U.S. patent application number 14/750799 was filed with the patent office on 2016-12-29 for high contrast projection screen with stray light rejection.
The applicant listed for this patent is Google Inc.. Invention is credited to Serge J. Bierhuizen, Andrei S. Kazmierski, Adam E. Norton.
Application Number | 20160377970 14/750799 |
Document ID | / |
Family ID | 55967446 |
Filed Date | 2016-12-29 |
United States Patent
Application |
20160377970 |
Kind Code |
A1 |
Norton; Adam E. ; et
al. |
December 29, 2016 |
HIGH CONTRAST PROJECTION SCREEN WITH STRAY LIGHT REJECTION
Abstract
A multi-layer projection screen includes a transparent substrate
having first and second sides, a stray light rejection layer, and a
lens array. The stray light rejection layer is disposed across the
first side of the transparent substrate. The stray light rejection
layer includes an array of pillar structures, wherein each pillar
structure of the array of pillar structures includes an entrance
aperture, an exit aperture, a substantially transparent pathway
extending from the entrance aperture to the exit aperture, and an
opaque side wall surrounding the transparent pathway. The lens
array is disposed across the second side of the transparent
substrate and optically aligned to the array of pillar structures.
The stray light rejection layer blocks display light received from
the lens array having an oblique trajectory that is greater than a
threshold angle from a normal of the second side of the transparent
substrate.
Inventors: |
Norton; Adam E.; (Palo Alto,
CA) ; Bierhuizen; Serge J.; (San Jose, CA) ;
Kazmierski; Andrei S.; (Pleasanton, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Google Inc. |
Mountain View |
CA |
US |
|
|
Family ID: |
55967446 |
Appl. No.: |
14/750799 |
Filed: |
June 25, 2015 |
Current U.S.
Class: |
353/38 ;
359/450 |
Current CPC
Class: |
G03B 21/006 20130101;
G02B 5/003 20130101; G02B 5/005 20130101; G03B 21/602 20130101;
G02B 5/021 20130101; G02B 5/0294 20130101; G03B 21/147 20130101;
G02B 3/0056 20130101; G02B 3/08 20130101; G02B 5/0278 20130101;
G02B 27/0018 20130101; G03B 21/625 20130101; G03B 21/208 20130101;
G02B 27/30 20130101; G02B 3/005 20130101 |
International
Class: |
G03B 21/625 20060101
G03B021/625; G03B 21/20 20060101 G03B021/20; G02B 3/08 20060101
G02B003/08; G02B 3/00 20060101 G02B003/00; G02B 5/02 20060101
G02B005/02; G03B 21/14 20060101 G03B021/14; G02B 5/00 20060101
G02B005/00 |
Claims
1. A multi-layer projection screen, comprising: a substantially
transparent substrate having first and second sides; a stray light
rejection layer disposed across the first side of the transparent
substrate, the stray light rejection layer including an array of
pillar structures, wherein each pillar structure of the array of
pillar structures includes: an entrance aperture; an exit aperture;
a substantially transparent pathway extending from the entrance
aperture to the exit aperture; and an opaque side wall surrounding
the transparent pathway; and a lens array disposed across the
second side of the transparent substrate and optically aligned to
the array of pillar structures such that each lens of the lens
array focuses first display light having a normal trajectory
relative to the second side of the transparent substrate through
the entrance and exit apertures of a corresponding pillar structure
while second display light having an oblique trajectory that is
greater than a threshold angle from the normal trajectory is
directed onto the opaque side wall and substantially blocked from
reaching the exit aperture.
2. The multi-layer projection screen of claim 1, wherein the opaque
side wall and transparent pathway are formed of materials having
substantially similar refractive indexes.
3. The multi-layer projection screen of claim 1, wherein the exit
aperture has a smaller cross-sectional area than the entrance
aperture.
