Sundeep Jolly

Toward BxDF display using multilayer diffraction

With a wide range of applications in product design and optical watermarking, computational BxDF display has become an emerging trend in the graphics community. In this paper, we analyze the design space of BxDF displays and show that existing approaches cannot reproduce arbitrary BxDFs. In particular, existing surface-based fabrication techniques are often limited to generating only specific angular frequencies, angle-shift-invariant radiance distributions, and sometimes only symmetric BxDFs. To overcome these limitations, we propose diffractive multilayer BxDF displays. We derive forward and inverse methods to synthesize patterns that are printed on stacked, high-resolution transparencies and reproduce prescribed BxDFs with unprecedented degrees of freedom within the limits of available fabrication techniques.

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.

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.

Direct Optical Fringe Writing of Diffraction Specific Coherent Panoramagrams in Photorefractive Polymer for Updatable Three-Dimensional Holographic Display

Progress in the development of an updatable holographic display system based around the direct transfer of computer-generated holographic fringe patterns from LCoS SLMs into photorefractive polymeric materials is presented. This architecture is poised as a simplifying alternative to previous demonstrations of updatable holographic displays in photorefractive polymeric materials based around conventional interference-based holographic stereogram techniques. Our system concept – comprised of fringe pattern generation on computer, fringe pattern transfer from SLM to photorefractive polymer, and spatial multiplexing for large-image generation – reintroduces accommodation cues to the resulting holographic images and represents a reduction of system footprint, complexity, and cost relative to the current interference-based systems. We present the adaptation of our Diffraction Specific Coherent Panoramagram fringe computation method – originally developed to drive AOM-based holographic displays at video rates while preserving all depth cues, including accommodation – to the current display architecture and depict methods for direct fringe transfer from SLM to photorefractive polymer. Preliminary results of horizontal parallax-only images on this display are presented and directions for performance improvements and system extensions are explored.

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

Abstract. 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.

Frequency Division of Color for Holovideo Displays using Anisotropic Leaky Mode Couplers

We present optimized fabrication parameters for RGB leaky mode couplers which are bandwidth-matched to GPU outputs to enable highly parallel holographic displays. We also present a semi-automatic characterization apparatus for frequency division of color devices.

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.

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.