This document describes a dual mode 3D display using a 2D lens array that allows 3D viewing in both landscape and portrait orientations. Key points: - A 2D lens array is fabricated using ink-jet printing, with spherical lenses instead of cylindrical lenses to provide the 3D effect in both orientations. - The lens pitch is designed based on average inter-pupil distance to ensure correct views. Horizontal and vertical pitch are equal to match optimal viewing distances and freedoms in both modes. - Lens power is optimized to balance 3D performance factors like crosstalk, viewing freedom, and moire contrast. - Experiments show the 2D array provides 3D in both orientations, but

1. Landscape/Portrait Dual Mode Lens Type 3D Display Using a 2D Lens Array
Ching-Tsun Chang, Wen-Lung Chen, Chih-Hung Shih, Wei-Ming Huang
* AU Optronics Corporation, No. 1, Li-Hsin Rd. 2, Hsinchu Science Park, Hsinchu 30078, Taiwan, R.O.C.
Abstract
Traditionally, a lenticular lens array, which is a one-dimensionally
periodic lens structure, is used in front of a image display, such as
LCD or OLED, to achieve human 3D perception. Due to its one-
dimensionally periodic property, most of this kind of 3D displays
can show 3D in only one display orientation. In this paper, we
utilize a 2D lens array instead to achieve human 3D perception in
both landscape and portrait display orientation. The 2D lens
array is fabricated using ink-jet printing (IJP) technology and the
3D function is demonstrated successfully.
Author Keywords
autostereoscopic; lenticular; barrier; ink-jet priting
1. Introduction
3D display technologies give people new and more impressive
viewing experiences and are under increasing development.
Among them, lenticular lens [1] and parallax barrier [2] are two
major technologies used to achieve autostereoscopic displays. No
matter which technology is used, they all provide 3D perception
through binocular disparity, by which left eye sees only left eye
image and right eye sees only right eye image through different
viewing angle. Under this condition, human brain fuses these two
images into 3D illusion. Figure.1 shows the binocular disparity
and the possible types of disparity that produce different 3D
depth.
(a)
(b)
Figure 1. Illustration of binocular disparity (a) and different
types of disparity (b).
The parallax barrier achieves 3D by blocking the right-eye signal
toward left eye and the left-eye signal toward right eye. It’s a
relatively simple way and the fabrication of parallax barrier is
compatible to LCD process. However, the parallax loses
brightness due to the blocking of light (Figure 2 (a)). The
lenticular lens doesn’t suffer the brightness loss as parallax
barrier. The lenticular lens refracts the left-eye signal to the left
eye and right-eye signal to the right eye (Figure 2 (b)).
(a)
(b)
Figure 2. The principle of parallax barrier (a) and lenticular
lens (b).
Both the stripe parallax barrier and lenticular lens can provide 3D
perception in one direction such as landscape viewing mode or
portrait viewing mode. Because the blocking effect of parallax
barrier and the lens convergence only happen in the direction
perpendicular to stripe parallax barrier or lenticular lens. For LC
barrier, landscape/portrait dual mode can be carried out by design
orthogonal ITO electrode on top and bottom plate in one cell.
However, lenticular lens can not do the same thing in one
lenticular lens sheet due to its physical structure.
To provide 3D effect in both landscape and portrait viewing
mode, the lens convergence effect in both mode is necessary. The
most straight-forward method is to use spherical lens with proper
aperture geometry instead of cylindrical lens. This paper uses
spherical lens 2D array with proper horizontal and vertical pitch.
It is called 2D lens array in this paper.
2. 2D Lens Array Design
As mentioned in previous section, we use 2D lens array to achieve
landscape/portrait dual mode 3D viewing. In this section, we are
going to explain the basic design parameter of 2D lens array.
As shown in figure 3, the lens pitch should be properly design to
ensure that people can see correct signals through each lens
element at the desired viewing distance. Because average inter-
pupil distance is about 65mm, we design the lens pitch based on
this condition. Figure 3 take parallax barrier as an example,
however, the pitch design is the same for both parallax barrier and
lenticular lens. Without proper pitch design, observer cannot see
3D across whole display.

