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Copyright of Journal of Community Service & Empowerment is the property of Journal of Community Service & Empowerment and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This text is an analysis of a series of pinhole photographs, by Anne Peschken and Marek Pisarsky (Urban Art), entitled East Side Story I (Myślibórz). Photo research on migration and arrival stories, 2019 on-going. The main thesis is that these photographs are a model example of images which, while addressing the theme of migration in the representational layer, also activate the processual and migratory nature of visual forms themselves. In order to substantiate this thesis, the East Side Story project is examined in the following contexts: critical border (art) studies; H. Belting's anthropology of the image; memory studies; re-enactment; the blurriness of images made with a pinhole camera; A. Berleant's re-thinking aesthetics and the notion of aesthetic embodiment. Reflecting on the tension between history, memory, identity and politics and activating the critical potential of borderscaping, Peschken and Pisarsky transform the landscape of the Polish-German borderland into an anachronistic narrative agent. The photographs from the East Side Story series are thus transgenerational corpographies of memory, showing that migration is a key and inalienable element of Polish history. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Environmental Education is the property of Canadian Journal of Environmental Education and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The neutron flux of the Compact Pulsed Hadron Source (CPHS) is about 2–3 orders of magnitude lower than that of large neutron sources, which means that the beam intensity should be improved to achieve good statistics. Multi‐pinhole collimation can be used to obtain a lower Q with an acceptable beam intensity in a very small angle neutron scattering (VSANS) instrument and a higher beam intensity for a larger sample size in a small‐angle neutron scattering (SANS) instrument. A new nine‐pinhole structure is used in a SANS instrument at CPHS to achieve an acceptable range and resolution of Q and a higher beam intensity compared to single‐pinhole collimation. The crosstalk issue associated with multi‐pinhole collimation is addressed using an optimized algorithm to achieve a higher safety margin and a larger pinhole size with a higher beam intensity at the sample. Different collimator aperture structures are compared on the basis of their noise production. Experiments are performed to verify the theory of calculating reflection noise from the inner surface of the collimator's aperture and parasitic noise from the beveled collimator structure. From a simulated SANS experiment using cold neutrons in the SANS instrument, it is clarified that multi‐pinhole collimators with an opening angle on the downstream side have better performance than those with an opening angle on the upstream side and straight‐cut collimators. Compared with a single‐pinhole collimation system, a nine‐pinhole collimation system increases the intensity at the sample by approximately sevenfold when the sample size is increased by 20‐fold for CPHS‐SANS, and the signal‐to‐noise ratio is improved by exploiting a specific collimator aperture structure. Our goal is to install a multi‐pinhole collimator based SANS instrument at CPHS in the future, and it is hoped that these results will serve to promote the utilization of multi‐pinhole collimation systems at other facilities. A small‐angle neutron scattering instrument based on a multi‐pinhole collimator system is used to increase neutron current at the sample compared with a single‐pinhole collimator system. Disadvantages such as crosstalk and reflection noise are overcome by the described optimization. [ABSTRACT FROM AUTHOR]

This work, comprised of pinhole photographs paired with written text, represents a series of ontological experiments with participants on a rafting expedition, on the Franklin River, lutruwita (Tasmania). Through photographic experiences in this landscape these experiments interrogated ideas about ways to represent places and ideas. We began with informal riverside workshops on pinhole photography followed by making pictures and developing them during the river journey. The home-made pinhole camera used by participants in the making of these photographs had neither a lens nor a viewfinder, thus the making of photographs demanded a certain sensual presence. The written expression of this work is partly comprised of reflections on the experiences of participants, some of whom engaged directly in this making. Participants were asked to consider what drew their attention to particular photographic images, and what feelings, emotions, experiences, memories or thoughts these chosen images evoked. These reflections are conjoined with musings on wild, self-willed and educational opportunities therein. The way in which this work is deliberately presented is reminiscent of a lyric philosophy (Zwicky 1992, 2003) that seeks to engage the reader, in this case through visual and linguistic representations, with patterned resonance. [ABSTRACT FROM AUTHOR]

Abstract Defects, such as a black pads and pinholes, are generated on the Ni/Au interface after the electroless nickel immersion gold (ENIG) process. The contamination of plating solutions, including dissolution of the solder resist (SR), side reaction products, and impurities (Cu, Ni, drag-in), can be a cause of the black pad phenomenon. In this study, electroless Ni plating was investigated to determine the correlation between SR dissolution and black pad generation. Three different SR components, monomer, hardener, and photoinitiator were used to examine the effects of the properties of the coating layer. The surface morphology, plating rate, and phosphorus (P) content of the electroless Ni layer with SR additives were analyzed. The black pad mechanism by SR dissolution was examined by electrochemical analysis including the open circuit voltage (OCV) and cyclic voltammetry (CV) in a three-electrode cell. When a few ppm of SR was added, the OCV increased compared to the pure solution. CV revealed a change in hysteresis loop in the oxidation region upon the addition of SR. The contamination in the solution promotes the oxidation reaction rather than the reduction reaction. Therefore, the content of P in the contaminated solution was higher than that of the pure solution, and defects, such as black pad and pinholes, were observed. Graphical abstract Unlabelled Image Highlights • The effects of the SR dissolution on the ENIG process were investigated. • The monomer, hardener and photo initiator were used as SR components. • The correlation between SR dissolution and surface defects was determined. • The increase in the content of P by SR dissolution is considered to increase defects. [ABSTRACT FROM AUTHOR]

