U.S. patent application number 17/114551 was filed with the patent office on 2021-03-25 for multi-view display device.
The applicant listed for this patent is KONINKLIJKE PHILIPS N.V.. Invention is credited to MARK THOMAS JOHNSON, BART KROON, EIBERT GERJAN VAN PUTTEN, OLEXANDR VALENTYNOVYCH VDOVIN.
Application Number | 20210088808 17/114551 |
Document ID | / |
Family ID | 1000005260853 |
Filed Date | 2021-03-25 |
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United States Patent
Application |
20210088808 |
Kind Code |
A1 |
KROON; BART ; et
al. |
March 25, 2021 |
MULTI-VIEW DISPLAY DEVICE
Abstract
The invention provides a multi-view display in which a view
forming arrangement comprises a first view forming structure spaced
by a first distance from the display panel for providing multiple
views across a first direction, and a second view forming
arrangement spaced by a second distance from the display panel for
providing multiple views across a second perpendicular direction.
The angular width of the multiple views in the two directions can
thus be independently defined.
Inventors: |
KROON; BART; (EINDHOVEN,
NL) ; VDOVIN; OLEXANDR VALENTYNOVYCH; (MAARHEEZE,
NL) ; VAN PUTTEN; EIBERT GERJAN; (Hertogenbosch,
NL) ; JOHNSON; MARK THOMAS; (ARENDONK, BE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KONINKLIJKE PHILIPS N.V. |
EINDHOVEN |
|
NL |
|
|
Family ID: |
1000005260853 |
Appl. No.: |
17/114551 |
Filed: |
December 8, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14895072 |
Dec 1, 2015 |
10890782 |
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PCT/EP2014/060469 |
May 21, 2014 |
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17114551 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02B 30/27 20200101 |
International
Class: |
G02B 30/27 20060101
G02B030/27 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 3, 2013 |
EP |
13170243.3 |
Claims
1. A multi-view display, comprising: a display panel; and a view
forming arrangement formed over the display panel for providing a
multi-view function, wherein the view forming arrangement comprises
a first view forming structure spaced by a first distance (t1) from
the display panel for providing multiple views across a first
direction, and a second view forming structure spaced by a second
distance (t2) from the first view forming structure for providing
multiple views across a second perpendicular direction,
characterised in that the angular width of the multiple views in
the two directions is independently defined with the angular widths
of the multiple views in the two directions in the ratio of smaller
angular width to larger angular width of 1:n where n<2 wherein
the first view forming structure closest to the display panel is
made of material with a first refractive index, and the second view
forming structure is made of material with a lower refractive
index.
2. A display as claimed in claim 1, wherein the view forming
arrangement comprises a first spacer layer over the display pane, a
first lenticular lens array over the first spacer layer, a second
spacer layer over the first lenticular lens array and a second
lenticular lens array over the second spacer layer.
3. A display as claimed in claim 2, wherein the first and second
lenticular lens arrays define convex lens interfaces, with respect
to the direction of light through the view forming arrangement from
the display panel.
4. A display as claimed in claim 3, wherein the first spacer layer,
the first lenticular lens array and the second lenticular lens
array are glass or plastic, and the second spacer layer is air.
5. A display as claimed in claim 2, wherein the first lenticular
lens array defines convex lens interfaces, and the second
lenticular lens array defines concave lens interfaces, with respect
to the direction of light through the view forming arrangement from
the display panel.
6. A display as claimed in claim 5, wherein the first spacer layer,
the first lenticular lens array and the second lenticular lens
array are glass or plastic with a first refractive index, and the
second spacer layer is glass or plastic with a second, lower
refractive index.
7. A display as claimed in claim 1, wherein the view forming
arrangement comprises a first spacer layer over the display panel,
a first barrier layer over the first spacer layer, a second spacer
layer over the first barrier layer and a second barrier layer over
the second spacer layer.
8. A hand held device comprising a display as claimed in claim 1.
Description
CROSS-REFERENCE TO PRIOR APPLICATIONS
[0001] This application a continuation of U.S. application Ser. No.
