Light field

About: Light field is a research topic. Over the lifetime, 5357 publications have been published within this topic receiving 87424 citations.

Light Field Super-Resolution Using Edge-Preserved Graph-Based Regularization

Abstract: The light field information would be captured through light field cameras and in different directions regarding 3D image view recordings. In this paper, in order to increase the spatio-angular super-resolution quality and to decrease the reconstruction error regarding the light field information, we use a graph-based light field super-resolution strategy. Accordingly, in order to apply the complementary data in the light field views, we use a graph regularizer for the total recovery of the information and an edge-preserving technique that represents an isometry between curves in the 2D manifold and 5D space of the RGB image views. Moreover, the reconstruction of the light field information is based on applying the alternating direction method of multipliers (ADMM) algorithm. Accordingly, a recent enhanced ADMM model has been used in this paper which is denominated as “Plug-and-Play” and permits the user to plug an image reconstruction technique and a denoising methodology as the first and second sub-problems respectively. On that account, we would be able to resolve the light field super-resolution problem considering the graph-based light field structure as the first sub-problem and the edge-preserving technique as the denoising methodology. Consequently, by applying the proposed super-resolution strategy, the super-resolved light field outcome would be more favorable in terms of visual quality and reconstruction errors in comparison with other state-of-the-art methodologies.

The average cosine due to an isotropic light source in the ocean

Abstract: The average cosine of the light field created by an isotropic point source (IPS) embedded in a homogeneous ocean is investigated with a Monte Carlo model. Two volume scattering functions (VSFs) are used in the model, taken from Petzold (1972), to compute the radiance distributions at various distances from the source. The simulated radiance distributions are compared with measurements of the point spread function made at Lake Pend Oreille, Idaho, during the 1992 optical closure experiment. An analytic model is presented for which is valid to at least 15 optical lengths from the source. The model shows that the mean light path, derived from , is a strong function of the single scattering albedo and the VSF. We found that errors in estimating the absorption coefficient by neglecting the increase in the mean light path, which is due to scattering, vary between 5% and 12% for nearly all natural waters. A mathematical proof is given that as the distance to the IPS goes to zero. An analytic expression is derived for close to a finite diffuse-isotropic source which shows that approaches one as the distance decreases, but at extremely close distances, as the distance to the surface of the source goes to zero. At distances beyond one attenuation length, for finite sources small compared to an attenuation length, behaves essentially as it would for a point source. An asymptotic model for as a function of the single scattering albedo is given with coefficients that depend on the VSF. Model results and comparisons with measured PSFs reveal the surprising result that the light field from an embedded isotropic point source in the ocean does not exhibit asymptotic behavior as far as 15 attenuation lengths from the source.

Fast incident light field acquisition and rendering

Abstract: We present a practical and inexpensive approach for the acquisition and rendering of static incident light fields. Incident light fields can be used for lighting virtual scenes or to insert virtual objects into real world video footage. The virtual objects are correctly lit and cast shadows in the same way as real objects in the scene. We propose to use an inexpensive planar mirror and a high dynamic range video camera to record incident light fields quickly, making our method suitable for outdoor use. The mirror serves as a moving virtual camera sampling the light field. To render with the acquired data we propose a hardware a ccelerated rendering algorithm that reproduces the complex lighting and shadows of the 4D light field. The algori thm is scalable and allows continuous trade between quality and rendering speed.

Light Field Super-Resolution: A Benchmark

Abstract: Lenslet-based light field imaging generally suffers from a fundamental trade-off between spatial and angular resolutions, which limits its promotion to practical applications. To this end, a substantial amount of efforts have been dedicated to light field super-resolution (SR) in recent years. Despite the demonstrated success, existing light field SR methods are often evaluated based on different degradation assumptions using different datasets, and even contradictory results are reported in literature. In this paper, we conduct the first systematic benchmark evaluation for representative light field SR methods on both synthetic and real-world datasets with various downsampling kernels and scaling factors. We then analyze and discuss the advantages and limitations of each kind of method from different perspectives. Especially, we find that CNN-based single image SR without using any angular information outperforms most light field SR methods even including learning-based ones. This benchmark evaluation, along with the comprehensive analysis and discussion, sheds light on the future researches in light field SR.

Experimental possibilities for observation of unidirectional momentum transfer to atoms from standing-wave light

Abstract: We discuss two possible processes that may lead to unidirectional momentum transfer to atoms from a near-resonant standing-wave light field. The first is Bragg scattering of the matter waves from the tilted light grating—this process leaves the atoms unexcited. The second is a multiphoton (Doppleron) process in which the atom, by sequential absorption/emission of photons from/into the two traveling-wave components of the standing wave (which appear at different frequencies owingto the motion of the atom in the field), can complete the energy resonance condition for excitation to its excited state. Detailed consideration of the inteferring process of spontaneous emission and experimental factors such as the interplay among interaction length, angular collimation of the standing wave, and transit-time frequency broadening of the light frequency show that the two processes are both potentially observable but under considerably different experimental conditions.