A structured light system with spinning fringe projection has been an excitement for three-dimensional (3-D) shape measurement since high-speed phase-shifting fringe patterns can be produced by mechanical spinning slide projectors. However, two cameras are typically required for 3-D reconstruction since the calibration method of spinning fringe projection is not well documented yet. This article introduces a computational framework for the calibration of spinning fringe projection profilometry using polar coordinate representation. In this preliminary study, we emulated the ideal spinning fringe projection with a video projector that can precisely control phase shifts with minimized harmonic errors. Results show that under the ideal scenario, our calibration method can reach an accuracy of 0.10 mm with a standard deviation of 0.73 mm by measuring a spherical object with 150 mm diameter. [ABSTRACT FROM AUTHOR]

There is always a tradeoff between the resolution and the signal-to-noise ratio (SNR) in confocal microscopy. In particular, the pinhole size is very important for maintaining a balance between them. In this paper, we propose a method for improving the lateral resolution and image SNR in confocal microscopy without making any changes to the hardware. By using the fluorescence emission difference (FED) approach, we divide the images acquired by different pinhole sizes into one image acquired by the central pinhole and several images acquired by ring-shaped pinholes. Then, they are added together with the deconvolution method. Simulation and experimental results for fluorescent particles and cells show that our method can achieve a far better resolution than a large pinhole and a higher SNR than a small pinhole. Moreover, our method can improve the performance of classic confocal laser scanning microscopy (CLSM) to a certain extent, especially CLSM with a continuously variable pinhole. [ABSTRACT FROM AUTHOR]

We present an improvement design of a two-dimensional (2D) angular-resolved proton spectrometer for wide-angle measurement of proton beams from high-intensity laser-solid interactions. By using a 2D selective entrance pinhole array with different periods in orthogonal axes, the angular resolution along one dimension is improved by a factor of 6.7. This improvement provides the accessibility to detect the spatial fine structures of the proton energy spectrum. [ABSTRACT FROM AUTHOR]

Scars from self-inflicted wounds, referred to as "hesitation marks," are usually linear, flat, poorly oriented, white in color, and often located on the forearm. Many patients do not undergo treatment for these due to limited available modalities. The aim of this study was to evaluate the efficacy and safety of the pinhole method using a 10,600 nm carbon dioxide (CO2) laser for treating hesitation marks on the forearm. We conducted a retrospective chart review of patients with hesitation marks treated by the pinhole method from March 2010 to April 2014. Eleven patients with hesitation marks (mean age 37.8 years; range, 23-67 years) were treated with the pinhole method over the 4-year study period. Subjects were treated via the pinhole method in one to six treatment sessions at 4- to 8-week intervals. Two blinded observers evaluated photographs taken at baseline and 3 months after the final treatment and assessed improvement using a quartile grading scale. Compared with baseline, there was mild to moderate improvement in all patients (mean score 3.0). The patient satisfaction survey revealed a mean improvement score of 2.82. The pinhole method using a CO2 laser may be an effective treatment option in patients with hesitation marks on the forearm. [ABSTRACT FROM AUTHOR]

In the heart of the 21st century, we have been surprised witnesses of a coarse pinhole projection among different professionals. This fact shows that in spite of the thorough study made by specialists, the so called Camera Obscura is something that has been talked about but only a few have experimented. Without the help of a lens, the image projected by a camera is dim and not clear. Only in ideal luminous circumstances, a good hole quality and total darkness would it be possible to efficiently trace the outline of the projected image. Once this fact has been confirmed since very old times, it was only a matter of time that curiosity or a stroke of luck led to place a lens in the little opening. While all these was going on, innumerable authors devoted to study the whole process. But, nevertheless, the graphic or written evidence that have reached us, is certainly poor. [ABSTRACT FROM AUTHOR]

With their large field of view, anamorphosis, and areas of enhanced magnification, panomorph lenses are an interesting choice for navigation systems for mobile robotics in which knowledge of the surroundings is mandatory. However, panomorph lenses special characteristics can be challenging during the calibration process. This study focuses on the calibration of two panomorph stereoscopic systems with a model and technique developed for narrow-angle lenses, the “Camera Calibration Toolbox for MATLAB.” In order to assess the performance of the systems, the mean reprojection error (MRE) related to the calibration and the reconstruction error of control points of an object of interest at various locations in the field of view are used. The calibrations were successful and exhibit MREs of less than one pixel in all cases. However, some poorly reconstructed control points illustrate that an acceptable MRE guarantees neither the quality of 3-D reconstruction nor its uniformity in the field of view. In addition, the nonuniformity in the 3-D reconstruction quality indicates that panomorph lenses require a more accurate estimation of the principal point (center of distortion) coordinates to improve the calibration and therefore the 3-D reconstruction. [ABSTRACT FROM AUTHOR]

