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[ACM Press the 24th ACM Symposium - Tokyo, Japan (2018.11.28-2018.12.01)] Proceedings of the 24th ACM Symposium on Virtual Reality Software and Technology - VRST '18 - Dynamic HDR environment capture for mixed reality
摘要： Rendering accurate and convincing virtual content into mixed reality (MR) scenes requires detailed illumination information about the real environment. In existing MR systems, this information is often captured using light probes [1, 8, 9, 17, 19–21], or by reconstructing the real environment as a preprocess [31, 38, 54]. We present a method for capturing and updating a HDR radiance map of the real environment and tracking camera motion in real time using a self-contained camera system, without prior knowledge about the real scene. The method is capable of producing plausible results immediately and improving in quality as more of the scene is reconstructed. We demonstrate how this can be used to render convincing virtual objects whose illumination changes dynamically to reflect the changing real environment around them.
关键词： 3D Reconstruction,HDR,Mixed Reality
更新于2025-09-09 09:28:46
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The attenuated spline reconstruction technique for single photon emission computed tomography
摘要： We present the attenuated spline reconstruction technique (aSRT) which provides an innovative algorithm for single photon emission computed tomography (SPECT) image reconstruction. aSRT is based on an analytic formula of the inverse attenuated Radon transform. It involves the computation of the Hilbert transforms of the linear attenuation function and of two sinusoidal functions of the so-called attenuated sinogram. These computations are achieved by employing the attenuation information provided by computed tomography (CT) scans and by utilizing custom-made cubic spline interpolation. The purpose of this work is: (i) to present the mathematics of aSRT, (ii) to reconstruct simulated and real SPECT/CT data using aSRT and (iii) to evaluate aSRT by comparing it to filtered backprojection (FBP) and to ordered subsets expectation minimization (OSEM) reconstruction algorithms. Simulation studies were performed by using an image quality phantom and an appropriate attenuation map. Reconstructed images were generated for 45, 90 and 180 views over 360 degrees with 20 realizations and involved Poisson noise of three different levels (NL), namely 100% (NL1), 50% (NL2) and 10% (NL3) of the total counts, respectively. Moreover, real attenuated SPECT sinograms were reconstructed from a real study of a Jaszczak phantom, as well as from a real clinical myocardial SPECT/CT study. Comparisons between aSRT, FBP and OSEM reconstructions were performed using contrast, bias and image roughness. The results suggest that aSRT can efficiently produce accurate attenuation-corrected reconstructions for simulated and real phantoms, as well as for clinical data. In particular, in the case of the clinical myocardial study, aSRT produced reconstructions with higher cold contrast than both FBP and OSEM. aSRT, by incorporating the attenuation correction within itself, may provide an improved alternative to FBP. This is particularly promising for ‘cold’ regions as those occurring in myocardial ischaemia.
关键词： analytic image reconstruction,single photon emission computed tomography (SPECT),attenuated Radon transform
更新于2025-09-09 09:28:46
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Super-Resolution Reconstruction of Multi-Polarization Sar Images Based on Projections Onto Convex Sets Algorithm
摘要： Resolution is one of the important indices to measure the quality of SAR images. Super-resolution reconstruction is a widely adopted resolution enhancement method. Many algorithms have been developed for the super-resolution reconstruction. Among these algorithms, this paper applies projections onto convex sets algorithm to SAR image reconstruction processing. The POCS can efficiently obtain high-resolution SAR images with enhanced details. However, the POCS requires many low-resolution SAR images of the same area to gain a better result, usually 10 to 20 images. Such requirement is very difficult to achieve when only single-polarization mode is included. In this paper, we propose a novel method that utilizes all the polarimetric images of the same original SAR data for the algorithm. Thus, the number of the available images is increased exponentially. The experiment results have demonstrated the effectiveness of our proposed method: The reconstructed high-resolution SAR image based on multi-polarimetric information is more detailed and clearer than that based on single-polarization information.
