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A system for acquiring, processing, and rendering panoramic light field stills for virtual reality
摘要： We present a system for acquiring, processing, and rendering panoramic light field still photography for display in Virtual Reality (VR). We acquire spherical light field datasets with two novel light field camera rigs designed for portable and efficient light field acquisition. We introduce a novel real-time light field reconstruction algorithm that uses a per-view geometry and a disk-based blending field. We also demonstrate how to use a light field prefiltering operation to project from a high-quality offline reconstruction model into our real-time model while suppressing artifacts. We introduce a practical approach for compressing light fields by modifying the VP9 video codec to provide high quality compression with real-time, random access decompression. We combine these components into a complete light field system offering convenient acquisition, compact file size, and high-quality rendering while generating stereo views at 90Hz on commodity VR hardware. Using our system, we built a freely available light field experience application called Welcome to Light Fields featuring a library of panoramic light field stills for consumer VR which has been downloaded over 15,000 times.
关键词： 6DOF,Light Fields,Virtual Reality
更新于2025-09-23 15:23:52
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Diagnostics of ultra-intense laser pulses using tunneling ionization
摘要： We revisit a recently proposed scheme (Ciappina et al 2019 Phys. Rev. A 99 043405) for accurate measurement of electromagnetic radiation intensities in a focus of high-power laser beams. The method is based on the observation of multiple sequential tunneling ionization of atoms and suggests determination of the peak intensity value from the appearance in the focal area ions with a certain charge number. Here we study the sensitivity of the approach to two essential factors: the focal volume effect and the tunneling ionization model chosen to calculate ionization rates. We show, on the one hand, that the results appear almost model independent for ionization of helium- and hydrogen-like ions and, on the other hand, that the focal averaging leaves the intensity-dependent features visible. Our findings are in favor to a practical implementation of the atomic diagnostics of extreme laser intensities.
关键词： intensity diagnostic,tunneling,extreme light fields,petawatt lasers,strong-field ionization
更新于2025-09-19 17:13:59
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Polarization nano-tomography of tightly focused light landscapes by self-assembled monolayers
摘要： Recently, four-dimensional (4D) functional nano-materials have attracted considerable attention due to their impact in cutting-edge fields such as nano-(opto)electronics, -biotechnology or -biomedicine. Prominent optical functionalizations, representing the fourth dimension, require precisely tailored light fields for its optimal implementation. These fields need to be like-wise 4D, i.e., nano-structured in three-dimensional (3D) space while polarization embeds additional longitudinal components. Though a couple of approaches to realize 4D fields have been suggested, their breakthrough is impeded by a lack of appropriate analysis techniques. Combining molecular self-assembly, i.e., nano-chemistry, and nano-optics, we propose a polarization nano-tomography of respective fields using the functional material itself as a sensor. Our method allows a single-shot identification of non-paraxial light fields at nano-scale resolution without any data post-processing. We prove its functionality numerically and experimentally, elucidating its amplitude, phase and 3D polarization sensitivity. We analyze non-paraxial field properties, demonstrating our method’s capability and potential for next generation 4D materials.
关键词： four-dimensional (4D) functional nano-materials,nano-optics,non-paraxial light fields,self-assembled monolayers (SAMs),polarization nano-tomography
更新于2025-09-12 10:27:22
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-matrix-with-time-dependence theory for ultrafast atomic processes in arbitrary light fields
摘要： We describe an ab initio and nonperturbative R-matrix with time-dependence theory for ultrafast atomic processes in light fields of arbitrary polarization. The theory is applicable to complex, multielectron atoms and atomic ions subject to ultrashort (particularly few-femtosecond and attosecond) laser pulses with any given ellipticity, and it generalizes previous time-dependent R-matrix techniques restricted to linearly polarized fields. We discuss both the fundamental equations, required to propagate the multielectron wave function in time, as well as the computational developments necessary for their efficient numerical solution. To verify the accuracy of our approach, we investigate the two-photon ionization of He, irradiated by a pair of time-delayed, circularly polarized, femtosecond laser pulses, and compare photoelectron momentum distributions, in the polarization plane, with those obtained from recent time-dependent close-coupling calculations. The predictive capabilities of our approach are further demonstrated through a study of single-photon detachment from F? in a circularly polarized, femtosecond laser pulse, where the relative contribution of the co- and counter-rotating 2p electrons is quantified.
