Light field Research Papers - Academia.edu (original) (raw)

- by
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- Applied Mathematics, Optics, Medical Imaging, Fiber Optics

An increase in random molecular vibrations of a solid owing to heating above the melting point leads to a decrease in its long-range order and a loss of structural symmetry. Therefore conventional liquids are isotropic media. Here we report on a light-induced isothermal transition of a polymer film from an isotropic solid to an anisotropic liquid state in which the

- by Michael Giersig
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- Microfluidics, Photochemistry, Crystallization, Nanotechnology

Image based rendering using undersampled light fields suffers from aliasing effects. These effects can be drastically reduced by using some geometric information. In pop-up light field rendering [18], the scene is segmented into coherent layers, usually corresponding to approximately planar regions, that can be rendered free of aliasing. As opposed to the supervised method in the pop-up light field, we propose an unsupervised extraction of coherent regions. The problem is posed in a multidimensional variational framework using the level set method [16]. Since the segmentation is done jointly over all the images, coherence can be imposed throughout the data. However, instead of using active hypersurfaces, we derive a semi-parametric methodology that takes into account the constraints imposed by the camera setup and the occlusion ordering. The resulting framework is a global multidimensional region competition that is consistent in all the images and efficiently handles occlusions. We show the validity of the method with some captured multi-view datasets. Other special effects by coherent region manipulation are also demonstrated.

- by heera bhalerao
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- Computer Science, Image-based Rendering, Light field, Level Set Method

Established conceptual models of the initiation and progression of spring phytoplankton blooms are reconsidered in light of recent observations. We use biological simulation modelling as a tool for the analysis of spring plankton blooms in shallow, coastal waters in temperate latitudes of the North Atlantic. The model shows that interannual variability in the timing of bloom initiation arises from year-to-year differences in incident irradiation, as determined by weather (cloudiness). This variability in timing results in some years when the spring bloom occurs in cold water temperatures near 0°C. Model results suggest that due to low temperature inhibition of heterotrophic consumption, more fresh organic material is delivered to the benthos in these cold-water blooms than when the bloom occurs in waters only 3°C warmer. Thus we suggest that variable bloom timing can be important to the trophodynamic fate of bloom products.

- by Leon Cammen and +1
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- Geochemistry, Oceanography, Carbon Cycle, Stratification

Image-based or light field rendering has received much recent attention as an alternative to traditional geometric methods for modeling and rendering complex objects. A light field represents the radiance flowing through all the points in a scene in all possible directions. We explore two new techniques for efficiently acquiring, storing, and reconstructing light fields in a (nearly) uniform fashion. Both techniques sample the light field by sampling the set of lines that intersect a sphere tightly fit around a given object. Our first approach relies on uniformly subdividing the sphere and representing this subdivision in a compact data structure which allows efficient mapping of image pixels or rays to sphere points and then to subdivision elements. We sample a light field by joining pairs of subdivision elements and store the resulting samples in a multi-resolution, highly compressed fashion that allows efficient rendering. Our second method allows a uniform sampling of all five dimensions of the light field, using hierarchical subdivision for directional space and uniform grid sampling for positional space. Light field models are acquired using parallel projections along a set of uniform directions. Depth information can also be stored for high-quality image rendering. The system can provide bounds on key sources of error in the representation and can be generalized to arbitrary scenes comprising multiple complex objects.

- by Donald Fussell
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- Data Structure, Light field

Light forces on small (Rayleigh) particles are usually described as the sum of two terms: the dipolar or gradient force and the scattering or radiation pressure force. The scattering force is traditionally considered proportional to the Poynting vector, which gives the direction and magnitude of the momentum flow. However, as we will show, there is an additional nonconservative contribution to the scattering force arising in a light field with nonuniform helicity. This force is shown to be proportional to the curl of the spin angular momentum of the light field. The relevance of the spin force is illustrated in the simple case of a 2D field geometry arising in the intersection region of two standing waves.

- by Juan José Sáenz
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- Physical sciences, Solar Radiation Pressure, Light field, Microstructures

A small field irradiation technique to deliver high doses of single fraction photon radiation to small, precisely located volumes (0.5 to 8 cm3) within the brain has been developed. Our method uses a modified Brown-Roberts-Wells (BRS), CT-guided, stereotactic system and a 6 MV linear accelerator equipped with a special collimator (diameters of 12.5 mm to 30.0 mm projected to isocenter) located 23 cm from isocenter. Target localization via planar angiography has been added. Treatment consists of a series of arcing beams using both gantry and couch rotations. During treatment, the patient's head is immobilized independently of the radiotherapy couch and is precisely positioned without reference to room lasers or light field. A precise verification of alignment precedes each treatment. Extensive performance tests have shown that a target, localized by CT, can be irradiated with a positional accuracy of 2.4 mm in any direction with 95% confidence. If angiography is used for localization, the results are better. The dose 1.0 cm outside the target volume is less than 20% of the prescribed dose for a medium sized collimator.

