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- 2018
- railway track
- kinematic characteristics
- stereo vision
- image blur
- distance estimation
- control system
- depth of field
- video monitoring
- hollows classification
- RGB-D camera
- Optoelectronic Information Science and Engineering
- Chongqing University of Posts and Telecommunications
- Bauman Moscow State Technical University
- Moscow State University of Railway Engineering
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Design and Analysis of Multilayer Solenoid Coil for Faraday Modulator
摘要： A well-designed polarimeter is integral to the realization of the highly sensitive atomic magnetometer. Amongst various detection schemes, optical polarimetry based on Faraday modulator is most commonly used owing to its angular sensitivity at low-frequency range. The multilayered solenoid coil is the key component of Faraday effect based optical detection system. This paper primarily deals with design and analysis of multilayered coil of Faraday modulator. All deterministic parameters that affect the optimum design have been identified and analyzed. Mathematical expressions have been obtained for axial field homogeneity; modulation depth and power dissipation manifesting direct dependence on coil geometry. The design parameters of the coil are optimized with respect to axial magnetic field homogeneity over region of interest and reduced power losses with suitable geometric construction. The influence of different geometrical and electromagnetic parameters on optimum design has been highlighted and guidelines for design procedure are given. Theoretical results have been compared with simulation and experimental results. The mathematical formulation could be implemented in a computer program for recurrence design and to assist the realization of an optimized design of Faraday modulator coil.
关键词： solenoid coil,Faraday modulator,modulation depth,magnetic field homogeneity,power dissipation
更新于2025-09-23 15:19:57
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[IEEE 2018 25th IEEE International Conference on Image Processing (ICIP) - Athens (2018.10.7-2018.10.10)] 2018 25th IEEE International Conference on Image Processing (ICIP) - Motion Occlusions for Automatic Generation of Relative Depth Maps
摘要： Recovering of the depth structure of a scene from monocular video content provides an important advantage in applications such as AR (placing and removing of objects) or 3D-TV and 3D cinema (2D-to-3D video conversion). In this paper, we present an automatic method to generate relative depth maps from monocular video sequences. It relies on the dynamic occlusion depth cue to recover the depth order of objects in the scene. The forward and backward motion analysis between each two consecutive frames allows the calculation of their dynamic occlusions. We estimate the motion using a modified version of the EpicFlow. Our modifications to this optical flow method made it coherent in forward-backward directions without compromising its performance. Thanks to this new feature, occlusions are simpler to calculate than the approaches used in the relevant literature. The obtained occlusions allow order deduction of the objects contained in the image. These objects are obtained using a segmentation approach which considers both color and motion. Ours results show a small improvement to the quality of the optical flow while adding the forward/backward coherence. With respect to the depth ordering our approach obtains slightly better results than the reference method while removing a computationally costly step from the processing.
关键词： depth ordering,occlusions,segmentation,relative depth map
更新于2025-09-19 17:15:36
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Evaluation of patients with diffuse unilateral subacute neuroretinitis by spectral domain optical coherence tomography with enhanced depth imaging
摘要： Background: The purpose of this study was to determine the value of spectral domain optical coherence tomography (SD-OCT) in assessing patients with diffuse unilateral subacute neuroretinitis (DUSN). Methods: This was an observational case series with clinical imaging correlation performed at the Retina and Vitreous Institute of Londrina and State University of Londrina, Paraná, Brazil. The series comprised ten consecutive patients with a confirmed diagnosis of DUSN, ie, seven patients with late-stage disease and three with early-stage disease, who were assessed by SD-OCT for mean macular, retinal nerve fiber layer, and choroidal thickness using enhanced depth imaging software. Results: Comparing the affected eye with the healthy fellow eye, significant diffuse atrophy of the retinal layers with a decrease in mean macular (P=0.004) and retinal nerve fiber layer (P=0.002) thickness was found in all cases. There was no difference in choroidal thickness (P=0.262). Conclusion: The correlation of SD-OCT results with central vision and funduscopic findings may explain the profound loss of visual function in patients with DUSN.
