Pinhole Size Research Articles

Comment on: Optimum pinhole size determination in pinhole pupilloplasty for higher-order aberrations.

Comment on: Optimum pinhole size determination in pinhole pupilloplasty for higher-order aberrations.

Vortex position detection using a scanning triangular aperture in a digital micromirror device

Optical vortices, as solutions to the wave equation, remain stable under ideal theoretical conditions. However, in experiments where beams produced with holograms and spatial light modulators introduce perturbations, their phase structures can be disrupted, leading to instability. Specifically, higher-order optical vortices (with topological charge |ℓ|>1 ) are inherently unstable in that they tend to separate in a series of optical vortices with unit topological charge (|ℓ|=1) even with small perturbations. In this work, we demonstrate a technique to detect the positions of optical vortices using a scanning triangular aperture in a digital micromirror device and a digital pinhole. We observe the diffraction patterns of a vortex through the triangular aperture, and we show that we can determine the center of an optical vortex (OV) by measuring the intensity at the center of a pattern using a digital pinhole. We investigate the changes in the measured signal for different triangular apertures and pinhole sizes. We observe that while smaller pinholes lead to a decrease in light intensity, the detected position of a single OV with unit topological charge is similar for all pinhole sizes. We also find that the triangular aperture size becomes important when locating vortex pairs. Using a triangular aperture with a radius R = 0.52 mm, we can resolve OV pairs at least 86.4μ m apart in our experiments. Our methods help pave the way to understanding the fundamental behavior of multiple vortex interactions in optical beams and also can be used when determining the position of an OV in metrology.

Experimental and modeling study of the effect of confinement on the thermal decomposition of organic materials

Simultaneous Thermal Analysis is widely used to study thermal decomposition of a variety of organic materials, and the choice of experimental conditions is very important to obtain reliable mass loss and heat flow curves. In this work we investigate the effect of confinement on the thermal decomposition of organic materials. As an example, we explore high-density polyethylene (HDPE) and one of its pyrolysis products, namely eicosane (C20H42), through experiments and modeling in open crucibles and crucibles closed with a pierced lid. A new model is developed for evaporation and sublimation from open and pinhole thermal-analysis pans. It considers the kinetic resistance of evaporation at the liquid-vapor interface, inhibition of evaporation by buildup of vapor inside the pan, thermal expansion of vapor inside the pan, and diffusion of vapor from the pan. The model is validated using simultaneous heat-flow and mass-loss measurements of n-eicosane evaporation for various pinhole sizes, down to 50 µm. The importance of product evaporation inhibition for measuring polymer decomposition was demonstrated using HDPE. This study sheds light on the effect of confinement on the mass loss rate of organic materials.

Optimum pinhole size determination in pinhole pupilloplasty for higher-order aberrations.

To determine optimal pinhole size (OPS) and establish a relationship with visual acuity (VA) and RMS (root mean square) values in cases with higher-order aberrations (HOAs) undergoing pinhole pupilloplasty (PPP). Private practice, India. Prospective, interventional study. RMS value for 6-mm-diameter optical zone was determined by Scheimpflug imaging (Pentacam). Patients with RMS value >0.3 μm were included. Preoperatively, a hand-held pinhole gauge with varied apertures determined the OPS, and single-pass four-throw technique was used to perform pupilloplasty with Purkinje-1 reflex as a marker for centration. VA with OPS, correlation of RMS values with OPS and pupil size, and Strehl ratio were the main outcome measures. 29 eyes with HOAs were analyzed; all patients chose 1.0 or 1.5 mm as OPS. The mean preoperative and postoperative pupil size was 3.25 ± 0.81 mm and 1.8 ± 0.54 mm ( P = .000), respectively. Postoperative mean pupil size when compared with OPS denoted that 14 eyes had a difference of <0.1 mm, 8 eyes ranged from 0.2 to 0.45 mm, and 7 eyes had ≥0.6 mm (range from 0.6 to 1.8 mm) difference from OPS. Eyes with higher RMS values needed smaller pupil gauge to achieve better VA. Preoperatively, vision with OPS correlated well with preoperative 6-mm RMS HOAs ( r = 0.728; P = .00). Postoperative UDVA correlated well with VA measured with OPS ( r = 0.847; P = .00). The preoperative and postoperative mean Strehl ratio was 0.109 ± 0.07 and 0.195 ± 0.11 ( P = .001), respectively. Higher RMS values required a smaller pupil to achieve optimum VA. PPP can help achieve pinhole size in accordance with patient's optimum pinhole requirement.

Image scanning microscopy: a vectorial physical optics analysis.