关键词： super-resolution reconstruction,multi-polarization information,POCS algorithm,SAR image
更新于2025-09-09 09:28:46
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Guidelines for Underwater Image Enhancement Based on Benchmarking of Different Methods
摘要： Images obtained in an underwater environment are often affected by colour casting and suffer from poor visibility and lack of contrast. In the literature, there are many enhancement algorithms that improve different aspects of the underwater imagery. Each paper, when presenting a new algorithm or method, usually compares the proposed technique with some alternatives present in the current state of the art. There are no studies on the reliability of benchmarking methods, as the comparisons are based on various subjective and objective metrics. This paper would pave the way towards the definition of an effective methodology for the performance evaluation of the underwater image enhancement techniques. Moreover, this work could orientate the underwater community towards choosing which method can lead to the best results for a given task in different underwater conditions. In particular, we selected five well-known methods from the state of the art and used them to enhance a dataset of images produced in various underwater sites with different conditions of depth, turbidity, and lighting. These enhanced images were evaluated by means of three different approaches: objective metrics often adopted in the related literature, a panel of experts in the underwater field, and an evaluation based on the results of 3D reconstructions.
关键词： automatic colour equalization,3D reconstruction,non-local dehazing,benchmark,lab,colour correction,screened poisson equation,CLAHE,underwater image enhancement,dehazing
更新于2025-09-09 09:28:46
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Direct Reconstruction of the Quantum Density Matrix by Strong Measurements
摘要： New techniques based on weak measurements have recently been introduced to the field of quantum state reconstruction. Some of them allow the direct measurement of each matrix element of an unknown density operator and need only OedT different operations, compared to d2 linearly independent projectors in the case of standard quantum state tomography, for the reconstruction of an arbitrary mixed state. However, due to the weakness of these couplings, these protocols are approximated and prone to large statistical errors. We propose a method which is similar to the weak measurement protocols but works regardless of the coupling strength: our protocol is not approximated and thus improves the accuracy and precision of the results with respect to weak measurement schemes. We experimentally apply it to the polarization state of single photons and compare the results to those of preexisting methods for different values of the coupling strength. Our results show that our method outperforms previous proposals in terms of accuracy and statistical errors.
关键词： weak measurements,quantum state tomography,quantum state reconstruction,strong measurements,density operator
更新于2025-09-09 09:28:46
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REGULARIZATION IMAGING ALGORITHM WITH ACCURATE G MATRIX FOR NEAR-FIELD MMW SYNTHETIC APERTURE IMAGING RADIOMETER
摘要： In order to improve the reconstruction accuracy of near-?eld SAIR, a novel regularization imaging algorithm based on an accurate G matrix is proposed in this paper. Due to the fact that the regularization reconstruction is usually an underdetermined problem, inaccurate operation matrix G will lead to great reconstruction error in the imaging results, or even the normal imaging cannot be obtained. In this paper, we establish an accurate G matrix based on the accurate imaging model of near-?eld SAIR. Compared with the traditional G matrix with some unnecessary approximations, the proposed G matrix without approximation can improve the reconstruction accuracy e?ectively. For improving the accuracy of matrix G further, the corresponding parameters are corrected according to the RMSE between the imaging results of the regularization method and modi?ed FFT method which is not sensitive to the parameters’ change. The e?ectiveness of this calibration method has been tested by 1D simulation experiments. Moreover, the 2D simulation experiments demonstrate that the proposed accurate G matrix can improve the imaging accuracy of regularization method e?ectively. Finally, the 1D imaging experiment is performed to test the e?ectiveness of the proposed method for the actual synthetic aperture imaging further.