Computer generated images are most easily generated as pinhole images whereas images obtained with optical lenses exhibit a Depth-of-Field (DOF) effect. This is due to the fact that optical lenses gather light across finite apertures whereas the simulation of a pinhole lens means that the light is gathered through an infinitesimal small aperture, thus producing sharp images at any depth. Simulating the physical process of gathering light across a finite aperture can be done for example with distributed ray tracing, but it is computationally much more expensive than the simulation through an infinitesimal aperture. The usual way of simulating lens effects is therefore to produce a pinhole image and then post processes the image to approximate the DOF. Post processing algorithms are fast but suffer from incorrect visibilities. In this paper, we propose a novel algorithm that tackles the visibility issue with a sparse set of views rendered through the optical center of the lens and several peripheral viewpoints distributed on the lens. All peripheral images are warped towards the central view to create a Layered-Depth-Image (LDI), so that all observed 3D points located on the same central view-ray are stacked on the same pixel of the LDI. Then, each pixel in the LDI is conceptually scattered into a Point-Spread-Function (PSF) and blended in depth order. While the scatter method is very inefficient on a GPU, we propose a selective-gather method for DOF synthesis, which scans the neighborhood of a pixel and blends the colors from the PSFs covering the pixel. Experiments show that the proposed algorithm can synthesize high-quality DOF effects close to the results of distributed ray tracing but at a much higher speed. [ABSTRACT FROM AUTHOR]

This paper shares our experiences using pinhole photography with adolescents as both a pedagogical tool to support and deepen adolescent experiences in wild nature, and as a visual methodological tool to elucidate their experiences. Reflecting on a journey that explored the nature-based experiences of two adolescents on a family canoe trip in Northern Canada, examples of findings are presented that contextualize study participants within the literature to illustrate pinhole photography's viability for the study of adolescent experiences in wild nature. Pinhole photography proved to be a medium to intensify the adolescents' embodied presence and sense of place, and helped them to anchor their experiences in wild nature for ensuing reflection and focused discussion. Pinhole photography's inherent strengths and challenges are discussed and recommendations presented for its future use as a methodological and "slow" pedagogical tool in the study of outdoor education and/or environmental education. [ABSTRACT FROM AUTHOR]

The article discusses the adoption of various skiagraphic techniques in the diagnosis of back pain. Topics discussed include the plano-convex lens and pinhole system features of the apparatus, the use of the tungsten lamp in conducting the experiments, and the calculation of the pinhole after the establishment of the pinhole-to-image distance.

Purpose: Recently, a multipinhole collimator with inserts that have both rectangular apertures and rectangular fields of view (FOVs) has been proposed for SPECT imaging since it can tile the projection onto the detector efficiently and the FOVs in transverse and axial directions become separable. The purpose of this study is to investigate the image properties of rectangular-aperture pinholes with submillimeter apertures sizes. Methods: In this work, the authors have conducted sensitivity and FOV experiments for 18 replicates of a prototype insert fabricated in platinum/iridium (Pt/Ir) alloy with submillimeter square-apertures. A sinqü fit to the experimental sensitivity has been performed for these inserts. For the FOV measurement, the authors have proposed a new formula to calculate the projection intensity of a flood image on the detector, taking into account the penumbra effect. By fitting this formula to the measured projection data, the authors obtained the acceptance angles. Results: The mean (standard deviation) of fitted sensitivity exponents q and effective edge lengths we were, respectively, 10.8 (1.8) and 0.38 mm (0.02 mm), which were close to the values, 7.84 and 0.396 mm, obtained from Monte Carlo calculations using the parameters of the designed inserts. For the FOV measurement, the mean (standard deviation) of the transverse and axial acceptances were 35.0 (1.2°) and 30.5° (1.6°), which are in good agreement with the designed values (34.3° and 29.9°). Conclusions: These results showed that the physical properties of the fabricated inserts with submillimeter aperture size matched our design well. [ABSTRACT FROM AUTHOR]

Purpose: The objective of this work was to investigate focal spot blooming effects on the spatial resolution of CT images and to evaluate an x-ray tube that uses dynamic focal spot control for minimizing focal spot blooming. Methods: The influence of increasing tube current at a fixed tube potential of 80 kV on high-contrast spatial resolution of seven different CT scanner models (scanners A-G), including one scanner that uses dynamic focal spot control to reduce focal spot blooming (scanner A), was evaluated. Spatial resolution was assessed using a wire phantom for the modulation transfer function (MTF) calculation and a copper disc phantom for measuring the slice sensitivity profile (SSP). The impact of varying the tube potential was investigated on two scanner models (scanners A and B) by measuring the MTF and SSP and also by using the resolution bar pattern module of the ACR CT phantom. The phantoms were scanned at 70-150 kV on scanner A and 80-140 kV on scanner B, with tube currents from 100 mA up to the maximum tube current available on each scanner. The images were reconstructed using a slice thickness of 0.6 mm with both smooth and sharp kernels. Additionally, focal spot size at varying tube potentials and currents was directly measured using pinhole and slit camera techniques. Results: Evaluation of the MTF and SSP data from the 7 CT scanner models evaluated demonstrated decreased focal spot blooming for newer scanners, as evidenced by decreasing deviations in MTF and SSP as tube current varied. For scanners A and B, where focal spot blooming effects as a function of tube potential were assessed, the spatial resolution variation in the axial plane was much smaller on scanner A compared to scanner B as tube potential and current changed. On scanner A, the 50% MTF never decreased by more than 2% from the 50% MTF measured at 100 mA. On scanner B, the 50% MTF decreased by as much as 19% from the 50% MTF measured at 100 mA. Assessments of the SSP, the bar patterns in the ACR phantom and the pinhole and slit camera measurements were consistent with the MTF calculations. Conclusions: Focal spot blooming has a noticeable effect on spatial resolution in CT imaging. The focal spot shaping technology of scanner A greatly reduced blooming effects. [ABSTRACT FROM AUTHOR]