Image scanning microscopy (ISM) achieves resolution beyond the diffraction limit by a factor of 2. However, prior ISM research predominantly employs scalar diffraction theory, neglecting critical physical effects such as polarization, aberrations, and Stokes shift. This paper presents a comprehensive vectorial ISM point spread function (PSF) model that accounts for these phenomena. By considering the effect of polarization in emission and excitation paths, as well as aberrations and Stokes shift, our model provides a more accurate representation of ISM. We analyze the differences between scalar and vectorial theories in ISM and investigate the impact of pinhole size and aberration strength on resolution. At a numerical aperture of 1.2, the full width half maximum (FWHM) discrepancy between scalar and vectorial ISM PSFs can reach 45 nm, representing a 30% deviation from the vectorial model. Additionally, we explore multiphoton excitation in ISM and observe increased FWHM for 2-photon and 3-photon excitation compared to 1-photon excitation. The FWHM of the 2-photon excitation ISM PSF increases by 20% and the FWHM of the 3-photon excitation ISM PSF increases by 28% compared to the 1-photon excitation ISM. In addition, we found that the optimal sweep factor for 2-photon ISM is 1.22, and the optimal sweep factor of 3-photon ISM is 1.12 instead of the 2 predicted by the one-photon scalar ISM theory. Our work improves the understanding of ISM and contributes to its advancement as a high-resolution imaging technique.

Comparative analysis of sublimation and thermal decomposition of TATB

AbstractThis experimental study investigated the effects of confinement, starting mass, and heating rate on TATB thermal decomposition and sublimation using a combined Thermo‐Gravimetric Analyzer and Differential Scanning Calorimetry (TGA/DSC) instrument. The confinement of volatile products was varied using different pinhole sizes with TGA/DSC pans. The measurements showed the open pan experiments without lids/pinholes resulted in complete sublimation of TATB between 320 °C and 360 °C. The heat of sublimation was determined to be 176 kJ/mol (42 kcal /mol), consistent with literature data obtained from other experimental techniques. The use of pinholes suppressed the sublimation of TATB such that the decrease in pinhole size resulted in 1) an increase in the enthalpy of reaction and an increase in the amount of carbonaceous material remaining at the end of decomposition, and 2) convergence of the two peak temperatures corresponding to maximum heat flow and maximum weight loss. Also, a transition from a two‐exotherm thermal decomposition behavior towards a single‐exotherm occurred as the pinhole size was decreased for a given starting mass or as the starting mass was increased for a given pinhole size. These results indicate the kinetics of TATB sublimation, TATB thermal decomposition, and gas diffusion out of a TGA/DSC pan can all compete and result in significantly different enthalpies, amounts of remaining materials, and peak temperatures depending on the pinhole size and starting mass used in the measurements. The results also indicate precise control of process variables (pinhole size, starting mass, and heating rate) in TGA/DSC measurements is required for thermal safety assessment of explosives.

Confocal Laser Scanning Microscope Imaging of Custom-Made Multi-Cylinder Phantoms: Theory and Experiment

In this work, the image formation in a confocal laser scanning microscope (CLSM) is investigated for custom-made multi-cylinder phantoms. The cylinder structures were fabricated using 3D direct laser writing and consist of parallel cylinders with radii of 5 and 10 μm for the respective multi-cylinder phantom, with overall dimensions of about 200×200×200 μm3. Measurements were performed for different refractive index differences and by varying other parameters of the measurement system, such as pinhole size or numerical aperture (NA). For theoretical comparison, the confocal setup was implemented in an in-house developed tetrahedron-based and GPU-accelerated Monte Carlo (MC) software. The simulation results for a cylindrical single scatterer were first compared with the analytical solution of Maxwell’s equations in two dimensions for prior validation. Subsequently, the more complex multi-cylinder structures were simulated using the MC software and compared with the experimental results. For the largest refractive index difference, i.e., air as the surrounding medium, the simulated and measured data show a high degree of agreement, with all the key features of the CLSM image being reproduced by the simulation. Even with a significant reduction in the refractive index difference by the use of immersion oil to values as low as 0.005, a good agreement between simulation and measurement was observed, particularly with respect to the increase in penetration depth.

