scholarly journals Hyperspectral environmental illumination maps: Characterizing directional spectral variation in natural environments

2019 ◽  
Author(s):  
Takuma Morimoto ◽  
Sho Kishigami ◽  
João M.M. Linhares ◽  
Sérgio M.C. Nascimento ◽  
Hannah E. Smithson
Keyword(s):  
Imaging System ◽  
Incident Angle ◽  
Incident Light ◽  
Natural Environments ◽  
Spectral Variation ◽  
Spectral Content ◽  
Outdoor Scenes ◽  
Directional Variation ◽  
Indoor Scenes ◽  
Spectral Channels

AbstractObjects placed in real-world scenes receive incident light from every direction, and the spectral content of this light may vary from one direction to another. In computer graphics, environmental illumination is approximated using maps that specify illumination at a point as a function of incident angle. However, to-date, existing public databases of environmental illumination maps specify only three colour channels (RGB). We have captured a new set of 12 environmental illumination maps (eight outdoor scenes; four indoor scenes) using a hyperspectral imaging system with 33 spectral channels. The data reveal a striking directional variation of spectral distribution of lighting in natural environments. We discuss limitations of using daylight models to describe natural environmental illumination.

scholarly journals Flexible time course of spatial frequency use during scene categorization

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Sandro L. Wiesmann ◽  
Laurent Caplette ◽  
Verena Willenbockel ◽  
Frédéric Gosselin ◽  
Melissa L.-H. Võ
Keyword(s):  
Time Course ◽  
Task Characteristics ◽  
Scene Categorization ◽  
Fine Grained ◽  
Spatial Frequencies ◽  
Outdoor Scenes ◽  
Indoor Scenes ◽  
Fine Pattern ◽  
Late Stages ◽  
Basic Level

AbstractHuman observers can quickly and accurately categorize scenes. This remarkable ability is related to the usage of information at different spatial frequencies (SFs) following a coarse-to-fine pattern: Low SFs, conveying coarse layout information, are thought to be used earlier than high SFs, representing more fine-grained information. Alternatives to this pattern have rarely been considered. Here, we probed all possible SF usage strategies randomly with high resolution in both the SF and time dimensions at two categorization levels. We show that correct basic-level categorizations of indoor scenes are linked to the sampling of relatively high SFs, whereas correct outdoor scene categorizations are predicted by an early use of high SFs and a later use of low SFs (fine-to-coarse pattern of SF usage). Superordinate-level categorizations (indoor vs. outdoor scenes) rely on lower SFs early on, followed by a shift to higher SFs and a subsequent shift back to lower SFs in late stages. In summary, our results show no consistent pattern of SF usage across tasks and only partially replicate the diagnostic SFs found in previous studies. We therefore propose that SF sampling strategies of observers differ with varying stimulus and task characteristics, thus favouring the notion of flexible SF usage.

Optical Analysis of Hole Patterned Ag Nanoparticle Structure

2021 ◽  
Vol 21 (8) ◽  
pp. 4192-4199
Author(s):  
Hyun-Ji Jeon ◽  
Ji-Yeon Kim ◽  
Jinnil Choi
Keyword(s):  
Metal Nanoparticles ◽  
Optical Transmission ◽  
Incident Angle ◽  
Incident Light ◽  
Localized Surface Plasmon ◽  
Optical Analysis ◽  
Optical Noise ◽  
Hole Configuration ◽  
Nanoparticle Structure ◽  
Sub Wavelength

A structure with periodic sub-wavelength nanohole patterns interacts with incident light and causes extraordinary optical transmission (EOT), with metal nanoparticles leading to localized surface plasmon resonance (LSPR) phenomena. To explore the effects of metal nanoparticles (NPs), optical analysis is performed for metal NP layers with periodic hole patterns. Investigation of Ag NP arrangements and comparisons with metal film structures are presented. Ag NP structures with different hole configuration are explored. Also, the effects of increasing light incident angle are investigated for metal NP structures where EOT peak at 460 nm wavelength is observed. Moreover, electric field distributions at each transmittance peak wavelengths and optical noise are analyzed. As a result, optical characteristics of metal NP structures are obtained and differences in resonance at each wavelength are highlighted.

scholarly journals Hyperspectral environmental illumination maps: characterizing directional spectral variation in natural environments

2019 ◽  
Vol 27 (22) ◽  
pp. 32277 ◽  
Author(s):  
Takuma Morimoto ◽  
Sho Kishigami ◽  
João M. M. Linhares ◽  
Sérgio M. C. Nascimento ◽  
Hannah E. Smithson
Keyword(s):  
Natural Environments ◽  
Spectral Variation

scholarly journals Surface plasmon-polaritons in deformed graphene excited by attenuated total internal reflection