We examine quantitatively the instrumental factors that affect the theoretical performance and practical application of conventional pinhole collimation and focusing optics for small-angle neutron scattering (SANS) measurements. We calculate the relative performance of pinhole collimation vis-à-vis focusing by grazing incidence elliptical mirrors and compare the results with a recent ray-tracing simulation to show that the performance gains due to focusing found in the simulation arise largely from assuming a much larger sample size. We also compare measurements of the parasitic scattering from pinhole collimation with that from focusing cylindrical quartz mirrors, and a focusing refractive optic, to stress the importance of signal-to-noise as the true measure of performance for SANS instruments. [ABSTRACT FROM AUTHOR]

The accurate determination of the local impulse response and the covariance in voxels from penalized maximum likelihood reconstructed images requires performing reconstructions from many noise realizations of the projection data. As this is usually a very time-consuming process, efficient analytical approximations based on the Fisher information matrix (FIM) have been extensively used in PET and SPECT to estimate these quantities. For 3D imaging, however, additional approximations need to be made to the FIM in order to speed up the calculations. The most common approach is to use the local shift-invariant (LSI) approximation of the FIM, but this assumes specific conditions which are not always necessarily valid. In this paper we take a single-pinhole SPECT system and compare the accuracy of the LSI approximation against two other methods that have been more recently put forward: the non-uniform object-space pixelation (NUOP) and the subsampled FIM. These methods do not assume such restrictive conditions while still increasing the speed of the calculations considerably. Our results indicate that in pinhole SPECT the NUOP and subsampled FIM approaches could be more reliable than the LSI approximation, especially when a high accuracy is required. [ABSTRACT FROM AUTHOR]

Pinhole SPECT for small animal has become a routine procedure in many applications of molecular biology and pharmaceutical development. There is an increasing demand in the whole body imaging of lab animals. A simple and direct solution is to scan the object along a helical trajectory, similar to a helical CT scan. The corresponding acquisition time can be greatly reduced, while the over-lapping and gap between consecutive bed positions can be avoided. However, helical pinhole SPECT inevitably leads to the tremendous increase in computational complexity when the iterative reconstruction algorithms are applied. We suggest a novel voxel-driven (VD) system model which can be integrated with geometric symmetries from helical trajectory for fast iterative image reconstruction. Such a model construction can also achieve faster calculation and lower storage requirement of the system matrix. Due to the independence among various symmetries, it permits parallel coding to further boost computation efficiency of forward/backward projection. From phantom study, the results also indicate that the proposed VD model can adequately model the helical pinhole SPECT scanner with manageable storage size of system matrix and clinically acceptable computation loading of reconstruction. [ABSTRACT FROM AUTHOR]

Purpose: Pinhole collimation is the most common method of high-resolution preclinical single photon emission computed tomography imaging. The collimators are usually constructed from dense materials with high atomic numbers, such as gold and platinum, which are expensive and not always flexible in the fabrication step. In this work, the authors have investigated the properties of a fusible alloy called Rose's metal and its potential in pinhole preclinical imaging. When compared to current standard pinhole materials such as gold and platinum, Rose's metal has a lower density and a relatively low effective atomic number. However, it is inexpensive, has a low melting point, and does not contract when solidifying. Once cast, the piece can be machined with high precision. The aim of this study was to evaluate the imaging properties for Rose's metal and compare them with those of standard materials. Methods: After validating their Monte Carlo code by comparing its results with published data and the results from analytical calculations, they investigated different pinhole geometries by varying the collimator material, acceptance angle, aperture diameter, and photon incident angle. The penetration-to-scatter and penetration-to-total component ratios, sensitivity, and the spatial resolution were determined for gold, tungsten, and Rose's metal for two radionuclides, 99Tcm and 125I. Results: The Rose's metal pinhole-imaging simulations show higher penetration/total and scatter/total ratios. For example, the penetration/total is 50% for gold and 75% for Rose's metal when simulating 99Tcm with a 0.3 mm aperture diameter and a 60° acceptance angle. However, the degradation in spatial resolution remained below 10% relative to the spatial resolution for gold for acceptance angles below 40° and aperture diameters larger than 0.5 mm. Conclusions: Extra penetration and scatter associated with Rose's metal contribute to degradation in the spatial resolution, but this degradation is not always substantial. The most important factor besides the collimator material was the acceptance angle. This should be kept to a minimum to prevent unnecessary scatter and penetration. For 125I, the difference in spatial resolution between gold and Rose's metal is very small, 2.2% in the worst-case scenario. Based on these results, the authors conclude that Rose's metal is an alternative to standard materials not only for low-energy photon imaging but also for medium-energy applications that require low-cost, flexible pinhole configurations and designs, and that can tolerate a degraded spatial resolution. [ABSTRACT FROM AUTHOR]

We present the pinhole iris-fixated diaphragm intraocular lens (IOL), which is a 1-piece black polycarbonate IOL with rigid iris-fixated haptics, an 8.5 mm overall length, a 6.0 mm diameter optic, and a central opening, the pinhole. The IOL was implanted in a 36-year-old man who had a history of debilitating dysphotopsia (star burst, halos, glare, and ghosting) and severe light sensitivity in his right eye following several interventions for keratoconus. The diameter of the central opening of the pinhole IOL, 2.0 mm, was based on the patient's corneal aberration profile. Postoperatively, the dysphotopic symptoms and photophobia markedly improved. We recommend the use of the pinhole iris-fixated IOL in patients with severe photophobia or dysphotopsia refractory to other treatment modalities. Financial Disclosure No author has a financial or proprietary interest in any material or method mentioned. [ABSTRACT FROM AUTHOR]