2. Figure 3. Proper pitch design make observer sees correct
signal through 3D optical device element.
With proper lens pitch design and a specific thickness between
lens and pixel plane, 3D optimal viewing distance is inversely
proportional to the size of horizontal minimum driving element
(not necessary equal to the minimum displaying element), which
is pixel size as RGB arranged vertically and one-third pixel size as
RGB arranged horizontally. Therefore, here comes the problem.
As shown in Figure 4 (a), if a 2D lens array element covers two
minimum driving elements in both landscape and portrait viewing
mode, the optimal viewing distance of one viewing mode is three
times the other. In order to match optimal viewing distance of
both viewing mode, the lens pitch of the viewing mode with
longer optimal viewing distance should be re-designed based on
one-third average inter-pupil distance. However, this causes
different horizontal viewing freedom in both viewing mode.
Therefore, we design that the 2D lens array has the horizontal lens
pitch equal to the vertical lens pitch to achieve optimal viewing
distance matching with nearly equal horizontal viewing freedom
in both viewing mode (Figure 4 (b)).
(a) (b)
Figure 4. Illustration of optimal viewing distance matching.
With lens pitch design fixed, we now move to lens power design.
As known, lens power is a main factor determining the final 3D
performance. With focus design (lens focus closed to the pixel
plane), 3D minimum crosstalk would be low and horizontal
viewing freedom high, but moiré contrast would be higher. With
de-focus design (lens focus away from pixel plane), the
performance goes to the inverse trend. Hence, we should try to
strike a balance between these indices by modulating the lens
power.
The model we select is 3.97” with resolution 854 × 480. And we
choose four different radius of curvature, 250µm, 390µm, 500µm,
650µm to compare the minimum crosstalk, horizontal viewing
freedom and moiré contrast.
3. 2D Lens Array Fabrication
In this paper, we select ink-jet printing as the technology
fabricating the 2D lens array. This technology let us easily prepare
2D lens array with accurate pitch and desired radius of curvature.
The first step of the process flow is to fabricate hydrophobic
transparent wall patterns by photolithography and these patterns
define the shape of the lens aperture. The second step is to drop
proper amount of lens material (the UV-curable high solid ink
containing <PDVTM
> for the high reflective index) in the region
confined by the hydrophobic patterns and the lens material forms
a spherical surface itself due to surface tension. The third step is
to crosslink the lens material by UV exposure. All the materials
used are provided by Nippon Steel Chemical Co., Ltd and the lens
material is printed by Ulvac. Inc.
As shown in Figure 5, the line width of the hydrophobic patterns
is about 16um. The final lens samples have a blank region
uncovered by lens because the hydrophobic property and the
amount of lens material dropped.
(a) (b)
Figure 5. The OM image of hydrophobic patterns (top) and
2D lens array (bottom). Both 2D lens array with rectangle and
square aperture are shown.
4. Experiment Result
2D lens array successfully provides 3D effect in both landscape
and portrait viewing mode. Figure 6 shows the optical
performance measurement results of 250µm radius of curvature
and square aperture. The brightness oscillation frequency in
portrait viewing mode is three times in landscape viewing mode
because the spatial frequency of transmittance of pixels in portrait
viewing mode is three times in landscape viewing mode. This is a
direct evidence that 2D lens array provides lens effect and 3D
effect in both landscape and portrait viewing mode.
The brightness non-uniformity in landscape viewing mode is
severe than portrait viewing mode. That is also due to different
pixel transmittance spatial frequency in two viewing modes. With
a specific physical lens structure, the lens spot size is ideally
identical in both viewing modes. The brightness is more uniform
if the spot size is more closed to the pixel transmittance spatial
frequency in that viewing mode. Hence, the spot size is more
closed to the pixel transmittance spatial frequency in portrait
viewing mode which is three times in landscape viewing mode.
The minimum crosstalk is about 10% in both viewing mode,
which is higher than that of lenticular lens. Because the brightness
non-uniformity and the crosstalk distribution profile, the blank
region might be one of the main source contributing to crosstalk.

