Polarization Fields: Dynamic Light Field Display using Multi-Layer LCDs

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Polarization Fields: Dynamic Light Field Display using Multi-Layer LCDs

Douglas Lanman1 Gordon Wetzstein2 Matthew Hirsch1 Wolfgang Heidrich2 Ramesh Raskar

1MIT Media Lab 2University of British Columbia







Abstract

We introduce polarization field displays as an optically-efficient

design for dynamic light field display using multi-layered LCDs.

Such displays consist of a stacked set of liquid crystal panels with a

single pair of crossed linear polarizers. Each layer is modeled as a

spatially-controllable polarization rotator, as opposed to a conven-

tional spatial light modulator that directly attenuates light. Color

display is achieved using field sequential color illumination with

monochromatic LCDs, mitigating severe attenuation and moir´ e oc-

curring with layered color filter arrays. We demonstrate such dis-

plays can be controlled, at interactive refresh rates, by adopting the

SART algorithm to tomographically solve for the optimal spatially-

varying polarization state rotations applied by each layer. We val-

idate our design by cons***cting a prototype using modified off-

the-shelf panels. We demonstrate interactive display using a GPU-

based SART implementation supporting both polarization-based

and attenuation-based architectures. Experiments characterize the

accuracy of our image formation model, verifying polarization field

displays achieve increased brightness, higher resolution, and ex-

tended depth of field, as compared to existing automultiscopic dis-

play methods for dual-layer and multi-layer LCDs.

Keywords: computational displays, light fields, automultiscopic

3D displays, tomography, multi-layer LCDs

1 Introduction

The emergence of consumer, glasses-based stereoscopic displays

has renewed interest in glasses-free automultiscopic alternatives.

Manufacturers are beginning to offer such displays, primarily using

two technologies: parallax barriers [Ives 1903] and integral imag-

ing [Lippmann 1908]. These approaches have well-documented

limitations compared to stereoscopic displays: decreased resolu-

tion, potentially reduced brightness, and narrow depths of field (ob-

jects separated from the display appear blurred). Alternatives are

being pursued, spanning volumetric to holographic systems; yet,

particularly for mobile devices, a display is required that leverages

existing or emerging spatial light modulation technologies compat-

ible with thin form factors and having minimal power consumption.

We are inspired by systems that address these issues using well-

developed LCD technology. Jacobs et al. [2003] demonstrate

dual-layer LCDs can be operated as parallax barriers, allowing

full-resolution 2D content and 3D modes with reduced resolu-

tion and brightness. Lanman et al. [2010] increase the optical

efficiency of dual-layer LCDs with content-adaptive parallax bar-

riers, although at the cost of increased computation. Several

researchers have considered automultiscopic multi-layer LCDs.

Loukianitsa and Putilin [2002; 2006] evaluate three-layer designs.

More recently, Gotoda [2010] and Wetzstein et al. [2011] propose

tomographically-optimized multi-layer LCDs. Yet, these works

share a common architecture: LCDs are stacked such that each

layer implements a spatial light modulator that attenuates light.

This paper introduces optically-efficient architectures and

computationally-efficient algorithms for automultiscopic display

using multi-layered LCDs. In contrast to prior work, we operate

these layered architectures as polarization field displays: con-

s***cted by covering multiple liquid crystal panels with a single

pair of crossed linear polarizers. Each layer, if properly designed,

functions as a polarization rotator, rather than as a light attenuator.

We propose an efficient tomographic solver, specially-suited to this

design, that enables interactive applications. Through polarization

field displays we endeavor to leverage existing and emerging LCD

technology for practical dynamic light field display.

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