Pinhole Imaging System Research Articles

Unsupervised deep learning method for single image super-resolution of the thick pinhole imaging system using deep image prior

Thick pinhole imaging system is widely used for diagnosing intense pulsed radiation sources. However, owing to the trade-off among spatial resolution, field of view (FOV) and signal-to-noise ratio (SNR), the imaging system normally falls short in achieving high-precision spatial diagnosis. In this paper, we propose an unsupervised deep learning method for single image super-resolution (SISR) of the thick pinhole imaging system. The point spread function (PSF) of the imaging system is obtained by analytical calculation and Monte Carlo simulation methods, and the mathematical model of the imaging system is established using a linear equation. To solve the ill-posed inverse problem, we adopt randomly initialized deep convolutional neural networks (DCNNs) as an image prior without pre-training, which is named deep image prior (DIP). The results demonstrate that, by utilizing the SISR technique to increase the number of pixels in reconstructed images, the proposed DIP algorithm can mitigate the spatial resolution degradation caused by an insufficient spatial sampling frequency of the camera. Compared with various classical algorithms, the proposed DIP algorithm exhibits superior capabilities in recovering high-frequency signals and suppressing ringing artifacts. Furthermore, the convergence and robustness of the proposed DIP algorithm under different random seeds and SNR conditions are also verified.

Characterization of experimental and simulated micrometer-scale soft x-ray-emitting laser plasmas: Toward predictive radiance calculations

Experimentally generated and simulated soft x-ray plasma images and spectra from 1064 nm-driven laser-produced plasmas from slab tin are presented. Produced are small, micrometer-scale emission volumes with principle imaged emission lying between 1.2 and 2.5 nm. Experimental images of the soft x-ray emission of these plasmas are generated using a pinhole imaging system, which enables spatial characterization of the plasmas, and a simple transmission grating spectrometer with a 100 nm pitch grating is used to facilitate the spectral characterization of these plasmas. Plasmas are simulated under similar experimental conditions to those used with the single-fluid, single-temperature radiation-hydrodynamics code RALEF-2D. Coupling the simulation output with optical modeling methods demonstrates its promise as a capability for modeling the spatial and spectral behavior of soft x-ray-emitting tin plasmas at such scales and laser energies.

Super-resolution image reconstruction of a neutron thick pinhole imaging system using image denoiser prior based on half quadratic splitting method

Thick pinhole imaging system is a powerful tool to diagnose intense pulsed radiation sources. However, high spatial resolution of a thick pinhole imaging system cannot be achieved due to the limitation of field of view (FOV) and detection efficiency. In this paper, we propose a novel super-resolution image reconstruction algorithm to improve the spatial resolution of a practical thick pinhole imaging system designed for 14.1 MeV neutrons with 100 mm FOV. Point spread function (PSF) of the imaging system is obtained through complete simulation methods, indicating that the spatial resolution of the imaging system is about 500 μ m. A 4 × super-resolution image reconstruction algorithm using image denoiser as implicit image prior, named image denoiser prior, based on half quadratic splitting (HQS) method is firstly applied to restore more details of neutron sources. The results show that the proposed algorithm performs better than the Richardson-Lucy (RL) algorithm with fewer artifacts and sharper boundaries in reconstructed images. Notably, at a low noise level, the proposed algorithm can surpass the Nyquist sampling limit of 200 μ m, which is determined by the equivalent camera pixel size, to achieve a spatial resolution of 150 μ m.

Full Field X-Ray Scatter Tomography.

In X-ray imaging, photons are transmitted through and absorbed by the target object, but are also scattered in significant quantities. Previous attempts to use scattered X-ray photons for imaging applications used pencil or fan beam illumination. Here we present 3D X-ray Scatter Tomography using full-field illumination for small-animal imaging. Synchrotron imaging experiments were performed on a phantom and the chest of a juvenile rat. Transmitted and scattered photons were simultaneously imaged with separate cameras; a scientific camera directly downstream of the sample stage, and a pixelated detector with a pinhole imaging system placed at 45° to the beam axis. We obtained scatter tomogram feature fidelity sufficient for segmentation of the lungs and major airways in the rat. The image contrast in the scatter tomogram slices approached that of transmission imaging, indicating robustness to the amount of multiple scattering present in our case. This opens the possibility of augmenting full-field 2D imaging systems with additional scatter detectors to obtain complementary modes or to improve the fidelity of existing images without additional dose, potentially leading to single-shot or reduced-angle tomography or overall dose reduction for live animal studies.

