Pinhole Array Research Articles

Direct multiple monochromatic x-ray imaging with a pinhole array and a laterally graded multilayer mirror.

Multiple monochromatic x-ray imaging (MMI) is a technique for diagnosing the emission spectra of tracer elements in laser-driven inertial confinement fusion experiments. This study proposes an MMI method that combines a simple pinhole array with a laterally graded multilayer mirror. The method directly obtains multiple monochromatic x-ray images by regulating the multilayer thickness in different mirror positions to compensate for the energy-broadening effect. This paper presents a comprehensive design scheme, the multilayer fabrication and experimental verification of the gradient MMI imaging performance. The experimental results show that the method achieves monochromatic imaging with a spectral resolution of ∼70-90eV in several keV energy regions. This paper presents a practical diagnostic approach for directly and synchronously capturing the spatial, temporal, and spectral information of laser plasma x rays.

Single shot point-diffraction interferometer by a plate beamsplitter

A single shot point-diffraction interferometer (PDI) is proposed in this paper, in which the object beam is split into two copies by means of a beamsplitting module consisting of one plate beamsplitter and one mirror. One of the reflected beams is spatially filtered as a reference beam by one pinhole array in the spectral plane. The split two beams share almost the same path, and by adjusting the inclined angle of the plate beamsplitter, the carrier frequency and legibility of the interferogram can be modulated easily. Moreover, the contrast of the interferogram can be adjusted by changing different plate beamsplitters. Compared to conventional common path off-axis interferometers, this PDI has a simple optical setup, easy optical implementation and outstanding measurement ability with high precision, measurement efficiency and stability. Several experimental results will be provided to demonstrate the effectiveness of the proposed system.

Viewing-Angle-Enhanced and Dual-View Compatible Integral Imaging 3D Display Based on a Dual Pinhole Array.

Conventional integral imaging (InIm) three-dimensional (3D) display has the defect of a small viewing angle and usually presents a single 3D image. In this paper, we propose a viewing-angle-enhanced and dual-view compatible InIm 3D display system. The crosstalk pixel areas within the conventional elemental images (EIs) that result in image crosstalk were effectively utilized either for viewing angle enhancement or for dual-view 3D display. In the viewing-angle-enhanced 3D display mode, a composite elemental image (CEI) that consisted of a normal EI and two view-enhanced EIs was imaged by a dual pinhole array and formed an extended 3D viewing area. A precisely designed mask array was introduced to block the overlapped rays between adjacent viewing areas to eliminate image crosstalk. While in the dual-view 3D display mode, a CEI was composed of image information of two different 3D scenes. With the help of the dual pinhole array and mask array, two different 3D images were reconstructed for the left and right perspectives. Experiments demonstrated that both the left and right sides were increased by 6 degrees from the conventional 3D viewing angle, and also, a dual-view 3D display effect that retains the same viewing angle as the conventional system was achieved. The proposed system has a compact structure and can be freely switched between two display modes.

Measurement of the Energy Fluence Radiated by a Z-Pinch X-Ray Source Using a Pinhole Array as an Attenuator

Measurement of the Energy Fluence Radiated by a Z-Pinch X-Ray Source Using a Pinhole Array as an Attenuator

High-resolution portable lens-free on-chip microscopy with RGB LED via pinhole array

High-resolution portable lens-free on-chip microscopy with RGB LED via pinhole array

A coded aperture with sub-mean free-path thickness for neutron implosion geometry imaging on inertial confinement fusion and inertial fusion energy experiments.

Inertial confinement fusion and inertial fusion energy experiments diagnose the geometry of the fusion region through imaging of the neutrons released through fusion reactions. Pinhole arrays typically used for such imaging require thick substrates to obtain high contrast along with a small pinhole diameter to obtain high resolution capability, resulting in pinholes that have large aspect ratios. This leads to expensive pinhole arrays that have small solid angles and are difficult to align. Here, we propose a coded aperture with scatter and partial attenuation (CASPA) for fusion neutron imaging that relaxes the thick substrate requirement for good image contrast. These coded apertures are expected to scale to larger solid angles and are easier to align without sacrificing imaging resolution or throughput. We use Monte Carlo simulations (Geant4) to explore a coded aperture design to measure neutron implosion asymmetries on fusion experiments at the National Ignition Facility (NIF) and discuss the viability of this technique, matching the current nominal resolution of 10 µm. The results show that a 10mm thick tungsten CASPA can image NIF implosions with neutron yields above 1014 with quality comparable to unprocessed data from a current NIF neutron imaging aperture. This CASPA substrate is 20 times thinner than the current aperture arrays for fusion neutron imaging and less than one mean free-path of 14.1MeV neutrons through the substrate. Since the resolution, solid angle, and throughput are decoupled in coded aperture imaging, the resolution and solid angle achievable with future designs will be limited primarily by manufacturing capability.

