James Barabas

Holovideo for everyone: a low-cost holovideo monitor

This work presents an architecture for a relatively low-cost, pc-driven holovideo monitor. The geometry uses minimal optics and is built to host a multi-channel acousto-optic modulator that can be driven by up-converted VGA signals. The displays target specifications include a standard vertical resolution (480 lines) output driven by an 18 channel acousto-optic modulator, 30Hz refresh-rate and multiple color operation. This paper reports early tests of this geometry with a single acousto-optic channel. The goal is to create a small but functional holographic display that can be readily replicated, easily driven and provide basic monitor functionality with a bill of materials in the hundreds, rather than thousands, of dollars.

Progress in holographic video displays based on guided-wave acousto-optic devices

The novel frequency-multiplexed modulator architecture of the MIT Mark III holo-video display poses a significant challenge in generation of appropriate video signals. Unlike in our previous work, here it is necessary to generate a group of adjacent single-sideband RF signals; as this display is intended to be manufacturable at consumer-electronics prices we face the added requirement of compact and inexpensive electronics that are compatible with standard PC graphics processors. In this paper we review the goals and architecture of Mark III and then describe our experiments and results in the use of a hardware/software implementation of Weavers single-sideband modulation method to upconvert six 200MHz baseband analog video signals to a set of RF signals covering a nearly contiguous 1GHz range. We show that our method allows efficient generation of non-overlapping signals without aggressive filtering.

Diffraction specific coherent panoramagrams of real scenes

We have previously introduced the Diffraction Specific Coherent Panoramagram - a multi-view holographic stereogram that provides correct visual accommodation as well as smooth motion parallax with far fewer views than a normal stereogram. This method uses scene depth information to generate directionally-varying wavefront curvature, and can be computed at interactive rates using off-the-shelf graphics processors. In earlier work we used z-buffer information associated with parallax views rendered from synthetic graphics models; in this paper we demonstrate the computation of Diffraction Specific Coherent Panoramagrams of real-world scenes captured by cameras.

Information processing for live photo mosaic with a group of wireless image sensors

Photo tourism [11] is a platform that allows users to transform unstructured online digital photos into a 3D experience. Nowadays, image sensors are being extensively used to allow images to be taken automatically and remotely, which facilitates the opportunity for live update of photo mosaics. In this paper, we present a novel framework for live photo mosaic with a group of wireless image sensor nodes, where the image data aggregation is accomplished in an efficient and distributed way. Essentially, we propose to conduct clustering and data compression at wireless image sensor network level while conserving the completeness of the feature point information [9] for reconstruction. Toward the realization of the whole system, we have built image sensor prototypes with commodity cameras and we validated our approach by indepth analysis, extensive simulations and field experiments.

P-3: Evaluation of Rendering Algorithms for Presenting Layered Information on Holographic Displays

This paper proposes evaluation of rendering methods for holographic display allowing a viewer to use monocular information to selectively focus on parts of the display volume. We describe an experiment for comparatively evaluating human performance across different holographic rendering methods, by requiring the identification of overlapping letters separated in depth.

Analysis on errors due to photon noise and quantization process with multiple images

In the scenes with deflective and/or reflective medium such as fogs or mirrors, where the contrast levels among the intensity values of the pixels in the image are very small, even a small estimation improvement on the intensity value of each pixel could make a big difference for the perceptual quality of the final image if we want to subtract the interference components from the original image. In this paper we analyze the average quantization error, total error and photon noise from multiple images with fixed and varied exposure time. We observe that by properly controlling and varying exposure time with multiple images, one can obtain an image with better performance than that of the conventional wisdom, where multiple images are taken repeatedly with the same exposure time.

Computational architecture for full-color holographic displays based on anisotropic leaky-mode modulators

The MIT Mark IV holographic display system employs a novel anisotropic leaky-mode spatial light modulator that allows for the simultaneous and superimposed modulation of red, green, and blue light via wavelength-division multiplexing. This WDM-based scheme for full-color display requires that incoming video signals containing holographic fringe information are comprised of non-overlapping spectral bands that fall within the available 200 MHz output bandwidth of commercial GPUs. These bands correspond to independent color channels in the display output and are appropriately band-limited and centered to match the multiplexed passbands and center frequencies in the frequency response of the mode-coupling device. The computational architecture presented in this paper involves the computation of holographic fringe patterns for each color channel and their summation in generating a single video signal for input to the display. In composite, 18 such input signals, each containing holographic fringe information for 26 horizontal-parallax only holographic lines, are generated via three dual-head GPUs for a total of 468 holographic lines in the display output. We present a general scheme for full-color CGH computation for input to Mark IV and furthermore depict the adaptation of the diffraction specific coherent panoramagram approach to fringe computation for the Mark IV architecture.

Progress in updatable photorefractive polymer-based holographic displays via direct optical writing of computer-generated fringe patterns

We have previously introduced an architecture for updatable photorefractive holographic display based around direct fringe writing of computer-generated holographic fringe patterns. 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. In this paper, motivations and goals for employing a direct fringe writing architecture for photorefractive holographic imagers are reviewed, new methods for PRP exposure by micro-optical fields generated via spatial light modulation and telecentric optics are described, and resulting holographic images are presented and discussed. Experimental results are reviewed in the context of theoretical indicators for system performance.

Depth perception and user interface in digital holographic television

A holographic television system, featuring realtime incoherent 3D capture and live holographic display is used for experiments in depth perception. Holographic television has the potential to provide more complete visual representations, including latency-free motion parallax and more natural affordances for accommodation. Although this technology has potential to improve realism in many display applications, we investigate benefits in uses where direct vision of a workspace is not possible. Applications of this nature include work with hazardous materials, teleoperation over distance, and laparoscopic surgery. In this study, subjects perform manual 3D object manipulation tasks where they can only see the workspace through holographic closed-circuit television. This study is designed to compare performance at manual tasks using holographic television compared to performance with displays that mimic 2D, and stereoscopic television.

How to build a holographic television system

The ultimate three-dimensional television viewing experience will be autostereoscopic (requiring no glasses), provide smooth parallax rather than just two views, and support other real-world perceptual cues to depth such as visual accommodation (focusing). Holography meets these requirements, but it is often felt that the scene-acquisition, bandwidth, and display pixel count requirements for holographic television will prove insurmountable. We describe the characteristics of a “true” holographic television display, review the input, transmission, and output needs, and describe our experiments in creating an end-to-end holographic television system with costs in only the hundreds of dollars, based upon a combination of various current consumer-electronics technologies and a novel light-modulator chip.