Imaging and reconstruction of high-energy proton beam spot before target based on secondary gamma rays.

The distribution and stability of the incident proton beam spot are critical for the stable operation of a high-power spallation target. This study proposes a method to capture images of the incident proton beam spot based on secondary gamma rays. The distribution of the backward secondary gamma rays irradiated by the primary proton beam on the incident surface of the target is close to the distribution of the protons and can be measured at a low-radiation position far from the target area. A relation of distributions between the incident protons and the secondary gammas is constructed by using the point response function of this pinhole imaging system. The proposed method of imaging is suitable for monitoring the distribution of the proton beam on the target in facilities that use a beam power of several megawatts or tens of megawatts, such as spallation neutron sources or accelerator-driven subcritical systems.

A time-resolved imaging system for the diagnosis of x-ray self-emission in high energy density physics experiments.

A diagnostic capable of recording spatially and temporally resolved x-ray self-emission data was developed to characterize experiments on the MAGPIE pulsed-power generator. The diagnostic used two separate imaging systems: a pinhole imaging system with two-dimensional spatial resolution and a slit imaging system with one-dimensional spatial resolution. The two-dimensional imaging system imaged light onto the image plate. The one-dimensional imaging system imaged light onto the same piece of image plate and a linear array of silicon photodiodes. This designallowed the cross-comparison of different images, allowing a picture of the spatial and temporal distribution of x-ray self-emission to be established. The designwas tested in a series of pulsed-power-driven magnetic-reconnection experiments.

Real-Time Beam Detection and Tracking From Pinhole Imaging System Based on Machine Learning

Real-Time Beam Detection and Tracking From Pinhole Imaging System Based on Machine Learning

7.2: A Novel FOD Solution with High‐PPI Flexible Sensor under OLED Panel

A novel FOD solution is presented in this paper. TFT‐based flexible photo sensors of 725 PPI and 1016 PPI were developed and characterized. Adapted to the OLED panel with integrated pinhole imaging system, the feasibility of large area FOD function was confirmed.

36‐5: A Novel FOD Solution with High‐PPI Flexible Sensor under OLED Panel

A novel FOD solution is presented in this paper. TFT‐based flexible photo sensors of 725 PPI and 1016 PPI were developed and characterized. Adapted to the OLED panel with integrated pinhole imaging system, the feasibility of large area FOD function was confirmed.

Pulsed-power-driven cylindrical aluminium liner implosions with a high aspect ratio at an 8 MA facility

First experimental investigations of foil aluminium liner implosions with a high aspect ratio of ∼ 103 at an 8 MA pulsed-power facility in China, motivated by possible application for magneto-inertial fusion, will be reported. Key diagnostics including UV cameras, micro-magnetic probes and x-ray pinhole imaging systems were fielded. Quasi-monochromatic UV images and optical streak data showed localized plasma formation at breakdown positions, suggesting that vacuum gaps in contact play a crucial role in long-time and non-uniform initiation. In liner ablation, quasi-periodic striation patterns were directly observed in UV self-emission images and were found to be azimuthally correlated with Rayleigh–Taylor instabilities. An m ≠ 0 azimuthal helical mode was obtained for the unmagnetized liner, which could be attributed to the large surface roughness that may act as an inherently and randomly seeded instability. Precursor plasma formation was confirmed by the observed x-ray emission on-axis at −70 ns by the end-on x-ray framing camera. Further quantitative current measurements taken by micro magnetic probes suggested that the current division due to precursor plasma was approximately 20% of the load current at −66 ns. Side-on imaging diagnostics indicated an evident liner implosion, however with a relatively low convergence ratio of ∼ 3.2 at stagnation. For the observed emission rings with much faster velocity in end-on x-ray images, possible mechanisms were discussed.

