Computer Graphics Laboratory ETH Zurich

ETH

Multi-Layered Automultiscopic Displays

N. Ranieri, S. Heinzle, Q. Smithwick, D. Reetz, L. S. Smoot, W. Matusik, M. Gross

Proceedings of Pacific Graphics 2012 (Hong Kong, 12-14 September, 2012), pp. 2135-2143
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Abstract

Our hybrid display model combines multiple automultiscopic elements volumetrically to support horizontal and vertical parallax at a larger depth of field and better accommodation cues compared to single layer elements. In this paper, we introduce a framework to analyze the bandwidth of such display devices. Based on this analysis, we show that multiple layers can achieve a wider depth of field using less bandwidth compared to single layer displays. We present a simple algorithm to distribute an input light field to multiple layers, and devise an efficient ray tracing algorithm for synthetic scenes. We demonstrate the effectiveness of our approach by both software simulation and two corresponding hardware prototypes.

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@article {CGF:CGF3206,
author = {Ranieri, Nicola and Heinzle, Simon and Smithwick, Quinn and Reetz, Daniel and Smoot, Lanny S. and Matusik, Wojciech and Gross, Markus},
title = {Multi-Layered Automultiscopic Displays},
journal = {Computer Graphics Forum},
volume = {31},
number = {7pt2},
publisher = {Blackwell Publishing Ltd},
issn = {1467-8659},
url = {http://dx.doi.org/10.1111/j.1467-8659.2012.03206.x},
doi = {10.1111/j.1467-8659.2012.03206.x},
pages = {2135--2143},
keywords = {I.3.1 [Computer Graphics]: Hardware Architecture—Three-dimensional displays},
year = {2012},
}
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Overview

Figure 1: Two display prototypes have been built to demonstrate our approach. A beamsplitter is used to overlay two automultiscopic displays as shown on the left side, a varifocal beamsplitter is used to virtually move a single automultiscopic display over time shown on the right side.

In this paper we introduce multi-layered automultiscopic displays for 4D light fields. Our hybrid display model volumetrically combines multiple automultiscopic layers and supports horizontal and vertical parallax, and it supports better accommodation cues than single layer elements. Furthermore, multi-layered displays are able to use the available display bandwidth more efficiently. The combined bandwidth of n layers only requires 1/n of the total ray count of a single layer display to show the same diffuse scene content with approximated occlusions. An efficient algorithm can be used to decompose an input light field for such multi-layered configurations. For synthetic scenes, we propose a very simple extension to existing ray tracers that supports spatial and angular anti-aliasing using super-sampling. In order to show the effectiveness of our approach, we simulate different configurations of multi-layered automultiscopic displays. We also present two physical prototypes implementing our display model. The first prototype uses two parallax-based color displays that are superimposed onto the same optical path using a beam-splitter. The second prototype uses a varifocal mirror to optically replicate one integral imaging-based monochrome display onto multiple depth planes using temporal multiplexing, supporting up to 24 layers of depth.

Results

Figure 2: Simulated display results. The overall depth of field increases when using multiple layers, supporting large parallax movement..

We evaluate the effectiveness of our approach using simulated results and results from both prototypes. The simulation results (Figure 2) show the effect of adding additional layers. With every additional layer, the depth of field increases leading to much sharper images for the outer depth ranges. In our simulation, we employed 36 timemultiplexing steps to show the results in full spatial resolution. Note, although a high number of multiplexing steps is extremely difficult to achieve with current display technology, we intend to demonstrate the effect of the increased depth of field without distracting resolution artifacts. Figure 3 shows results captured with our beam-splitter prototype. Although using only two layers, the depth of field is already noticeably enhanced when using more bandwidth than a single layer display. The results also show that the same depth of field of a single layer display can be reproduced by two displays using only half of the overall ray count. The results of the varifocal display prototype are shown in Figure 3. The possible depth of field (18.8cm) at wide viewing angles of 18 is huge compared to existing displays. Furthermore, by using up to 24 layers, the layer spacing exceeds the limits of human depth resolution. Therefore, our varifocal display prototype can provide nearly correct accommodation cues for content close to the display volume. Although the prototype is able to support monochrome images only, the resulting parallax movement is visible in the accompanying video.

Figure 3: Real results shown on our display prototypes, captured with a Canon Eos 1D Mark III, ISO 3200 and 1/4s exposure time.

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