Fabrication of waveguide spatial light modulators via femtosecond laser micromachining

We have previously introduced an anisotropic leaky-mode modulator as a waveguide-based, acousto-optic solution for spatial light modulation in holographic video display systems. Waveguide fabrication for these and similar surface acoustic wave devices relies on proton exchange of a lithium niobate substrate, which involves the immersion of the substrate in an acid melt. While simple and effective, waveguide depth and index profiles resulting from proton exchange are often non-uniform over the device length or inconsistent between waveguides fabricated at different times using the same melt and annealing parameters. In contrast to proton exchange, direct writing of waveguides has the appeal of simplifying fabrication (as these methods are inherently maskless) and the potential of fine and consistent control over waveguide depth and index profiles. In this paper, we explore femtosecond laser micromachining as an alternative to proton exchange in the fabrication of waveguides for anisotropic leaky-mode modulators

Progress in off-plane computer-generated waveguide holography for near-to-eye 3D display

Waveguide holography refers to the use of holographic techniques for the control of guided-wave light in integrated optical devices (e.g., off-plane grating couplers and in-plane distributed Bragg gratings for guided-wave optical filtering). Off-plane computer-generated waveguide holography (CGWH) has also been employed in the generation of simple field distributions for image display. We have previously depicted the design and fabrication of a binary-phase CGWH operating in the Raman-Nath regime for the purposes of near-to-eye 3-D display and as a precursor to a dynamic, transparent flat-panel guided-wave holographic video display. In this paper, we describe design algorithms and fabrication techniques for multilevel phase CGWHs for near-to-eye 3-D display

The Impact of New Multimedia Representations on Hardware and Software Systems

The generation of video and audio coding methods to follow the present, pioneering generation have not yet been standardized, but it is possible to predict many of their characteristics. I discuss these, with particular reference to their impact on the design of software and hardware systems for multimedia. Keywords: video compression, model-based coding, data-flow computing, digital signal processing 1. BACKGROUND Compressed digital video and audio have become common. The price of dedicated processing circuits has dropped to the point that they are cost-effective for consumer applications, while general-purpose processor performance is increasing to the point that standard personal computers can support digital multimedia applications with little or no additional hardware support. But digital media representations are a moving target, and now that we know appropriate hardware/software design methodologies and optimizations to achieve real-time performance for the current generation ..

Direct fringe writing architecture for photorefractive polymer-based holographic displays: analysis and implementation

An optical architecture for updatable photorefractive polymer-based holographic displays via the direct fringe writing of computer-generated holograms is presented. In contrast to interference-based stereogram techniques for hologram exposure in photorefractive polymer (PRP) materials, the direct fringe writing architecture simplifies system design, reduces system footprint and cost, and offers greater affordances over the types of holographic images that can be recorded. This paper reviews motivations and goals for employing a direct fringe writing architecture for photorefractive holographic imagers, describes our implementation of direct fringe transfer, presents a phase-space analysis of the coherent imaging of fringe patterns from spatial light modulator to PRP, and presents resulting experimental holographic images on the PRP resulting from direct fringe transfer.MIT Media Lab ConsortiumUnited States. Office of the Director of National Intelligence. Intelligence Advanced Research Projects Activity (Air Force Research Laboratory Contract FA8650-10-C-7034

Semiautomatic 3-D model extraction from uncalibrated 2-D camera views

Scenes that contain every-day man-made objects often possess sets of parallel lines and orthogonal planes, the projective features of which possess enough structural information to constrain possible scene element geometries as well as a camera's intrinsic and extrinsic parameters. In particular, in a scene with three mutually orthogonal sets of parallel lines, detection of the corresponding three vanishing points of the imaged lines allows us to determine the camera's image-relative principal point and effective focal length. In this paper we introduce a new technique to solve for radial and decentering lens distortion directly from the results of vanishing point estimation, thus precluding the need for special calibration templates. This is accomplished by using an iterative method to solve for the parameters that minimize vanishing point dispersion. Dispersion here is measured as covariance of vanishing point estimation error projected on the Gaussian sphere whose origin is the esti..

Generation of Blue Noise Arrays by Genetic Algorithm

Halftoning or quantizing by means of a threshold array is simple, fast, and easily parallelized: a matrix of threshold values is tiled across the image and each output pixel is colored white if the image value exceeds the threshold value and is colored black otherwise. The computational efficiency and locality of the compare operation makes this technique suitable for applications in printing and motion video quantization. In the past, threshold arrays have generally been used with regular-appearing patterns such as clustered-dot "classical" halftoning or Bayer's dispersed-dot patterns. Ulichney has presented a heuristic method for generating blue-noise threshold arrays which do not appear regular, and offer the visual advantages of error-diffusion without its computational costs. Such heuristic methods are capable of generating high-quality threshold arrays, but they are not flexible or controllable enough to enable tuning for particular applications or output device characteristics. We present instead..

Segmentation of an Image Sequence Using Multi-Dimensional Image Attributes

Whether for purposes of compression efficiency, image editing, interactive multimedia authoring, or database search, it is often useful to be able to segment images or image sequences into regions corresponding to objects. In this paper we describe a segmentation scheme that takes account of multiple image characteristics, developing a multi-modal statistical model of regions based on a small amount of user-supplied training data. 1. INTRODUCTION Researchers have shown the compression advantages of coding video as a set of regions that can be defined by motion or texture models. [1], [2], [3] Segmentation of video can likewise enable special effects (e.g. placing actors into a synthetic set) or authoring of interactive or personalizable programming. [4] In cases where semantics are as important as compression, though, one finds that generally objects in the real world do not correspond to a simple clustering model of a single parameter like motion; it is also true that the desired seg..

Segmentation of Frames in a Video Sequence Using Motion and Other Attributes

Motion-compensated video coders typically segment a scene into arbitrary tiles, resulting in a compressed bitstream which is not physically or semantically related to the scene structure. This paper presents a method for segmenting video frames and coding motion of regions, where the regions are defined in terms of a number of different properties. The goal is a video coder which gives good compression while identifying coherent regions in a manner useful for both human users and automated scene-understanding processes. Both a supervised and an unsupervised clustering algorithm are used to segment an image sequence; both algorithms make use of multiple features including motion, texture, position, and color. By utilizing both the structure and motion information, we preserve the semantic/structural content of the different regions, and simultaneously remove the redundancy (in successive frames) by describing the motion information in each region with a six-parameter affine model. In th..

Segmentation Of An Image Sequence Using Multi-Dimensional Image Attributes

Whether for purposes of compression efficiency, image editing, interactive multimedia authoring, or database search, it is often useful to be able to segment images or image sequences into regions corresponding to objects. In this paper we describe a segmentation scheme that takes account of multiple image characteristics, developing a multi-modal statistical model of regions based on a small amount of user-supplied training data

Reflection of Presence: Toward more natural and responsive telecollaboration

The purpose of Reflection of Presence is to create a framework for a telepresence environment that intelligently responds and adapts itself to its inhabitants in order to enhance interpersonal communication or collaboration. The metaphor is that of a "magic mirror" in which one not only sees a reflection of oneself, but also reflections of the other remotely-located participants, just as if everyone is standing in the same room looking at each other through a real mirror. Using visual and auditory cues, segmented images of participants are dynamically layered into a single display using varying transparency, position and scale to reflect center of attention and degree of presence. Wireless tangible interfaces allow participants to customize their shared space and collaboratively manipulate and annotate media objects in the background. The system is novel in that it is implemented totally as a set of cooperating scripts instead of through a low-level programming language, enabling rapid..