This paper is comprised of written text and photographs of wild experiences that relive a series of ontological experiments. The text represents reflections on these experiences. The photographs, artistic expressions of the same experiences, have been made with a homemade pinhole camera-without a lens and viewfinder-thus demanding special sensual presence during creation. The form of this experimental work is reminiscent of a lyric philosophy that seeks to engage the participant-reader of text and viewer of images-with these experiments. Component pairings are arranged for viewing with text on the left and photographs on the right. Together these parings invite participants to explore patterned resonances in the world. Implicit throughout are considerations of relationships between wildness, wild learning, and a form of wild pedagogy. [ABSTRACT FROM AUTHOR]

Barrier layers were coated by plasma enhanced atomic layer deposition. They had inevitable defects for several reasons and these defects deteriorated the diffusion barrier properties. The size of the pinhole defect decreased with the increase of the layer thickness resulting in enhanced barrier properties, until the thickness reached 20 nm for a single-component aluminum oxide (Al 2 O 3 ) or zirconium oxide (ZrO 2 ) layer. No more enhancement of barrier properties was observed with a further increase of layer thickness, since the defects tended to grow in single-component layers. Alternation of Al 2 O 3 and ZrO 2 layers prevented defect growth by covering the defects with another component, and enhanced the barrier properties when compared with single-component layers. Increase of the number of Al 2 O 3 /ZrO 2 stacks with the same total layer thickness remarkably reduced the water vapor transmission rates value to below 5 × 10 − 5 g/m 2 day at 38 °C and 100% relative humidity. The Al 2 O 3 /ZrO 2 multilayer formed on a polyethylene naphthalate substrate at optimized conditions showed light transmittance greater than 86% at a wavelength of 550 nm, for application as flexible display substrate. [ABSTRACT FROM AUTHOR]

Multi-pinhole collimators are often used in pre-clinical SPECT systems because they have a better resolution-sensitivity tradeoff than parallel hole collimators when imaging small objects. Most multi-pinhole collimators are designed to allow no or only a limited amount of overlap between the different pinhole projections because the ambiguity introduced by multiplexing pinholes can result in artifacts. The origin of these artifacts is still not fully understood, but previous research has already shown that data incompleteness could be part of the explanation. Therefore, we developed a method to investigate data completeness in multiplexing multi-pinhole systems and showed that a certain activity distribution can be successfully reconstructed when the nonmultiplexed data is complete or when the overlap can be sufficiently de-multiplexed. We validated this method using computer simulated phantom data of different multiplexing systems. We also studied contrast-to-noise and nonprewhitening matched filter signal-to-noise ratio (NPW-SNR) to compare the image quality in a single pinhole system with multiplexing systems. We found that our method can indeed be used to evaluate data completeness in multiplexing systems and found no artifacts in the systems that had complete data. Sensitivity increased significantly with multiplexing but we found only small, nonsignificant differences in contrast-to-noise ratio. However, the NPW-SNR did slightly improve in the multiplexing setups. We conclude that more multiplexing does not necessarily result in more artifacts and that even a high amount of multiplexing can still result in artifact-free images if the nonmultiplexed data is complete or when the overlap can be sufficiently de-multiplexed. [ABSTRACT FROM PUBLISHER]

We present a study on the improvement of the spatial quality of a laser beam, called modal filtering, suitable to high-energy lasers. The method is theoretically compared with the classical pinhole filtering technique in the case of an astigmatic Gaussian beam, illustrating, in this particular case, its efficiency for filtering low spatial frequencies. Experimental study of the modal filtering of a temporally chirped beam from a Ti:Sapphire chirped-pulse-amplification system is presented. Beam profile, wavefront and pulse duration after compression were measured, showing a dramatic improvement of beam quality and no modifications of the temporal distribution. High-order harmonic generation in a rare gas, a highly nonlinear process which is phase-matching dependent, was used to test the effect of the filter and showed a clear enhancement of the generation. [ABSTRACT FROM AUTHOR]

Hard x-rays from laser-produced hot electrons (>10 keV) in backlit pinhole imagers can give rise to a background signal that decreases signal dynamic range in radiographs. Consequently, significant uncertainties are introduced to the measured optical depth of imaged plasmas. Past experiments have demonstrated that hard x-rays are produced when hot electrons interact with the high-Z pinhole substrate used to collimate the softer He-a x-ray source. Results are presented from recent experiments performed on the OMEGA-60 laser to further study the production of hard x-rays in the pinhole substrate and how these x-rays contribute to the background signal in radiographs. Radiographic image plates measured hard x-rays from pinhole imagers with Mo, Sn, and Ta pinhole substrates. The variation in background signal between pinhole substrates provides evidence that much of this background comes from x-rays produced in the pinhole substrate itself. A Monte Carlo electron transport code was used to model x-ray production from hot electrons interacting in the pinhole substrate, as well as to model measurements of x-rays from the irradiated side of the targets, recorded by a bremsstrahlung x-ray spectrometer. Inconsistencies in inferred hot electron distributions between the different pinhole substrate materials demonstrate that additional sources of hot electrons beyond those modeled may produce hard x-rays in the pinhole substrate. [ABSTRACT FROM AUTHOR]

