Low Contrast Sub-wavelengths Grating Lenses

MRS Advances ◽  
2017 ◽  
Vol 2 (14) ◽  
pp. 805-810
Author(s):  
Mao Ye ◽  
Ya Sha Yi
Keyword(s):  
Subwavelength Structures ◽  
Low Contrast ◽  
Optical Cavities ◽  
Subwavelength Grating ◽  
Write Heads ◽  
Light Concentration ◽  
The Difference ◽  
Concentration Properties ◽  
Controllable Fabrication ◽  
Micro Lens

ABSTRACTIn this work, we have demonstrated the light concentration from zero-contrast gratings (ZCG) subwavelength structures and compared the light concentration properties of previously proposed high-contrast gratings (HCG) to the ZCG micro concentrating lenses. To address the challenges of potential HCG fabrication, the difference between ZCG and HCG micro lenses is investigated numerically and found both of these subwavelength grating structures have similar light concentration characteristics. To gain deeper understanding of this phenomenon, we have explored the light concentration formation process and discussed the concentration mechanism in detail. Our work will be promising to provide a new ZCG micro lens potentially with easier and more controllable fabrication and could be utilized for various integrated nanophotonics applications, from optical cavities, read/write heads and concentrating photovoltaics.

Removal of inelastically scattered electrons substantially increases phase contrast on frozen-hydrated molecules

1987 ◽  
Vol 45 ◽  
pp. 652-653
Author(s):  
John P. Langmore ◽  
Brian D. Athey
Keyword(s):  
Electron Diffraction ◽  
Phase Contrast ◽  
Low Dose ◽  
Dark Field ◽  
Biological Structure ◽  
Bright Field ◽  
Low Contrast ◽  
Negative Stain ◽  
The Difference ◽  
Better Than

Although electron diffraction indicates better than 0.3nm preservation of biological structure in vitreous ice, the imaging of molecules in ice is limited by low contrast. Thus, low-dose images of frozen-hydrated molecules have significantly more noise than images of air-dried or negatively-stained molecules. We have addressed the question of the origins of this loss of contrast. One unavoidable effect is the reduction in scattering contrast between a molecule and the background. In effect, the difference in scattering power between a molecule and its background is 2-5 times less in a layer of ice than in vacuum or negative stain. A second, previously unrecognized, effect is the large, incoherent background of inelastic scattering from the ice. This background reduces both scattering and phase contrast by an additional factor of about 3, as shown in this paper. We have used energy filtration on the Zeiss EM902 in order to eliminate this second effect, and also increase scattering contrast in bright-field and dark-field.

scholarly journals A Microlens Super-Surface Film with Regular Graded Circular Hole-Like Subwavelength Structures for Highly Focusing Strength

Coatings ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 776
Author(s):  
Jinshuang Wu ◽  
Leimengting Zhang ◽  
Yahong Li ◽  
Yixin Zhang ◽  
Bowei Yang ◽  
...  
Keyword(s):  
Circular Hole ◽  
Focal Length ◽  
Surface Film ◽  
Subwavelength Structures ◽  
Lens Array ◽  
Direct Laser ◽  
Short Focal Length ◽  
Micro Lens Array ◽  
Micro Lens ◽  
Sub Wavelength

Using the fact that a sub-wavelength structure exhibits the same thermal expansion coefficient as a micro-lens array, we design a micro-lens super-surface film with regular circular hole-like subwavelength structures to realize the high performances of central highly focusing strength and short focal length. In addition, based on the Fresnel—Kirchhoff diffraction theory, the influences of subwavelength structural period and height on the focusing performance of a micro-lens are analyzed. Furthermore, the finite-difference time-domain method is utilized to optimize the structural parameters. Via direct laser writing and an inductively coupled plasma process, we fabricated a square micro-lens array consisting of a 1000 × 1000 micro-lens unit with a sub-wavelength structure, and the optical focusing performance was measured in the visible light band. Finally, the experimental results indicate that the focal length is decreased to 15 μm, the focal spot central energy is increased by 7.3%, and the light transmission, enhanced via inserting sub-wavelength structures, corresponds to 3%. This proves that the designed micro-lens array with a regular-graded circular hole-like subwavelength structure can achieve central high focusing and a short focal length. This has applications in several fields of wavefront detection and light field imaging systems.