3. Figure 6. Optical performance measurement results of 250µm
radius of curvature and square aperture.
Figure 7 shows the OM images of 2D lens array of different radii
of curvature. The width of blank region gets wider with the radius
of curvature. That is because less lens material is used to achieve
lower lens sag. From the figure, blank region width is about 8µm
for 250µm radius of curvature, 12µm for 390µm and 500µm, and
much larger than 16µm for 650µm.
(a) (b)
(c) (d)
Figure 7. OM images of 2D lens array of 650µm (a), 500µm
(b), 390µm (c), 250µm (d).
As observer sees through a lenticular lens or a 2D lens array at a
specific viewing angle, lenses converge the light through lens
aperture into a small spot and project onto a specific position of
pixel plane. Blank region is uncovered by lens elements and
provides no convergence function. Hence, the blank region is
projected onto incorrect position and causes high crosstalk. The
wider the blank region is, the higher the minimum crosstalk.
Figure 8 shows the optical performance measurement results of
different radius curvature. From the figure, the minimum crosstalk
increases with the width of blank region. Moreover, the lens effect
in two orthogonal directions is hardly controlled identical if blank
region is closed to or larger than the size of hydrophobic patterns.
Hence, the crosstalk performance is unbalanced between
landscape and portrait viewing mode for 2D lens array with larger
blank region.
(a)
(b)
(c)
Figure 8. Optical performance measurement results of 390µm
(a), 500µm (b) and 650µm radius of curvature and square
aperture.
Since the intensity distribution is the result of convolution of the
lens transmittance distribution projected onto pixel plane and the
pixel transmittance distribution, we try to simulate the effect of
the blank region. Figure 9 shows the simulated spot distribution
with and without blank region for 250µm radius of curvature. For
lens without blank region all energy passing lens aperture is
converged to a spot. For lens with blank region the energy passing
through lens-covered region is converged to a spot and lens-
uncovered region is directly projected onto pixel plane. Hence, the
blank region contributes to a background crosstalk even if the spot
is projected within the pixels displaying correct signals.
Figure 10 shows the simulation results. From the top figure, 8μm
blank region contributes to about 4% minimum crosstalk at one
arbitrary viewing position. (The horizontal axis represents the spot
position on pixel plane not the viewing angle.) Due to lens effect
in two orthogonal directions and two-dimensional pixel
transmittance distribution, the horizontal crosstalk distribution
should depend on the vertical position of observers. The bottom
figure shows the effect of observer position and the theoretically
highest minimum crosstalk is about 8% which is closed to the

4. experiment results.
Figure 9. The simulated spot distribution with and without
blank region for 250µm radius of curvature.
(a)
(b)
Figure 10. The simulation result of effect of blank region.
Figure 11. 3.9” lens type 3D display using a 2D lens array.
5. Summary
In this paper, we demonstrate the landscape/portrait dual mode 3D
display using 2D lens array and explain the design concept. We
also explain the source of minimum crosstalk. Therefore, it’s
possible to achieve much better performance with narrower blank
region.
On watching this prototype, 3D function works well in both
viewing mode. This kind of 3D display can also display 2D image
by suitable content arrangement. As this technology is applied in
the image display with higher PPI, such as retina display, it can
provide 3D as well as 2D with good image quality.
6. Acknowledgements
This paper is partially supported by Nippon Steel Chemical Co. ,
Ltd. and Ulvac. Inc.. The substrate with the transparent wall and
the UV curable ink for the lens was kindly provided by Nippon
Steel Chemical Co., Ltd.. The 3D lens was kindly formed by
Ulvac. Inc..
7. References
[1] G. J. Woodgate, J. Harrold, “High Efficiency Reconfigurable
2D/3D Autostereoscopic Display”, SID 03 DIGEST pp394-
397.
[2] H.J. Lee, “A High Resolution Autostereoscopic Display
Using a Time Division Parallax Barrier”, SID 06 DIGEST
pp81-84.
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