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- 摘要
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- 实验方案
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Analysis of Light Propagation on Physiological Properties of Neurons for Nanoscale Optogenetics
摘要： Miniaturization of implantable devices is an important challenge for future Brain-Computer Interface applications, and in particular for achieving precise neuron stimulation. For stimulation that utilizes light, i.e., optogenetics, the light propagation behavior and interaction at the nanoscale with elements within the neuron is an important factor that needs to be considered when designing the device. This paper analyses the effect of light behavior for a single neuron stimulation, and focuses on the impact from different cell shapes. Based on the Mie Scattering theory, the paper analyzes how the shape of the soma and the nucleus contributes to the focusing effect resulting in an intensity increase, which ensures that neurons can assist in transferring light through the tissue towards the target cells. At the same time, this intensity increase can in turn also stimulate neighboring cells leading to interference within the neural circuits. The paper also analyzes the ideal placements of the device with respect to the angle and position within the cortex that can enable axonal biophoton communications, which can contain light within the cell to avoid interference.
关键词： Optogenetics,Geometrical Optics Analysis,Nano Communications,Mie scattering
更新于2025-09-23 15:23:52
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On Geometric Optics over a Spherical Earth With an Exponential Refraction Index
摘要： The ray based method of geometrical optics can be used for wave propagation a over spherical earth with good results. A previous such a method also includes an exponential refraction index. This method gives good results for large terminal heights and distances, but for small distances, it has some shortcomings. In this paper, an improvement is proposed which remove these shortcomings. Also, as the method depends on numerical procedures, some improved numerical calculations are put forward.
关键词： refraction,geometrical optics,Electromagnetic propagation
更新于2025-09-23 15:21:21
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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 - Electromagnetic Modeling of Ships in Maritime Scenarios: Geometrical Optics Approximation
摘要： Global Navigation Satellite System-Reflectometry (GNSS-R), is succesfully employed for ocean altimetric and scatterometric applications. Recently, it has been suggested that GNSS-R can also be used for ship detection applications. To this purpose, an accurate electromagnetic modeling of the bistatic radar cross section of a ship lying over the sea surface would be very helpful. However, existing models are typically limited to monostatic configurations, thus restricting their applicability in multistatic scenarios, such as GNSS-R systems. In this work, we show a procedure to determine the bistatic radar cross section of a ship target, under the geometrical optics approximation. Numerical results show the impact of the geometry of acquisition and polarization on the bistatic radar cross section.
关键词： geometrical optics,radar cross section,Electromagnetic scattering,ship detection
更新于2025-09-23 15:21:21
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Structured-illumination Makyoh-topography: optimum grid position and its constraints
摘要： Complementing conventional Makyoh topography with structured illumination using a sparse square grid, the large-scale surface shape can be calculated with a deflectometry approach, while the sample’s morphology can still be imaged. However, the grid’s image must be sharp not to mask the Makyoh image of the sample morphology. In this paper, the instrumental conditions for the grid sharpness are established. The two main types of Makyoh set-ups (lens and mirror based) are analysed. It is shown that the lens-based set-ups allow the position of the grid to be sharp on the Makyoh image. However, for mirror-based set-ups this is not possible because of geometrical instrumental constraints. The calculations are corroborated with experiments.
关键词： Makyoh topography,surface defects,structured illumination,deflectometry,geometrical optics,flatness testing
更新于2025-09-23 15:21:01
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Estimation of the Absorption Effect on Light Scattering by Atmospheric Ice Crystals for Wavelengths Typical for Problems of Laser Sounding of the Atmosphere
摘要： Results of analyzing the numerical calculation of light scattering matrices for ice crystals of arbitrary shape with allowance for absorption are presented. The matrices are obtained within the framework of the geometrical optics approximation. The effect of absorption on properties of light backscattering is estimated for problems of laser sounding of the atmosphere. The results demonstrate that taking into account the absorption when the wavelength is shifted inward the IR range leads to a decrease in the scattered radiation intensity. The effect of absorption for wavelengths of 0.355 and 0.532 μ m does not exceed hundredths of a percent; for 1.064 μ m, several percent; and for the near IR range, it can exceed tens of percent.