scholarly journals The difference in dose and image quality between magnification methods used after the introduction of larger 60-inch operator screens

BJR|Open ◽  
2020 ◽  
Vol 2 (1) ◽  
pp. 20190044
Author(s):  
Hywel Mortimer-Roberts ◽  
Michael R Rees
Keyword(s):  
Image Quality ◽  
Radiation Dose ◽  
Communication Systems ◽  
Image Resolution ◽  
Low Contrast ◽  
Test Tool ◽  
Reduce Radiation Dose ◽  
The Difference ◽  
Picture Archiving And Communication ◽  
Area Product

Objective: To determine whether the use of display matrix magnification on larger operator screens without the use of conventional magnification can reduce radiation dose to the patient, and what effect it would have on image quality. Methods: The kerma-area product (KAP) resulting from standard projections in cardiac angiography were measured when an anthropomorphic phantom was imaged using conventional magnification method and display matrix magnification. The image quality was also evaluated by three observers using a TOR 18FG test tool for both magnification method. Results: The mean radiation KAP for the seven views with conventional magnification was 36.65 µGy m−2 whilst a reduction in KAP of 20.4% is possible using display matrix magnification (p < 0.05). The image resolution during acquisition was identical between both methods and only slightly reduced for the display matrix (1.6 LP mm−1) compared to conventional magnification (1.8 LP mm−1) when images were stored and retrieved on a Picture Archiving and Communication Systems (PACS) system. Both methods retained the same low-contrast detectability to PACS, with only a slight increase in detectability of 18 for display matrix magnification compared to 17 for conventional. Conclusion: Using display matrix magnification instead of conventional equipment magnification significantly reduces radiation does in all standard cardiac views without reducing image quality for the operator. This reduction in radiation dose is significant (p < 0.05) for the patients. The resolution did not change during acquisition, but contrast improved slightly (0.9% threshold contrast), but lost resolution of 0.2 LP mm−1 when archived to PACS. Advances in knowledge: This is a new method of reducing significant dose to the patient during cardiology examinations and may encourage further studies in other fluoroscopy lead examination to see if it could work for them.

scholarly journals Detection of Multi-pixel Low Contrast Object on a Real Sea Surface

2021 ◽  
Author(s):  
Victor Golikov ◽  
Oleg Samovarov ◽  
Daria Chernomorets ◽  
Marco Rodriguez-Blanco
Keyword(s):  
Spectral Characteristics ◽  
False Alarm Probability ◽  
Sea Surface ◽  
Statistical Characteristics ◽  
Statistical Parameters ◽  
Low Contrast ◽  
Video Images ◽  
Floating Object ◽  
The Difference ◽  
Floating Objects

The video images captured at long range usually have low contrast floating objects of interest on a sea surface. A comparative experimental study of the statistical characteristics of reflections from floating objects and from the agitated sea surface showed the difference in the correlation and spectral characteristics of these reflections. The functioning of the recently proposed modified matched subspace detector (MMSD) is based on the separation of the observed data spectrum on two subspaces: relatively low and relatively high frequencies. In the literature the MMSD performance has been evaluated in generally and moreover using only a sea model (additive Gaussian background clutter). This paper extends the performance evaluating methodology for low contrast object detection and moreover using only the real sea dataset. This methodology assumes an object of low contrast if the mean and variance of the object and the surrounding background are the same. The paper assumes that the energy spectrum of the object and the sea are different. The paper investigates a scenario in which an artificially created model of a floating object with specified statistical parameters is placed on the surface of a real sea image. The paper compares the efficiency of the classical Matched Subspace Detector (MSD) and MMSD for detecting low-contrast objects on the sea surface. The article analyzes the dependence of the detection probability at a fixed false alarm probability on the difference between the statistical means and variances of a floating object and the surrounding sea.

scholarly journals An Ensembled Spatial Enhancement Method for Image Enhancement in Healthcare

2022 ◽  
Vol 2022 ◽  
pp. 1-12
Author(s):  
Muhammad Hameed Siddiqi ◽  
Amjad Alsirhani
Keyword(s):  
Image Enhancement ◽  
Intensity Variation ◽  
Low Contrast ◽  
Naked Eye ◽  
Enhancement Method ◽  
Laplacian Filter ◽  
Spatial Method ◽  
The Difference ◽  
Averaging Filter ◽  
Spatial Enhancement