关键词： near-field MMW synthetic aperture imaging radiometer,Regularization imaging algorithm,accurate G matrix,reconstruction accuracy
更新于2025-09-09 09:28:46
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Cranial anatomy of the gorgonopsian Cynariops robustus based on CT-reconstruction
摘要： Gorgonopsia is one of the major clades of non-mammalian synapsids, and includes an array of large-bodied carnivores that were the top terrestrial predators of the late Permian. Most research on the clade has focused on these largest members; small-bodied gorgonopsians are relatively little-studied. Here, we redescribe a small gorgonopsian skull (MB. R.999) from the late Permian (Tropidostoma Assemblage Zone) of South Africa on the basis of neutron and synchrotron CT reconstructions, which yield new data on internal cranial morphology in Gorgonopsia. Because of the largely undistorted nature of MB.R.999, we were also able to reconstruct unossified areas such as the brain endocast and the otic labyrinth. MB.R.999 can be referred to the taxon Cynariops robustus based on its general skull proportions, postcanine tooth count, preparietal morphology, and vomerine morphology. We refer additional small gorgonopsian specimens from the Victoria West area to Cynariops robustus, and consider Cynarioides grimbeeki and Cynarioides laticeps to be synonymous with C. robustus. Inclusion of Cynariops in a phylogenetic analysis of Gorgonopsia recovers it within a large clade of African taxa, more closely related to Lycaenops and rubidgeines than Eriphostoma or Gorgonops.
关键词： cranial anatomy,late Permian,CT-reconstruction,Gorgonopsia,Cynariops robustus
更新于2025-09-09 09:28:46
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Forensic Imaging for Causal Investigation of Death
摘要： A 63-year-old man was found in the street after overrun by a car. Postmortem CT revealed multiple bone fractures, but surprisingly all without any relevant hemorrhage which would have been expected under such circumstances. A round radiopaque formation was found in the duodenum, which was reminiscent of ingested tablets. The toxicological analysis revealed high concentrations of zopiclone and alcohol. By combining radiologic and forensic results, zopiclone and alcohol intoxication were concluded as the cause of death, followed by a postmortem overrun accident.
关键词： Forensic imaging,Computed tomography,Pre-autopsy CT,Forensic reconstruction,Virtopsy
更新于2025-09-09 09:28:46
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Discrete Total Variation with Finite Elements and Applications to Imaging
摘要： The total variation (TV)-seminorm is considered for piecewise polynomial, globally discontinuous (DG) and continuous (CG) finite element functions on simplicial meshes. A novel, discrete variant (DTV) based on a nodal quadrature formula is defined. DTV has favorable properties, compared to the original TV-seminorm for finite element functions. These include a convenient dual representation in terms of the supremum over the space of Raviart–Thomas finite element functions, subject to a set of simple constraints. It can therefore be shown that a variety of algorithms for classical image reconstruction problems, including TV-L 2 denoising and inpainting, can be implemented in low- and higher-order finite element spaces with the same efficiency as their counterparts originally developed for images on Cartesian grids.
关键词： Image reconstruction,Discrete total variation,Dual problem,Numerical algorithms
更新于2025-09-09 09:28:46
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Lattice considerations for the use of an X-band transverse deflecting structure (TDS) at SINBAD, DESY
摘要： An X-band TDS is a well-known device for the characterization of the longitudinal properties of an electron bunch in a linear accelerator. It is planned that a novel X-band TDS with variable polarization will be installed within the next few years at SINBAD, an upcoming accelerator R&D facility at DESY. There are several measurements that can be performed with the TDS, each with specific optics requirements to reach the highest possible resolution and keep induced energy spread to a tolerable level. Quadrupoles will be installed between the TDS and the screen to help satisfy these conditions. In this paper, the requirements for the bunch length measurements, a novel 3D charge density reconstruction technique and slice energy measurements are discussed and some simulation results for the slice energy measurement using example lattices are presented.
关键词： DESY,slice energy measurements,X-band TDS,3D charge density reconstruction,electron bunch,longitudinal properties,SINBAD
更新于2025-09-09 09:28:46