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We present a simulator for light field displays. This simulator operates in real-time, allowing for VR-based evaluation of display designs. This allows for rapid exploration of display parameters (e.g. angular and hogel resolution...
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We present a simulator for light field displays. This simulator operates in real-time, allowing for VR-based evaluation of display designs. This allows for rapid exploration of display parameters (e.g. angular and hogel resolution, field of view, etc.) and evaluation of artifacts from light field processing such as rendering.
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Stacks of metal gratings placed above a photodiode have been demonstrated to show a strong sinusoidal response to angle. Although these devices, called angle sensitive pixels (ASPs), enable new imaging modalities on CMOS, such as ...
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Stacks of metal gratings placed above a photodiode have been demonstrated to show a strong sinusoidal response to angle. Although these devices, called angle sensitive pixels (ASPs), enable new imaging modalities on CMOS, such as light field capture, their optical sensitivity is limited by the metallic gratings. In this paper, we provide a detailed characterization of the angular response of ASPs and report on a new set of optically efficient structures for angle detection. By analyzing the properties of the Talbot effect, we present a quantitative model for the angular sensitivity, , of an ASP and qualitatively describe the dependence of modulation depth, , on the grating parameters. We then describe structures that employ phase gratings and interleaved diffusion diodes to provide angle sensitivity while improving the quantum efficiency by . A post-CMOS process flow for the fabrication of phase gratings is described. Finally, we show that ASPs that use p diffusion diodes embedded in an n-well diode improve their modulation efficiency by over 50% compared with interleaved diodes that share the p-substrate.
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In standard photography, vignetting is considered mainly as a radiometric effect because it results in a darkening of the edges of the captured image. In this paper, we demonstrate that for light field cameras, vignetting is more ...
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In standard photography, vignetting is considered mainly as a radiometric effect because it results in a darkening of the edges of the captured image. In this paper, we demonstrate that for light field cameras, vignetting is more than just a radiometric effect. It modifies the properties of the acquired light field and renders most of the calibration procedures from the literature inadequate. We address the problem by describing a model and camera-agnostic method to evaluate vignetting in phase space. This enables the synthesis of vignetted pixel values, which applied to a range of pixels yield images corresponding to the white images that are customarily recorded for calibrating light field cameras. We show that the commonly assumed reference points for microlens-based systems are incorrect approximations to the true optical reference, i.e., the image of the center of the exit pupil. We introduce a novel calibration procedure to determine this optically correct reference point from experimental white images. We describe the changes vignetting imposes on the light field sampling patterns and, therefore, the optical properties of the corresponding virtual cameras using the equivalent camera array model [L. Mignard-Debise, J. Restrepo, and I. Ihrke, "A unifying first-order model for light-field cameras: The equivalent camera array," IEEE Trans. Comput. Imag., vol. 3, no. 4, pp. 798-810, Dec. 2017] and apply these insights to a custom-built light field microscope.
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Choosing a proper lighting approach is a crucial task in designing visual inspection systems. It becomes especially challenging for complex-shaped, transparent objects, which change the directional distribution of incoming light i...
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Choosing a proper lighting approach is a crucial task in designing visual inspection systems. It becomes especially challenging for complex-shaped, transparent objects, which change the directional distribution of incoming light in various ways. We overcome this challenge by constructing a light field display and deploy it as a highly tunable lighting device. Thereby, an object-specific light field can be generated, which highlights the features of the object under test with maximum contrast. We explain the calibration procedure, the rendering pipeline and present examples of customized illuminations.
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A theoretical framework to analyze the rate-distortion performance of a light field coding and streaming system is proposed. This framework takes into account the statistical properties of the light field images, the accuracy of t...
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A theoretical framework to analyze the rate-distortion performance of a light field coding and streaming system is proposed. This framework takes into account the statistical properties of the light field images, the accuracy of the geometry information used in disparity compensation, and the prediction dependency structure or transform used to exploit correlation among views. Using this framework, the effect that various parameters have on compression efficiency is studied. The framework reveals that the efficiency gains from more accurate geometry, increase as correlation between images increases. The coding gains due to prediction suggested by the framework match those observed from experimental results. This framework is also used to study the performance of light field streaming by deriving a view-trajectory-dependent rate-distortion function. Simulation results show that the streaming results depend both the prediction structure and the viewing trajectory. For instance, independent coding of images gives the best streaming performance for certain view trajectories. These and other trends described by the simulation results agree qualitatively with actual experimental streaming results.