The pinhole effect on proton exchange membrane fuel cell (PEMFC) current density distribution and temperature distribution

The proton exchange membrane (PEM) is a critical portion of a proton exchange membrane fuel cell (PEMFC). However, it is strongly influenced by pinhole defects owing to degradation during its operation or manufacture. Such defects may accelerate chemical polymer decomposition, eventually causing fuel cell failure and other safety issues. Thus, it is necessary to detect and characterize pinhole degradation while determining the effect of pinhole on electrochemical behavior and fuel cell performance. Herein, pinholes of different sizes (10 and 100 µm) were fabricated on a 50-cm2 catalyst-coated membrane (CCM) and characterized using commercial current scan shunt (CSS) S++ Simulation Services (Hephas Energy) to investigate the effects of pinhole size on current density and temperature distributions of the PEMFC. Our analyses show that hydrogen crossover from the anode to the cathode through a pinhole can cause hydrogen diffusion and a hydrogen oxidation reaction (HOR) on the cathode electrode surface under certain conditions. Consequently, local reverse currents and hot spots are detected around the pinhole position under open-circuit voltage (OCV) and the corresponding current and temperature distribution trends are uniform. Conversely, the reverse current immediately disappeared from the current distribution map because water exists under operation conditions, resulting in membrane swelling and pinhole sealing. Thus, hydrogen crossover decreased and local reverse currents reappeared as a result of anode overpressure during fuel cell operation. The local reverse current becomes weaker when using the same-sized pinhole under the same anode overpressure because the overall current density increases. Furthermore, owing to the presence of water, the capillary force for the 100-µm pinhole was higher than that for the 10-µm pinhole, indicating that more anode overpressure is required to generate a local reverse current. Thus, the position and size of the pinhole can be effectively detected using in situ characterization.

SPLIT-PIN software enabling confocal and super-resolution imaging with a virtually closed pinhole

In point-scanning microscopy, optical sectioning is achieved using a small aperture placed in front of the detector, i.e. the detection pinhole, which rejects the out-of-focus background. The maximum level of optical sectioning is theoretically obtained for the minimum size of the pinhole aperture, but this is normally prevented by the dramatic reduction of the detected signal when the pinhole is closed, leading to a compromise between axial resolution and signal-to-noise ratio. We have recently demonstrated that, instead of closing the pinhole, one can reach a similar level of optical sectioning by tuning the pinhole size in a confocal microscope and by analyzing the resulting image series. The method, consisting in the application of the separation of photons by lifetime tuning (SPLIT) algorithm to series of images acquired with tunable pinhole size, is called SPLIT-pinhole (SPLIT-PIN). Here, we share and describe a SPLIT-PIN software for the processing of series of images acquired at tunable pinhole size, which generates images with reduced out-of-focus background. The software can be used on series of at least two images acquired on available commercial microscopes equipped with a tunable pinhole, including confocal and stimulated emission depletion (STED) microscopes. We demonstrate applicability on different types of imaging modalities: (1) confocal imaging of DNA in a non-adherent cell line; (2) removal of out-of-focus background in super-resolved STED microscopy; (3) imaging of live intestinal organoids stained with a membrane dye.

A broadband picometer resolution visible CCD spectrometer based on virtually imaged phased array technology.

Coincidental realization of broadband spectral coverage and high resolution in one spectrometer system has always been a challenge. Here, we report the development of a high-resolution visible CCD spectrometer based on the virtually imaged phase array (VIPA) technique. By using a thin glass plate and a reflective grating, a two-dimensional cross-dispersion was realized. A broadband coverage of ∼14.94 THz and a high resolution of ∼1 GHz at 632.996 nm were achieved with a simple structure. The effects of the surface quality of VIPA etalon, the pixel size of the CCD camera, the pinhole size of the input beam, and the focal length of the imaging lens on the resolution of the spectrometer and the transverse spot size on the detector plane were considered. A comparison between the experimental results by changing the imaging lens and the theoretical calculation results proved a better simulation of these two parameters, which is a helpful contribution to the design and construction of a VIPA spectrometer. The developed spectrometer will provide a useful tool for the study of high-resolution spectroscopy and for simultaneous multi-species trace detection.

A phasor-based approach to improve optical sectioning in any confocal microscope with a tunable pinhole.

