Showing papers on "Light field published in 2002"

Quantum control of energy flow in light harvesting.

Abstract: Coherent light sources have been widely used in control schemes that exploit quantum interference effects to direct the outcome of photochemical processes. The adaptive shaping of laser pulses is a particularly powerful tool in this context: experimental output as feedback in an iterative learning loop refines the applied laser field to render it best suited to constraints set by the experimenter. This approach has been experimentally implemented to control a variety of processes, but the extent to which coherent excitation can also be used to direct the dynamics of complex molecular systems in a condensed-phase environment remains unclear. Here we report feedback-optimized coherent control over the energy-flow pathways in the light-harvesting antenna complex LH2 from Rhodopseudomonas acidophila, a photosynthetic purple bacterium. We show that phases imprinted by the light field mediate the branching ratio of energy transfer between intra- and intermolecular channels in the complex's donor acceptor system. This result illustrates that molecular complexity need not prevent coherent control, which can thus be extended to probe and affect biological functions.

A real-time distributed light field camera

Abstract: We present the design and implementation of a real-time, distributed light field camera. Our system allows multiple viewers to navigate virtual cameras in a dynamically changing light field that is captured in real-time. Our light field camera consists of 64 commodity video cameras that are connected to off-the-shelf computers. We employ a distributed rendering algorithm that allows us to overcome the data bandwidth problems inherent in dynamic light fields. Our algorithm works by selectively transmitting only those portions of the video streams that contribute to the desired virtual views. This technique not only reduces the total bandwidth, but it also allows us to scale the number of cameras in our system without increasing network bandwidth. We demonstrate our system with a number of examples.

Light field mapping: efficient representation and hardware rendering of surface light fields

Abstract: A light field parameterized on the surface offers a natural and intuitive description of the view-dependent appearance of scenes with complex reflectance properties. To enable the use of surface light fields in real-time rendering we develop a compact representation suitable for an accelerated graphics pipeline. We propose to approximate the light field data by partitioning it over elementary surface primitives and factorizing each part into a small set of lower-dimensional functions. We show that our representation can be further compressed using standard image compression techniques leading to extremely compact data sets that are up to four orders of magnitude smaller than the input data. Finally, we develop an image-based rendering method, light field mapping, that can visualize surface light fields directly from this compact representation at interactive frame rates on a personal computer. We also implement a new method of approximating the light field data that produces positive only factors allowing for faster rendering using simpler graphics hardware than earlier methods. We demonstrate the results for a variety of non-trivial synthetic scenes and physical objects scanned through 3D photography.

Understanding the forbidden pitch and assist feature placement

Abstract: Optical proximity effect is a well-known phenomenon in photolithography. Such an effect results from the structural interaction between the main feature and the neighboring features. Recent observations have shown that such structural interactions not only affect the critical dimension of the main feature at the image plane, but also the exposure latitude of the main feature. In this paper, it has been shown that the variation of the critical dimension as well as the exposure latitude of the main feature is a direct consequence of light field interference between the main feature and the neighboring features. Depending on the phase of the field produced by the neighboring features, the main feature critical dimension and exposure latitude can be improved by constructive light field interference, or degraded by destructive light field interference. The phase of the field produced by the neighboring features can be shown to be in the location where the field produced by the neighboring features can be shown to be dependent on the pitch as well as the illumination angle. For a given illumination, the forbidden pitch lies in the location where the field produced by the neighboring features interferes with the field of the main feature destructively. The theoretical analysis given here offers the tool to map out the forbidden pitch locations for any feature size and illumination conditions. More importantly, it provides the theoretical ground for illumination design in order to suppress the forbidden pitch phenomenon, and for scattering bar placement to achieve optimal performance as well.

Conditional generation of N -photon entangled states of light

Abstract: We propose a scheme for conditional generation of two-mode N-photon path-entangled states of traveling light field. These states may find applications in quantum optical lithography and they may be used to improve the sensitivity of interferometric measurements. Our method requires only single-photon sources, linear optics (beam splitters and phase shifters), and photodetectors with single-photon sensitivity.