- by Nasser Maleki
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- Radiation, Nuclear medicine, Radiotherapy, Performance Evaluation
- by DERBOV VLADIMIR
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- Quantum Physics, Quantum Optics, Light field, Coherent States

For testing the integration of the remote sensing related technologies into the water quality monitoring programs of Lake Garda (the largest Italian lake), the spatial and spectral resolutions of Hyperion and the capability of physics-based approaches were considered highly suitable. Hyperion data were acquired on 22nd July 2003 and water quality was assessed (i) defining a bio-optical model, (ii) converting the Hyperion atsensor radiances into subsurface irradiance reflectances, and (iii) adopting a bio-optical model inversion technique. The bio-optical model was parameterised using specific inherent optical properties of the lake and light field variables derived from a radiative transfer numerical model. A MODTRAN-based atmospheric correction code, complemented with an air/water interface correction was used to convert Hyperion at-sensor radiances into subsurface irradiance reflectance values. These reflectance values were comparable to in situ reflectance spectra measured during the Hyperion overpass, except at longer wavelengths (beyond 700 nm), where reflectance values were contaminated by severe atmospheric adjacency effects. Chlorophyll-a and tripton concentrations were retrieved by inverting two Hyperion bands selected using a sensitivity analysis applied to the bio-optical model. The sensitivity analysis indicated that the assessment of coloured dissolved organic matter was not achievable in this study due to the limited coloured dissolved organic matter concentration range of the lake, resulting in reflectance differences below the environmental measurement noise of Hyperion. The chlorophyll-a and tripton image-products were compared to in situ data collected during the Hyperion overpass, both by traditional sampling techniques (8 points) and by continuous flow-through systems (32 km). For chlorophyll-a the correlation coefficient between in situ point stations and Hyperion-inferred concentrations was 0.77 (data range from 1.30 to 2.16 mg m − 3 ). The Hyperion-derived chlorophyll-a concentrations also match most of the flow-through transect data. For tripton, the validation was constrained by variable re-suspension phenomena. The correlation coefficient between in situ point stations and Hyperion-derived concentrations increased from 0.48 to 0.75 (data range from 0.95 to 2.13 g m − 3 ) if the sampling data from the re-suspension zone was avoided. The comparison of Hyperionderived tripton concentrations and flow-through transect data exhibited a similar mismatch. The results of this research suggest further studies to address compatibilities of validation methods for water body features with a high rate of change, and to reduce the contamination by atmospheric adjacency effects on Hyperion data at longer wavelengths in Alpine environment. The transferability of the presented method to other sensors and the ability to assess water quality independent from in situ water quality data, suggest that management relevant applications for Lake Garda (and other subalpine lakes) could be supported by remote sensing.

- by Arnold Dekker
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- Technology, Remote Sensing, Water quality, Modeling

This paper presents a camera that samples the 4D light field on its sensor in a single photographic exposure. This is achieved by in-serting a microlens array between the sensor and main lens, creat-ing a plenoptic camera. Each microlens... more

- by Mathieu Brédif
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- Digital Photography, High Speed, Light field, Depth of Field

We construct a multi-field inflationary model consisting of multiple K\"ahler moduli derived from type IIB string compactification in the large volume limit. The model consists of both heavy and light fields, with the former being frozen during the inflationary period and the latter acting as the inflaton(s). We study the evolution of all the fields during and after inflation until the preheating era when all the fields oscillate around their vacuum expectation values. Our numerical analysis shows that the curvature perturbations have an almost scale invariant power spectrum with nssimeq0.96n_s \simeq 0.96nssimeq0.96.

- by guoqin Ren
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- String Theory, Numerical Analysis, High Energy Physics, Oscillations

This paper present s a v olumetric representation for the global illumination within a space based on the radiometric quantity irradiance. We call this representation the irradiance volume. Although irradiance is traditionally computed only for surfaces, we extend its de nition to all points and directions in space. The irradiance volume supports the reconstruction of believable approximations to the illumination in situations that overwhelm traditional global illumination algorithms. A theoretical basis for the irradiance volume is discussed and the methods and issues involved with building the volume are described. The irradiance volume method shows good performance in several practical situations.