关键词： cirrus clouds,absorption,light scattering,ice crystals,geometrical optics
更新于2025-09-19 17:13:59
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Light Pressure on an Inhomogeneous Spherical Particle in the Field of Laser Tweezers
摘要： The light pressure on an inhomogeneous spherical dielectric particle consisting of a shell and a core with different refractive indices is considered. The forces acting on this particle in a laser beam with a Gaussian intensity profile have been found in the geometrical optics approximation. The radiation propagation is analyzed by taking into account the different refractive indices of the core, the shell, and the medium surrounding the particle. The light pressure is shown to depend significantly on the core radius, which allows the core size to be estimated from the spatial dynamics of the particle in the field of optical tweezers.
关键词： laser tweezers,refractive indices,inhomogeneous spherical particle,geometrical optics approximation,light pressure
更新于2025-09-16 10:30:52
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Propagation of Electromagnetic Waves through an Invisible Gradient-Index Lens with Negative Refractive Index
摘要： A radially inhomogeneous (gradient-index) lens made of material with a negative refractive index, invisible from the viewpoint of geometrical optics, is proposed and designed. The design includes derivation and solution of an equation for determining the refractive index profile, as well as derivation of an expression allowing calculation of the ray trajectories in the lens. Propagation of a plane wave through a cylindrical modification of the proposed lens both for the case of E-polarization and for the case of H-polarization is analyzed numerically using the hybrid projection method. The results obtained for the RCS of the lens are compared to the similar performance of a positive-index lens described in the previous publications.
关键词： numerical methods,RCS,geometrical optics,invisible lens,Electromagnetic wave propagation,negative refractive index,gradient-index lens
更新于2025-09-09 09:28:46
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Optical concentrator from a hyperbolic liquid-crystal metamaterial
摘要： We examine the optical properties of two different configurations of a cylindrical device made from a hyperbolic metamaterial with optical axis defined by circular and radial director fields. The hyperbolic metamaterial is a uniaxial anisotropic medium for which the ratio between ordinary and extraordinary permittivities is negative, leading to a particular effective geometry with two timelike coordinates in the metric (Kleinian signature). By using differential geometry tools we are able to perform a comparison between a simple geometrical optics treatment and the wave formalism that shows the concentration of light along the cylinder axis for the case of the circular field configuration, whatever the injection conditions are.
关键词： optical concentrator,geometrical optics,wave formalism,light concentration,hyperbolic liquid-crystal metamaterial
更新于2025-09-09 09:28:46
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RECTANGULAR WAVE BEAM BASED GO/PO METHOD FOR RCS SIMULATION OF COMPLEX TARGET
摘要： The rectangular wave beams-based geometrical optics (GO) and physical optics (PO) hybrid method is applied to the radar cross section (RCS) simulation of complex target. In the implementation process, the incident wave beam is divided into plenty of regular rectangular wave beams. The RCS of target is subsequently harvested from the sum of the contributions from rectangular wave beams. And Open Graphics Library (OpenGL) is used to accelerate ray tracing for the GO/PO method. Here, each pixel corresponds to a rectangular wave beam, which improves the defect that the pixel number should be larger than the patch number on the model and the e?ciency in the general OpenGL based GO/PO method. In addition, the patch size in the presented method can be arbitrary as long as the model is described accurately with these patches. The simulation results prove this point and show that the proposed rectangular wave beam-based GO/PO method is feasible and can keep a high calculation accuracy and e?ciency with a low pixel number.
关键词： ray tracing,geometrical optics,OpenGL,rectangular wave beams,radar cross section,physical optics
更新于2025-09-04 15:30:14
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Geometrical optics and geodesics in thin layers
摘要： The propagation of a light ray in a thin layer (film) within geometrical optics is considered. It is assumed that the ray is captured inside the layer due to reflecting walls or total internal reflection (in the case of a dielectric layer). It has been found that for a very thin film (the length scale is imposed by the curvature of the surface at a given point) the equations describing the trajectory of the light beam are reduced to the equation of a geodesic on the limiting curved surface. There have also been found corrections to the trajectory equation resulting from the finite thickness of the film. Numerical calculations performed for a couple of exemplary curved layers (cone, sphere, torus, and catenoid) confirm that for thin layers the light ray which is repeatedly reflected propagates along the curve close to the geodesic but as the layer thickness increases, these trajectories move away from each other. Because the trajectory equations are complicated nonlinear differential equations, their solutions show some chaotic features. Small changes in the initial conditions result in remarkably different trajectories. These chaotic properties become less significant the thinner the layer under consideration.
关键词： thin layers,geometrical optics,light propagation,geodesics,curved surfaces
更新于2025-09-04 15:30:14