Background Measurements of refractive errors through subjective or automated refraction are not always possible in rapid assessment studies and community vision screening programs; however, measurements of vision with habitual correction and with a pinhole can easily be made. Although improvements in vision with a pinhole are assumed to mean that a refractive error is present, no studies have investigated the magnitude of improvement in vision with pinhole that is predictive of refractive error. The aim was to measure the sensitivity and specificity of 'vision improvement with pinhole' in predicting the presence of refractive error in a community setting. Methods Vision and vision with pinhole were measured using a log MAR chart for 488 of 582 individuals aged 15 to 50 years. Refractive errors were measured using non-cycloplegic autorefraction and subjective refraction. The presence of refractive error was defined using spherical equivalent refraction ( SER) at two levels: SER greater than ± 0.50 D sphere ( DS) and SER greater than ±1.00 DS. Three definitions for significant improvement in vision with a pinhole were used: 1. Presenting vision less than 6/12 and improving to 6/12 or better, 2. Improvement in vision of more than one log MAR line and 3. Improvement in vision of more than two log MAR lines. Results For refractive error defined as spherical equivalent refraction greater than ± 0.50 DS, the sensitivities and specificities for the pinhole test predicting the presence of refractive error were 83.9 per cent (95% CI: 74.5 to 90.9) and 98.8 per cent (95% CI: 97.1 to 99.6), respectively for definition 1. Definition 2 had a sensitivity 89.7 per cent (95% CI: 81.3 to 95.2) and specificity 88.0 per cent (95% CI: 4.4 to 91.0). Definition 3 had a sensitivity of 75.9 per cent (95% CI: 65.5 to 84.4) and specificity of 97.8 per cent (95% CI: 95.8 to 99.0). Similar results were found with spherical equivalent refraction greater than ±1.00 DS, when tested against the three pinhole-based definitions. Conclusion Refractive error definitions based on improvement in vision with the pinhole shows good sensitivity and specificity at predicting the presence of significant refractive errors. These definitions can be used in rapid assessment surveys and community-based vision screenings. [ABSTRACT FROM AUTHOR]

Abstract: A three-dimensional (3D) watermark integral imaging-based watermarking algorithm operating in the cellular automata (CA) domain is presented. Instead of using conventional two-dimensional (2D) watermarking, in this proposed method, an elemental image array (EIA) obtained by recording the rays emanating from a 3D watermark through a pinhole array is used as a watermark to be embedded into the coefficients of CA-transformed pattern. A series of depth-dependent 3D plane images can be reconstructed by the volumetric computational reconstruction (VCR) technique. The embedded 2D EIA is composed of many elemental images possessing their own perspectives of the 3D watermark. The hologram-like 3D properties of the 2D EIA can make a robust reconstruction of the watermark available even though the embedded watermark data may be damaged by image-processing attacks. To embed the watermark imperceptibly, a masking model is introduced to adapt the watermark embedding strength by exploiting the characteristics of the human vision system. In addition, a CA transform with various CA bases and rule numbers can provide many transform planes for watermark embedding. To demonstrate the usefulness of the proposed method, we carry out preliminary experiments and present the experimental results. [Copyright &y& Elsevier]

Two-dimensional space-resolved temperature and density images of an inertial confinement fusion (ICF) implosion core have been diagnosed for the first time. Argon-doped, direct-drive ICF experiments were performed at the Omega Laser Facility and a collection of two-dimensional space-resolved spectra were obtained from an array of gated, spectrally resolved pinhole images recorded by a multi-monochromatic x-ray imager. Detailed spectral analysis revealed asymmetries of the core not just in shape and size but in the temperature and density spatial distributions, thus characterizing the core with an unprecedented level of detail. [ABSTRACT FROM AUTHOR]

The ideal pinhole imaging model commonly assumed for an ordinary two-dimensional digital image correlation (2D-DIC) system is neither perfect nor stable because of the existence of small out-of-plane motion of the test sample surface that occurred after loading, small out-of-plane motion of the sensor target due to temperature variation of a camera and unavoidable geometric distortion of an imaging lens. In certain cases, these disadvantages can lead to significant errors in the measured displacements and strains. Although a high-quality bilateral telecentric lens has been strongly recommended to be used in the 2D-DIC system as an essential optical component to achieve high-accuracy measurement, it is not generally applicable due to its fixed field of view, limited depth of focus and high cost. To minimize the errors associated with the imperfectness and instability of a common 2D-DIC system using a low-cost imaging lens, a generalized compensation method using a non-deformable reference sample is proposed in this work. With the proposed method, the displacement of the reference sample rigidly attached behind the test sample is first measured using 2D-DIC, and then it is fitted using a parametric model. The fitted parametric model is then used to correct the displacements of the deformed sample to remove the influences of these unfavorable factors. The validity of the proposed compensation method is first verified using out-of-plane translation, out-of-plane rotation, in-plane translation tests and their combinations. Uniaxial tensile tests of an aluminum specimen were also performed to quantitatively examine the strain accuracy of the proposed compensation method. Experiments show that the proposed compensation method is an easy-to-implement yet effective technique for achieving high-accuracy deformation measurement using an ordinary 2D-DIC system. [ABSTRACT FROM AUTHOR]