Method of identifying an extreme interaction pitch region, methods of designing mask patterns and manufacturing masks, device manufacturing methods and computer programs

Abstract: Optical proximity effects (OPEs) are a well-known phenomenon in photolithography. OPEs result from the structural interaction between the main feature and neighboring features. It has been determined by the present inventors that such structural interactions not only affect the critical dimension of the main feature at the image plane, but also the process latitude of the main feature. Moreover, it has been determined that the variation of the critical dimension as well as the process latitude of the main feature is a direct consequence of light field interference between the main feature and the neighboring features. Depending on the phase of the field produced by the neighboring features, the main feature critical dimension and process latitude can be improved by constructive light field interference, or degraded by destructive light field interference. The phase of the field produced by the neighboring features is dependent on the pitch as well as the illumination angle. For a given illumination, the forbidden pitch region is the location where the field produced by the neighboring features interferes with the field of the main feature destructively. The present invention provides a method for determining and eliminating the forbidden pitch region for any feature size and illumination condition. Moreover, it provides a method for performing illumination design in order to suppress the forbidden pitch phenomena, and for optimal placement of scattering bar assist features.

Feedback on the motion of a single atom in an optical cavity.

Abstract: We demonstrate feedback on the motion of a single neutral atom trapped in the light field of a high-finesse cavity. Information on the atomic motion is obtained from the transmittance of the cavity. This is used to implement a feedback loop in analog electronics that influences the atom's motion by controlling the optical dipole force exerted by the same light that is used to observe the atom. In spite of intrinsic limitations, the time the atom stays within the cavity could be extended by almost 30% beyond that of a comparable constant-intensity dipole trap.

Near-field enhanced Raman spectroscopy using side illumination optics

Abstract: We demonstrate near-field enhanced Raman spectroscopy with the use of a metallized cantilever tip and highly p-polarized light directed onto the tip with side illumination optics using a long working distance objective lens. The highly p-polarized light field excites surface plasmon polaritons localized at the tip apex, which results in the enhanced near-field Raman scattering. In this article, we achieved an enhancement factor of 4000 for Rhodamine 6G molecules adsorbed on a silver island film. The side illumination is also applicable to an opaque sample and to near-field photolithography.

Light field mapping

Abstract: A light field parameterized on the surface offers a natural and intuitive description of the view-dependent appearance of scenes with complex reflectance properties. To enable the use of surface li...

Atom lithography with a holographic light mask.

Abstract: In atom lithography with optical masks, deposition of an atomic beam on a given substrate is controlled by a standing light-wave field. The lateral intensity distribution of the light field is transferred to the substrate with nanometer scale. We have tailored a complex pattern of this intensity distribution through diffraction of a laser beam from a hologram that is stored in a photorefractive crystal. This method can be extended to superpose 1000 or more laser beams. The method is furthermore applicable during growth processes and thus allows full 3D structuring of suitable materials with periodic and nonperiodic patterns at nanometer scales.

Feature-based light field morphing

Abstract: We present a feature-based technique for morphing 3D objects represented by light fields. Our technique enables morphing of image-based objects whose geometry and surface properties are too difficult to model with traditional vision and graphics techniques. Light field morphing is not based on 3D reconstruction; instead it relies on ray correspondence, i.e., the correspondence between rays of the source and target light fields. We address two main issues in light field morphing: feature specification and visibility changes. For feature specification, we develop an intuitive and easy-to-use user interface (UI). The key to this UI is feature polygons, which are intuitively specified as 3D polygons and are used as a control mechanism for ray correspondence in the abstract 4D ray space. For handling visibility changes due to object shape changes, we introduce ray-space warping. Ray-space warping can fill arbitrarily large holes caused by object shape changes; these holes are usually too large to be properly handled by traditional image warping. Our method can deal with non-Lambertian surfaces, including specular surfaces (with dense light fields). We demonstrate that light field morphing is an effective and easy-to-use technqiue that can generate convincing 3D morphing effects.

