this roadmap article, we have focused on the most recent advances in terahertz (THz) imaging with particular attention paid to the optimization and miniaturization of the THz imaging systems. Such systems entail enhanced functionality, reduced power consumption, and increased convenience, thus being geared toward the implementation of THz imaging systems in real operational conditions. The article will touch upon the advanced solid-state-based THz imaging systems, including room temperature THz sensors and arrays, as well as their on-chip integration with diffractive THz optical components. We will cover the current-state of compact room temperature THz emission sources, both optolectronic and electrically driven; particular emphasis is attributed to the beam-forming role in THz imaging, THz holography and spatial filtering, THz nano-imaging, and computational imaging. A number of advanced THz techniques, such as light-field THz imaging, homodyne spectroscopy, and phase sensitive spectrometry, THz modulated continuous wave imaging, room temperature THz frequency combs, and passive THz imaging, as well as the use of artificial intelligence in THz data processing and optics development, will be reviewed. This roadmap presents a structured snapshot of current advances in THz imaging as of 2021 and provides an opinion on contemporary scientific and technological challenges in this field, as well as extrapolations of possible further evolution in THz imaging.

scholarly journals A Structurally Variable Hinged Tetrahedron Framework from DNA Origami

2011 ◽  
Vol 2011 ◽  
pp. 1-9 ◽  
Author(s):  
David M. Smith ◽  
Verena Schüller ◽  
Carsten Forthmann ◽  
Robert Schreiber ◽  
Philip Tinnefeld ◽  
...  
Keyword(s):  
Self Assembly ◽  
Gel Electrophoresis ◽  
Imaging Techniques ◽  
Building Blocks ◽  
Dna Origami ◽  
Microscopy Technique ◽  
Wire Frame ◽  
Wide Range ◽  
Potential Applications ◽  
Linker Molecules

Nanometer-sized polyhedral wire-frame objects hold a wide range of potential applications both as structural scaffolds as well as a basis for synthetic nanocontainers. The utilization of DNA as basic building blocks for such structures allows the exploitation of bottom-up self-assembly in order to achieve molecular programmability through the pairing of complementary bases. In this work, we report on a hollow but rigid tetrahedron framework of 75 nm strut length constructed with the DNA origami method. Flexible hinges at each of their four joints provide a means for structural variability of the object. Through the opening of gaps along the struts, four variants can be created as confirmed by both gel electrophoresis and direct imaging techniques. The intrinsic site addressability provided by this technique allows the unique targeted attachment of dye and/or linker molecules at any point on the structure's surface, which we prove through the superresolution fluorescence microscopy technique DNA PAINT.

scholarly journals Fast, Robust, and Low-Cost Microwave Imaging of Multiple Non-Metallic Pipes

Electronics ◽  
2021 ◽  
Vol 10 (15) ◽  
pp. 1762
Author(s):  
Yuki Gao ◽  
Maryam Ravan ◽  
Reza K. Amineh
Keyword(s):  
Antenna Arrays ◽  
Oil And Gas ◽  
Imaging System ◽  
Imaging Techniques ◽  
Low Cost ◽  
Microwave Imaging ◽  
Airport Security ◽  
Destructive Testing ◽  
Security Screening ◽  
Industrial Sectors

The use of non-metallic pipes and composite components that are low-cost, durable, light-weight, and resilient to corrosion is growing rapidly in various industrial sectors such as oil and gas industries in the form of non-metallic composite pipes. While these components are still prone to damages, traditional non-destructive testing (NDT) techniques such as eddy current technique and magnetic flux leakage technique cannot be utilized for inspection of these components. Microwave imaging can fill this gap as a favorable technique to perform inspection of non-metallic pipes. Holographic microwave imaging techniques are fast and robust and have been successfully employed in applications such as airport security screening and underground imaging. Here, we extend the use of holographic microwave imaging to inspection of multiple concentric pipes. To increase the speed of data acquisition, we utilize antenna arrays along the azimuthal direction in a cylindrical setup. A parametric study and demonstration of the performance of the proposed imaging system will be provided.

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