14/895,072 filed Dec. 1, 2015 which claims the benefit of
International Application No. PCT/EP2014/060469 filed on May 21,
2014, which claims the benefit of European Patent Application No.
13170243.3 filed Jun. 3, 2013. These applications are hereby
incorporated by reference herein.
FIELD OF THE INVENTION
[0002] This invention relates to multi-view displays.
BACKGROUND OF THE INVENTION
[0003] A multi-view display is typically created by applying a
special layer to a 2D display. Known options for this layer are a
barrier for barrier displays, a lenticular lens sheet for
lenticular displays or a microarray of lenses.
[0004] No matter which option is chosen, the effect is that
depending on the viewpoint of an eye (or camera) a different image
is projected, thus providing stereoscopic vision (stereopsis)
without needing special glasses. This is what is meant by "auto"
stereoscopic.
[0005] FIG. 1 shows the basic principle for a display using a
lenticular lens array. The display comprises a conventional (2D)
display panel 2 having an array of pixels 4 over which a view
forming arrangement 6 is provided. This comprises lenticular lenses
8. If each lens overlies 4 pixels in the display width direction,
then light from those four pixels will be projected in different
directions, thereby defining different viewing areas, numbered V1
to V4 in FIG. 2. In each of these viewing areas, an image is
projected which is formed as the combination of all pixels with the
same relative position with respect to the lenses.
[0006] The same effect can be achieved with barriers, which limit
the output direction with which light is emitted from each pixel.
Thus, in each output direction, a different set of pixels can be
viewed.
[0007] The increase in angular resolution (i.e. the multiple views)
results in a diminishing of the spatial resolution (i.e. the
resolution of each individual view). In the case of vertical
lenticular sheets and barriers, this resolution reduction is
entirely in the horizontal direction. By slanting the lenticular
sheet the resolution reduction can be spread over both horizontal
and vertical directions providing for a better picture quality.
[0008] FIGS. 2 and 3 show examples of 3D lenticular display
constructions.
[0009] FIG. 2 shows the least complicated design, comprising a
lenticular lens sheet 6 over the display panel, with a spacer 10
between. The curved faces of the lenticular lenses face outwardly,
so that convex lenses are defined.
[0010] FIG. 3 shows a preferred design which has better performance
under wide viewing angles. The curved lens surfaces face the
display panel, and a replica layer 12 is used to define a planar
internal surface. This replica can be a glue (typically a polymer)
that has a refractive index that is different from that of the
lenticular lens, so that the lens function is defined by the
refractive index difference between the lens material and the
replica material. A glass or polycarbonate slab is used as the
spacer 10, and the thickness is designed to provide a suitable
distance for the lenticular lens to focus on the display panel.
Preferably the refractive index of the slab is similar to the
refractive index of the glue. It is well known that a 2D/multi-view
switchable display can be desirable.
[0011] By making the lens of a multi-view display electrically
switchable, it becomes possible for example to have a high 2D
resolution mode (with no lens function) in combination with a 3D
mode. Other uses of switchable lenses are to increase the number of
views time-sequentially as disclosed in WO 2007/072330 or to allow
multiple 3D modes WO 2007/072289.
[0012] The known method to produce a 2D/3D switchable display is to
replace the lenticular lens by a lens-shaped cavity filled with
liquid crystal material. The lens function can be turned on/off
either by electrodes that control the orientation of LC molecules
or else by changing the polarization of the light (for example
using a switchable retarder). The use of graded refractive index
lenses has also been proposed, in which a box-shaped cavity is
filled with liquid crystal and an electrode array controls the
orientation of LC molecules to create a gradient-index lens (this
is disclosed for example in WO 2007/072330). An electrowetting
lens, which is formed of droplets of which the shape is controlled
by an electric field has also been proposed for 2D/3D switching.
Finally, the use of electrophoretic lenses has also been proposed,
for example in WO 2008/032248.