Dual‐view integral imaging display with adjustable optimal viewing distance

AbstractWe propose a dual‐view integral imaging display that provides two three‐dimensional scenes at the same time. An adjustable pinhole array is generated by using a liquid crystal panel. The horizontal pitch of pinhole is adjustable, while the vertical one is unadjustable. The center of each elemental image is deviation from that of the corresponding pinhole. The light rays emitted from two kinds of elemental images are propagated into the left and right viewing directions. The horizontal viewing ranges are unrelated to the horizontal pitch of pinhole and the optimal viewing distance. By changing the horizontal pitch of pinhole, the optimal viewing distance is easily adjusted without loss of viewing angle. We developed an experimental apparatus and verified the proposed hypothesis.

Structured illumination microscopy with a phase-modulated spinning disk for optical sectioning.

Among various super-resolution microscopic techniques, structured illumination microscopy (SIM) stands out for live-cell imaging because of its higher imaging speed. However, conventional SIM lacks optical sectioning capability. Here we demonstrate a new, to the best of our knowledge, approach using a phase-modulated spinning disk (PMSD) that enhances the optical sectioning capability of SIM. The PMSD consists of a pinhole array for confocal imaging and a transparent polymer layer for light phase modulation. The light phase modulation was designed to cancel the zeroth-order diffracted beam and create a sharp lattice illumination pattern using the interference of four first-order diffracted beams. In the detection optical path, the PMSD serves as a spatial filter to physically reject about 80% of the out-of-focus signals, an approach that allows for real-time optical reconstruction of super-resolved images with enhanced contrast. Furthermore, the simplicity of the design makes it easy to upgrade a conventional fluorescence microscope to a PMSD SIM system.

Neutron Pinhole Characterization and Analysis for Three-Dimensional As-Built Model Reconstruction

The neutron pinhole array, used to collect neutron burn, X-ray, and more recently, gamma emission images, has been in use at the National Ignition Facility since 2011. Since then, there has been the ever-continuing challenge of meeting tighter alignment and resolution requirements. Part of that challenge is being able to accurately characterize the as-built variances from the nominal design associated with the manufacturing and assembly of the pinhole array. To overcome this specific challenge, multiple processes are taken to obtain high-precision profiles of the various features of each pinhole array. This paper highlights the processes used as well as the steps taken to compile the significant amount of data and turn it into an accurate as-built reconstructed model of the NIS1-U–assembled pinhole array.

Confocal Single-Pixel Imaging

Obtaining depth-selective images requires gating procedures such as spatial, nonlinear, or coherence gating to differentiate light originating from different depths of the volume of interest. Nonlinear gating requires pulsed excitation sources and excitation probes, limiting easy usage. Coherence gating also requires broadband sources and interferometry requiring specialized stable setups. Spatial gating can be used both for fluorescence and reflection geometry and various light sources and thus has the least requirements on hardware, but still requires the use of a pinhole which makes it difficult to use for photography or widefield imaging schemes. Here, we demonstrate that we can utilize a single digital micromirror device (DMD) to simultaneously function as a dynamic illumination modulator and automatically synchronized dynamic pinhole array to obtain depth-sectioned widefield images. Utilizing the multiplexed measurement advantage of single-pixel imaging, we show that the depth and ballistic light gating of the confocal single pixel imaging scheme can be utilized to obtain images through glare and multiple scattering where conventional widefield imaging fails to recover clear images due to saturation or random scattered noise.

Fast Numerical Reconstruction of Integral Imaging Based on a Determined Interval Mapping

In this paper, a fast numerical reconstruction of the integral imaging based on a determined interval mapping is proposed. To reduce the computation time, the proposed method employs the determined interval mapping instead of the use of magnification. In the numerical reconstruction procedure, the acquired elemental image array (EIA) from the 3D object is displayed. The flipped elemental image (EI)s are numerically formed by the virtual pinhole array. Then, the determined interval depending on the reconstruction plane is calculated and applied to each flipped EI. These flipped EIs are shifted to match the determined interval at the reconstruction plane and superimposed together. After this superimposed image is divided by the number of the superposition, the position error between the location of the shifted EI and the pixel position of the reconstruction plane is corrected by interpolation. As a result, the refocused image depending on the reconstruction plane can be reconstructed rapidly. From the experimental result, we confirmed that the proposed method largely decreased the computation time compared with the conventional method. In addition, we verified that the quality of the reconstruction by the proposed method is higher than the conventional method by the use of the structural similarity index method.

Deep learning method for pinhole array color image reconstruction.