2019 ◽  
Vol 5 (1) ◽  
pp. 7-11
Author(s):  
Maksim O. Usik ◽  
Igor V. Bychkov ◽  
Vladimir G. Shavrov ◽  
Dmitry A. Kuzmin
Keyword(s):  
Surface Plasmon ◽  
Surface Plasmon Polaritons ◽  
Total Internal Reflection ◽  
Incident Angle ◽  
Incident Light ◽  
Attenuated Total Reflection ◽  
Reflection Method ◽  
Molding Flow ◽  
Plasmon Polaritons ◽  
Effective Excitation

Abstract In the present work we theoretically investigated the excitation of surface plasmon-polaritons (SPPs) in deformed graphene by attenuated total reflection method. We considered the Otto geometry for SPPs excitation in graphene. Efficiency of SPPs excitation strongly depends on the SPPs propagation direction. The frequency and the incident angle of the most effective excitation of SPPs strongly depend on the polarization of the incident light. Our results may open up the new possibilities for strain-induced molding flow of light at nanoscales.

scholarly journals 3D Object Detection Using Scale Invariant and Feature Reweighting Networks

2019 ◽  
Vol 33 ◽  
pp. 9267-9274 ◽  
Author(s):  
Xin Zhao ◽  
Zhe Liu ◽  
Ruolan Hu ◽  
Kaiqi Huang
Keyword(s):  
Object Detection ◽  
Network Architecture ◽  
Point Clouds ◽  
Scale Invariant ◽  
3D Object ◽  
Outdoor Scenes ◽  
Indoor Scenes ◽  
Bounding Boxes ◽  
The One ◽  
3D Object Detection

3D object detection plays an important role in a large number of real-world applications. It requires us to estimate the localizations and the orientations of 3D objects in real scenes. In this paper, we present a new network architecture which focuses on utilizing the front view images and frustum point clouds to generate 3D detection results. On the one hand, a PointSIFT module is utilized to improve the performance of 3D segmentation. It can capture the information from different orientations in space and the robustness to different scale shapes. On the other hand, our network obtains the useful features and suppresses the features with less information by a SENet module. This module reweights channel features and estimates the 3D bounding boxes more effectively. Our method is evaluated on both KITTI dataset for outdoor scenes and SUN-RGBD dataset for indoor scenes. The experimental results illustrate that our method achieves better performance than the state-of-the-art methods especially when point clouds are highly sparse.

scholarly journals FDTD Modelling of Silver Nanoparticles Embedded in Phase Separation Interface of H-PDLC

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Kun Gui ◽  
Jihong Zheng ◽  
Kangni Wang ◽  
Daoping Li ◽  
Songlin Zhuang
Keyword(s):  
Silver Nanoparticles ◽  
Phase Separation ◽  
Incident Angle ◽  
Incident Light ◽  
Near Field ◽  
Double Resonance ◽  
Blue Shift ◽  
Resonance Peak ◽  
Localized Surface Plasmon ◽  
Silver Nps

We report localized surface plasmon resonance (LSPR) of silver nanoparticles (NPs) embedded in interface of phase separation of holographic polymer-dispersed liquid crystal (H-PDLC) gratings using Finite-Difference Time Domain method. We show that silver NPs exhibit double resonance peak at the interface, and these peaks are influenced by the angle of incident light. We observe a blue shift of the wavelength of resonance peak as the incident angle increases. However, the location of silver NPs at the interface has nearly no effect on the wavelength of resonance peak. Also we show near-field and far-field properties surrounding silver NPs and find that field distribution can be controlled through rotation of incident angle. Therefore, LSPR properties of silver NPs within H-PDLC gratings can be excited by appropriate wavelength and angle of the incident light.

scholarly journals Printing special surface components for THz 2D and 3D imaging

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Bo Yan ◽  
Zhigang Wang ◽  
Xing Zhao ◽  
Lie Lin ◽  
Xiaolei Wang ◽  
...  
Keyword(s):  
Imaging System ◽  
Incident Light ◽  
Optical Design ◽  
Bessel Beam ◽  
Three Dimensional ◽  
Focal Depth ◽  
Traditional System ◽  
Special Surface ◽  
3D Printed ◽  
Aspherical Mirrors

AbstractThe paper reports an off-axis large focal depth THz imaging system which consists of three 3D printed special surface components (two aspherical mirrors and an axicon). Firstly, the optical design software is used to design and optimize the aspherical parabolic mirror. Secondly, the optimized mirror is prepared by a 3D printing and metal cladding method. Thirdly, a THz axicon is designed for generation of quasi-Bessel Beam and a new geometric theoretical model of oblique incident light for axicon is established. Finally, the imaging system based on the special surface components is constructed. Its maximum diffraction-free distance is about 60 mm, which is 6 times higher than the traditional system. To verify the effectiveness, THz two-dimensional imaging experiments and three-dimensional computed tomography experiment are carried out. The results are consistent with the design and calculations.

scholarly journals SREVAS: Shading Based Surface Refinement under Varying Albedo and Specularity