[0013] As mentioned above, there is always a trade-off between
spatial and angular resolution. Displays with lenticular lenses and
vertical barriers offer horizontal parallax only, allowing for
stereopsis and horizontal motion parallax and occlusion, but not
vertical motion parallax and occlusion. As a result, the
autostereoscopic function is matched to the orientation of the
display. Only with full (horizontal and vertical) parallax can the
3D effect be made independent of the screen orientation.
[0014] However, at least in the medium term, display panels will
not have sufficient resolution to enable full parallax at HD
resolution, at least not with large numbers of views. There is
therefore a problem for devices that are designed to operate in
portrait and landscape mode, such as handheld devices.
[0015] This problem has been recognized, and some of the solutions
above which provide 2D/3D switching capability have been extended
to include multiple 3D modes, such as portrait and landscape modes.
In this way, three modes are enabled: 2D, 3D portrait and 3D
landscape.
[0016] Full parallax may be possible already for a system
comprising just two views, thus resulting in only moderate
resolution loss and therefore the switching between 3D modes can be
avoided. If a non-switching approach is to be used, the minimal
microlens array design that is dual view and dual orientation has
2.times.2 views and preserves the maximum amount of spatial
resolution.
[0017] The common RGB stripe pixel layout comprises red, green and
blue sub-pixel columns. Each sub-pixel has an aspect ratio of 1:3
so that each pixel triplet has a 1:1 aspect ratio. The lens system
typical translates such rectangular 2D sub-pixels into rectangular
3D pixels.
[0018] When a microlens is associated with such a display panel,
for example with each microlens over a 2.times.2 sub-array of
pixels, the lens design has the problem that the viewing cone in
one of the two orthogonal directions is three times as wide as in
the other.
[0019] FIG. 4 shows this effect, and shows each group of 4
sub-pixels with three pixels on and one off, and with a 10%
defocus. This means the focal length of the lenses differs by 10%
compared to the lens-display distance. This is to prevent sharp
focusing of the black mask pattern between the pixels.
[0020] The peaks in the light intensity plots show the positions of
the repeated views (i.e. within different viewing cones) of a given
pixel. They show the light power per unit area (in Watts per
mm.sup.2) at different positions across the display screen. One
plot is for the landscape mode and the other is for the portrait
mode. Thus, the pitch of the repeating pattern corresponds to the
viewing cone width. Clearly, in the direction across the long
sub-pixel axis (the x-axis), the viewing cone width is much larger
than in the direction across the short sub-pixel axis (the
y-axis).
[0021] The bright areas represent illuminance distributions from
each group of 3 pixels turned on, on a plane situated at the
optimum observation distance from the display. The x- and y-axes
represent linear displacements.
[0022] Small viewing cone angles have a tangent which may be
approximated by the lenticular pitch divided by the thickness of
the stack. For the RGB stripes layout, the lenticular pitch in one
direction is three times as much as in the other as can be seen
from FIG. 4, so the viewing cone will be three times as wide as
well. As a consequence, at certain (fixed) viewing distance, in one
direction (e.g. portrait) the user has to hold the device carefully
to avoid getting out of the cone, while for the other direction it
may be difficult to find the 3D zone because the views are so wide.
There is therefore a need for a full parallax autostereoscopic
display, which enables the viewing cone sizes in the two orthogonal
display orientations to be independently defined.
[0023] US 2013/0069938 discloses a display unit which in one
example has two orthogonal lenticular arrays.
SUMMARY OF THE INVENTION
[0024] The invention is defined by the claims.
[0025] According to the invention, there is provided a multi-view
display, comprising: a display panel; and a view forming
arrangement formed over the display panel for providing a
multi-view function, wherein the view forming arrangement comprises
a first view forming structure spaced by a first distance from the
display panel for providing multiple views across a first
direction, and a second view forming structure spaced by a second
distance from the first view forming structure for providing
multiple views across a second perpendicular direction, such that
the angular width of the multiple views in the two directions is
independently defined, wherein the angular widths of the multiple
views in the two directions are in the ratio of smaller angular
width to larger angular width of 1:n where n<2. This arrangement
separates the provision of multiple views across the display
between two view forming structures, each for different orthogonal
directions. Together, they provide full parallax, so that the
display can be viewed in portrait or landscape mode without
requiring any switching function. Preferably, n<1.5, even more
preferably n<1.2.