Automated source tracking with a pinhole imaging system during high-dose-rate brachytherapy treatment

The transportation accuracy of sealed radioisotope sources influences the therapeutic effect of high-dose-rate (HDR) brachytherapy. We have developed a pinhole imaging system for tracking an Ir-192 radiation source during HDR brachytherapy treatment. Our system consists of a dual-pinhole collimator, a scintillator, and a charge-coupled device (CCD) camera. We acquired stereo-shifted images to infer the source position in three dimensions using a dual pinhole collimator with 1.0 mm diameter pinholes. The CCD camera captured consecutive images of scintillation light that corresponds to the source positions every 2 s. The system automatically tracks scintillation light points using template-matching technique and measured the source positions therefrom. By integrating a series of CCD images, we could infer the source dwell time from the pixel values in the integrated image.We investigated the tracking accuracy of our system in monitoring simulated brachytherapy as it would be performed for cervical cancer by using water as a stand-in for human tissue. Ir-192 pellet was moved through a water tank using tandem and ovoid applicators. The CCD camera captured clear images of the scintillation light produced by the underwater Ir-192 source in conditions equivalent to common clinical situations. The differences between the measured and the reference 3D source positions and dwell times were 1.5 ± 0.7 mm and 0.8 ± 0.4 s, respectively.This system has the potential to track in vivo Ir-192 source in real time and may prove a useful tool for quality assurance during HDR brachytherapy treatments in clinical settings.

Transient Radiation Imaging Based on a ZnO:Ga Single-Crystal Image Converter

A ZnO:Ga single crystal with an applicable size of φ40 × 1 mm was prepared using the hydro-thermal method. The crystal exhibits good crystallinity and scintillation properties with a 63.94-arcsec full-width at half-maximum (FWHM) in the X-ray rocking curve (XRC) spectrum, 8% luminous non-uniformity, emission at 389 nm in the X-ray excited luminescence spectrum, fast response and 5.5% BGO luminous intensity. Furthermore, an X-ray pinhole imaging system of nanosecond temporal resolution with a ZnO:Ga single-crystal image converter was established to diagnose the cathode electron emission spatial distribution of an intense current diode. Results for shutter times of 4 μs and 5 ns were obtained, which directly represent the cathode electron spatial distribution throughout the entire pulse duration and during a certain moment of the pulse, respectively. The results demonstrate that the large ZnO:Ga single crystal can diagnose the spatial distribution of cathode electron emission in an intense current diode with high temporal resolution and provide new solutions for high-temporal-resolution diagnosis of a pulse radiation field.

A novel X-ray spectrometer for plasma hot spot diagnosis

A novel X-ray spectrometer is designed to diagnose the different conditions in plasmas. It can provide both X-ray spectroscopy and plasma image information simultaneously. Two pairs of elliptical crystal analyzers are used to measure the X-ray spectroscopy in the range of 2–20 keV. The pinhole imaging system coupled with gated micro-channel plate(MCP) detectors are developed, which allows 20 images to be collected in a single individual experiment. The experiments of measuring spectra were conducted at “Shenguang-II upgraded laser” in China Academy of Engineering Physics to demonstrate the utility of the spectrometer. The X-ray spectroscopy information was obtained by the image plate(IP). The hot spot imaging experiments were carried out at “Shenguang-III prototype facility”. We have obtained the hot sport images with the spectrometer, and the signal to noise ratio of 30∼40 is observed.

Proton pinhole imaging on the National Ignition Facility.

Pinhole imaging of large (mm scale) carbon-deuterium (CD) plasmas by proton self-emission has been used for the first time to study the microphysics of shock formation, which is of astrophysical relevance. The 3 MeV deuterium-deuterium (DD) fusion proton self-emission from these plasmas is imaged using a novel pinhole imaging system, with up to five different 1 mm diameter pinholes positioned 25 cm from target-chamber center. CR39 is used as the detector medium, positioned at 100 cm distance from the pinhole for a magnification of 4 ×. A Wiener deconvolution algorithm is numerically demonstrated and used to interpret the images. When the spatial morphology is known, this algorithm accurately reproduces the size of features larger than about half the pinhole diameter. For these astrophysical plasma experiments on the National Ignition Facility, this provides a strong constraint on simulation modeling of the experiment.

偏离中心入射的γ针孔成像系统点扩展函数

The Point Spread Function(PSF)of a pinhole imaging system forγ-Ray has been studied through Monte Carlo method.The PSFs under 0,0.5,1,1.5 and 2 pixel bias five different conditions have been obtained and analyzed by fitting the simulating data with Gauss function,the corresponding Modulation Transfer Function(MTF)can be obtained,and the spatial resolutions under these five conditions are compared.As the results show,when the excursion is little,the PSF′deviation obtained by Gauss function fitting will be less and can meet the requirement of accuracy,but when the excursion is larger,the fitting deviation will be more.In addition,a ideal baffle between pinhole and detector will reduce the error and improve the spatial resolution remarkably.