2020 ◽  
Vol 12 (21) ◽  
pp. 3488
Author(s):  
Zhihua Hu ◽  
Yaolin Hou ◽  
Pengjie Tao ◽  
Jie Shan
Keyword(s):  
Stereo Vision ◽  
Specular Reflection ◽  
Low Cost ◽  
Shape From Shading ◽  
Specular Reflectance ◽  
Specular Reflections ◽  
New Development ◽  
Outdoor Scenes ◽  
Indoor Scenes ◽  
Surface Refinement

Shape-from-shading and stereo vision are two complementary methods to reconstruct 3D surface from images. Stereo vision can reconstruct the overall shape well but is vulnerable in texture-less and non-Lambertian areas where shape-from-shading can recover fine details. This paper presents a novel, generic shading based method to refine the surface generated by multi-view stereo. Different from most of the shading based surface refinement methods, the new development does not assume the ideal Lambertian reflectance, known illumination, or uniform surface albedo. Instead, specular reflectance is taken into account while the illumination can be arbitrary and the albedo can be non-uniform. Surface refinement is achieved by solving an objective function where the imaging process is modeled with spherical harmonics illumination and specular reflectance. Our experiments are carried out using images of indoor scenes with obvious specular reflection and of outdoor scenes with a mixture of Lambertian and specular reflections. Comparing to surfaces created by current multi-view stereo and shape-from-shading methods, the developed method can recover more fine details with lower omission rates (6.11% vs. 24.25%) in the scenes evaluated. The benefit is more apparent when the images are taken with low-cost, off-the-shelf cameras. It is therefore recommended that a general shading model consisting of varying albedo and specularity shall be used in routine surface reconstruction practice.

scholarly journals Fusing Multimodal Video Data for Detecting Moving Objects/Targets in Challenging Indoor and Outdoor Scenes

2019 ◽  
Vol 11 (4) ◽  
pp. 446 ◽  
Author(s):  
Zacharias Kandylakis ◽  
Konstantinos Vasili ◽  
Konstantinos Karantzalos
Keyword(s):  
Object Detection ◽  
Moving Objects ◽  
Local Coordinate System ◽  
Image Plane ◽  
Hyperspectral Data ◽  
Video Data ◽  
Outdoor Scenes ◽  
Indoor Scenes ◽  
Video Sensors ◽  
Indoor And Outdoor

Single sensor systems and standard optical—usually RGB CCTV video cameras—fail to provide adequate observations, or the amount of spectral information required to build rich, expressive, discriminative features for object detection and tracking tasks in challenging outdoor and indoor scenes under various environmental/illumination conditions. Towards this direction, we have designed a multisensor system based on thermal, shortwave infrared, and hyperspectral video sensors and propose a processing pipeline able to perform in real-time object detection tasks despite the huge amount of the concurrently acquired video streams. In particular, in order to avoid the computationally intensive coregistration of the hyperspectral data with other imaging modalities, the initially detected targets are projected through a local coordinate system on the hypercube image plane. Regarding the object detection, a detector-agnostic procedure has been developed, integrating both unsupervised (background subtraction) and supervised (deep learning convolutional neural networks) techniques for validation purposes. The detected and verified targets are extracted through the fusion and data association steps based on temporal spectral signatures of both target and background. The quite promising experimental results in challenging indoor and outdoor scenes indicated the robust and efficient performance of the developed methodology under different conditions like fog, smoke, and illumination changes.

Numerical Calculation of Optical Properties of Linear Nano-Graphite Particles

2012 ◽  
Vol 538-541 ◽  
pp. 877-881
Author(s):  
Ya Feng Liu ◽  
Chao Jun Huang
Keyword(s):  
Cross Section ◽  
Incident Angle ◽  
Incident Light ◽  
Efficiency Factor ◽  
Scattering Cross Section ◽  
Differential Scattering Cross Section ◽  
Extinction Efficiency ◽  
Graphite Particles ◽  
Scattering Cross ◽  
Variation Tendency

Using the discrete dipole approximation method, the absorption, scattering, extinction efficiency factor and differential scattering cross section of four kinds of nano-graphite particles under different incident angle are numerical calculated, the result shown that the value of the absorption, scattering, extinction efficiency factor and differential scattering cross section of linear nano-graphite particles are symmetric on the incident angle. There are the same variation tendency of absorption and extinction efficiency factor changed with the incident angle, when the incident light parallel with the linear nano-graphite particles, both the absorption and extinction are the strongest, and when the incident light perpendicular the linear nano-graphite particles, both the absorption and extinction are the weakest. The variation tendency of scattering efficiency factor changed with incident angle depended on the number of single graphite and the arrangement of linear nano-graphite particles. The value of differential scattering cross section is the smallest while the incident light parallel with the linear nano-graphite particles, however, the biggest while the incident light perpendicular the linear nano-graphite particles.

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