[0026] These angular widths thus differ by less than 100% (i.e. the
larger is no more than double the smaller), and more preferably
even less, for example less than 50% (the larger is no more than
1.5 times the smaller) or even less than 20% (the larger is no more
than 1.2 times the smaller). This makes the viewing cones of
similar size. By "angular width of the multiple views" is meant the
angle over which one full set of views is displayed along one of
the viewing directions. It corresponds to the angle over which a
set of pixels corresponding to the set of unique views in one of
the viewing directions can be viewed through a single view forming
element (i.e. lens or barrier opening). At a more remote viewing
angle these pixels becomes visible through an adjacent view forming
element.
[0027] Preferably, both view forming structures are operable at the
same time so that no switching between modes is needed. The display
light passes through both view forming structures. One provides
parallax in one direction and the other provides parallax in the
other direction. Thus, the display can be rotated between
orientations without needing any switching of the display
configuration. However, one or both of the view forming structures
can be made electrically switchable, in known manner.
[0028] By providing the same angular width (which is often termed
the cone width) in the two orthogonal directions the optical
performance can be matched in the different orientations. In order
to provide this matching, the spacing distances as well as the
materials used in the stack (such as the spacer materials) can be
selected. If materials of the same refractive index are used, the
design simplifies with only the geometric distance needing to be
taken into account. The size of the view forming elements (lenses
or barriers--which together make up the view forming structures) is
typically dictated by the underlying pixel configuration, since
each individual view forming element is intended to overly a
certain number of sub-pixels of the display, which then determines
the number of views to be formed.
[0029] The display panel may comprise rectangular sub-pixels.
Rectangular pixels give rise to the viewing cone variation in
different orientations when microlenses are used. The aspect ratio
of the sub-pixels can be 1:3, which is typically the case for RGB
striped pixel configurations.
[0030] The first view forming structure preferably has a periodic
structure, with a period based on the number of sub-pixel
dimensions in a first direction across the sub-pixels (but the
period is corrected to provide focusing to the desired viewing
distance), and the second view forming structure has a periodic
structure, with a period based on the number of sub-pixel
dimensions in a second orthogonal direction across the sub-pixels
(but again the period is corrected to provide focusing to the
desired viewing distance).
[0031] If the period for each view forming structure is based on
the number of sub-pixels numbers as mentioned above, it means that
the same number of views is generated in the landscape and portrait
modes, by providing the same number of sub-pixels per view forming
element. When the underlying sub-pixels are rectangular, this
results in different required pitch for the two view forming
arrangements.
[0032] The periods for the two view forming structures can be based
on different numbers of sub-pixels for portrait and landscape
modes. This will result in different resolution loss in the two
orientations but can still correct for different viewing cone
sizes.
[0033] The first view forming structure closest to the display
panel can be made of material with a first refractive index n, and
the second view forming structure can be made of material with a
smaller refractive index. This arrangement enables the thickness of
the optical stack to be kept to a minimum.
[0034] In a preferred example,
p 1 ( t 1 / n 1 ) = k p 2 ( t 1 / n 1 ) + ( t 2 / n 2 )
##EQU00001##
in which p.sub.1 is the period of the first view forming structure,
t.sub.1 is the height of the first view forming structure over the
display panel and n.sub.1 is the refractive index of the material
between the display panel and the first view forming structure,
p.sub.2 is the period of the second view forming structure, t.sub.2
is the height of the second view forming structure over the first
view forming structure, and n.sub.2 is the refractive index of the
material between the first and second view forming structures,
wherein k is between 0.5 and 2, more preferably between 0.75 and
1.5, more preferably between 0.9 and 1.1.