The following paper proposes a combination of a supervised encoder-decoder neural network with coded apertures. Coded apertures provide improved sensitivity and signal-to-noise ratio (SNR) in planar images. The unique array design of this method overcomes the spatial frequency cutoff found in standard multi-pinhole arrays. In this design, the pinholes were positioned to minimize loss in spatial frequencies. The large number of pinholes results in significant overlapping on the detector. To overcome the overlapping issue, reconstruction of the object from the obtained image is done using inverse filtering methods. However, traces of duplications remain leading to a decline in SNR, contrast, and resolution. The proposed technique addresses the challenge of image distortion caused by the lack of accuracy in the inverse filter methods, by using a deep neural network. In this work, the coded aperture is combined with a deep convolutional neural network (CNN) to remove noise caused by pinhole imaging and inverse filter limitations. Compared to only using Wiener filtering, the proposed method delivers higher SNR, contrast, and resolution. The imaging system is presented in detail with experimental results that illustrate its efficiency.

X-ray volumetric quantitative phase imaging by Foucault differential filtering with linear scanning

Non-interferometric X-ray quantitative phase imaging (XQPI), much simpler than the interferometric scheme, has provided high-resolution and reliable phase-contrast images. We report on implementing the volumetric XQPI images using concurrent-bidirectional scanning of the orthogonal plane on the optical axis of the Foucault differential filter; we then extracted data in conjunction with the transport-intensity equation. The volumetric image of the laminate microstructure of the gills of a fish was successfully reconstructed to demonstrate our XQPI method. The method can perform 3D rendering without any rotational motion for laterally extended objects by manipulating incoherent X-rays using the pinhole array.

Novel Chromatic Differential Confocal Matrix Sensor Using Multiband Spectral Images

In this letter, a novel chromatic differential confocal matrix (CDCM) sensor is proposed and demonstrated for accurate and fast three-dimensional (3D) profiling without mechanical scanning. In contrast to conventional chromatic confocal microscopy (CCM) methods that require spectral expansion and a peak-intensity-wavelength detection algorithm for axial positioning, our CDCM employs the intensity difference between a pair of spectral confocal images to accurately discriminate surface height. Due to the elimination of spectral expansion required by a conventional CCM, the CDCM has an at least one order of magnitude higher axial sensitivity and surface profiling efficiency than a conventional CCM. In the CDCM, axial scanning is achieved by residual chromatic aberration of an achromatic objective and by constructing a difference intensity signal between two spectral confocal images. Spectral confocal images are acquired in a parallel manner by using a digital micromirror device as an array of illumination pinholes and digitally applying the virtual detection pinhole concept. Quantitative evaluation experiments with the proof-of-principle sensor system indicate that with a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10\times $ </tex-math></inline-formula> NA 0.25 objective, the CDCM can achieve better than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.1~\mu \text{m}$ </tex-math></inline-formula> axial accuracy with an axial measurement range of approximately <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$28~\mu \text{m}$ </tex-math></inline-formula> , a lateral resolution of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.87~\mu \text{m}$ </tex-math></inline-formula> .

Compact multichannel spectrometer employed for soft x-ray spectrum diagnostics at the Shenguang-III Laser Facility.

The quantitative measurement of plasma soft x-ray spectra is an important diagnostic problem in indirect-drive laser inertial confinement fusion (ICF). We designed, built, and tested a compact multichannel soft x-ray spectrometer with both spatial and temporal resolution capabilities for the detection of the spatiotemporal distribution of soft x-ray spectra. The spectrometer occupies a small solid angle, and the close measurement angle used for each channel enables the measurement of the angular distribution of emitting soft x-rays in ICF experiments. The spectrometer comprises pinhole, filter, and multilayer flat mirror arrays, and an x-ray streak camera. Its energy range is 0.1 - 3 keV. The dispersive elements of the spectrometer were calibrated at the Beijing Synchrotron Radiation Facility. The accuracy of the calibration was ≤ 5%, and the combined energy resolution (E/ΔE) of the calibrated dispersive elements of each channel was higher than 10. Finally, the instrument was tested at the Shenguang-III Laser Facility. The measurement results of x-ray radiation flux are agreed well with the experimental results of the M-band flat-response x-ray diode, demonstrating the feasibility of the proposed spectrometer configuration.

Design of the high-yield time-gated x-ray hot-spot imager for OMEGA.