Confocal fluorescence microscopy is a well‐established imaging technique capable of generating thin optical sections of biological specimens. Optical sectioning in confocal microscopy is mainly determined by the size of the pinhole, a small aperture placed in front of a point detector. In principle, imaging with a closed pinhole provides the highest degree of optical sectioning. In practice, the dramatic reduction of signal‐to‐noise ratio (SNR) at smaller pinhole sizes makes challenging the use of pinhole sizes significantly smaller than 1 Airy Unit (AU). Here, we introduce a simple method to “virtually” perform confocal imaging at smaller pinhole sizes without the dramatic reduction of SNR. The method is based on the sequential acquisition of multiple confocal images acquired at different pinhole aperture sizes and image processing based on a phasor analysis. The implementation is conceptually similar to separation of photons by lifetime tuning (SPLIT), a technique that exploits the phasor analysis to achieve super‐resolution, and for this reason we call this method SPLIT‐pinhole (SPLIT‐PIN). We show with simulated data that the SPLIT‐PIN image can provide improved optical sectioning (i.e., virtually smaller pinhole size) but better SNR with respect to an image obtained with closed pinhole. For instance, two images acquired at 2 and 1 AU can be combined to obtain a SPLIT‐PIN image with a virtual pinhole size of 0.2 AU but with better SNR. As an example of application to biological imaging, we show that SPLIT‐PIN improves confocal imaging of the apical membrane in an in vitro model of the intestinal epithelium.Research HighlightsWe describe a method to boost the optical sectioning power of any confocal microscope. The method is based on the sequential acquisition of multiple confocal images acquired at different pinhole aperture sizes. The resulting image series is analyzed using the phasor‐based separation of photons by lifetime tuning (SPLIT) algorithm. The SPLIT‐pinhole (SPLIT‐PIN) method produces images with improved optical sectioning but preserved SNR. This is the first time that the phasor analysis and SPLIT algorithms are used to exploit the spatial information encoded in a tunable pinhole size and to improve optical sectioning of the confocal microscope.

A modified mode-mismatched thermal lens spectrometry Z-scan model: An exact general approach

In this work we introduce a modified pump-probe mode-mismatched thermal lens Z-scan theoretical model for measurement of thermo-optical properties including absorption coefficient and thermal diffusivity of semitransparent liquids. We present an exact solution for the theoretical thermal lens (TL) signal which agrees pretty well with the experimental one under different experimental configurations. The TL signal as a function of the detector position (L) has been analyzed using the pinhole size (ρ0) as a critical parameter. We illustrate its validity by calculating the TL signal in Z-scan experiment and situation with small and large values of L as well as measuring the absorption coefficient and thermal diffusivity of water.

12‐3: Investigation of Fingerprint on Display Technology for FLI Display

We developed pinhole matrix optical solution of fingerprint on display technology for FLI OLED to avoid its low module transmittance. We investigated the influence of pinhole size and touch metal lines on the fingerprint on FLI technology in both regid and foldable display based on a 6.2inch QHD resolution OLED panel.

Assessment of Pinhole for Visual Acuity Recoverment in Patients with Myopia

Refractive errors are difficulties with concentrating retina light accurately because of the cornea or eye shape. The mostly mutual refractive error types are near sightedness, farsightedness, astigmatism, and presbyopia. Refractive errors can be fixed with contact lenses or glasses, or fix the refractive error with surgery. One of the most valuable way to correct the visual acuity is the usage of glasses as pinhole. Glasses as pinhole are typically eyeglasses with lenses that are full of a grid of tiny holes. They help eyes concentrate through shielding vision from indirect light rays. Through allowing less light into the eye, few people can see more clearly.1 In this work, the pinhole technique will be described with their usage to correct the visual acuity. In addition, 40 patients with myopia and astigmatism have been tested using the pinhole to assess the more useful pinhole size for the visual acuity correction. Results: The finding revealed no difference of significance in refractive error of both myopic left (p= 0.07) and right eyes (p= 0.06) without and with glasses as pinhole. Also there was no significant different for gender (male, female), and there was no significant different between patients with age ≤20years and patients with age &gt;50 years values. Conclusion: The findings propose that glasses as pinhole did not recover the refractive myopic participant’s error.

Single-Shot 3D Topography of Transmissive and Reflective Samples with a Dual-Mode Telecentric-Based Digital Holographic Microscope.

Common path DHM systems are the most robust DHM systems as they are based on self-interference and are thus less prone to external fluctuations. A common issue amongst these DHM systems is that the two replicas of the sample’s information overlay due to self-interference, making them only suitable for imaging sparse samples. This overlay has restricted the use of common-path DHM systems in material science. The overlay can be overcome by limiting the sample’s field of view to occupy only half of the imaging field of view or by using an optical spatial filter. In this work, we have implemented optical spatial filtering in a common-path DHM system using a Fresnel biprism. We have analyzed the optimal pinhole size by evaluating the frequency content of the reconstructed phase images of a star target. We have also measured the accuracy of the system and the sensitivity to noise for different pinhole sizes. Finally, we have proposed the first dual-mode common-path DHM system using a Fresnel biprism. The performance of the dual-model DHM system has been evaluated experimentally using transmissive and reflective microscopic samples.