4. The multi-layer projection screen of claim 3, wherein each
opaque side wall separating adjacent transparent pathways has a
T-shaped cross-section.
5. The multi-layer projection screen of claim 3, wherein the
transparent pathway has a truncated cone shaped cross-section.
6. The multi-layer projection screen of claim 3, wherein the
transparent pathway has a cross-sectional shape comprising: a
truncated cone adjacent to the entrance aperture; and a rectangular
nipple adjacent to the exit aperture.
7. The multi-layer projection screen of claim 1, further
comprising: a diffuser disposed across the exit aperture of each
pillar structure and upon which an image plane for the first
display light is formed, wherein the diffuser increases a
divergence of the first display light.
8. The multi-layer projection screen of claim 7, wherein the
diffuser comprises one of: a texture applied across an entire
emission surface of the stray light rejection layer; or a texture
applied to the transparent pathway at the exit aperture of each
pillar structure of the array of pillar structures.
9. The multi-layer projection screen of claim 7, wherein the
diffuser comprises one of: a diffusive material layer disposed
across an entire emission surface of the stray light rejection
layer; or diffusive material disposed within transparent pathway
proximate to the exit aperture of each pillar structure of the
array of pillar structures.
10. The multi-layer projection screen of claim 1, wherein the
threshold angle is approximately 5 degrees.
11. The multi-layer projection screen of claim 1, wherein the array
of pillar structures further comprises: a plurality of trenches
formed in a material layer that forms the transparent pathway of
each pillar structure; dark ink filled into the plurality of
trenches; and a planarized top surface of the dark ink forming an
emission surface of the stray light rejection layer.
12. The multi-layer projection screen of claim 1, wherein the lens
array comprises a two-dimensional array of microlenses.
13. The multi-layer projection screen of claim 1, wherein the lens
array comprises: a first one dimensional ("1D") array of
cylindrical lenses; and a second 1D array of cylindrical lenses
orthogonally oriented relative to the first 1D array of cylindrical
lenses.
14. The multi-layer projection screen of claim 13, wherein the
stray light rejection layer comprises a first stray light rejection
layer and wherein the array of pillar structures comprises a first
1D array of pillar structures, the multi-layer projection screen
further comprising: a second stray light rejection layer including
a second 1D array of pillar structures orthogonally oriented
relative to the first 1D array of pillar structures, wherein the
second stray light rejection layer is interposed between the first
and second 1D array of cylindrical lenses, wherein the first 1D
array of cylindrical lenses is aligned to the first 1D array of
pillar structures of the first stray light rejection layer and the
second 1D array of cylindrical lenses is aligned to the second 1D
array of pillar structures of the second stray light rejection
layer.
15. The multi-layer projection screen of claim 1, wherein the array
of pillar structures comprises a two-dimensional array of pillar
structures.
16. A rear projection display, comprising: a projection screen
including: a substantially transparent substrate having first and
second sides; a stray light rejection layer disposed across the
first side of the transparent substrate, the stray light rejection
layer including an array of pillar structures, wherein each pillar
structure of the array of pillar structures includes an entrance
aperture, an exit aperture, a substantially transparent pathway
extending from the entrance aperture to the exit aperture, and an
opaque side wall surrounding the transparent pathway; and a lens
array disposed across the second side of the transparent substrate
and optically aligned to the array of pillar structures, wherein
the stray light rejection layer blocks display light received from
the lens array having an oblique trajectory that is greater than a
threshold angle from a normal of the second side of the transparent
substrate; a display layer including a transmissive pixel array to
project an image onto the projection screen from a backside of the
projection screen; and an illumination layer including an
illumination source to illuminate a backside of the transmissive
pixel array.
17. The rear projection display of claim 16, wherein the opaque
side wall and transparent pathway are formed of materials having
substantially similar refractive indexes.
18. The rear projection display of claim 16, wherein the exit
aperture has a smaller cross-sectional area than the entrance
aperture.