Time-resolved x-ray self-emission imaging of hot spots in inertial confinement fusion experiments along several lines of sight provides critical information on the pressure and the transient morphology of the hot spot on the University of Rochester's OMEGA Laser System. At least three quasi-orthogonal lines of sight are required to infer the tomographic information of the hot spots of deuterium-tritium cryogenic layered implosions. OMEGA currently has two time-gated x-ray hot-spot imagers: the time-resolved Kirkpatrick-Baez x-ray microscope and the single-line-of-sight, time-resolved x-ray imager (SLOS-TRXI). The time-gated x-ray hot-spot imager (XRHSI) is being developed for use on OMEGA as the third line of sight for the high-yield operation of up to 4 × 1014 neutrons. XRHSI follows the SLOS-TRXI concept; however, it will have improved spatial and temporal resolutions of 5μm and 20ps, respectively. The simultaneous operation of the three instruments will provide 3-D reconstructions of the assembled hot-spot fuel at various times through peak thermonuclear output. The technical approach consists of a pinhole array imager and demagnifying time-dilation drift tube that are coupled to two side-by-side hybrid complementary metal-oxide semiconductor (hCMOS) image sensors. To minimize the background and to harden the diagnostics, an angled drift-tube assembly shifting the hCMOS sensors out of the direct line of sight and neutron shielding will be applied. The technical design space for the instrument will be discussed and the conceptual design will be presented.

Water Flow Improvement by Pinhole Outlet in Batch-Type Wet Cleaning Bath for Large-Diameter Wafers

The pinhole water outlet fabricated near the top of bath walls could produce a simple water flow with less water recirculation in the batch-type wet cleaner for 300 mm-diameter silicon wafers. The pinholes having a 2 mm diameter were arranged in three different configurations: (i) the right and left side walls have the pinhole outlets, while the front and back side walls did not, (ii) the distance between the nearest neighbor pinholes was less than 1.5 cm and (iii) the pinhole arrays were at the depth of 3, 4.5 and 6 cm beneath the water surface. The water motion was studied by computational fluid dynamics and visualization, during the wafer operations. When 10 cm of the wafer bottom was immersed in the water, the calculation showed that 90% of the particles, released from the 1 cm depth beneath the water surface, was removed from the bath within 10 s. By observations throughout the sequential wafer operations of dipping, holding and lifting, the blue-colored tracer ink that had been painted at the wafer surface simply went toward the outlet without any considerable recirculation. The range of the water flow rate without causing any recirculation was additionally studied.

Two-axis XUV/SR Imaging System with Temporal-spatial Resolution for Wire Array Z-pinch on Qin-1

Qin-1 is a Z-pinch pulse power generator. Due to the diagnostic requirements of its wire array Z-pinch, a two-axis temporal-spatial resolution XUV/SR imaging system has been developed. The system is composed of filters, two gated pinhole cameras, and a synchronized electric control system. Each camera consists of a pinhole array, a four-frame microchannel plate image intensifier and a CMOS camera. The whole system can synchronously diagnose plasma from two directions with a time resolution of 3 ns. The spatial resolution of the system is approximately 51 μm when the diameter of the pinhole is 20 μm and incident radiation is greater than 455 eV. By using the system, the implosion of symmetric loads and asymmetric loads was investigated. The generation, ablation and compression of the coronal plasma and instabilities in the implosion axis at stagnation can be directly observed from two views. The results indicated that the position of the implosion axis is related to the mass distribution of the wire array and provided more details about bright spots on individual wire arrays. In addition, the diagnostic results of a single wire with energy resolution were acquired.

Angular-Resolved Thomson Parabola Spectrometer for Laser-Driven Ion Accelerators.

This article reports the development, construction, and experimental test of an angle-resolved Thomson parabola (TP) spectrometer for laser-accelerated multi-MeV ion beams in order to distinguish between ionic species with different charge-to-mass ratio. High repetition rate (HHR) compatibility is guaranteed by the use of a microchannel plate (MCP) as active particle detector. The angular resolving power, which is achieved due to an array of entrance pinholes, can be simply adjusted by modifying the geometry of the experiment and/or the pinhole array itself. The analysis procedure allows for different ion traces to cross on the detector plane, which greatly enhances the flexibility and capabilities of the detector. A full characterization of the TP magnetic field is implemented into a relativistic code developed for the trajectory calculation of each pinhole beamlet. We describe the first test of the spectrometer at the VEGA 3 laser facility at CLPU, Salamanca (Spain), where up to protons and carbon ions from a laser-irradiated Al foil are detected.

A method to measure the uniformity of the virtual image distance in an augmented reality or virtual reality device

AbstractThe virtual image distance in an augmented reality (AR) or virtual reality (VR) device is an important factor in determining its performance. In this paper, a method for measuring the virtual image distance and its uniformity is proposed. The setup for measurement consists of a two‐dimensional spatial sensor array on the translational stage and a pinhole array plate placed in front of the AR or VR device. As the distance between the pinhole plate and the two‐dimensional spatial sensor array were changed, the positions of the rays through each pinhole were measured by a two‐dimensional spatial sensor array. The ray trajectories through each pinhole were obtained by fitting these positions to straight lines. The relative distances between these ray trajectories were calculated with respect to the distance from the pinhole plate. This method is effective for measuring the uniformity, such as the azimuthal dependence of the virtual image distance or the dependence of the virtual image distance on the distance from the optical axis of the VR lens.