U.S. patent application number 11/032828 was filed with the patent office on 2005-09-22 for providing optical elements over emissive displays.
Invention is credited to Matthies, Dennis L., Shen, Zilan.
Application Number | 20050206807 11/032828 |
Document ID | / |
Family ID | 25418857 |
Filed Date | 2005-09-22 |
United States Patent
Application |
20050206807 |
Kind Code |
A1 |
Matthies, Dennis L. ; et
al. |
September 22, 2005 |
Providing optical elements over emissive displays
Abstract
A display may be formed of a plurality of abutted tiles, each
tile contributing a portion of the overall displayed image. Optical
elements may be selectively situated between pixels to improve the
optical performance of the display. In some embodiments, these
optical elements may facilitate the use of relatively thicker cover
glasses over the display tiles.
Inventors: |
Matthies, Dennis L.;
(Princeton, NJ) ; Shen, Zilan; (West Windsor,
NJ) |
Correspondence
Address: |
Timothy N. Trop
TROP, PRUNER & HU, P.C.
STE 100
8554 KATY FWY
HOUSTON
TX
77024-1805
US
|
Family ID: |
25418857 |
Appl. No.: |
11/032828 |
Filed: |
January 11, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11032828 |
Jan 11, 2005 |
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09904268 |
Jul 12, 2001 |
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6873380 |
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Current U.S.
Class: |
349/67 ;
257/E25.02; 257/E33.071 |
Current CPC
Class: |
G02F 1/13336 20130101;
H01L 25/0753 20130101; H01L 2924/0002 20130101; H01L 2924/0002
20130101; H01L 27/3293 20130101; H01L 33/58 20130101; H01L 51/5262
20130101; H01L 2924/00 20130101 |
Class at
Publication: |
349/067 |
International
Class: |
G02F 001/1335 |
Claims
What is claimed is:
1-24. (canceled)
25. A display comprising: a sheet including upper and lower sides;
a plurality of light emitting elements positioned on said lower
side; and a plurality of slots formed in the lower side of said
sheet between adjacent light emitting elements.
26. The display of claim 25 wherein said slots are coated to make
them reflective.
27. The display of claim 25 including conductors extending through
said slots to contact said light emitting elements.
28. The display of claim 25 where said slots are filled with a
black material.
29. The display of claim 25 wherein the indices of reflection
between the material in said slots and said plate are sufficiently
different to cause reflections to occur along the surface of said
slots.
30. The display of claim 25 wherein said slots are Vee shaped.
Description
BACKGROUND
[0001] This invention relates generally to emissive displays
including organic light emitting device (OLED) displays, light
emitting diode (LED) displays and electro luminescence (EL)
displays.
[0002] Emissive displays generally include a cover glass or
transparent sheet over the light emissive elements. The transparent
sheet generally is substantially transparent to light emissions.
The thinner the glass sheet, normally the less its optical
effects.
[0003] In displays made by combining a plurality of tiles, each
including a cover glass, gaps may exist between adjacent tiles. The
thicker the glass that is utilized, the more apparent are these
gaps to viewers of such displays.
[0004] While the use of thin cover glasses has many advantages, it
also has concomitant cost disadvantages. Thinner glass generally
breaks more easily. In addition, manufacturing equipment is
designed for certain minimum glass thicknesses. Using thinner glass
may result in cost penalties or require the development of
specialized equipment for handling glass processing.
[0005] Thus, the thicker the cover glass that is utilized, the more
apparent are any gaps between adjacent tiles. The composite image
of a large area display is the result of the images contributed by
each of the tiles making up the large area display. To the extent
that the individual tiles may be delineated because of the
inter-tile gaps, the overall seamless effect of the display is
lessened. Therefore, it is desirable to produce large area displays
in which the individual tiles making up the displays are as
invisible and undiscernible as possible.
[0006] Thus, while using thicker glass has many practical
advantages, it may also increase the likelihood that seams between
adjacent tiles become visible. Therefore, there is a need for a way
to make the gaps between adjacent tiles less visible in large area
displays.
[0007] State of the art tile displays, such as video walls, use
mullions between individual tiles to hide the physical gap.
