Abstract

We present a novel concept of a wide viewing angle liquid-crystal display (LCD) light shutter, taking advantage of the highly symmetric 180°-twisted liquid-crystal (LC) configuration and the light propagation starting with a single mode. In a specific case of the high voltage driven LCD light shutter, the resulting very high overall symmetry allows for the efficient angular compensation of the light attenuation in the optically closed state using just a simple, specifically tuned, negative-birefringent c-plate retarder. The latter can be adapted to compensate for the positive optical birefringence of the homeotropically aligned LC molecules as well as also for a great deal of the angular dependence of the crossed polarizers. We show that the additional partial compensation of the angular dependence of the crossed polarizers can be explained by a combined effect of the positive birefringence of the homeotropically aligned LC molecules, negative-birefringence c-plate retarder, and an in-plane residual positive birefringence (a-plate) of the boundary layers of the LC molecules.

© 2008 Optical Society of America

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Figures (6)

Fig. 1
Fig. 1

Simplified three-layer model of the LC cell for a light shutter in the optically closed state. The homeotropically oriented central layer is approximated by a positive-birefringent c-plate and the two boundary planarly oriented layers are two positive- birefringent a-plates.

Fig. 2
Fig. 2

LC director field in the 5 μm LC cell optically closed to the extent necessary for the typical light shutter applications (such as personal eye protection and stereovision).

Fig. 3
Fig. 3

LCD light shutter block diagram showing polarizer (specific case where transmission axis is perpendicular to the alignment of the LC boundary layers), LC cell, retarder R and analyzer.

Fig. 4
Fig. 4

(a) Angular dependence computer modeling of com pensated 180 ° LCD light shutter, (b) compensated TN LCD light shutter, and (c) uncompensated TN LCD light shutter.

Fig. 5
Fig. 5

The trace of polarization in the Poincaré sphere representation. The optical stack of retarders moves the final polarization F toward the extinction point E.

Fig. 6
Fig. 6

Angular dependence measurements of the light attenuation around the symmetry axis of the crossed polarizers for the proposed new, compensated 180 ° -twisted LCD light shutter (dark line) compared to the standard, uncompensated TN LCD light shutter (gray line).

Equations (5)

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c + = Δ n LC × 0.9 d LC = 450 nm .
a + = Δ n LC × 0.05 d LC = 25 nm .
c | c + | .
δ = 4 arctan tan ϕ 1 1 n 2 sin θ π ,
R = Δ n d sin 2 ζ cos θ ,

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