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- 摘要
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- 实验方案
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Acquiring spatially varying appearance of printed holographic surfaces
摘要： We present two novel and complimentary approaches to measure diffraction effects in commonly found planar spatially varying holographic surfaces. Such surfaces are increasingly found in various decorative materials such as gift bags, holographic papers, clothing and security holograms, and produce impressive visual effects that have not been previously acquired for realistic rendering. Such holographic surfaces are usually manufactured with one dimensional diffraction gratings that are varying in periodicity and orientation over an entire sample in order to produce a wide range of diffraction effects such as gradients and kinematic (rotational) effects. Our proposed methods estimate these two parameters and allow an accurate reproduction of these effects in real-time. The first method simply uses a point light source to recover both the grating periodicity and orientation in the case of regular and stochastic textures. Under the assumption that the sample is made of the same repeated diffractive tile, good results can be obtained using just one to five photographs on a wide range of samples. The second method is based on polarization imaging and enables an independent high resolution measurement of the grating orientation and relative periodicity at each surface point. The method requires a minimum of four photographs for accurate results, does not assume repetition of an exemplar tile, and can even reveal minor fabrication defects. We present point light source renderings with both approaches that qualitatively match photographs, as well as real-time renderings under complex environmental illumination.
关键词： Diffraction,real-time rendering,spectral,polarization,wave optics
更新于2025-09-23 15:23:52
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Ultracompact low-pass modal filters based on shortcuts to adiabaticity
摘要： A versatile approach to the design of photonic ultracompact low-pass modal filters is proposed. The idea stems from the shortcut to adiabaticity protocol, originally developed for quantum-mechanical systems and recently introduced in full-wave optics. This method allows one to achieve efficient rejection of higher order modes in a broad wavelength range for any two-dimensional multimode optical waveguide in an ultracompact configuration of the filter. A study case, corroborated by finite-element method numerical simulations, is reported for slab waveguides.
关键词： integrated optics,shortcut to adiabaticity,modal filters,full-wave optics
更新于2025-09-11 14:15:04
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Wave-optics uncertainty propagation and regression-based bias model in GNSS radio occultation bending angle retrievals
摘要： A new reference occultation processing system (rOPS) will include a Global Navigation Satellite System (GNSS) radio occultation (RO) retrieval chain with integrated uncertainty propagation. In this paper, we focus on wave-optics bending angle (BA) retrieval in the lower troposphere and introduce (1) an empirically estimated boundary layer bias (BLB) model then employed to reduce the systematic uncertainty of excess phases and bending angles in about the lowest 2 km of the troposphere and (2) the estimation of (residual) systematic uncertainties and their propagation together with random uncertainties from excess phase to bending angle profiles. Our BLB model describes the estimated bias of the excess phase transferred from the estimated bias of the bending angle, for which the model is built, informed by analyzing refractivity fluctuation statistics shown to induce such biases. The model is derived from regression analysis using a large ensemble of Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) RO observations and concurrent European Centre for Medium-Range Weather Forecasts (ECMWF) analysis fields. It is formulated in terms of predictors and adaptive functions (powers and cross products of predictors), where we use six main predictors derived from observations: impact altitude, latitude, bending angle and its standard deviation, canonical transform (CT) amplitude, and its fluctuation index. Based on an ensemble of test days, independent of the days of data used for the regression analysis to establish the BLB model, we find the model very effective for bias reduction and capable of reducing bending angle and corresponding refractivity biases by about a factor of 5. The estimated residual systematic uncertainty, after the BLB profile subtraction, is lower bounded by the uncertainty from the (indirect) use of ECMWF analysis fields but is significantly lower than the systematic uncertainty without BLB correction. The systematic and random uncertainties are propagated from excess phase to bending angle profiles, using a perturbation approach and the wave-optical method recently introduced by Gorbunov and Kirchengast (2015), starting with estimated excess phase uncertainties. The results are encouraging and this uncertainty propagation approach combined with BLB correction enables a robust reduction and quantification of the uncertainties of excess phases and bending angles in the lower troposphere.
关键词： wave-optics uncertainty propagation,bending angle retrievals,refractivity fluctuation statistics,GNSS radio occultation,boundary layer bias model
更新于2025-09-10 09:29:36
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Applied Nanophotonics || Lightwaves in restricted geometries
摘要： The subject of this chapter is propagation, reflection, and evanescence of electromagnetic waves in continuous and complex media and structures to introduce the basics of wave optics and its implementation in novel nanophotonic conceptions. Electromagnetic waves propagate in a medium with positive permittivity, reflect at every permittivity step, and evanesce in a metal featuring negative permittivity. Combination of different dielectrics allows for wave confinement, tunneling, and energy storage, and gives rise to the photonic crystals notion. Combination of a metal with a dielectric material in nanostructures allows for optical material design like stained glass and very high local concentration of incident field to arrive at the notion of nanoplasmonics and optical antennas.
关键词： wave optics,photonic crystals,optical antennas,nanophotonics,electromagnetic waves,nanoplasmonics
更新于2025-09-09 09:28:46
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[IEEE ICASSP 2018 - 2018 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP) - Calgary, AB (2018.4.15-2018.4.20)] 2018 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP) - High-Speed Light Field Image Formation Analysis Using Wavefield Modeling with Flexible Sampling
摘要： Understanding the image formation inside plenoptic cameras is significant for the investigations of improving the low spatial resolution. Most researches explore the image formation from the perspective of geometric optics. However, as the hardware components in combination with low-aperture optical systems become smaller and smaller, geometric analysis will no longer be valid due to diffraction effects. In this paper, a wave-optic-based model is proposed that uses the Fresnel diffraction equation to propagate the whole object field into the plenoptic systems. The proposed model employs averaging of intensities on the sensor from uncorrelated coherent wave to avoid interference during propagations among the optical component planes. Besides, by utilizing the method of multiple partial propagations, the proposed model is much flexible at sampling on propagation planes. In order to verify the effectiveness of the proposed model, numerical simulations are conducted by comparing with existing wave optic model under different optical configurations of plenoptic cameras. Results demonstrate that the proposed model can describe the light field image formation properly. In addition, the time for image formation has been reduced by a factor of 19.22 using the proposed model.
关键词： Plenoptic cameras,multiple partial propagations,image formation,Fresnel diffraction equation,wave optics
更新于2025-09-09 09:28:46
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[IEEE 2018 - 3DTV-Conference: The True Vision - Capture, Transmission and Display of 3D Video (3DTV-CON) - Helsinki (2018.6.3-2018.6.5)] 2018 - 3DTV-Conference: The True Vision - Capture, Transmission and Display of 3D Video (3DTV-CON) - VIEWING SIMULATION OF INTEGRAL IMAGING DISPLAY BASED ON WAVE OPTICS
摘要： We present an accurate model of integral imaging display based on wave optics. The model enables accurate characterization of the display through simulated perceived images by the human visual system. Thus, it is useful to investigate the capabilities of the display in terms of various quality factors such as depth of field and resolution, as well as delivering visual cues such as focus. Furthermore, due to the adopted wave optics formalism, simulation and analysis of more advanced techniques such as wavefront coding for increased depth of field are also possible.
关键词： point spread function,wave optics,Integral imaging,simulation
更新于2025-09-04 15:30:14