However, if these mullions are discernible to the user, they are
objectionable because they break the continuity of the image.
[0008] Another structure commonly found in non-tiled displays is a
pattern of black lines. The black lines, like a mullion, produce
inter-pixel black lines. A black line is put between the pixels to
absorb ambient light in those areas in order to increase the
display contrast. Black lines are found in non-modular displays
such as cathode ray tubes and liquid crystal displays. With these
displays, the black lines are smaller than the mullions. They are
placed in the plane of the pixels, located between the pixels.
Because the pattern of black lines is periodic and placed between
pixels, it does not break the continuity of the image.
[0009] Thus, there is a need for ways to make the seams of large
area displays less visible.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a schematic depiction of one embodiment of the
present invention;
[0011] FIG. 2 is a partial, enlarged cross-sectional view of
another embodiment of the present invention;
[0012] FIG. 3 is a partial, enlarged cross-sectional view of still
another embodiment of the present invention;
[0013] FIG. 4 is a partial, enlarged cross-sectional view of still
another embodiment of the present invention;
[0014] FIG. 5 is a partial, enlarged cross-sectional view of still
another embodiment of the present invention;
[0015] FIG. 6 is a partial, enlarged cross-sectional view of yet
another embodiment of the present invention;
[0016] FIG. 7 is a partial, enlarged cross-sectional view of
another embodiment of the present invention;
[0017] FIG. 8 is a partial, enlarged cross-sectional view of
another embodiment of the present invention; and
[0018] FIG. 9 is a partial, enlarged cross-sectional view of
another embodiment of the present invention.
DETAILED DESCRIPTION
[0019] Referring to FIG. 1, a pair of adjacent display tiles 10 and
12 may combine to create a portion of an overall large area display
made up of a plurality of tiles 10 and 12. The region between
display tiles 10 and 12, indicated as A, is described herein as the
gap. The gap A includes an upper surface which is closest to the
viewer and a gap region that proceeds along the entire thickness of
the tiles 10 and 12. At the top of the gap A, differences in
surface reflection, such as the angle of reflection and its
intensity, are most important. Below the top of the gap surface in
the gap region, the differences in refraction, reflection and
absorption are important if they are different in the region of the
tiles between the pixels that are not straddling a gap.
[0020] Two rays are shown emanating from the lower surface of the
gap A and extending upwardly at an angle Oc called the critical
angle. At the critical angle, a ray is refracted to an angle
parallel to the top surface of each layer 10 or 12. Light reaching
the surface with angles less than the critical angle exits the
layers 10 and 12 and light reaching the surface with angles larger
than the critical angle is totally internally reflected.
[0021] Because of the critical angle, light emitted from a point
within the layers 10 and 12 can escape from the panels by traveling
at most a lateral distance of dc which is equal to the thickness of
the layers 10 or 12 times the tangent of the critical angle.
Therefore, light from any part of the gap A can be completely
blocked by putting a black strip 14 of width W.sub.m equal to
2d.sub.c over the gap A. Because of the symmetry of the relevant
optics, this same black strip 14 also blocks any external rays (not
shown) from detecting the gap A.
[0022] If the strip 14 width is less than 2d.sub.c but wider than
the width of the top of the gap A, then it will completely hide the
top of the gap A and a portion of a gap region near the top of the
gap A. Thus, the strip 14 makes the top of the gap A and part or
all of the underlying gap region invisible to a user. In practice,
the black strip 14 may be slightly wider to account for any finite
width of the gap A and for any tolerance for the mis-positioning of
the black strip 14 directly over the gap A.
[0023] Using a black strip 14 that is wide enough to hide the
entire gap A top and gap region makes the gap A substantially
invisible. If mullions (not shown) are used around the edges of the
display, a visual discontinuity may result because of the
difference in widths of the mullions versus the black strips 14.
Making the black strips 14 identical to the mullions may make this
discontinuity less noticeable. Also the use of the strips 14 may
increase the contrast of the displayed image. In some embodiments,
the same techniques may be used over the regions between pixels
that are used between the layers 10 and 12 to provide greater
uniformity.
[0024] Referring to FIG. 2, a pair of transparent layers 10 and 12
may be abutted together to form part of an overall large area
display. The gap A may be defined between the layers 10 and 12.