19. The rear projection display of claim 18, wherein each opaque
side wall separating adjacent transparent pathways has a T-shaped
cross-section.
20. The rear projection display of claim 18, wherein the
transparent pathway has a truncated cone shaped cross-section.
21. The rear projection display of claim 18, wherein the
transparent pathway has a cross-sectional shape comprising: a
truncated cone adjacent to the entrance aperture; and a rectangular
nipple adjacent to the exit aperture.
22. The rear projection display of claim 16, further comprising: a
diffuser disposed across the exit aperture of each pillar structure
and upon which an image plane for the display light is formed,
wherein the diffuser increases a divergence of the display
light.
23. The rear projection display of claim 22, wherein the diffuser
comprises one of: a texture applied across an entire emission
surface of the stray light rejection layer; or a texture applied to
the transparent pathway at the exit aperture of each pillar
structure of the array of pillar structures.
24. The rear projection display of claim 22, wherein the diffuser
comprises one of: a diffusive material layer disposed across an
entire emission surface of the stray light rejection layer; or
diffusive material disposed within transparent pathway proximate to
the exit aperture of each pillar structure of the array of pillar
structures.
25. The rear projection display of claim 16, wherein the array of
pillar structures further comprises: a plurality of trenches formed
in a material layer that forms the transparent pathway of each
pillar structure; dark ink filled into the plurality of trenches;
and a planarized top surface of the dark ink forming an emission
surface of the stray light rejection layer.
26. The rear projection display of claim 16, further comprising a
Fresnel collimator disposed between the display layer and the lens
array to reduce a divergence of the display light output from the
transmissive pixel array.
Description
TECHNICAL FIELD
[0001] This disclosure relates generally to the field of optics,
and in particular but not exclusively, relates to display
screens.
BACKGROUND INFORMATION
[0002] Conventional rear projection screens use a thin diffusing
layer in the form of a matte screen. An image is projected onto the
back of the diffusing layer, where it is diffused and scattered
into the viewing environment. The diffusing layer provides an image
surface and its diffusive nature serves to increase the viewing
angles from which the image can be observed. In order to provide
good image quality, it is desirable for these projection screens to
provide high image contrast and sharp image quality.
[0003] Conventional rear projection screens often suffer from poor
image contrast in well-lit rooms, at least in part, from the
scattering of ambient light back into the viewing environment. This
backscattered ambient light deleteriously affects the black levels,
and therefore contrast, of the rear projection screen. Furthermore,
conventional rear projection screens often suffer from reduced
image sharpness or image blur due to stray light in the projection
path preceding the image plane of the projection screen. Stray
light (i.e., display light with sufficiently large non-normal
angles) emitted from the display source at a given display pixel
location should be prevented from entering the optical path
reserved for an adjacent display pixel prior to the display light
reaching the image plane.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] Non-limiting and non-exhaustive embodiments of the invention
are described with reference to the following figures, wherein like
reference numerals refer to like parts throughout the various views
unless otherwise specified. The drawings are not necessarily to
scale, emphasis instead being placed upon illustrating the
principles being described.
[0005] FIG. 1 is cross-sectional illustration of a rear projection
display including a multi-layer projection screen that blocks stray
light, in accordance with an embodiment of the disclosure.
[0006] FIG. 2 is a cross-sectional illustration of a multi-stack
Fresnel collimator, in accordance with an embodiment of the
disclosure.
[0007] FIGS. 3A & 3B illustrate example lens arrays, in
accordance with embodiments of the disclosure.
[0008] FIG. 4A is a cross-sectional illustration of a stray light
rejection layer having opaque side walls with T-shaped
cross-sections, in accordance with an embodiment of the
disclosure.
[0009] FIG. 4B is a cross-sectional illustration of a stray light
rejection layer with transparent pathways having truncated cone
cross-sections, in accordance with an embodiment of the
disclosure.