[0035] This means the ratio of the period of the one view forming
structure to an effective optical distance (distance divided by
refractive index) of the one view forming structure from the
display panel and the ratio of the period of the other view forming
structure to an effective optical distance (distance divided by
refractive index) of the other view forming structure from the
display panel are made to be similar. This results in the viewing
cones being substantially the same. The ratios can of course be
equal (k=1).
[0036] This equation simplifies to geometric distances only if the
refractive index values are the same.
[0037] In one set of examples, the view forming arrangement
comprises a first spacer layer over the display panel, a first lens
layer (e.g. lenticular lens array) over the first spacer layer, a
second spacer layer over the first lens layer and a second lens
layer (e.g. lenticular lens array) over the second spacer
layer.
[0038] The spacer sizes and materials enable control over the
viewing cone angles. The first and second lens layers can define
convex lens interface shapes, with respect to the direction of
light through the view forming arrangement from the display panel.
In this case, the first spacer layer, the first lens layer and the
second lens layer can be glass or plastic, and the second spacer
layer is air.
[0039] In another example, the first lens layer defines convex lens
interface shapes, and the second lens layer defines concave lens
interface shapes, with respect to the direction of light through
the view forming arrangement from the display panel. In this case,
the first spacer layer, the first lens layer and the second lens
layer can be glass or plastic with a first refractive index, and
the second spacer layer is glass or plastic with a second, lower
refractive index.
[0040] In an alternative set of examples, the view forming
arrangement can comprise a first spacer layer over the display
panel, a first barrier layer over the first spacer layer, a second
spacer layer over the first barrier layer and a second barrier
layer over the second spacer layer. The invention can thus be
applied to barrier type displays as well as to lenticular lens type
displays.
BRIEF DESCRIPTION OF THE DRAWINGS
[0041] Examples of the invention will now be described in detail
with reference to the accompanying drawings, in which:
[0042] FIG. 1 shows a known multi-view display to explain the basic
principle of operation;
[0043] FIG. 2 shows a first example of known lens design;
[0044] FIG. 3 shows a second example of known lens design;
[0045] FIG. 4 is used to explain the problem of different viewing
cone sizes for different display orientations;
[0046] FIG. 5 shows a first example of view forming arrangement of
the invention;
[0047] FIG. 6 shows how the problem of different viewing cone sizes
for different display orientations is resolved by the design of
FIG. 5;
[0048] FIG. 7 shows a second example of view forming arrangement of
the invention; and
[0049] FIG. 8 shows a third example of view forming arrangement of
the invention based on barriers instead of lenses.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0050] The invention provides a multi-view display in which a view
forming arrangement comprises a first view forming structure spaced
by a first distance from the display panel for providing multiple
views across a first direction, and a second view forming structure
spaced by a second distance from the display panel for providing
multiple views across a second perpendicular direction. The angular
width of the multiple views in the two directions can thus be
independently defined.
[0051] A regular microlens display does not allow independent
design of the viewing cone in first and second directions. In fact,
the viewing cone ratio equals the sub-pixel aspect ratio multiplied
by the ratio of number of views along the two directions:
a p a l N P N l ##EQU00002##
where a.sub.p and a.sub.l are the sub-pixel dimensions along the
two directions (for instance portrait and landscape).
[0052] A regular microlens is suitable when
a p a l N P N l ##EQU00003##
is close to the desirable viewing cone ratio.
[0053] The invention provides a display that performs like a
microlens display, but does allow independent design of the viewing
cones.
[0054] FIG. 5 shows a first example of view forming arrangement of
the invention in the form of a lens stack.
[0055] The lens arrangement comprises a first lens arrangement 20
spaced from the surface of the display panel 2 by a bottom spacer
22. The first lens arrangement and spacer have a combined thickness
of t1 so that the lens surfaces are a distance t1 from the display
panel 2. A second lens arrangement 24 is spaced from the first lens
arrangement 20 by a second spacer 26. The second lens arrangement
and the second spacer have a combined thickness of t2 so that the
lens surfaces are a distance t2 from the first lens arrangement and
at a distance of t1+t2 from the display panel 2. The two lens
arrangements are designed with sufficient focus on the pixels in
the display panel module.