Each of the layers 10 and 12 may have coated on its lower surface
one or more light emitting elements 15. In the case shown in FIG.
2, a set of three light emitting elements 15 are provided, one for
each color of a tricolor color space such as red, green, blue (RGB)
color space.
[0025] Each of the light emitting elements 15 closest to the gap A
emits light having a ray most adjacent to the gap A and indicated
by the letters B and C. As a result, a space D may be defined over
the strip 14 that is not impacted by any emitted light. In
particular, the strip 14 may be sized so that it obscures the gap A
while refraining from blocking substantial light emitted by the
light emitting elements 15.
[0026] In some embodiments of the present invention, the light
emitting elements 15 may be any emissive elements including an
organic light emitting device (OLED), a light emitting diode (LED),
or an electroluminescent display (EL), to mention a few examples.
However, the other display technologies may be utilized including
liquid crystal display technologies in some embodiments.
[0027] In FIG. 3, each layer 10 and 12 is overlaid by a layer 16.
In some embodiments, the layers 10 and 12 may be formed of glass.
In some embodiments, the layer 16 may be formed of glass or plastic
that is, at least in part, transparent. In particular, the layer 16
may include transparent regions 20 positioned more directly over
the light emitting elements 15 and non-transparent regions 18
intermediate between adjacent regions 20. The layers 10 and 12 may
be integrated to a layer 16 for example by conventional bonding
techniques including heat welding and adhesive bonding as two
examples.
[0028] In some embodiments, the non-transparent regions 18 may be
rectangular or square and may be black in color throughout their
thickness. The sides 19 of the region 18 may be coated to make them
more reflective. This may be done by providing a mirrored or white
surface as two examples. As a result, the rays B and C described in
connection with FIG. 2 may be reflected from the sides 19 as
indicated at E and F. In this way, light may still not be blocked,
as was the case in FIG. 2, but a gap blocking, non-transparent
region 18 of greater vertical dimensions may be provided.
[0029] Because of the imposition of the region 18 close to the
light emitting elements 15, the gap A may be more effectively
hidden. Also, in some cases the layers 10 and 12, reinforced by the
layer 16, may be thinner.
[0030] In some cases, the layer 16 may be abutted against an
adjacent layer 16 producing gaps between adjacent layers 16. These
gaps may be obscured in some cases by using an overlying sheet 40.
This overlying sheet 40, which may be called an optical integrating
plate, may be utilized to assemble the various tiles that include
the layers 10 and 12. The plate 40 may include mullions 42 to cover
the gaps A. Those tiles together form the composite image of a
large area display. In addition, an optical integrating plate may
provide a diffusing effect to obscure any gaps between layers 16 in
some cases.
[0031] The layer 16 may be formed in a variety of different
fashions. It may be possible to diffuse a non-transparent material
into the regions 18 while masking the transparent regions 20.
However, as another embodiment, a lithography process may be used
to etch a plurality of holes in the layer 16. The layer 16 may be
transparent in general. Each of those holes may then be coated with
a suitably reflective layer to form the sides 19. The remaining
holes may then be filled with a dark or black material to form the
regions 18.
[0032] Turning next to FIG. 4, in this case, black material 22 is
formed in the layer 16a in a triangular shape. The sides 23 of the
black material 22 may be oriented at an angle so as not to block
the emitted rays B and C. Thus, in some cases, the sides 23 need
not be made reflective, as was the case in the embodiment shown in
FIG. 3.
[0033] However, in some cases, it may still be possible for some
light to impact the sides 23 of the triangular black material 22.
In such cases, it may still be desirable to make the sides 23
reflective. For example, as shown in FIG. 5, reflective sides 26
may be provided on a black triangular material 24 in a sheet 16b.
The resulting reflected rays E and F reduce the loss of light which
might otherwise occur. The embodiment shown in FIG. 5 may be
advantageous, particularly in situations where relatively thick
layers 10 and 12 are utilized. In the embodiments of FIGS. 4 and 5,
an optical integrating plate 40 may be used as described in
connection with FIG. 3.