Experimental Image of Pinhole Using CdZnTe Detector

The imaging detector of the nuclear radiation is applied widely in radiation detection, the safety monitor and nuclear medical imaging. We aimed to make scientific researches on nuclear radiant source through the pinhole imaging system .The imaging system was designed that base on the Imarad 16×16 pixel-array CdZnTe semiconductor detector. The detector has high sensitivity to low energy under 200kev at room temperature. We applied the detector and pinhole system to obtain the image of the radiant source that the energy was up 200kev.The detection efficiencies of 38.92 mm×38.92 mm by 5 mm thick CdZnTe pixel-array detector were measured. The capability of the whole system was test and evaluated. The rough image of the radiant source was achieved through the test. When the location of the source and pinhole parameter were changed, the image would vary correspondingly. The accurate image could acquired by means of image reconstruction .So it is feasible that the research about the localization and qualification of the nuclear radiation is making use of the pinhole system.

Study of Supper Resolution Processing Methods for Thick Pinhole Image

An image super resolution reconstruction method was used to improve the spatial resolution of the thick pinhole imaging system and to mitigate the limitations of the image spatial resolution of the hardware of the image diagnostic system. The thick pinhole is usually applied into the diagnostics of the high energy neutron radiation image. Due to the impacts among its energy flux, spatial resolution and effective field of view, in dealing with the large area radiation source, the spatial resolution of the thick pinhole neutron image cannot meet the requirements for high precision modeling of the radiation source image. In this paper, the Lucy-Richardson image super resolution reconstruction method was used to simulate the thick pinhole imaging and super resolution image reconstruction. And the spatial resolution of the image could be increased by over three times after the image super resolution reconstruction. Besides, in dealing with the pseudo-noise, plum blossom shape appeared in the image super resolution reconstruction. The analysis of the source of the pseudo-noise was made based on the simulation of the image reconstruction under various conditions according to the characteristics of the thick pinhole image configuration.

Modelling image profiles produced with a small field of view gamma camera with a single pinhole collimator

Gamma cameras making use of parallel-hole collimators have a long history in medical imaging. Pinhole collimators were used in the original gamma camera instruments and have been used more recently in dedicated organ specific systems, intraoperative instruments and for small animal imaging, providing higher resolution over a smaller field of view than the traditional large field of view systems.With the resurgence of interest in the use of pinhole collimators for small field of view (SOV) medical gamma cameras, it is important to be able to accurately determine their response under various conditions. Several analytical approaches to pinhole response have been reported in the literature including models of 3D pinhole imaging systems. Success has also been reported in the use of Monte Carlo simulations; however this approach can require significant time and computing power.This report describes a 2D model that was used to investigate some common problems in pinhole imaging, the variation in resolution over the field of view and the use of `point' sources for quantifying pinhole response.

Parameters Evaluation of Neutron Pinhole Imaging System Based on Geant4

Neutron imaging by large pinhole is an important part for image acquisition and high-speed transmission in process of fast radiation. In order to get desirable results in experiments, it is necessary to judge performance of various designs qualitatively or quantitatively before experiments. In this paper, we simulate the millimeter-level pinhole imaging system based on Geant4 and analyze the effects of system parameters on imaging. The numerical results can provide theoretical foundation for system designing and simulation data for image analyzing.

神光原型诊断设备：门控针孔分幅相机的研制

In order to install an X-ray Pinhole Framing Camera(X-PFC) conveniently and run smoothly in the SG3 prototype system(SG3-PS) of Inertial Confinement Fusion(ICF),a novel type X-PFC was developed on the basis of original models and a conical barrel pinhole imaging system was desined to eliminate the stray light and to obtain the pinhole imaging in the SG3-PS.The matching parameters were evidently improved by designing a long micro-strip in new tube,which could keep the number of imagings to be still 16 frames in the limited space by using new type fluorescent screen,steady clamp method and the way of sealing up with two optics fiber plates.The save quality of new tube was improved greatly by gating pulse voltage on the screen.Furthermore,the high-voltage pulse generators and all of monitoring facilities were assembled in the cylinder barrel type vacuum seal configuration by PC104.Experiments show that all kinds of technical indexes have been upgraded when some parts of the new camera structure are redesigned and experimental results are received better.