Quantum optical effects in semiconductor microcavities

Abstract: Investigations of quantum effects in semiconductor quantum well microcavities interacting with laser light in the strong coupling regime are presented. Modification of quantum fluctuations of the outgoing light are expected due to the non-linearity originating from coherent exciton-exciton scattering. In the strong coupling regime, this scattering translates into a four-wave mixing interaction between the mixed exciton-photon states, the polaritons. Squeezing and giant amplification of the polariton field and of the outgoing light field fluctuations are predicted. However, polariton-phonon scattering is shown to yield excess noise in the output field, which may destroy the non classical effects. Experiments demonstrate evidence for giant amplification due to coherent four-wave mixing of polaritons. Noise reduction below the thermal noise level was also observed.

Roof part for vehicle has light field beneath roof part formed by illuminating it with light from illumination device and bearer surface illuminated by light from source forms light panel

Abstract: The vehicle roof has a roof part (3) and a light field beneath the roof part that is formed by illuminating it with light from an illumination device (10). A bearer surface (13) for the underside of the roof surface is arranged at a distance and forms the light field when illuminated by light from the light source.

Understanding the forbidden pitch phenomenon and assist feature placement

Abstract: Optical proximity effect is a well-known phenomenon in photolithography. Such an effect results from the structural interaction between the main feature and the neighboring features. Recent observations have shown that such structural interactions not only affect the critical dimension of the main feature at the image plane, but also the exposure latitude of the main feature. In this paper, it has been shown that the variation of the critical dimension as well as the exposure latitude of the main feature is a direct consequence of light field interference between the main feature and the neighboring features. Depending on the phase of the field produced by the neighboring features, the main feature exposure latitude can be improved by constructive light field interference, or degraded by destructive light field interference. The phase of the field produced by the neighboring features can be shown to be dependent on the pitch as well as the illumination angle. For a given illumination, the forbidden pitch lies in the location where the field produced by the neighboring features interferes with the field of the main feature destructively. The theoretical analysis given here offers the tool to map out the forbidden pitch locations for any feature size and illumination conditions. More importantly, it provides the theoretical ground for illumination design in order to suppress the forbidden pitch phenomenon, and for scattering bar placement to achieve optimal performance as well.

Verification of mlc leaf position and of radiation and light field congruence

Abstract: A system includes acquisition of first electronic image data representing a phantom located at a first position and irradiated by a first radiation field emitted by a radiation emitter, acquisition of second electronic image data representing the phantom located at a second position based at least on a first light field emitted by a light emitter and irradiated by a second radiation field emitted by the radiation emitter, generation of third electronic image data by correcting the second electronic image data based at least on the first electronic image data, and determination of a deviation between the first light field and the second radiation field based at least on the third electronic image data

The plenoptic illumination function

Abstract: Image-based modeling and rendering has been demonstrated as a cost-effective and efficient approach to virtual reality applications. The computational model that most image-based techniques are based on is the plenoptic function. Since the original formulation of the plenoptic function does not include illumination, most previous image-based virtual reality applications simply assume that the illumination is fixed. We propose a formulation of the plenoptic function, called the plenoptic illumination function, which explicitly specifies the illumination component. Techniques based on this new formulation can be extended to support relighting as well as view interpolation. To relight images with various illumination configurations, we also propose a local illumination model, which utilizes the rules of image superposition. We demonstrate how this new formulation can be applied to extend two existing image-based representations, panorama representation such as QuickTime VR and two-plane parameterization, to support relighting with trivial modifications. The core of this framework is compression, and we therefore show how to exploit two types of data correlation, the intra-pixel and the inter-pixel correlations, in order to achieve a manageable storage size.