[0010] FIG. 4C is a cross-sectional illustration of a stray light
rejection layer with transparent pathways having cross-sections
resembling a truncated cone with a rectangular nipple, in
accordance with an embodiment of the disclosure.
[0011] FIGS. 5A-5D illustrate example diffusers upon which an image
plane for display light is formed, in accordance with embodiments
of the disclosure.
[0012] FIG. 6 is an exploded view illustration of a multi-layer
projection screen that interleaves one-dimensional rejection layers
with one-dimensional lens arrays, in accordance with an embodiment
of the disclosure.
[0013] FIG. 7 is a perspective view illustrating functional layers
of a rear projection display, in accordance with an embodiment of
the disclosure.
DETAILED DESCRIPTION
[0014] Embodiments of an apparatus, system, and method of
fabrication for a high contrast projection screen with stray light
rejection are described herein. In the following description
numerous specific details are set forth to provide a thorough
understanding of the embodiments. One skilled in the relevant art
will recognize, however, that the techniques described herein can
be practiced without one or more of the specific details, or with
other methods, components, materials, etc. In other instances,
well-known structures, materials, or operations are not shown or
described in detail to avoid obscuring certain aspects.
[0015] Reference throughout this specification to "one embodiment"
or "an embodiment" means that a particular feature, structure, or
characteristic described in connection with the embodiment is
included in at least one embodiment of the present invention. Thus,
the appearances of the phrases "in one embodiment" or "in an
embodiment" in various places throughout this specification are not
necessarily all referring to the same embodiment. Furthermore, the
particular features, structures, or characteristics may be combined
in any suitable manner in one or more embodiments.
[0016] FIG. 1 is cross-sectional illustration of a rear projection
display 100 including a multi-layer projection screen that blocks
stray light, in accordance with an embodiment of the disclosure.
The illustrated embodiment of rear projection display 100 includes
an illumination source 105, a display panel 110, a collimator 115,
and a multi-layer projection screen 120. The illustrated embodiment
of multi-layer projection screen 120 includes a lens array 125, a
transparent substrate 130, a stray light rejection layer 135, and a
diffuser layer 140.
[0017] During operation illumination source 105 emits display light
145 onto display panel 110. Illumination source 105 may be
implemented using a variety of lamp technologies including light
emitting diodes ("LED"), fluorescent lights, or otherwise. In the
illustrated embodiment, illumination source 105 is a point source
illuminator that generates divergent light. Of course, multi-layer
projection screen 120 may be used with other types of illumination
sources.
[0018] Display light 145 illuminates the backside of display panel
110, which spatially modulates an image onto display light 145. In
the illustrated embodiment, display panel 110 is a transmissive
pixel array, such as a liquid crystal display ("LCD"). Of course,
other display panel technologies may be using including liquid
crystal on silicon ("LCoS") panels, organic LED ("OLED") display
panels, or otherwise. Although FIG. 1 illustrates display panel 110
in a rear illumination configuration, front illumination
configuration may be implemented. Furthermore, direct emission
panels (e.g., OLED) may be used, thus in these embodiments
illumination source 105 would be integral with display panel 110.
If alternative display technologies, such as OLED, LCoS, or direct
microLED arrays are used, one or more additional optical layers may
need to be introduced to control the angular spread of the emitted
light.
[0019] In the illustrated embodiment, display light 145 output from
display panel 110 is divergent. As such, collimator 115 is
interposed between multi-layer projection screen 120 and display
panel 110. Collimator 115 reduces the divergence of display light
145 such that it is substantially collimated along a trajectory
that is near normal to a surface of transparent substrate 130. In
practice, collimators (including collimator 115) are not 100%
effective and thus some light remains divergent from scattered or
diffracted light. Furthermore, display light incident near the
periphery of display panel 110 or incident upon internal seams of
any one of the components of rear projection display 100 may be
refracted/reflected along non-normal trajectories. This light is
referred to as "stray light" (e.g., stray light 150), which reduces
the sharpness or fidelity of the image generated by rear projection
display 100. For the purposes of this application, stray light 150
is defined as display light incident upon the backside of
multi-layer projection screen 120 having an oblique trajectory that
deviates more than a threshold angle from a normal 155 of
transparent substrate 130 or other planar surfaces of multi-layer
projection screen 120. In one embodiment, the threshold angle is
approximately 5 degrees. Of course, in other embodiments, the
threshold angle may be greater or smaller than 5 degrees.