- by Peter Shirley
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- Cognitive Science, Computer Graphics, Global Illumination, Light field

This paper describes an algorithm that provides fast propagation and real-time walkthrough for globally illuminated synthetic scenes. A type of light field data structure is used for propagating radiance outward from emitters through the scene, accounting for any kind of L(S|D) * light path. The light field employed is constructed by choosing a regular point subdivision over a hemisphere, to give a set of directions, and then corresponding to each direction there is a rectangular grid of parallel rays. Each rectangular grid of rays is further subdivided into rectangular tiles, such that each tile references a sequence of 2D images containing outgoing radiances of surfaces intersected by the rays in that tile. We present a novel propagation algorithm running entirely on the Graphics Processing Unit (GPU). It is incremental in that it can resolve visibility along a set of parallel rays in O(n) time and can produce a light field for a moderately complex scene -with complex illumination stored in millions of elements -in minutes and for simpler scenes in seconds. It is approximate but gracefully converges to a correct solution as verified by comparing images with path traced counterparts. We show how to render globally lit images directly from the GPU data structure without CPU involvement at real-time frame rates and high resolutions.

- by Mel Slater
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- Data Structure, Real Time, Global Illumination, High Resolution

We present an approach to convert a small portion of a light field with extracted depth information into a cinematic effect with simulated, smooth camera motion that exhibits a sense of 3D parallax. We develop a taxonomy of the cinematic conventions of these effects, distilled from observations of documentary film footage and organized by the number of subjects of interest in the scene. We present an automatic, content-aware approach to apply these cinematic conventions to an input light field. A face detector identifies subjects of interest. We then optimize for a camera path that conforms to a cinematic convention, maximizes apparent parallax, and avoids missing information in the input. We describe a GPUaccelerated, temporally coherent rendering algorithm that allows users to create more complex camera moves interactively, while experimenting with effects such as focal length, depth of field, and selective, depth-based desaturation or brightening. We evaluate and demonstrate our approach on a wide variety of scenes and present a user study that compares our 3D cinematic effects to their 2D counterparts.

- by Alex Colburn
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- Image-based Rendering, Data Structure, Temporal coherence, User Study

- by Claudia Giardino
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- Technology, Remote Sensing, Water quality, Modeling

Wentworth, S.D.P. (2005) Neonatal phototherapy-today's lights, lamps and devices. Infant 1(1): 14-19. 1. Spectrum, irradiance and effective light field area vary between devices. 2. Four basic light sources are used for phototherapy devices. 3. Not all phototherapy devices are equally effective. 4. Intensive phototherapy can be achieved using more than one phototherapy device.

- by Stephanie Wentworth
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- Light therapy, Infant, Spectrum, Light field

Spatial light modulators (SLMs) can be used to optically reconstruct the complex amplitude of a wavefield. The reconstructed wavefield in the far-field is corrupted by effects arising from the non-ideal modulation properties and the discrete nature of SLMs. These effects are regarded as drawbacks and particularly disturb the visual impression and reduce the light efficiency of the reconstruction in the region of interest. In this paper we present a novel method to improve the quality of the reconstructed light field by eliminating the higher diffraction orders and by modifying hologram data based on the characteristic modulation properties of the SLM. We achieve the elimination of the higher orders optically using only one lens in a 4 f configuration with an appropriate amplitude mask inserted in the Fourier plane. For compensating the non-ideal modulation properties of the SLM we characterize the device to alter the digital hologram data in an appropriate way. The basic principle of this technique and its experimental verification are described.

- by Mostafa Agour
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- Signal Processing, Higher Order Thinking, Holography, Spatial Light Modulator

In this paper we present a system for rendering with real-time global illumination in virtual reality (VR). We describe the virtual light field rendering algorithm and show how it is suitable for real-time VR applications and describe how it is integrated with the XVR system for real-time GPU-based rendering in a CAVE TM . This rendering method achieves real-time rendering of L(S|D) * E solutions in time independent of illumination complexity and largely independent of geometric complexity. The method also supports dynamic changes to scene elements, such as a virtual character that moves through the scene with appropriate shadows and reflections.

- by Bernhard Spanlang
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- Cognitive Science, Computer Graphics, Virtual Reality, Software

Figure 1: 3D interaction with thin displays. We modify an LCD to allow co-located image capture and display. (Left) Mixed on-screen 2D multi-touch and off-screen 3D interactions. Virtual models are manipulated by the user's hand movement. Touching a model brings it forward from the menu, or puts it away. Once selected, free-space gestures control model rotation and scale. (Middle) Multi-view imagery recorded in real-time using a mask displayed by the LCD. (Right, Top) Image refocused at the depth of the hand on the right; the other hand, which is closer to the screen, is defocused. (Right, Bottom) Real-time depth map, with near and far objects shaded green and blue, respectively.