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Presently available high-power laser pulses of ponderomotive energy U-p >> 2mc(2) should permit the fundamental processes of quantum electrodynamics in such fields, in particular, the formation of electron positron pairs in impact...
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Presently available high-power laser pulses of ponderomotive energy U-p >> 2mc(2) should permit the fundamental processes of quantum electrodynamics in such fields, in particular, the formation of electron positron pairs in impacts of laser pulses with highly charged ions, to be observed. We evaluate the highly non-linear production rates of this process and investigate the most favorable conditions of pair production, in particular, either along the direction of linear polarization or in the propagation direction of the laser pulse. For femtosecond radiation pulses, it is possible to represent the laser beam by a monochromatic and linearly polarized electromagnetic plane wave. This approximation considerably simplifies the calculations required.
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Light field imaging has emerged as a technology allowing to capture richer visual information from our world. As opposed to traditional photography, which captures a 2D projection of the light in the scene integrating the angular ...
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Light field imaging has emerged as a technology allowing to capture richer visual information from our world. As opposed to traditional photography, which captures a 2D projection of the light in the scene integrating the angular domain, light fields collect radiance from rays in all directions, demultiplexing the angular information lost in conventional photography. On the one hand, this higher dimensional representation of visual data offers powerful capabilities for scene understanding, and substantially improves the performance of traditional computer vision problems such as depth sensing, post-capture refocusing, segmentation, video stabilization, material classification, etc. On the other hand, the high-dimensionality of light fields also brings up new challenges in terms of data capture, data compression, content editing, and display. Taking these two elements together, research in light field image processing has become increasingly popular in the computer vision, computer graphics, and signal processing communities. In this paper, we present a comprehensive overview and discussion of research in this field over the past 20 years. We focus on all aspects of light field image processing, including basic light field representation and theory, acquisition, super-resolution, depth estimation, compression, editing, processing algorithms for light field display, and computer vision applications of light field data.
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This paper introduces the path integral (PI) to the analysis of radially polarized (RP) beams' tight focusing problem. The PI makes the contribution of each incident ray on the focal region visible and then makes it pos-sible to c...
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This paper introduces the path integral (PI) to the analysis of radially polarized (RP) beams' tight focusing problem. The PI makes the contribution of each incident ray on the focal region visible and then makes it pos-sible to choose the filter's parameters more intuitively and precisely. Based on the PI, a zero point construction (ZPC) phase filtering method is realized intuitively. With ZPC, the focal properties of RP solid and annular beams before and after filtering were analyzed. The results show that the combination of a large NA annular beam and phase filtering can result in superior focus properties. (c) 2023 Optica Publishing Group
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We have examined the physical meaning of the geometric gauge associated with the photon position operator and find that localized photon states are not spherically symmetric and may have orbital angular momentum and optical vortic...
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We have examined the physical meaning of the geometric gauge associated with the photon position operator and find that localized photon states are not spherically symmetric and may have orbital angular momentum and optical vortices determined by the choice of gauge.
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Image-based rendering techniques are a powerful alternative to traditional polygon-based computer graphics. This paper presents a novel light field rendering technique which performs per-pixel depth correction of rays for high-qua...
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Image-based rendering techniques are a powerful alternative to traditional polygon-based computer graphics. This paper presents a novel light field rendering technique which performs per-pixel depth correction of rays for high-quality reconstruction. Our technique stores combined RGB and depth values in a parabolic 2D texture for every light field sample acquired at discrete positions on a uniform spherical setup. Image synthesis is implemented on the GPU as a fragment program which extracts the correct image information from adjacent cameras for each fragment by applying per-pixel depth correction of rays. We show that the presented image-based rendering technique provides a significant improvement compared to previous approaches. We explain two different rendering implementations which make use of a uniform parametrisation to minimise disparity problems and ensure full six degrees of freedom for virtual view synthesis. While one rendering algorithm implements an iterative refinement approach for rendering light fields with per pixel depth correction, the other approach employs a raycaster, which provides superior rendering quality at moderate frame rates. GPU based per-fragment depth correction of rays, used in both implementations, helps reducing ghosting artifacts to a non-noticeable amount and provides a rendering technique that performs without exhaustive pre-processing for 3D object reconstruction and without real-time ray-object intersection calculations at rendering time.
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