[0056] For thin lenses, the thickness of the lens array can be
ignored. The viewing cone half-angle .theta.1 in the material of
the spacer in the first direction as implemented by the first lens
array 22 is given by tan .theta.1=p1/2t1, as can be seen from FIG.
5.
[0057] As an approximation, if the viewing cone angle is small, the
full viewing cone angle in the material .alpha.1=2.theta.1 can be
approximated by tan .alpha.1=p1/t1.
[0058] For the example of the two spacers having the same
refractive index, the viewing cone half-angle in the material of
the spacer in second direction as implemented by the second lens
arrangement is given by tan .theta.2=p2/2(t1+t2), or as an
approximation for the full viewing cone tan
.alpha.2=p2/(t1+t2).
[0059] If, for example, viewing cones should be designed to be
similar, then:
p 1 t 1 .apprxeq. p 2 t 1 + t 2 ##EQU00004##
[0060] In the case the two spacers are made of materials with
different refractive indices and in the approximation of thin
lenses, the above condition of having similar viewing cones in two
directions of observation in air can be written as
p 1 ( t 1 / n 1 ) .apprxeq. p 2 ( t 1 / n 1 ) + ( t 2 / n 2 )
##EQU00005##
where n.sub.1 and n.sub.2 are refractive indices of the material of
the first and the second spacer respectively.
[0061] This equation takes account of the refractive index values
in the stack. If the refractive index n.sub.1=n.sub.2, then the
second equation simplifies to the first, and only the geometric
distance needs to be taken into account. The refractive index of
the lenses also need to be taken into account for a complete
optical analysis, although typically the spacers are thicker than
the lenses so that the spacers dominate.
[0062] The reason why a value t/n is required when taking account
of the refractive index values is that the cone angles are
calculated in the medium, but the effective 3D cone angles which
the user perceives are in air.
[0063] According to Snell's law
n.times.sin(.alpha..sub.n)=sin(.alpha..sub.air) Using the
approximation for small angles:
n.times.p/t=p/t.sub.effective so that t.sub.effective=t/n.
[0064] For example, in the case of an RGB striped display, where
the pixel components have a height to width ratio of 3:1, for the
design with the same number of views in two observation directions
(for instance 2.times.2 view design) the pitches of the lens-stack
relate as 3p.sub.1=p.sub.2, so 2t.sub.1.apprxeq.t.sub.2
[0065] This means the spacer that is sandwiched by the lenses is
optically thicker than the spacer between the display panel and the
first lens 20.
[0066] The lens design of the invention can use non-switchable
lenses, so that full parallax is provided permanently. The same
viewing cone performance is obtained for either display
orientation.
[0067] There is some freedom in implementing the invention.
[0068] The lens curvatures can be positive or negative, for example
as explained with reference to FIGS. 2 and 3.
[0069] In some configurations, a spacer can be integrated with a
lens by making the planar side of the lens thicker.
[0070] Either one or both of the lenses could be made as a
switchable lens, for instance using one of the techniques that are
described above. This could be used to enable the lens function to
be switched off completely for a 2D mode, or it could be used to
enable parallax in one direction only but with a higher resolution
in another direction.
[0071] In a system with thick lenses and various refractive
indexes, the above relations are only rough approximations. In
practice, a balance will be found through numerical simulation and
by choosing materials, lens shapes and spacer thicknesses in
conjunction. These parameters are typically optimized such that the
viewing cone is similar in both directions (e.g. portrait and
landscape).
[0072] It may be desired to decrease the total thickness of the
structure to reduce weight and size for a portable device. For this
reason, in a preferred embodiment it will be advantageous to
realize the lower spacer with a higher refractive index, whilst the
top spacer should have a lower refractive index, for example air.