Most medical images are low in contrast because adequate details that may prove vital decisions are not visible to the naked eye. Also, due to the low-contrast nature of the image, it is not easily segmented because there is no significant change between the pixel values, which makes the gradient very small Hence, the contour cannot converge on the edges of the object. In this work, we have proposed an ensembled spatial method for image enhancement. In this ensembled approach, we first employed the Laplacian filter, which highlights the areas of fast intensity variation. This filter can determine the sufficient details of an image. The Laplacian filter will also improve those features having shrill disjointedness. Then, the gradient of the image has been determined, which utilizes the surrounding pixels for the weighted convolution operation for noise diminishing. However, in the gradient filter, there is one negative integer in the weighting. The intensity value of the middle pixel might be deducted from the surrounding pixels, to enlarge the difference between the head-to-head pixels for calculating the gradients. This is one of the reasons due to which the gradient filter is not entirely optimistic, which may be calculated in eight directions. Therefore, the averaging filter has been utilized, which is an effective filter for image enhancement. This approach does not rely on the values that are completely diverse from distinctive values in the surrounding due to which it recollects the details of the image. The proposed approach significantly showed the best performance on various images collected in dynamic environments.

scholarly journals Resonant diffraction gratings with polarization-dependent efficiencies

2020 ◽  
Vol 238 ◽  
pp. 05002
Author(s):  
Julian Wüster ◽  
Patrick Feßer ◽  
Arne Behrens ◽  
Stefan Sinzinger
Keyword(s):  
Manufacturing Process ◽  
Degree Of Freedom ◽  
Experimental Results ◽  
Optical Systems ◽  
Subwavelength Structures ◽  
Diffractive Optical Elements ◽  
Optical Elements ◽  
Additional Degree ◽  
Subwavelength Grating ◽  
Wide Range

Subwavelength-structures with different fill factors in the lateral dimensions result in unique phase shifts for the different polarization states of transmitted light. By using this additional degree of freedom for diffractive optical elements, we yield additional functionalities for compact optical systems with DOEs. As a fully operable example we present a binary subwavelength-grating which acts as a polarizing beamsplitter for TE- and TM-polarization over a wide range of incidence angles. We show our design approach, the manufacturing process with Soft-UV-Nanoimprint-Technology, as well as experimental results. We will also lay out possibilities for the design and application of multilevel polarization-functionalized gratings.

scholarly journals Evaluation of Self-Produced Phantom Usafulness for image Quality Control of Radiation Generator for Diagnosis

2021 ◽  
Vol 12 (6) ◽  
pp. 828-834
Author(s):  
Ye-Won Park Et.al
Keyword(s):  
Quality Control ◽  
Medical Care ◽  
Qualitative Evaluation ◽  
High Contrast ◽  
Contrast Resolution ◽  
Low Contrast ◽  
X Ray ◽  
Image Quality Control ◽  
Exposure Dosage ◽  
The Difference

Background/Objectives: Quality control can improve the quality of medical care along with the stability of diagnostic X-ray generator. Regular quality control provides reliable quality control of the machine and maintains consistency of general imaging using radiation for efficient diagnosis. Methods/Statistical analysis: A phantom for quality control of diagnostic X-ray generator was produced using a 3D printer. Quantitative and qualitative evaluation of the phantom utility was conducted by modifying images acquired using S and D companies’ tools with Source to Image-Receptor Distance (SID) levels ranging between 130 cm and 180 cm. The evaluation indices were determined based on the analysis of field compliance, uniformity, low and high-contrast resolution, and linearity. Findings: The evaluation was conducted by acquiring and changing the radiographic image to SIDs between 130 cm and 180 cm using the indigenous phantom. The field compliance of S and D companies in terms of quantitative evaluation indices was both appropriate within ± 1% according to the SID change. To ensure a uniform SID 130 cm, the internal and external means of S company were 893 and 943, respectively, while those of the D company were 228.1 and 261.4, respectively. At an SID of 180 cm, the internal and external means of the S company were 928.1 and 958.4, respectively, while those of the D company were 257.2 and 299, respectively. A characteristic of the DR system was identified to ensure linearity, altered exposure dosage according to the step wedge height, and the difference in SI values according to the characteristics of the equipment and linearity. The qualitative evaluation indices were determined by identifying the size of the hole under high-contrast resolution up to 0.8㎜ and the bar size up to 1.6 lp/㎜. The low contrast resolution was evaluated with a C-D pattern, and at SID 130 cm, the S company scored 124.6 points and the D company 116 points, and at 180 cm, the S company scored 111.4 and the D company 104.6 points. Improvements/Applications: The utility of the homegrown phantom in quality control was confirmed for each index. The medical institutions are required to introduce quality control regulations for general image examination using radiation. It is helpful to efficiently manage old equipment and improve public health and medical care by linking with the health insurance fee.