关键词： ultrafast atomic processes,R-matrix,circularly polarized laser pulses,single-photon detachment,time-dependence,photoelectron momentum distributions,arbitrary light fields,multielectron atoms
更新于2025-09-11 14:15:04
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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) - Graph-based Transforms for Predictive Light Field Compression based on Super-Pixels
摘要： In this paper, we explore the use of graph-based transforms to capture correlation in light fields. We consider a scheme in which view synthesis is used as a first step to exploit inter-view correlation. Local graph-based transforms (GT) are then considered for energy compaction of the residue signals. The structure of the local graphs is derived from a coherent super-pixel over-segmentation of the different views. The GT is computed and applied in a separable manner with a first spatial unweighted transform followed by an inter-view GT. For the inter-view GT, both unweighted and weighted GT have been considered. The use of separable instead of nonseparable transforms allows us to limit the complexity inherent to the computation of the basis functions. A dedicated simple coding scheme is then described for the proposed GT based light field decomposition. Experimental results show a significant improvement with our method compared to the CNN view synthesis method and to the HEVC direct coding of the light field views.
关键词： Light Fields,Super-pixels,Graph Transforms,Compression
更新于2025-09-11 14:15:04
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[IEEE 2018 25th IEEE International Conference on Image Processing (ICIP) - Athens, Greece (2018.10.7-2018.10.10)] 2018 25th IEEE International Conference on Image Processing (ICIP) - A Pipeline for Lenslet Light Field Quality Enhancement
摘要： In recent years, light ?elds have become a major research topic and their applications span across the entire spectrum of classical image processing. Among the different methods used to capture a light ?eld are the lenslet cameras, such as those developed by Lytro. While these cameras give a lot of freedom to the user, they also create light ?eld views that suffer from a number of artefacts. As a result, it is common to ignore a signi?cant subset of these views when doing high-level light ?eld processing. We propose a pipeline to process light ?eld views, ?rst with an enhanced processing of RAW images to extract sub-aperture images, then a colour correction process using a recent colour transfer algorithm, and ?nally a denoising process using a state of the art light ?eld denoising approach. We show that our method improves the light ?eld quality on many levels, by reducing ghosting artefacts and noise, as well as retrieving more accurate and homogeneous colours across the sub-aperture images.
关键词： Denoising,Plenoptic RAW Processing,Lenslet Decoding,Colour Transfer,Light Fields
更新于2025-09-10 09:29:36
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Distinguishing Refracted Features using Light Field Cameras with Application to Structure from Motion
摘要： To be effective, robots will need to reliably operate in scenes with refractive objects in a variety of applications; however, refractive objects can cause many robotic vision algorithms, such as structure from motion, to become unreliable or even fail. We propose a novel method to distinguish between refracted and Lambertian image features using a light field camera. While previous refracted feature detection methods are limited to light field cameras with large baselines relative to the refractive object, our method achieves comparable performance, and we extend these capabilities to light field cameras with much smaller baselines than previously considered, where we achieve up to 50% higher refracted feature detection rates. Specifically, we propose to use textural cross correlation to characterize apparent feature motion in a single light field, and compare this motion to its Lambertian equivalent based on 4-D light field geometry. For structure from motion, we demonstrate that rejecting refracted features using our distinguisher yields lower reprojection error, lower failure rates, and more accurate pose estimates when the robot is approaching refractive objects. Our method is a critical step toward allowing robots to operate in the presence of refractive objects.
关键词： Computer vision for automation,light fields,computational imaging,visual-based navigation
更新于2025-09-04 15:30:14