- by Zachary Seldess
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- Mixed Reality, Optical Sensor, 3-D Reconstruction, Real Time

We demonstrate the first example of a closed-loop adaptive control experiment in the soft-x-ray spectral region. The branching ratio of the dissociative photoionization of sulfur hexafluoride (SF 6 ) can be maximized and minimized by applying tailored soft-x-ray femtosecond light fields. The spectrally shaped coherent soft-x-ray pulses are produced by high-harmonic generation driven by phase-shaped femtosecond laser pulses. The stability of the shaped high-harmonic output is high enough to perform adaptive control experiments, albeit its strong nonlinear dependence on the driving laser pulse shape. This experiment opens the door to the application of pulse-shaping and coherent-control techniques in the soft-x-ray range.

- by Christian Spielmann
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- Optics, Optimal Control, Adaptive Control, Femtosecond Laser

We review the modifications and implications of the effect of light forces on atoms when the field is enclosed in an optical resonator of high finesse. The systems considered range from a single atom strongly coupled to a single mode of a high-Q microcavity to a large ensemble of atoms in a highly degenerate quasi-confocal resonator. We set up general models that allow us to obtain analytic expressions for the optical potential, friction, and diffusion. In the bad-cavity limit the modified cooling properties can be attributed to the spectral modifications of light absorption and spontaneous emission in a form of generalized and enhanced Doppler cooling. For the strong coupling regime in a good cavity, we identify the dynamical coupling between the light field intensity and the atomic motion as the central mechanism underlying the cavity-induced cooling. The dynamical cavity cooling, which does not rely on spontaneous emission, can be enhanced by multimode cavity geometries because of the effect of coherent photon redistribution between different modes. The model is then generalized to include several distinct frequencies to account for more general trap geometries. Finally we show that the field-induced buildup of correlations between the motion of different particles plays a central role in the scaling behavior of the system. Depending on the geometry and parameters, its effect ranges from strong destructive interference, slowing down the cooling process, to self-organized crystallization, implying atomic self-trapping and faster cooling to lower temperatures by cooperative coherent scattering.

- by H. Ritsch
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- Applied Mathematics, Solar Radiation Pressure, Optical physics, Spontaneous Emission

We present a prototype medical data visualization system exploiting a light field display and custom direct volume rendering techniques to enhance understanding of massive volumetric data, such as CT, MRI, and PET scans. The system can be integrated with standard medical image archives and extends the capabilities of current radiology workstations by supporting real-time rendering of volumes of potentially unlimited size on light field displays generating dynamic observer-independent light fields. The system allows multiple untracked naked-eye users in a sufficiently large interaction area to coherently perceive rendered volumes as real objects, with stereo and motion parallax cues. In this way, an effective collaborative analysis of volumetric data can be achieved. Evaluation tests demonstrate the usefulness of the generated depth cues and the improved performance in understanding complex spatial structures with respect to standard techniques.

- by Marco Agus and +1
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- Cognitive Science, Real-time rendering, Data Visualization, Medical Visualization

Stereoscopic rendering and 3D stereo displays are quickly becoming mainstream. The natural extension is autostereoscopic multi-view displays which, by the use of parallax barriers or lenticular lenses, can accommodate many simultaneous viewers without the need for active or passive glasses. As these displays, for the foreseeable future, will support only a rather limited number of views, there is a need for high-quality interperspective antialiasing. We present a specialized algorithm for efficient multi-view image generation from a camera line using ray tracing, which builds on previous methods for multi-dimensional adaptive sampling and reconstruction of light fields. We introduce multi-view silhouette edges to detect sharp geometrical discontinuities in the radiance function. These are used to significantly improve the quality of the reconstruction. In addition, we exploit shader coherence by computing analytical visibility between shading points and the camera line, and by sharing shading computations over the camera line.

