- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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3D Affine: An Embedding of Local Image Features for Viewpoint Invariance Using RGB-D Sensor Data
摘要： Local image features are invariant to in-plane rotations and robust to minor viewpoint changes. However, the current detectors and descriptors for local image features fail to accommodate out-of-plane rotations larger than 25°–30°. Invariance to such viewpoint changes is essential for numerous applications, including wide baseline matching, 6D pose estimation, and object reconstruction. In this study, we present a general embedding that wraps a detector/descriptor pair in order to increase viewpoint invariance by exploiting input depth maps. The proposed embedding locates smooth surfaces within the input RGB-D images and projects them into a viewpoint invariant representation, enabling the detection and description of more viewpoint invariant features. Our embedding can be utilized with different combinations of descriptor/detector pairs, according to the desired application. Using synthetic and real-world objects, we evaluated the viewpoint invariance of various detectors and descriptors, for both standalone and embedded approaches. While standalone local image features fail to accommodate average viewpoint changes beyond 33.3°, our proposed embedding boosted the viewpoint invariance to different levels, depending on the scene geometry. Objects with distinct surface discontinuities were on average invariant up to 52.8°, and the overall average for all evaluated datasets was 45.4°. Similarly, out of a total of 140 combinations involving 20 local image features and various objects with distinct surface discontinuities, only a single standalone local image feature exceeded the goal of 60° viewpoint difference in just two combinations, as compared with 19 different local image features succeeding in 73 combinations when wrapped in the proposed embedding. Furthermore, the proposed approach operates robustly in the presence of input depth noise, even that of low-cost commodity depth sensors, and well beyond.
关键词： nonparametric spherical k-means,3D points projection,6D pose estimation,viewpoint invariance,wide baseline matching,denoising and interpolation,local image feature embedding,out-of-plane rotations
更新于2025-09-19 17:15:36
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Structural and Optical Properties of Ga2Se3 Crystals by Spectroscopic Ellipsometry
摘要： Optical and crystalline structure properties of Ga2Se3 crystals were analyzed utilizing ellipsometry and x-ray diffraction (XRD) experiments, respectively. Components of the complex dielectric function (e = e1 + ie2) and refractive index (N = n + ik) of Ga2Se3 crystals were spectrally plotted from ellipsometric measurements conducted from 1.2 eV to 6.2 eV at 300 K. From the analyses of second-energy derivatives of e1 and e2, interband transition energies (critical points) were determined. Absorption coefficient–photon energy dependency allowed us to achieve a band gap energy of 2.02 eV. Wemple and DiDomenico single effective oscillator and Spitzer–Fan models were accomplished and various optical parameters of the crystal were reported in the present work.
关键词： critical points,optical properties,optical constants,Semiconductors
更新于2025-09-19 17:15:36
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Third glare point effect in 90?°Interferometric Laser Imaging for Droplet Sizing
摘要： A detailed analysis of Interferometric Laser Imaging for Droplet Sizing is performed at the scattering angle 90?, in order to identify the influence of a third glare point on the measurements performed. Experimentally, p = 3 scattering, which involves surface waves, is shown to have an important impact on droplet sizing.
关键词： Glare points,Debye’s orders,ILIDS,Interferometric particle imaging,Light scattering
更新于2025-09-19 17:13:59
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Wave packet dynamics in slowly modulated photonic graphene
摘要： Mathematical analysis on electromagnetic waves in photonic graphene, a photonic topological material which has a honeycomb structure, is one of the most important current research topics. By modulating the honeycomb structure, numerous topological phenomena have been observed recently. The electromagnetic waves in such media are generally described by the 2-dimensional wave equation. It has been shown that the corresponding elliptic operator with a honeycomb material weight has Dirac points in its dispersion surfaces. In this paper, we study the time evolution of the wave packets spectrally concentrated at such Dirac points in a modulated honeycomb material weight. We prove that such wave packet dynamics is governed by the Dirac equation with a varying mass in a large but ?nite time. Our analysis provides mathematical insights to those topological phenomena in photonic graphene.
关键词： Photonic graphene,Dirac points,Bloch decomposition,Honeycomb structure
更新于2025-09-19 17:13:59
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Automated Method for Detection of Missing Road Point Regions in Mobile Laser Scanning Data
摘要： The paper proposes a method supported by MATLAB for detection and measurement of missing point regions (MPR) which may cause severe road information loss in mobile laser scanning (MLS) point clouds. First, the scan-angle thresholds are used to segment the road area for MPR detection. Second, the segmented part is mapped onto a binary image with a pixel size of ε through rasterization. Then, MPR featuring connected 1-pixels are identi?ed and measured via image processing techniques. Finally, the parameters regarding MPR in the image space are reparametrized in relation to the vehicle path recorded in MLS data for a better understanding of MPR properties on the geodetic plane. Tests on two MLS datasets show that the output of the proposed approach can e?ectively detect and assess MPR in the dataset. The ε parameter exerts a substantial in?uence on the performance of the method, and it is recommended that its value should be optimized for accurate MPR detections.