[0034] In some cases, if the index of refraction of the material 24
is sufficiently lower than the index of refraction of the
surrounding region 20, it may not be necessary to make the sides 26
reflective. Instead, the rays may be reflected due to the
differences in indices of refraction between the material 24 and
the region 20. In some cases, embodiments of the type shown in
FIGS. 4 and 5 may exhibit less contrast improvement for the overall
display compared to those of the type shown in FIG. 7 because of
reflections off of the tapered sides 26 or 23. Thus, in situations
where high contrast is desired, embodiments of the type shown in
FIG. 3 may be preferable. In cases where the redistribution of the
light may become a problem, embodiments of the type shown in FIG. 4
may be preferable.
[0035] Referring next to FIG. 6, an optical structure may be
provided that improves the optical separation between pixels. This
structure may be made as a vertically laminated or multilayer
structure, as shown in FIG. 6, or may be formed from a single
layer. Each of the layers 10 and 12 may be associated with one or
more hemispherical lenses 20a that may be described as microlenses.
The lenses 20a may be formed of glass, plastic or other transparent
materials.
[0036] The lenses 20a provide a means of concentrating emitted
light from a pixel light emitting element 15 into the viewing
space, providing a brighter display. Lenses 20a may also reduce the
internally reflected light by waveguiding the light outwardly from
the display. This is because the lenses 20a may increase the
critical angle of the outbound light in some embodiments. Each lens
20a may be either one or two dimensional. In the case of linear
lenses or one dimensional lenses, the lens 20a may be oriented
horizontally so as to concentrate the light into a smaller vertical
viewing zone.
[0037] Between each adjacent layer 10 or 12, over the gap A, a dark
region 28 may be formed for example by deposition. The dark region
28 obscures the underlying gap A as was the case in previously
described embodiments. In this case, the lateral extension of the
region 28 may avoid obscuring the outbound light from the light
emitting elements 15. The effect of the lenses 20a is indicated by
the rays B and C, which are the rays most adjacent to gap A. The
rays B and C are refracted, as indicated at G and H, towards the
center of each lens 20a, effectively concentrating the resulting
outbound light.
[0038] The use of lenses 20b (with a greater aspect ratio than
those shown in FIG. 6) is illustrated in FIG. 7. In some cases, the
lenses 20b may use refraction as well as internal reflection as
indicated by the arrows E and F in FIG. 7. In some cases, a
reflective coating may be applied to the external sides 30 of the
lenses 20b. In other cases, total internal reflection may be
utilized. A black matrix material 28a is situated between adjacent
lenses 20b. In the embodiment shown in FIG. 7, the matrix material
28a may cover the sides 30 of the lenses 20b because of the use of
internal reflection.
[0039] The use of a unitary cover plate 32 is shown in FIG. 8. In
this example, the plate 32 may replace both the layers 10 and 12
and any overlying layer such as the layer 20. This may be possible
because the plate 32 may be formed with integral optical elements
38. The plate 32 may be molded to the shape that is desired using
plastic as one example. In other cases, the desired shape may be
formed by grinding, sawing, abrasive jets, etching or other
formation techniques. The elements 38 defined in the plate 32 may
be triangular in one embodiment of the present invention. The
triangular elements 38 reflect incoming light and obscure
underlying gaps.
[0040] The elements 38 may be coated or filled with black or
reflective materials to make optics that isolate or concentrate
light from the pixels defined by elements 15. Thus, as shown in
FIG. 9, a filler 40 is used in place of the open spaces (FIG. 8)
that may make up part of the elements 38.
[0041] Where a coating is utilized as indicated at 38 in FIG. 8,
the remaining opening area 34 may be utilized to locate electrodes,
connections and other features. Thus, a contact 36 may be provided
to metal or other conductive lines to reach the light emitting
layer 15 in one embodiment.
[0042] The elements 38 may be open spaces with air which has a
relatively low index of refraction. This may create, in some
embodiments, total internal reflection without the need for a
coating. Gaps may be defined between adjacent plates 32.
[0043] While the present invention has been described with respect
to a limited number of embodiments, those skilled in the art will
appreciate numerous modifications and variations therefrom. It is
intended that the appended claims cover all such modifications and
variations as fall within the true spirit and scope of this present
invention.
* * * * *