In multi-pinhole SPECT, overlapping the projections from different pinholes has been used to increase sensitivity. However, the prevailing view is that the overall quality of the reconstructed image is not improved by the overlaps in the projections. It is often stated in literatures that overlaps introduce ambiguous information, which can lead to nonuniqueness of solution for the inverse problem, and thus artifacts are introduced in the reconstructed image. On the other hand, contrary to the prevailing view, a recent study on slit-slat collimators shows that artifacts can be removed with the “help” of an extra complete nonoverlapped projection data set. In this paper, two types of artifact-free projection overlaps are defined in general, and the criteria for designing artifact-free multi-pinhole systems with overlaps are proposed. It is shown that once the criteria are satisfied, the solution of the inverse problem is unique, and thus no artifact is expected in the reconstructed image. Via extensive simulation study, various artifact-free overlapping multi-pinhole systems are designed and validated. It is shown that overlaps in the artifact-free systems can improve contrast-to-noise ratio (CNR). With a proper design, the CNR for an artifact-free overlapping system can be significantly higher than that for the corresponding nonoverlapping system. The improved image quality is also confirmed with noisy reconstructions. [ABSTRACT FROM AUTHOR]

We perform an optimization of pinhole neutron guide systems under systematically varying conditions. It is investigated how neutron guide systems consisting of a parabolic feeder inside the biological shielding followed by a pinhole and an elliptical guide perform with different pinhole sizes and divergence requirements. We have clarified in which situations such a guide system is a viable choice and when the parabolic feeder is necessary in terms of neutron transport. The advantage of this design is the reduction of background from fast thermal neutrons compared to a system without a pinhole, hence the smallest possible pinhole is of interest. It is found that instruments with divergence requirements of ±1.0° will have excellent neutron transport with a 3×3cm2 pinhole, while lower divergence requirements of ±0.5° can do with a smaller pinhole of 2×2cm2. The feeder effectively reduces the necessary pinhole size, and is especially beneficial for short instruments. In addition to these qualities, a feeder will often smoothen the divergence profile, mostly for longer instruments. [ABSTRACT FROM AUTHOR]

Abstract: This study investigates the effect of print head design on the electrohydrodynamic printed resolution of silk fibroin. Needles with large orifices measuring at 800μm were used to build five different print heads. The print heads were manufactured, tested, and optimized using four different silk fibroin solution concentrations of 10wt.%, 15wt.%, 20wt.%, and 22wt.% at applied voltages that ranged from 10 to 20kV with two different flow rates of 1.5μl/min and 2.0μl/min. Each print head design behaved in a unique manner in terms of printed line characteristics as the flow rate, voltage and concentration were varied. The highest printed resolution of the order of 1μm was achieved using the pinhole reservoir print head. Possible explanations for each of the observed behaviors and design criteria for future print heads are discussed. [Copyright &y& Elsevier]

Abstract: A methodology for measuring the telecentricity of illumination system in lithography tool based on the pinhole imaging is proposed. Illumination light goes through the pinhole located on the reticle plane and forms the pupil-fill image in CCD image sensor. Based on the Fresnel diffraction theory, the image intensity of source in CCD photosurface and the optimization of pinhole size are discussed. By simulating, effects of the stability of telecentricity measuring from non-uniformity of light field and pinhole defocus in different illumination patterns are analyzed respectively. Simulation results prove the effectiveness of this new method. [Copyright &y& Elsevier]

In the past decade Kirkpatrick-Baez (KB) mirrors have been established as powerful focusing systems in hard X-ray microscopy applications. Here a ptychographic characterization of the KB focus in the dedicated nano-imaging setup GINIX (Göttingen Instrument for Nano-Imaging with X-rays) at the P10 coherence beamline of the PETRA III synchrotron at HASLYLAB/DESY, Germany, is reported. More specifically, it is shown how aberrations in the KB beam, caused by imperfections in the height profile of the focusing mirrors, can be eliminated using a pinhole as a spatial filter near the focal plane. A combination of different pinhole sizes and illumination conditions of the KB setup makes the prepared optical setup well suited not only for high-resolution ptychographic coherent X-ray diffractive imaging but also for moderate-resolution/large-field-of-view propagation imaging in the divergent KB beam. [ABSTRACT FROM AUTHOR]

An integral imaging (II) display is proposed which consists of a display panel and a gradient-aperture pinhole array. The gradient-aperture pinhole array is symmetrical in both horizontal and vertical directions. The leftmost and rightmost pinholes are used to fix the horizontal viewing angle, and the uppermost and nethermost pinholes are used to fix the vertical viewing angle. To increase the optical efficiency, the aperture widths of other pinholes are gradually increased from both sides to the middle in the horizontal and vertical directions, respectively. A prototype of the proposed II display is developed. Its horizontal viewing angle is equal to that of the conventional one, while its optical efficiency is higher than that of the conventional one. [ABSTRACT FROM AUTHOR]

We developed SPECT imaging capability on a LabPET animal scanner to provide an integrated PET/SPECT dual-modality imaging system. The add-on SPECT sub-system was enabled by 1) mechanically integrating a multiple-pinhole collimator in the PET detector ring, and 2) configuring the detectors to acquire singles events in the 120–160 keV range. We report on the design parameters, data acquisition protocols and initial performance assessment of this cost-effective SPECT imaging solution. Phantom and animal images demonstrating the relevance of the system for various imaging tasks in preclinical research are presented. [ABSTRACT FROM PUBLISHER]