关键词： occlusion,image processing,missing points,point cloud,mobile laser scanning
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Magic Crossing Points of Temperature Dependent Cascaded Frequency Conversions in Nonlinear Photonic Crystals
摘要： In this study, we investigated the temperature dependence of cascaded parametric generations in nonlinear photonic crystals based on 2D periodically poled LiTaO3 (2D-PPLT) of square lattice structure. After establishing simultaneous multi-groups of frequency conversion from optical parametric generation (OPG) [1], it was found that the interaction of the signal ((cid:79)s), the idler ((cid:79)i) and the pump can further lead to several cascaded nonlinear processes such as SHG, SFG and DFG. The latter suggest existence of what can be called “magic” crossing points when mapping the nonlinear interactions vs temperature. We used a square lattice of 2D-PPLT with a period of 8.52μm and a filling factor of 38%. The crystal length was 2cm with a thickness of 0.5mm and pumped with a pulse 532nm green laser with a peak power of 80kW and a pulse width of 0.5ns. The measured spectra of the cascaded frequency conversion processes reveal 10 wavelength peaks at 393nm, 402nm,518nm, 532nm, 548nm, 787nm, 820nm, 1518nm, 1576nm and 1642nm at a crystal temperature of T= 110°C. More importantly, when the parametrically generated wavelengths were mapped as a function of the sample temperature (Fig. 1.a), an interesting phenomenon was observed at T = 64°C where four groups of wavelengths crossing at (cid:79) = 399nm ((cid:95)1(cid:178)), 532nm ((cid:95)2(cid:178)), 798nm ((cid:95)3(cid:178)), and 1596nm ((cid:95)4(cid:178)) concurred. By changing the crystal temperature, it would be possible to switch the involved nonlinear optical processes from degenerated to non- degenerated states. In addition to that, it implied a novel approach to generate entangled photons with controlled spectral features by parametric down conversion in a 2D nonlinear crystal [2]. We, then, took advantage of the Sellmeier equation for the crystal refractive index to evaluate the temperature effect on the QPM-parametric processes. Our study indicates that it is essential to carefully exert the parameters of Sellmeier equation reported in literature. Little changes of Sellmerier coefficients might induce an important misunderstanding of experimental data as well as erroneous design of efficient QPM frequency-conversion devices. The weight of this effect is more important when considering cascaded nonlinear interactions.
关键词： temperature dependence,nonlinear photonic crystals,magic crossing points,cascaded parametric generations,Sellmeier equation
更新于2025-09-16 10:30:52
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Modulated photonic-crystal surface-emitting laser with elliptical lattice points for two-dimensional coupling enhancement
摘要： Modulated photonic-crystal surface-emitting lasers (M-PCSELs) are new semiconductor lasers that can emit a laser beam in arbitrary directions. Therefore, they can be regarded as a next-generation light source for light detection and ranging. In this manuscript, we numerically investigate the characteristics of M-PCSELs, including one- and two-dimensional optical coupling constants and radiation constants, by using three-dimensional coupled wave theory. We also carry out lattice point designs and show that the two-dimensional optical coupling can be enhanced by more than four times over our previous M-PCSEL devices by employing elliptical lattice points. Moreover, we find that two-dimensional optical coupling can be maintained even when large lattice point position modulations are introduced for large radiation constants. These results indicate that more stable two-dimensional oscillation and a higher slope efficiency are expected in M-PCSELs with elliptical lattice points.
关键词： elliptical lattice points,M-PCSELs,radiation constants,Modulated photonic-crystal surface-emitting lasers,two-dimensional optical coupling
更新于2025-09-12 10:27:22
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Weyl points in systems of multiple semiconductor-superconductor quantum dots
摘要： As an analogy to the Weyl point in k-space, we search for energy levels which close at a single point as a function of a three-dimensional parameter space. Such points are topologically protected in the sense that any perturbation which acts on the two-level subsystem can be corrected by tuning the control parameters. We find that parameter-controlled Weyl points are ubiquitous in semiconductor-superconductor quantum dots and that they are deeply related to Majorana zero modes. In this paper, we present several semiconductor-superconductor quantum-dot devices which host parameter-controlled Weyl points. Furthermore, we show how these points can be observed experimentally via conductance measurements.
关键词： semiconductor-superconductor quantum dots,conductance measurements,Majorana zero modes,Weyl points
更新于2025-09-11 14:15:04
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Parity-Time-Anyonic Coupled Resonators System With Tunable Exceptional Points
摘要： The Hermiticity of physical observable is the fundamental axioms in quantum mechanics. However, it is found that several non-Hermitian Hamiltonian still have real eigenvalues, especially the parity-time symmetric system. The property of parity-time symmetry leads the system to various nontrivial physics with interesting counterintuitive features around the exceptional point. In this study, we investigate the dynamics of parity-time-anyonic Hamiltonian under the tunable exceptional points related to an arbitrary phase of the system. We show that the parity-time symmetry can be achieved in a quasi-parity-time-symmetric system. Also the phase dependence symmetry is discussed based on the simulated results.
关键词： tunable exceptional points,coupled resonators,Parity-time-anyonic
更新于2025-09-11 14:15:04
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Non-Hermitian ring?laser gyroscopes with enhanced Sagnac sensitivity
摘要： Gyroscopes are essential to many diverse applications associated with navigation, positioning and inertial sensing1. In general, most optical gyroscopes rely on the Sagnac effect—a relativistically induced phase shift that scales linearly with the rotational velocity2,3. In ring laser gyroscopes (RLGs), this shift manifests as a resonance splitting in the emission spectrum, which can be detected as a beat frequency4. The need for ever more precise RLGs has fuelled research activities aimed at boosting the sensitivity of RLGs beyond the limits dictated by geometrical constraints, including attempts to use either dispersive or nonlinear effects5–8. Here we establish and experimentally demonstrate a method using non-Hermitian singularities, or exceptional points, to enhance the Sagnac scale factor9–13. By exploiting the increased rotational sensitivity of RLGs in the vicinity of an exceptional point, we enhance the resonance splitting by up to a factor of 20. Our results pave the way towards the next generation of ultrasensitive and compact RLGs and provide a practical approach for the development of other classes of integrated sensor.
关键词： Sagnac sensitivity,Non-Hermitian,ultrasensitive sensors,ring laser gyroscopes,exceptional points
更新于2025-09-11 14:15:04