- by Ghost Vc
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- Cognitive Science, Edge Detection, Ray Tracing, Adaptive Sampling

Computer generated images by default render the entire scene in perfect focus. Both camera optics and the human visual system have limited depth of field, due to the finite aperture or pupil of the optical system. For more realistic computer graphics as well as to enable artistic control over what is and what is not in focus, it is desirable to add depth of field blurring. Starting with the work of Potmesil and Chakravarty[33][34], there have been numerous approaches to adding depth of field effects to computer graphics. Published work in depth of field for computer graphics has been previously surveyed by Barsky [2][3]. Later, interactive depth of field techniques were surveyed by Demers [12]. Subsequent to these surveys, however, there have been important developments. This paper surveys depth of field approaches in computer graphics, from its introduction to the current state of the art. Figure 1: (left) Image before and after depth of field has been added via postprocessing (cou...

- by Todd Kosloff
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- Computer Graphic, Light field, Human Visual System, Depth of Field

The final copy of this thesis has been examined by the signatories, and we find that both the content and the form meet acceptable presentation standards of scholarly work in the above mentioned discipline. iii Thomann, Isabell (Ph.D., Physics) Generation, Temporal Characterization and Applications of Femtosecond-/ Attosecond Extreme Ultraviolet Pulses Thesis directed by Prof. Margaret M. Murnane

Confining a laser field between two high reflectivity mirrors of a high-finesse cavity can increase the probability of a given cavity photon to be scattered by an atom traversing the confined photon mode. This enhanced coupling between light and atoms is successfully employed in cavity quantum electrodynamics experiments and led to a very prolific research in quantum optics. The idea

- by Eva Weig and +1
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- Cavity Quantum Electrodynamics, Quantum Optics, Brownian Motion, Light field

The development of microfluidic devices is still hindered by the lack of robust fundamental building blocks that constitute any fluidic system. An attractive approach is optical actuation because light field interaction is contactless and dynamically reconfigurable, and solutions have been anticipated through the use of optical forces to manipulate microparticles in flows. Following the concept of "optical chip" advanced from the optical actuation of suspensions, we propose in this survey new routes to extend this concept to microfluidic two-phase flows. First, we investigate the destabilization of fluid interfaces by the optical radiation pressure and the formation of liquid jets. We analyze the droplet shedding from the jet tip and the continuous transport in laser-sustained liquid channels. In a second part, we investigate a dissipative light-flow interaction mechanism consisting in heating locally two immiscible fluids to produce thermocapillary stresses along their interface. This opto-capillary coupling is implemented in adequate microchannel geometries to manipulate two-phase flows and propose a contactless optical toolbox including valves, droplet sorters and switches, droplet dividers or droplet mergers. Finally, we discuss radiation pressure and opto-capillary effects in the context of the "optical-chip" where flows, channels and operating functions would all be performed optically on the same device.

- by Régis Wunenburger
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- Two Phase Flow, Solar Radiation Pressure, Optical physics, Light field

Guided by the aim to construct light fields with spin-like orbital angular momentum (OAM), that is light fields with a uniform and intrinsic OAM density, we investigate the OAM of strictly periodic arrays of optical vortices with rectangular symmetry. We find that the OAM per unit cell depends on the choice of unit cell and can even change sign when the unit cell is translated. This is the case even if the OAM in each unit cell is intrinsic, that is independent of the choice of measurement axis. We show that spin-like OAM can be found only if the OAM per unit cell vanishes. Our results are applicable to the z component of the angular momentum of any x-and y-periodic momentum distribution in the xy plane, and can also be applied to other periodic light beams and arrays of rotating solids or liquids.

- by M. Vasnetsov
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- Orbital Angular Momentum of Light, Optical physics, Physical Optics, Light field

We review optical phenomena associated with the internal energy redistribution which accompany propagation and transformations of monochromatic light fields in homogeneous media. The total energy flow (linear-momentum density, Poynting vector) can be divided into spin part associated with the polarization and orbital part associated with the spatial inhomogeneity. We give general description of the internal flows in the coordinate and momentum (angular spectrum) representations for both nonparaxial and paraxial fields. This enables one to determine local densities and integral values of the spin and orbital angular momenta of the field. We analyse patterns of the internal flows in standard beam models (Gaussian, Laguerre-Gaussian, flat-top beam, etc.), which provide an insightful picture of the energy transport. The emphasize is made to the singular points of the flow fields. We describe the spin-orbit and orbit-orbit interactions in the processes of beam focusing and symmetry breakdown. Finally, we consider how the energy flows manifest themselves in the mechanical action on probing particles and in the transformations of a propagating beam subjected to a transverse perturbation.