关键词： enhanced depth imaging,diffuse unilateral subacute neuroretinitis,optical coherence tomography,eye infections,parasitic,retinitis
更新于2025-09-19 17:15:36
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First prototyping of a dedicated PET system with the hemisphere detector arrangement
摘要： A strong demand is expected for high-sensitivity, high-resolution, and low-cost brain positron emission tomography (PET) imaging for early diagnosis of dementia as well as for general neuroscience studies. Therefore, we have proposed novel geometries of a hemisphere detector arrangement for high-sensitivity brain imaging, in which an add-on detector at the chin position or neck position helps in sensitivity uniformity improvement. In this study, we developed the first prototype system for proof-of-concept using 4-layer depth-of-interaction detectors, each of which consisted of 16×16×4 Zr-doped GSO crystals with dimensions of 2.8×2.8×7.5 mm3 and a high-sensitivity 64-channel flat-panel photomultiplier tube. We used 47 detectors to form a hemisphere detector with a hemisphere shape of 25 cm inner diameter and 50 cm outer diameter, and we used seven detectors for each of the add-on detectors. The hemisphere detector was realized by multiple rings having different numbers of detectors and a cross-shaped top detector unit covering the top. Performance evaluation showed uniform spatial resolutions of 3-4 mm by the filtered back-projection method. Peak sensitivity was measured as more than 10% at a region near the top of the head, which was achieved with the help of the top detector unit. In addition, using the prototype system, we performed the first FDG clinical test with a healthy volunteer. The results showed that the proposed geometries had high potential for realizing high-sensitivity, high-resolution, and low-cost brain PET imaging. As for the add-on detector position, it was shown that the neck position resulted in higher sensitivity and wider field of view (FOV) than the chin position because the add-on detector at the neck position can be placed continuously to the hemisphere detector and close to the FOV.
关键词： brain imaging,helmet-type PET,dementia,positron emission tomography,brain PET,depth-of-interaction
更新于2025-09-19 17:15:36
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[ACM Press SIGGRAPH ASIA 2016 Symposium on Visualization - Macau (2016.12.05-2016.12.08)] SIGGRAPH ASIA 2016 Symposium on Visualization on - SA '16 - Evaluating the perception of semi-transparent structures in direct volume rendering techniques
摘要： Direct volume rendering (DVR) provides the possibility to visualize volumetric data sets as they occur in many scientific disciplines. A key benefit of DVR is that semi-transparency can be facilitated in order to convey the complexity of the visualized data. Unfortunately, semi-transparency introduces new challenges in spatial comprehension of the visualized data, as the ambiguities inherent to semi-transparent representations affect spatial comprehension. Accordingly, many visualization techniques have been introduced to enhance the spatial comprehension of DVR images. In this paper, we conduct a user evaluation in which we compare standard DVR with five visualization techniques which have been proposed to enhance the spatial comprehension of DVR images. In our study, we investigate the perceptual performance of these techniques and compare them against each other to find out which technique is most suitable for different types of data and purposes. In order to do this, a large-scale user study was conducted with 300 participants who completed a number of micro-tasks designed such that the aggregated feedback gives us insight on how well these techniques aid the end user to perceive depth and shape of objects. Within this paper we discuss the tested techniques, present the conducted study and analyze the retrieved results.
关键词： Volume rendering,transparency,depth perception
更新于2025-09-19 17:15:36
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Reconstructing 3D Face Models by Incremental Aggregation and Refinement of Depth Frames
摘要： Face recognition from two-dimensional (2D) still images and videos is quite successful even with “in the wild” conditions. Instead, less consolidated results are available for the cases in which face data come from non-conventional cameras, such as infrared or depth. In this article, we investigate this latter scenario assuming that a low-resolution depth camera is used to perform face recognition in an uncooperative context. To this end, we propose, first, to automatically select a set of frames from the depth sequence of the camera because they provide a good view of the face in terms of pose and distance. Then, we design a progressive refinement approach to reconstruct a higher-resolution model from the selected low-resolution frames. This process accounts for the anisotropic error of the existing points in the current 3D model and the points in a newly acquired frame so that the refinement step can progressively adjust the point positions in the model using a Kalman-like estimation. The quality of the reconstructed model is evaluated by considering the error between the reconstructed models and their corresponding high-resolution scans used as ground truth. In addition, we performed face recognition using the reconstructed models as probes against a gallery of reconstructed models and a gallery with high-resolution scans. The obtained results confirm the possibility to effectively use the reconstructed models for the face recognition task.
关键词： anisotropic error,3D reconstruction,3D face recognition,Depth data
更新于2025-09-19 17:15:36
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Luminescence and dielectric properties of Ni2+ ions added to calcio yttria borophosphate glasses for optoelectronic uses
摘要： Glass materials of composition CaO – Y2O3 – B2O3 – P2O5 added with different concentrations of NiO (Ni2+: CYBP) are synthesized by conventional rapid melt quenching method. Various physical properties of these glasses such as polaron radius (rp), molar volume (Vm), optical basicity (Λth) and refractive index (μ) are studied. As an elastic characterization Young’s modulus (Y), Poison ratio (σ) and micro hardness (H) of these glasses are studied. These grades suggest that the prepared materials are mechanically hard and exhibiting covalently interlinked structure. Further these samples are characterized by various techniques such as differential thermal analysis, thermoluminiscence, optical absorption, photoluminescence, Ionic conductivity and dielectric dispersion. The thermoluminiscence grades such as peak temperature maximum (Tm), shape symmetry factor (μsf) and activation energies ( Eτ, Eδ and Eω) are studied at various UV irradiation levels. These results strongly recommended that the both electron and hole trap centers were created at the deeper trap levels and contribute higher orders of thermoluminiscence emission with in these glasses subjected to higher orders of temperature and UV irradiation. The various optical absorption and photoluminescence factor's such as, optical band gap (Eo), nephelauxetic ratio (β), emission cross section (Ω), branching ratio (ζ) and radiative life times (τ) are studied. These grades found to be maximum for the material which has 0.5 mol% of NiO concentration may be most suggestible for optoelectronic application. The dc and ac conductivity (σdc & σac) of these glasses are estimated. The various dielectric parameter’s such as loss tangent (Tan (φ)), temperature region of relaxation (ΔT), density of states near Fermi level (N(Ef)), activation energies of both dipoles and conduction (Ed & Ec) are also calculated. These reports clearly disclose that the octahedrally located Ni2+ ions are increasing with increase NiO concentration with in present calcio yttria borophosphate glasses.