scholarly journals Light Trapping with Silicon Light Funnel Arrays

2018 ◽  
Author(s):  
Ashish Prajapati ◽  
Yuval Nissay ◽  
Tamir Gabay ◽  
Gil Shalev
Keyword(s):  
Light Trapping ◽  
Near Field ◽  
Three Dimensional ◽  
Solar Spectrum ◽  
Absorption Enhancement ◽  
Surface Element ◽  
Subwavelength Structures ◽  
Broadband Absorption ◽  
Substrate Complex ◽  
Light Concentration

Silicon light funnels are three-dimensional subwavelength structures in the shape of inverted cones with respect to the incoming illumination. Light funnel arrays can serve as an efficient absorbing layers on account of their light trapping capabilities associated with the presence of high density complex Mie modes. Specifically, light funnel arrays exhibit broadband absorption enhancement of the of the solar spectrum. In the current study, we numerically explore the optical coupling between surface light funnel arrays and underlying substrates. We show that the absorption in LF array-substrate complex is higher than the absorption in LF arrays of the same height (~10% increase). This, we suggest, imply that a LF array serves as an efficient surface element that imparts additional momentum components to the impinging illumination, and hence optically excites the substrate by near-field light concentration, excitation of traveling guided modes in the substrate and mode hybridization.

Change detection in sparse repeat CT scans with non-rigid deformations

2021 ◽  
pp. 1-21
Author(s):  
Naomi Shamul ◽  
Leo Joskowicz
Keyword(s):  
Change Detection ◽  
Experimental Studies ◽  
Region Of Interest ◽  
Recall Rate ◽  
Image Space ◽  
Ct Scans ◽  
Two Phase ◽  
Low Contrast ◽  
The Difference ◽  
Radon Space

BACKGROUND: Detecting and interpreting changes in the images of follow-up CT scans by the clinicians is often time-consuming and error-prone due to changes in patient position and non-rigid anatomy deformations. Thus, reconstructed repeat scan images are required, precluding reduced dose sparse-view repeat scanning. OBJECTIVE: To develop a method to automatically detect changes in a region of interest of sparse-view repeat CT scans in the presence of non-rigid deformations of the patient’s anatomy without reconstructing the original images. METHODS: The proposed method uses the sparse sinogram data of two CT scans to distinguish between genuine changes in the repeat scan and differences due to non-rigid anatomic deformations. First, size and contrast level of the changed regions are estimated from the difference between the scans’ sinogram data. The estimated types of changes in the repeat scan help optimize the method’s parameter values. Two scans are then aligned using Radon space non-rigid registration. Rays which crossed changes in the ROI are detected and back-projected onto image space in a two-phase procedure. These rays form a likelihood map from which the binary changed region map is computed. RESULTS: Experimental studies on four pairs of clinical lung and liver CT scans with simulated changed regions yield a mean changed region recall rate >  86%and a mean precision rate >  83%when detecting large changes with low contrast, and high contrast changes, even when small. The new method outperforms image space methods using prior image constrained compressed sensing (PICCS) reconstruction, particularly for small, low contrast changes (recall = 15.8%, precision = 94.7%). CONCLUSION: Our method for automatic change detection in sparse-view repeat CT scans with non-rigid deformations may assist radiologists by highlighting the changed regions and may obviate the need for a high-quality repeat scan image when no changes are detected.

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