- by Konstantin Bliokh
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- Optics, Spin-Orbit Coupling, Optical physics, Spectrum

There is a need for a processor to perform real-time automatic target classification (ATC) that is compact and consumes little electrical power. Optical processors have the potential to provide the needed computational power in a small package. Substantial efforts have been expended in the development of spatial light modulators (SLMs) to meet the ATC requirements, but performance achieved thus far is still lacking. A new class of optical devices, spatial light rebroadcasters (SLRs) have been developed recently with potential performance far exceeding current SLMs. Instead of modulating the input light field, SLR absorbs the incident radiation and re-emits when triggered to do so. The triggering can be accomplished with an optical signal which also carries spatial information. The storage capability and the relationship between the intensities of the incident (input), triggering (readout) and emitted (output) radiations can be used to perform parallel processing of two-dimensional s...

- by Nikola Subotic
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- Signal Processing, Parallel Processing, Integrated Optics, Artificial Intelligent

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 • -* 1 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, • -* 1/2 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. defined PSFs are empirically nearly equal. In general, however, they should be distinguished. Paper number 95JC00461. 0148-0227/95/95 J C-00461 $05.00 Aside from its powerful use as the OIR of an optical medium, the light field due to an IPS embedded in the ocean can, in principle, be mathematically transformed to yield all of the inherent optical properties (IOPs) of the medium. Sorenson and Honey [1968], for example, conjectured that the beam attenuation, volume absorption, and backward scattering coefficients can all be determined from radiance and irradiance measurements of an IPS. Sorenson and Honey's conjectures were experimentally verified as good approximations [Honey and Maffione, 1992; Maffione, 1993; Maffione and Honey, 1991; Maffione et al., 1991, !993]. Wells [1969] first presented the transformation of the PSF to the volume scattering function (VSF) in the small-angle approximation. Although Wells' transformation to the VSF has yet to be experimentally tested in the sense of closure, it was recently numerically tested and found to be accurate within the small-angle scattering limit up to about six attenuation lengths [Jaffe, 1995]. To the authors' knowledge, the only known exact transformation to an inherent optical property from an IPS light field was presented by Maffione et al. [1993]. They showed that the absorption coefficient a could be obtained exactly , from the scalar irradiance and divergence of the vector irradiance by simply transforming Gershun's [ 1936] equation to spherical coordinates. For homogeneous water the problem reduces to one spatial coordinate, the radial distance r from the source, and the resulting solution is given by 13,179 13,180 MAFFIONE AND JAFFE: AVERAGE COSINE OF ISOTROPIC SOURCE

- by Jules Jaffe
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- Monte Carlo, Multidisciplinary, Light field, Geophysical

- by G. Mourou and +1
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- Light field

X-ray and light field alignment evaluation is carried out during linac quality assurance programs. In this paper, we compare the size of the light field measured by a photodiode and by a more traditional visual observation with the size of the x-ray field. The comparison between actual light field size, measured with the photodiode, and light field size measured by human eye allow us to verify the reliability of human eye in the evaluation of this parameter. The visual field is always larger than real light field; however, it agrees better with the x-ray field. It matches the light field if we take into account the 25% (؎ 1%) of the decrement line of the maximum central lightening; however, this method simulates better the actual field employed in radiation treatments.

- by Milena Frigerio
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- Visual perception, Radiosurgery, X Rays, Quality Assurance

A schematic diagram of a radial section showing the various layers of the retina published in 1887 by Ferrucio Tartuferi. Tartuferi was Professor of Ophthalmology at the University of Messina in Sicily and was interested primarily in clinical eye diseases. This study, "Sull anatomia della retina" (International Monatsschrift Anatomie Physiolgie 4:421-441), appeared a year before Ramón y Cajal's first work on the retina. Courtesy of Robert Rodieck. …one day in winter, on my return home, my mother, seeing that I was cold, offered me some tea, a thing I did not ordinarily physiological ! optics image! formation retinal! processing inference photo! transduction

- by Brian Wandell
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- Color Constancy, Light field

We present PiCam (Pelican Imaging Camera-Array), an ultra-thin high performance monolithic camera array, that captures light fields and synthesizes high resolution images along with a range image (scene depth) through integrated parallax detection and superresolution. The camera is passive, supporting both stills and video, low light capable, and small enough to be included in the next generation of mobile devices including smartphones. Prior works [Rander et al. 1997; Yang et al. 2002; Zhang and Chen 2004; Tanida et al. 2001; Tanida et al. 2003; Duparré et al. 2004] in camera arrays have explored multiple facets of light field capture - from viewpoint synthesis, synthetic refocus, computing range images, high speed video, and micro-optical aspects of system miniaturization. However, none of these have addressed the modifications needed to achieve the strict form factor and image quality required to make array cameras practical for mobile devices. In our approach, we customize many ...