[0020] Stray light 150 detracts from the image quality of rear
projection display 100 since light output from a given display
pixel of display panel 110 and intended for a given image pixel
location on the projection screen could end up incident on the
image pixel location associated with an adjacent display pixel.
This scenario is deleterious to image quality. Accordingly,
multi-layer projection screen 120 includes stray light rejection
layer 135, which blocks stray light 150 from reaching diffuser
layer 140 upon which the image plane for display light 145 is
formed. Not only does multi-layer projection screen 120 reduce or
block stray light 150, but it also serves to increase the display
contrast of the projection screen by reducing ambient
reflections.
[0021] The collimated display light 145 is incident upon lens array
125 after passing through collimator 115. Lens array 125 focuses
display light 145 across transparent substrate 130, through
transparent pathways between opaque side walls within stray light
rejection layer 135, and onto diffuser layer 140. If portions of
display light 145 have sufficiently oblique trajectories that
exceed the threshold angle (e.g., stray light 150), these rays end
up incident upon the opaque side walls and absorbed or blocked. In
one embodiment, the opaque side walls are fabricated of a material
having an index of refraction substantially similar to that of the
transparent pathways to discourage total internal reflections of
stray light 150 and encourage absorption of stray light 150.
[0022] As previously mentioned, diffuser layer 140 operates as the
image plane for display light 145 and serves to increase the
divergence of display light 145 emitted from the frontside of rear
projection display 100 into the viewing environment. In other
words, diffuser layer 140 increases acceptable viewing angles for
rear projection display 100.
[0023] Not only does stray light rejection layer 135 improve image
sharpness by reducing stray light 150 from one pixel entering into
the optical path of an adjacent pixel, but stray light rejection
layer 135 also serves to increase image contrast. In the
illustrated embodiment, the opaque side walls surrounding the
transparent pathways of each pillar structure are formed of a dark
or black pigmented material (e.g., black polymer). As such the
front side of stray light rejection layer 135 is perceived as a
substantially black surface, which reduces back reflections of
ambient light. To further reduce back reflection of ambient light,
the surface area of the exit apertures of each pillar structure of
stray light rejection layer 135 is smaller than its corresponding
entrance aperture adjacent to transparent substrate 130. Various
embodiments of stray light rejection layer 135 are discussed in
greater detail in connection with FIGS. 4A-4C.
[0024] FIG. 2 is a cross-sectional illustrating of a multi-stack
Fresnel collimator 200, in accordance with an embodiment of the
disclosure. Fresnel collimator 200 is one possible implementation
of collimator 115 illustrated in FIG. 1. The illustrated embodiment
of Fresnel collimator 200 includes a first Fresnel collimator 205
and a second Fresnel collimator 210 stack there over. Each Fresnel
collimator operates to reduce the divergence of display light 215
received from a display panel (e.g., display panel 110) in at least
one dimension. For example, Fresnel collimators 205 and 210 may be
orthogonally aligned to reduce the divergence of display light 215
in two orthogonal dimensional such that display light 220 is
substantially collimated with a trajectory near normal (e.g.,
normal 155) to transparent substrate 130. In one embodiment, the
majority of display light 220 has a less than 5 degree divergence
from normal 155. However, in practice some display light 220 will
end up refracted or reflected off trajectory as stray light 150.