For the existing monocular vision methods of pose (or position and orientation) measurement based on the Perspective-n-Point problem, camera calibrations and image corrections are complicated and difficult due to the lens distortion. Additionally, as their theoretical models, the pinhole imaging model and the collinear equation only offer an ideal approximation for the imaging process of the area array camera. Thus, the measurement possesses inevitable systematic errors. To avoid these problems, a new pose measuring method is proposed, which replaces the area array camera and its collinear equation with two line array cameras and their incident light plane equations, respectively. For these two line array cameras, their mechanical assembly requirements and calibration steps are also analysed; they only require that the two optical centre lines of their cylindrical lenses be perpendicular to each other, and only need to be calibrated for the relationship between the coordinate of the image line and the incident angle of the incident light plane. The experiment results of P4P pose measurement with the proposed method showed only significant random errors and no significant systematic error, confirming that this method has eliminated the problems caused by the image distortion and model approximation. [ABSTRACT FROM AUTHOR]

Concentration solar arrays require greater solar tracking precision than conventional photovoltaic arrays. This paper presents a high precision lowcost dual axis sun tracking systembased on image processing for concentration photovoltaic applications. An imaging device is designed according to the principle of pinhole imaging, making sun rays to be received on a screen through pinhole and to be a sun spot. The location of the spot is used to adjust the orientation of the solar panel. A fuzzy logic controller is developed to achieve this goal. A prototype was built, and experimental results have proven the good performance of the proposed system and low error of tracking. The operation of this system is independent of geographical location, initial calibration, and periodical regulations. [ABSTRACT FROM AUTHOR]

Peak power density stability and beam-wander precision of probe laser are important factors affecting the inspection results in the precision thingilm optical measurements. Pinholes are frequently used as a spatial filter in the optical inspection system. In this work, five different diameters of pinhole are investigated experimentally. It is found that pinhole diameter of 0.3 mm is considered to be a promising candidate for mounting in front of probe laser for silicon thin-film optical inspection due to better peak power density stability and better beam-wander precision. [ABSTRACT FROM AUTHOR]

Purpose: This paper presents new spectral measurements of a tungsten-target digital breast tomosynthesis (DBT) system, including spectra of 43-49 kVp. Methods: Raw x-ray spectra of 20-49 kVp were directly measured from the tube port of a Selenia Dimensions DBT system using a CdTe based spectrometer. Two configurations of collimation were employed: one with two tungsten pinholes of 25μm and 200μm diameters, and the other with a single pinhole of 25μm diameter, for acquiring spectra from the focal spot and from the focal spot as well as its vicinity. Stripping correction was applied to the measured spectra to compensate distortions due to escape events. The measured spectra were compared with the existing mammographic spectra of the TASMIP model in terms of photon fluence per exposure, spectral components, and half-value layer (HVL). HVLs were calculated from the spectra with a numerical filtration of 0.7 mm aluminum and were compared against actual measurements on the DBT system using W/Al (target-filter) combination, without paddle in the beam. Results: The spectra from the double-pinhole configuration, in which the acceptance aperture pointed right at the focal spot, were harder than the single-pinhole spectra which include both primary and off-focus radiation. HVL calculated from the single-pinhole setup agreed with the measured HVL within 0.04 mm aluminum, while the HVL values from the double-pinhole setup were larger than the single-pinhole HVL by at most 0.1 mm aluminum. The spectra from single-pinhole setup agreed well with the TASMIP mammographic spectra, and are more relevant for clinical purpose. Conclusions: The spectra data would be useful for future research on DBT system with tungsten targets. [ABSTRACT FROM AUTHOR]

Virtual-pinhole PET (VP-PET) imaging is a new technology in which one or more high-resolution detector modules are integrated into a conventional PET scanner with lower resolution detectors. It can locally enhance the spatial resolution and contrast recovery near the add-on detectors, and depending on the configuration, may also increase the sensitivity of the system. This novel scanner geometry makes the reconstruction problem more challenging compared to the reconstruction of data from a stand-alone PET scanner, as new techniques are needed to model and account for the non-standard acquisition. In this paper, we present a general framework for fully 3D modeling of an arbitrary VP-PET insert system. The model components are incorporated into a statistical reconstruction algorithm to estimate an image from the multi-resolution data. For validation, we apply the proposed model and reconstruction approach to one of our custom-built VP-PET systems--a half-ring insert device integrated into a clinical PET/CT scanner. Details regarding the most important implementation issues are provided. We show that the proposed data model is consistent with the measured data, and that our approach can lead to reconstructions with improved spatial resolution and lesion detectability. [ABSTRACT FROM AUTHOR]

SPECT is primarily used in the clinic for cardiac myocardial perfusion imaging. However, for SPECT, sensitivity is impaired due to the need for collimation. System resolution FWHM is poor as well (\sim 1~cm). In this work the resolution of a curved detector was theoretically derived. The advantage of a curved detector over a flat detector with pinhole collimation was demonstrated for cardiac applications using theoretical derivations as well as a ray-tracing voxel-based forward projector. For the flat detector using parameters close to what was expected for the new multi-pinhole GE Discovery system, it is shown that using a paraboloid detector one may obtain a better system resolution (about 29% better on the average), keeping same pinhole opening. Alternately, sensitivity gains of as much as 2.25 may be obtained, for similar resolutions as a flat detector by just using a different pinhole with higher hole-diameter. [ABSTRACT FROM AUTHOR]