A Numerical Study of Effect of Operating Conditions on Hydrogen Crossover Through Perforated PFSA Membrane

In this work, a three-dimensional monophasic mass transport PEMFC model has been established in order to investigate the gas pressure distribution and to quantify the hydrogen crossover through the Nafion PEM side. The model is performed using finite element approach under a commercial software platform. The effects of anodic inlet gas pressure and membrane pinhole location have been investigated. In addition, the hydrogen flow rate by permeation and the hydrogen flow rate leak across the pinhole have been estimated at different reaction rate values and pinhole sizes. The results show that the hydrogen crossover distribution is inhomogeneous. It begins with a strong increase in the inlet channel side, and ends with a large decrease in the outlet channel. The effect of variation of inlet gas pressure on hydrogen crossover is stronger in comparison with that due to the variation of pinhole size or functioning temperature, especially in case of high reaction rate. In addition, the presence of pinhole favors a slightly increase in hydrogen flow rate across the membrane at the outlet channel side.

High Power Density Beam Measurement of a Single Beamlet Multi-Grid Prototype H- Negative Ion Accelerator

Beam optics of the ITER prototype accelerator with 88 mm acceleration gap length has been examined through H- beam acceleration tests at the ITER target beam perveance. The beam optics has been examined for beam energies up to 790 keV under the ITER target perveance. The total grid heat load was successfully reduced to 10 %, which was lower than the allowable value of 15 %. The beam emittance of the ITER perveance has been measured for the first time by using newly developed emittance measurement system consisting of carbon-fiber-composite (CFC) plate with pin-holes. The emittance of 790 keV H- beam shows the divergence angle of the beam core is satisfied with the ITER requirement of <7 mrad. Measurement at the beam periphery was made possible by modifying the pin-hole size of pepper-pot apertures, and the observed divergent components were 20 mrad. The ratio of the diverged beam became lower with the increase of the beam energy. This result contributes the design of the ITER accelerator and the beam line components.

Effect of injection strategy for nanofluid transport on thermal damage behavior inside biological tissue during magnetic hyperthermia

Magnetic hyperthermia is an alternative to conventional one for cancer treatment, which damages malignant cells by controlling treatment temperature to an acceptable range. The treatment temperature distribution mainly depends on both magnetic nanoparticles (MNPs) distribution inside malignant tissue and the heat released by the MNPs after subjecting to an alternating magnetic field. The spatial distribution of MNPs inside malignant tissue is strongly affected by many factors studied and to be studied, which can be injection rate, injection time, injection dose, the pinhole size of syringe, and also diffusion time. Contrary to traditional injection with high rate (50 ul/min), this study proposes three injection strategies with low rate (5 ul/min) for nanofluid injection including continuous injection with constant rate, continuous injection with variable rate, and intermittent injection with constant rate under the same nanofluid dose (0.3 ml). All these injection strategies are proposed in order to obtain better nanofluid concentration distribution and further improve the treatment temperature distribution and the thermal damage situation for the malignant tissue. Simulation results show that all these proposed injection strategies, especially the continuous injection with variable rate, can effectively improve the physical field distribution for the nanofluid concentration, the treatment temperature, and the thermal damage situation inside malignant tissue.

Effects of beam divergence and polychromaticity on small angle x-ray scattering measurements with laser plasma sources

We explore the feasibility of small angle x-ray scattering (SAXS) measurements with intense laser-induced plasma sources. Such x-ray sources are inherently polychromatic and divergent. We simulate SAXS patterns using monochromatic and polychromatic x-ray sources with different divergences of polydisperse particle systems with different size distributions. The beam divergence is adjusted via varying x-ray source size, pinhole size, and the source-to-pinhole distance. Three typical laser plasma He-α sources (Fe, Cu, and Ge) are considered. The scattering curves are analyzed using the modified Guinier approach and the total non-negative least squares method. We demonstrate certain feasibility of SAXS measurements using laser plasma sources with a finite size, without a monochromator and additional software desmearing.

Effect Of Use Of Different Types Of Materials In Car Interior Parts On Parts Assembly And Perceived Quality

In the automotive industry, where perceived quality is of paramount importance, plastic pins and plastic hole mounting types are generally used in vehicle interior components. Two components made of the same material, production and assembly can be performed by assuming equal pin-hole tolerances. In this article, there are geometric dimensioning and tolerance engineering studies aiming to increase perceived quality in the issues of assembly, visibility, sound and interference that may arise from differences in the tolerance of pin-hole sizes between the pin made of magnesium and the hole made of polypropylene. In this context, visibility and interference analyzes were carried out in virtual environment for problems that may arise from tolerance differences