Stray light 150 may result from boundary interfaces, material
flaws, or other inconsistencies in the design or manufacture of
rear projection display 100.
[0025] Although FIG. 2 illustrates a dual stack of Fresnel
collimators, in other embodiments, anywhere from one to many (e.g.,
four) layers of Fresnel collimators may be implemented. These
Fresnel collimators may be linear, one dimensional collimators or
circular, two dimensional collimators. In one embodiment, the
multi-layer Fresnel collimator 200 may be bonded onto the backside
of lens array 125. Other collimating optics may be used.
[0026] FIGS. 3A & 3B illustrate example lens arrays for
implementing lens array 125, in accordance with various embodiments
of the disclosure. For example, FIG. 3A illustrates a dual stack of
one-dimensional ("1D") cylindrical lens arrays 305 and 310 having
orthogonal orientations. Collectively, cylindrical lens arrays 305
and 310 focus near collimated display light 145 in two dimensions.
FIG. 3B illustrates a 2D array of micro-lenses 315 that also
focuses display light 145 in two dimensions. FIG. 3B illustrates a
2D array of hexagonal microlenses, but other lens shapes (e.g.,
circular microlenses) may also be used. Cylindrical lens array 305,
310 and mirco-lenses 315 may be fabricated from high index
transparent plastic disposed across a low index transparent plastic
sheet. Of course, other fabrication materials may be used.
[0027] FIGS. 4A-4C illustrate various example implementations of
stray light rejection layer 135 illustrated in FIG. 1. For example,
FIG. 4A is a cross-sectional illustration of a stray light
rejection layer 405 having opaque side walls 410 with T-shaped
cross-sections, in accordance with a first embodiment of the
disclosure. Opaque side walls 410 define transparent pathways 415
each having an entrance aperture 420 and an exit aperture 425. The
opaque sides 410 and transparent pathways 415 together form a 2D
array of pillar structures 430 that make up stray light rejection
layer 405.
[0028] As illustrated, exit apertures 425 have a smaller
cross-sectional area than entrance apertures 420. This provides
room for display light 145 to converge into exit apertures 420 and
provides a mostly dark surface for high contrast on the emission
surface of stray light rejection layer 405. The embodiment
illustrated in FIG. 4A may have the following demonstrative
dimensions D1=50 to 100 um, D2=50 to 150 um, D3=40 to 100 um, D4=5
to 20 um. Of course, these dimensions are mere examples and other
dimensions may be used.
[0029] FIG. 4B is a cross-sectional illustration of a stray light
rejection layer 440 with a 2D array of pillar structures 445 formed
by transparent pathways 450 and opaque sidewalls 455, in accordance
with an embodiment of the disclosure. The illustrated transparent
pathways 450 and opaque sidewalls 455 have cross-sectional shapes
that resemble truncated cones and define exit apertures 460 that
are smaller than their corresponding entrance apertures 465.
[0030] FIG. 4C is a cross-sectional illustration of a stray light
rejection layer 470 with a 2D array of pillar structures 475, in
accordance with anther embodiment of the disclosure. 2D array of
pillar structures 475 are formed by transparent pathways and opaque
side walls 477. The transparent pathways have cross-sections
resembling a truncated cone section 480 adjacent an entrance
aperture and a rectangular nipple section 485 adjacent to an exit
aperture.
[0031] The 2D array of pillar structures illustrated in FIGS. 4A-C
are merely representative and other cross-sectional shapes that
provide smaller exit apertures than entrance apertures may be
fabricated. A variety of different fabrication techniques may be
used to form the stray light rejection layer on one side of
transparent substrate 130 and lens array 125 on the other. In one
embodiment, a rolling replication technique may be used where
transparent substrate 130 (e.g., a sheet of Polyethylene
terephthalate (PET) clear plastic) is fed under a rolling drum
press. As transparent substrate 130 is fed under the drum press a
transparent curable plastic is continuously dispensed over the
surface of transparent substrate 130 in front of the drum press.