In this manner, the total stack thickness is reduced whilst
maintaining the optical ratio (e.g. 3:1) to maintain cone sizes. A
further consequence of such an approach is that the lens interfaces
will preferably have opposite curvatures.
[0073] Two example solutions will now be presented.
1. Air Gap Solution
[0074] This solution can have the structure as shown in FIG. 5.
Spacer 22 is glass/plastic, for example with refractive index
1.5.
[0075] Lens 20 is glass/plastic and plano-convex as shown in FIG.
5.
[0076] Spacer 26 is an air gap with mechanical supports to provide
the desired fixed distance.
[0077] Lens 24 is glass/plastic and also plano-convex (as shown in
FIG. 5).
[0078] FIG. 6 shows a simulation of the performance of the
structure of FIG. 5, showing the illuminance on a detector plane
placed at the optimal viewing distance from the display, with three
views out of four turned on. FIG. 6 shows that non-equal viewing
cone distributions for the regular microlens (FIG. 4) changes to
equal viewing cones. FIG. 6 is similar to FIG. 4 and again shows
the light power per unit area (in Watts per mm.sup.2) at different
positions across the display screen. One plot is for the landscape
mode and the other is for the portrait mode.
2. Low Refractive Index Difference Solution
[0079] This solution can have the structure shown in FIG. 7. In
this context, a low refractive index is in the range 1.3-1.5
(typically 1.4), a high refractive index is in the range 1.45-1.75
(typically 1.6), and a low refractive index difference is in the
range 0.1-0.3 (typically 0.2).
[0080] Spacer 22 is glass/plastic with high refractive index. Lens
20 is integrated with spacer 22 and is the same glass/plastic with
the same high refractive index and is plano-convex.
[0081] The spacer 26 has a low refractive index. The lens/spacer
unit 20,22 is laminated to the second spacer 26 with low
index-matching glue.
[0082] The second lens 24 also has a high refractive index and is
plano-convex, and is laminated to the spacer 26 with low
index-matching glue. However, the second lens is inverted compared
to the first lens, so that it defines a concave lens shape with
respect to the direction of display light through the lens stack.
The first lens 20 is thus arranged as shown in FIG. 2 and the
second lens 24 is arranged as shown in FIG. 3.
[0083] There can be more than two refractive index values in the
system, but each interface gives reflections that add to the 3D
crosstalk. Unnecessary interfaces should thus be avoided.
[0084] The two examples above are based on the use of lenticular
lenses. FIG. 8 shows in schematic form an alternative approach in
which the same design methodology is applied to a barrier type
display. A first barrier layer 70 is over a first spacer layer (not
shown) which is over the display panel 2, and the second barrier
layer 72 is over the second spacer layer (not shown).
[0085] The spacing sizes are selected using the methodology above,
with the barrier opening widths and pitch dependent on the
underlying pixel structure, in the same way as for the lenticular
designs.
[0086] The display panel typically has a sub-pixel grid with
elongated sub-pixels, for example as in the RGB stripe display.
Elongated sub-pixels are also used in other pixel configurations
and the invention can be applied more generally.
[0087] The invention can be applied to phones, tablets and cameras
with autostereoscopic displays.
[0088] The two view forming layers may have orthogonal lenticulars
or barriers, but even for the portrait/landscape function, they may
not be orthogonal. For example they may be vertical in one mode but
slanted to the vertical in the other mode. A typical slant is
arctan(1/6)=9.46 degrees. Thus, the lenticulars may be orthogonal
or at 80.54 degrees for this example of slant. Other slant angles
are of course possible.
[0089] Other variations to the disclosed embodiments can be
understood and effected by those skilled in the art in practicing
the claimed invention, from a study of the drawings, the
disclosure, and the appended claims. In the claims, the word
"comprising" does not exclude other elements or steps, and the
indefinite article "a" or "an" does not exclude a plurality. The
mere fact that certain measures are recited in mutually different
dependent claims does not indicate that a combination of these
measured cannot be used to advantage. Any reference signs in the
claims should not be construed as limiting the scope.
* * * * *