关键词： emission cross section,nephelauxetic ratio,micro hardness,trap depth parameters,Ni2+: CYBP glass materials,temperature region of relaxation
更新于2025-09-19 17:15:36
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Development of the X’tal Cube PET Detector With Segments of (0.77 mm) <sup>3</sup>
摘要： The depth-of-interaction detector which can identify gamma-ray detection position along the depth direction is essential for a PET scanner to reduce parallax error. The X’tal cube we have developed is composed of a scintillation crystal block segmented into cubes. Six arrays of multipixel photon counters (MPPCs) cover six surfaces of the crystal block. We developed the new X’tal cube consisting of 0.77 mm cubic segments. A (13.1 mm)3 LYSO crystal block had 3-D segmentation in a 17 × 17 × 17 array fabricated by the laser engraving technique. 4 × 4 MPPC arrays with a size of (13 mm)2 were used. Active area of each MPPC was (3.0 mm)2. To evaluate segment identification performance, we irradiated with gamma-rays from a 22Na source and obtained a 3-D position histogram made by the 3-D Anger-type calculation with all MPPC signals. The histogram showed 17 segments in a row can be identified clearly. Further, to measure its intrinsic spatial resolution with incident angles of 0° and 45°, gamma-rays in a fan-beam were irradiated and scanned onto the X’tal cube. Spatial resolutions of 0.74 ± 0.10 mm and 0.89 ± 0.10 mm were obtained by both scan experiments, respectively.
关键词： X’tal cube,submillimeter resolution,Depth-of-interaction (DOI) detector
更新于2025-09-19 17:15:36
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Experimental study on the 3D-flow field of a free-surface vortex using stereo PIV
摘要： In order to analyse the flow characteristics of free-surface vortexes and to validate the Burgers vortex model by using stereo particle image velocimetry, experiments are conducted in a 600 mm diameter vortex tank. Measured axial velocities indicate that 10–25% of the flow is transported through the vortex core. The velocity profiles show that the axial flow is concentrated in a domain bounded by two times the core radius. Despite Burgers’ assumption of radially independent axial velocity profiles, the model quantifies the tangential velocity profile within a relative uncertainty of circa 10%. The measurements show that it seems valid to use Burgers’ model to obtain an estimate for the core radius by taking the average axial velocity over a radial domain of approximately 2.2 times the core radius. The Burgers model quantifies the air core depth with an uncertainty of 20% relative to the measurements. When compared with the magnitude of vorticity diffusion by molecular viscosity, the experiments show that there is no significant diffusion by radial turbulence.
关键词： vortex dynamics,Burgers vortex model,Air core depth,vortex core radius,axial vortex flow,stereo particle image velocimetry (SPIV),experiments
更新于2025-09-19 17:15:36
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Dual layer doI detector modules for a dedicated mouse brain PET/MRI
摘要： This work discusses two system geometries including their associated block detectors. Both configurations were based on a dual layer offset structure with small crystals sizes, in the order of 1×1×4/6 mm3, to provide discrete depth of interaction information. The detector for configuration “A” was based on a 4×4 silicon photomultiplier (SiPM) array attached to an optical diffusor, and a 12×12 as well as a 9×11 LSO crystal array, to achieve optimal system sensitivity. This configuration was evaluated by a double layer of 12×12 crystals. Configuration “B” was composed of three 2×2 SiPM arrays equipped with a 1 mm diffusor to read out an LSO stack of 20×6 and 19×5 individual crystals. The average peak-to-valley ratio of the inner/outer layer was 3.5/3.6 for detector “A”, and 3.4/2.8 for detector “B”. The average full width at half maximum (FWHM) energy resolution of the block detectors were 22.24±3.36% for “A” and 30.67±5.37% for “B”. The FWHM of the full block timing resolution of the inner/outer layer was 1.4 ns/1.2 ns for detector “A” and 1.8 ns/1.4 ns for “B”. The performance of the crystal position profile, the energy, and timing resolution indicate that configuration “A” is more appropriate for a mouse brain PET/MRI system.
关键词： PET/MRI,Depth of interaction,brain,small animal brain imaging,PET/RF,integrated MRI-coil,preclinical imaging,PET
更新于2025-09-19 17:15:36