Highlight substitution in light fields

Abstract: Highlights occur especially when recording medical (color) images during micro-invasive operations. They disturb the physicians who can sometimes only guess the tissue at the position of the highlights. We present a new technique of highlight removal. A so-called light field is generated from the recorded image sequence. Then a binary highlight mask is computed for each image and used as confidence map for the light field pixels. The result is a light field in which pixels at highlight positions are interpolated by pixels which were not over-imposed by highlights. This leads to light fields with better images. We demonstrate and evaluate the technique on medical and synthetic image sequences.

Comparison of radiance and polarization values observed in the Mediterranean Sea and simulated in a Monte Carlo model

Abstract: Measurements of the radiance and degree of polarization made in 1971 in the Mediterranean Sea are presented along with the simulation of all observed quantities by a Monte Carlo technique. It is shown that our independent scattering treatment utilizing a Stokes vector formalism to describe the polarization state of the light field produces remarkably good agreement with those values measured in situ.

Multi-view Geometry Estimation for Light Field Compression

Abstract: Geometry-aided light field compression requires accurate geometry for the efficient representation of the light field image data. In this work, we propose a method to directly estimate a geometry model from the light field images, such that it maximizes the compression efficiency. Previous work on this problem [8] uses least-squares to solve a set of optical-flow based equations. This approach suffers from stability problems and gives sub-optimal results, due to outliers included in the set of equations. We propose an extension to this approach that addresses some of its short-comings. Specifically, we use weighted least-squares to identify and suppress the effects of outliers and a multi-resolution estimation algorithm for the geometry model. The experiments performed on real and synthetic data show that our technique stabilizes the algorithm, decreases the total running time by a factor of 10 and decreases bit-rate by up to over the previous work. For the synthetic light field sequences, we show that this achieves the optimal achievable compression efficiency, under our constrained arrangement.

Optical decay from a Fabry-Perot cavity faster than the decay time

Abstract: The dynamical response of an optical Fabry–Perot cavity is investigated experimentally. We observe oscillations in the transmitted and the reflected light intensity if the frequency of the incoupled light field is rapidly changed. In addition, the decay of a cavity-stored light field is accelerated if the phase and the intensity of the incoupled light are switched in an appropriate way. The theoretical model by M. J. Lawrence [J. Opt. Soc. Am. B16, 523 (1999)] agrees with our observations.

Scam light field rendering

Abstract: In this paper we present a new variant of the light field representation that supports improved image reconstruction by accommodating sparse correspondence information. This places our representation somewhere between a pure, two-plane parameterized, light field and a lumigraph representation, with its continuous geometric proxy. Our approach factorises the rays of a light field into one of two separate classes. All rays consistent with a given correspondence are implicitly represented using a new auxiliary data structure, which we call a surface camera (or scam). The remaining rays of the light field are represented using a standard two-plane parameterized light field. We present an efficient rendering algorithm that combines ray samples from scams with those from the light field. The resulting image reconstructions are noticeably improved over that of a pure light field.

Relighting with the Reflected Irradiance Field: Representation, Sampling and Reconstruction

Abstract: Image-based relighting (IBL) is a technique to change the illumination of an image-based object/scene. In this paper, we define a representation called the reflected irradiance field which records the light reflected from a scene as viewed at a fixed viewpoint as a result of moving a point light source on a plane. It synthesizes a novel image under a different illumination by interpolating and superimposing appropriate recorded samples. Furthermore, we study the minimum sampling problem of the reflected irradiance field, i.e., how many light source positions are needed. We find that there exists a geometry-independent bound for the sampling interval whenever the second-order derivatives of the surface BRDF and the minimum depth of the scene are bounded. This bound ensures that when the novel light source is on the plane, the error in the reconstructed image is controlled by a given tolerance, regardless of the geometry. We also analyze the bound of depth error so that the extra reconstruction error can also be governed when the novel light source is off-plane. Experiments on both synthetic and real surfaces are conducted to verify our analysis.

