Daniel E. Smalley

Anisotropic leaky-mode modulator for holographic video displays

Every holographic video display is built on a spatial light modulator, which directs light by diffraction to form points in three-dimensional space. The modulators currently used for holographic video displays are challenging to use for several reasons: they have relatively low bandwidth, high cost, low diffraction angle, poor scalability, and the presence of quantization noise, unwanted diffractive orders and zero-order light. Here we present modulators for holographic video displays based on anisotropic leaky-mode couplers, which have the potential to address all of these challenges. These modulators can be fabricated simply, monolithically and at low cost. Additionally, these modulators are capable of new functionalities, such as wavelength division multiplexing for colour display. We demonstrate three enabling properties of particular interest—polarization rotation, enlarged angular diffraction, and frequency domain colour filtering—and suggest that this technology can be used as a platform for low-cost, high-performance holographic video displays.

Holographic video display based on guided-wave acousto-optic devices

We introduce a new holo-video display architecture (Mark III) developed at the MIT Media Laboratory. The goal of the Mark III project is to reduce the cost and size of a holo-video display, making it into an inexpensive peripheral to a standard desktop PC or game machine which can be driven by standard graphics chips. Our new system is based on lithium niobate guided-wave acousto-optic devices, which give twenty or more times the bandwidth of the tellurium dioxide bulk-wave acousto-optic modulators of our previous displays. The novel display architecture is particularly designed to eliminate the high-speed horizontal scanning mechanism that has traditionally limited the scalability of Scophony- style video displays. We describe the system architecture and the guided-wave device, explain how it is driven by a graphics chip, and present some early results.

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.

Frequency division color characterization apparatus for anisotropic leaky mode light modulators

This paper presents an optical apparatus for characterizing frequency multiplexing of color in leaky mode, anisotropic waveguide modulators. This type of characterization is particularly useful for informing the design of full color holographic video displays. The primary function of the apparatus is to map the frequency response and angular overlap of red, green, and blue outputs. The apparatus also allows measurements of other parameters such as scan center frequency, optical and RF bandwidth, and scan linearity.

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.

Optimized guided-to-leaky-mode device for graphics processing unit controlled frequency division of color

We present fabrication parameters for an annealed proton-exchanged lithium niobate guided-wave modulator, which has been optimized for frequency division color multiplexing. We present waveguide parameters that maximize individual color frequency bands while reducing the aggregate drive bandwidth to match the 200xa0MHz bandwidth of commodity graphics processing unit (GPU) outputs. By matching the device bandwidth to that of the GPU outputs, we have made possible highly parallel and scalable color waveguide displays.

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.