- by Priyam Chatterjee
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- Information Systems, Superresolution, Light field, Depth Map

The underwater light field and phytoplankton abundance in the Gulf of Eilat were studied at station A1 during 1996-2000. In summer, a deep chlorophyll maximum developed at about 80 m, characterized by high concentrations of Prochlorococcus, while during the mixing time, Prochlorococcus, Synechococcus, and eukaryotic algae were found throughout the water column. Chlorophyll concentrations in the euphotic zone were low (0.1-0.6 mg L À1) and as such, the phytoplankton influence on light attenuation was minor. The vertical attenuation coefficient, K d (PAR) (photosynthetically available radiation), showed seasonal fluctuation, with a summer minimum of 0.04mAˋ1andaspringmaximumof0.04 m À1 and a spring maximum of 0.04mAˋ1andaspringmaximumof0.065 m À1. The euphotic zone ranged to depths between 80 and 115 m. Phytoplankton absorption spectra were shown to be dependent on depth. During summer stratification, as a response to the exponential decrease of light in the water column, the phytoplankton exhibited photoacclimation, evident as a marked increase in cellular chlorophyll with increasing depth. Light in the Gulf is not a limiting factor even down to more than 100 m, except when combined with stratification, e.g., nutrient limitation, does it affect phytoplankton abundance and composition.

- by Noga Stambler
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- Radiation, Multidisciplinary, Mixing, Concentration

A new miniaturized camera system that is capable of 3-dimensional imaging in real-time is presented. The compact imaging device is able to entirely capture its environment in all three spatial dimensions. It reliably and simultaneously delivers intensity data as well as range information on the objects and persons in the scene. The depth measurement is based on the time-of-flight (TOF) principle. A custom solid-state image sensor allows the parallel measurement of the phase, offset and amplitude of a radio frequency (RF) modulated light field that is emitted by the system and reflected back by the camera surroundings without requiring any mechanical scanning parts. In this paper, the theoretical background of the implemented TOF principle is presented, together with the technological requirements and detailed practical implementation issues of such a distance measuring system. Furthermore, the schematic overview of the complete 3D-camera system is provided. The experimental test results are presented and discussed. The present camera system can achieve sub-centimeter depth resolution for a wide range of operating conditions. A miniaturized version of such a 3D-solid-state camera, the SwissRanger TM 2, is presented as an example, illustrating the possibility of manufacturing compact, robust and cost effective ranging camera products for 3D imaging in real-time.

- by mirja g
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- Manufacturing, Stereoscopy, 3-D Imaging, Time of Flight

1] Colored Dissolved Organic Matter (CDOM) distribution and signatures provide vital information about the amount and composition of organic material in aquatic environments. This information is critical for deciphering the sources and biogeochemical pathways of organic carbon, and thus vital to the understanding of carbon cycling and budgets. Waters of the West Florida Shelf are heavily influenced by many river systems on Florida's Gulf Coast that, to the first order, control CDOM distributions on the shelf. Three storm events during 2004 and 2005 (Hurricane Charley, Hurricane Wilma, and a Winter Storm) profoundly altered the typical distribution of CDOM fluorescence and absorption properties on the Southern West Florida Shelf. Seasonal surveys revealed that changes in the underwater light field as a result of major hurricanes and resuspension events are linked closely with a number of factors prior to a storm's passing such as the presence of persistent blooms, rainfall and discharge. Additionally, storm track and wind direction were found to play a significant role in CDOM signatures.

- by Paula Coble
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- Carbon Cycle, Multidisciplinary, Seasonality, First-Order Logic

We consider a laser driven and dissipative system of two coupled cavities with Jaynes-Cummings nonlinearity. In particular, we investigate both incoherent and coherent laser driving, corresponding to different experimental situations. We employ Arnoldi time evolution as a numerical tool to solve exactly the many-body master equation describing the non-equilibrium quantum system. We evaluate the fluorescence spectrum and the spectrum of the second-order correlation function of the emitted light field. Finally, we relate the measured spectra of the dissipative quantum system to excitations of the corresponding non-dissipative quantum system. Our results demonstrate how to interpret spectra obtained from dissipative quantum systems and specify what information is contained therein.

We demonstrate experimentally a solid-state quantum memory for photons at telecommunication wavelengths. Weak light fields at the single photon level are stored for a time up to 600 ns in an Erbium-doped Y2SiO5 crystal at 2.6 K and retrieved on demand. The memory is based on photon echoes with controlled reversible inhomogeneous broadening. This is implemented with an external field gradient using the linear Stark effect.