System and method for feature-based light field morphing and texture transfer

Abstract: A “light field morpher,” as described herein, provides a computationally efficient system and method for image-based three-dimensional (3D) morphing and texture transfer of 3D objects by morphing “light fields” or “lumigraphs,” associated with source and target 3D objects. The light field morpher is applicable to morphing of objects having either or both Lambertian, or non-Lambertian surfaces, including surfaces having complex properties such as fur, subsurface scattering, and hypertextures, without the need for object modeling, or otherwise recovering detailed object geometry. Light field morphing begins by first specifying corresponding 2D and 3D feature elements, such as, “feature lines,” “feature polygons,” and “background edges,” in the input light fields representing the source and target light fields. Once the feature elements have been specified, “ray-space warping” of both light fields then warps those light fields to produce feature alignment. These warped light fields are then blended to produce a light field morph.

Two-photon interferometry for high-resolution imaging

Abstract: This paper discusses the advantages of using non-classical states of light for two aspects of optical imaging: the creation of microscopic images on photosensitive substrates, which constitutes the foundation for optical lithography, and the imaging of microscopic objects. In both cases, the classical resolution limit given by the Rayleigh criterion is approximately half of the optical wavelength. It has been shown, however, that by using multi-photon quantum states of the light field, and a multi-photon sensitive material or detector, this limit can be surpassed. A rigorous quantum mechanical treatment of this problem is given, some particularly widespread misconceptions are addressed, and turning quantum imaging into a practical technology is discussed.

Axial Magnetic Fields in Relativistic Self-Focusing Channels

Abstract: Based on an improved cavitation model for the electron dynamics, an exact analysis is presented of the generation of axial magnetic fields in the relativistic self-focusing channels produced by circularly polarized light in plasmas. Two kinds of waveguiding structures are considered: single-channel waveguides and plasma filaments surrounded by a light field. It is found that due to large electron density gradients in the cavitation plasma, magnetic fields of megagauss values with opposite directions separated by a neutral sheet, where the magnetic field passes through zero, can be produced.

Motion-light parametric amplifier and entanglement distributor

Abstract: We propose a scheme for entangling the motional mode of a trapped atom with a propagating light field via a cavity-mediated parametric interaction. We then show that if this light field is subsequently coupled to a seconddistant atom via a cavity-mediated linear-mixing interaction, it is possible to transfer the entanglement from the light beam to the motional mode of the second atom to create an Einstein-Podolsky-Rosen-type entangled state of the positions and momenta of two distantly separated atoms.

Geometry refinement for light field compression

Abstract: In geometry-aided light field compression, a geometry model is used for disparity-compensated prediction of light field images from already encoded light field images. This geometry model, however, may have limited accuracy. We present an algorithm that refines a geometry model to improve the overall light field compression efficiency. This algorithm uses an optical-flow technique to explicitly minimize the disparity-compensated prediction error. Results from experiments performed on both real and synthetic data sets show bit-rate reductions of approximately 10% using the improved geometry model over a silhouette-reconstructed geometry model.

Producing energetic, tunable, coherent x-rays with long wavelength light

Abstract: An apparatus and method are provided for producing x-rays by generating high harmonic radiation with long wavelength light. The use of long wavelength light increases the acceleration time of the electrons in the light field. Keeping the atomic species and light intensity unchanged, the x-ray photon energy increases by a factor of two to four when the fundamental wavelength increases by a factor of two.

Coherent exchange of momentum between atoms and light

Abstract: We have demonstrated that coherent control of the momentum exchange between a light field and atoms can be implemented in frequency-modulated light. The optical parameters are chosen to drive the atoms between ground and excited states by adiabatic rapid passage in counterpropagating modulated light beams. We apply the optical force transversely to a thermal atomic beam, and the deflection provides a measure of the force. The modulation period is 2?/?s<