- by James Acker
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- Ocean Color, Spectrum, Light field, Colored Dissolved Organic Matter

The realization of nonclassical states is an important task for many applications of quantum information processing. Usually, properly tailored interactions, different from goal to goal, are considered in order to accomplish specific tasks within the general framework of quantum state engineering. In this paper we remark on the flexibility of a cross-Kerr nonlinear coupling in hybrid systems as an important ingredient in the engineering of nonclassical states. The general scenario we consider is the implementation of high cross-Kerr nonlinearity in cavity-quantum electrodynamics. In this context, we discuss the possibility of performing entanglement transfer and swapping between a qubit and a continuous-variable state. The recently introduced concept of entanglement reciprocation is also considered and shown to be possible with our scheme. We reinterpret some of our results in terms of applications of a generalized Ising interaction to systems of different nature.

Compressive Sensing is an emerging field based on the revelation that a small group of nonadaptive linear projections of a compressible signal contains enough information for reconstruction and processing. In this paper, we propose algorithms and hardware to support a new theory of Compressive Imaging. Our approach is based on a new digital image/video camera that directly acquires random projections of the light field without first collecting the pixels/voxels. Our camera architecture employs a digital micromirror array to perform optical calculations of linear projections of an image onto pseudorandom binary patterns. Its hallmarks include the ability to obtain an image with a single detection element while measuring the image/video fewer times than the number of pixels/voxels; this can significantly reduce the computation required for video acquisition/encoding. Since our system relies on a single photon detector, it can also be adapted to image at wavelengths that are currently impossible with conventional CCD and CMOS imagers. We are currently testing a prototype design for the camera and include experimental results.

- by Shriram Sarvotham
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- Compressed Sensing, Light field, Digital Image, Random Matrices

We propose a general mathematical framework for dealing with Light Fields:

- by Todor Georgiev
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- Fluid Dynamics, Optical Flow, Historic conservation law, Light field

During summer 2008, as part of the Circumpolar Flaw Lead system study, we measured phytoplankton photosynthetic parameters to understand regional patterns in primary productivity, including the degree and timescale of photoacclimation and how variability in environmental conditions influences this response. Photosynthesis-irradiance measurements were taken at 15 sites primarily from the depth of the subsurface chlorophyll a (Chl a) maximum (SCM) within the Beaufort Sea flaw lead polynya. The physiological response of phytoplankton to a range of light levels was used to assess maximum rates of carbon (C) fixation (P m * ), photosynthetic efficiency (a * ), photoacclimation (E k ), and photoinhibition (b * ). SCM samples taken along a transect from under ice into open water exhibited a [3-fold increase in a * and P m * , showing these parameters can vary substantially over relatively small spatial scales, primarily in response to changes in the ambient light field. Algae were able to maintain relatively high rates of C fixation despite low light at the SCM, particularly in the large ([5 lm) size fraction at open water sites. This may substantially impact biogenic C drawdown if species composition shifts in response to future climate change. Our results suggest that phytoplankton in this region are well acclimated to existing environmental conditions, including sea ice cover, low light, and nutrient pulses. Furthermore, this photoacclimatory response can be rapid and keep pace with a developing SCM, as phytoplankton maintain photosynthetic rates and efficiencies in a narrow ''shade-acclimated'' range.

- by Kevin Arrigo and +2
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- Climate Change, Sea Ice, Biological Sciences, Spatial Scale

We deduce and study an analytical expression for Fresnel diffraction of a plane wave by a spiral phase plate (SPP) that imparts an arbitrary-order phase singularity on the light field. Estimates for the optical vortex radius that depends on the singularity's integer order n (also termed topological charge, or order of the dislocation) have been derived. The near-zero vortex intensity is shown to be proportional to 2n , where is the radial coordinate. Also, an analytical expression for Fresnel diffraction of the Gaussian beam by a SPP with nth-order singularity is analyzed. The far-field intensity distribution is derived. The radius of maximal intensity is shown to depend on the singularity number. The behavior of the Gaussian beam intensity after a SPP with second-order singularity ͑n =2͒ is studied in more detail. The parameters of the light beams generated numerically with the Fresnel transform and via analytical formulas are in good agreement. In addition, the light fields with first-and second-order singularities were generated by a 32-level SPP fabricated on the resist by use of the electron-beam lithography technique.

- by Svetlana Khonina and +1
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- Electron Beam Lithography, Dislocations, Optical physics, Second Order
- by Michael Borowitzka
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- Water quality, Aquatic Plants, Aquatic Macrophytes, Functional diversity