The drum press then forms trenches corresponding to the opaque side
walls of the 2D array of pillars into the transparent curable
plastic. After UV or thermal curing of the molded transparent
plastic, dark or black pigment is filled into the trenches,
planarized (e.g., squeegeed), and cured.
[0032] Alternatively, lithographic techniques may be used to form
the transparent pathways through stray light rejection layer 135.
For example, light may be focused through lens array 125 to pattern
transparent pathways through stray light rejection layer 135 using
standard photolithography techniques. This technique benefits from
passive self-alignment between lens arrays 125 and the transparent
pathways of stray light rejection layer 135.
[0033] FIGS. 5A-5D illustrate example implementations of diffuser
layer 140 upon which an image plane for display light 145 is
formed, in accordance with embodiments of the disclosure. FIG. 5A
illustrates how diffusive material 505 is disposed within the
transparent pathway proximate to the exit aperture of each pillar
structure. Diffusive material 505 has a scattering effect on
display light 145 causing the divergence of display light 145 to
increase upon emission from the emission surface of stray light
rejection layer 135. Diffusive material 505 may be implemented
using a variety of techniques, such as embedding scattering
particles within the transparent material of the transparent
pathways. In one embodiment, the scattering particles may be
transparent particles or beads having a different refractive index
than the surrounding material of the transparent pathways. This
embedded transparent particle technique reduces deleterious
backscattering down the transparent pathways while increasing the
divergence of the emitted display light 145.
[0034] FIG. 5B illustrated an embodiment where a diffusive material
layer 510 is disposed across the entire emission surface of stray
light rejection layer 135. Diffusive material layer 510 may be
fabricated using similar materials to diffusive material 505. FIG.
5C illustrates an embodiment where a texture 515 is formed into the
emission surface of each transparent pathway 520. In one
embodiment, texture 515 is the result of scoring, pressing,
emblazoning, stamping, or otherwise roughing the surface of each
transparent pathway 520. FIG. 5D illustrates an embodiment where a
texture 525 is applied across the entire emission surface of stray
light rejection layer 135. Diffusive material 505, diffusive
material layer 510, textures 515, and texture 525 illustrate
various structures for implementing diffuser layer 140. In various
embodiments, one or more of the techniques illustrated in FIGS.
5A-D may be combined to improve the effectiveness of diffuser layer
140.
[0035] FIG. 6 is an exploded view illustration of a multi-layer
projection screen 600 that interleaves one-dimensional stray light
rejection layers with one-dimensional lens arrays, in accordance
with an embodiment of the disclosure. Multi-layer projection screen
600 operates using the same principles as described above in
connection with multi-layer projection screen 120, except that the
functionality of stray light rejection layer 135 (FIG. 1) is
separated into two stray light rejection layers 605 and 610 and the
functionality of lens array 125 (FIG. 1) is separated into two
non-adjacent 1D lens arrays 615 and 620. While stray light
rejection layer 135 is formed as a 2D array of pillar structures
that block stray light 150 in two dimensions, each stray light
rejection layer 605 and 610 includes a 1D array of pillar
structures that block stray light 150 along only a single
dimension. However, the 1D array of pillar structures within stray
light rejection layer 605 are orthogonally oriented relative to
those in stray light rejection layer 610 such that collectively 2D
blocking of stray light is achieved in a distributed manner.
Similarly, 1D lens arrays 615 and 620 each focus light along a
single dimension, but are also orthogonally oriented relative to
each other. As illustrated in FIG. 6, 1D lens array 615 is aligned
with stray light rejection layer 605 to focus the display light and
block stray light along one dimension while 1D lens array 620 is
aligned with stray light rejection layer 610 to focus the display
light and block stray light in an orthogonal dimension. It should
be appreciated that multi-layer projection screen 600 may be
implemented using one-dimensional implementations of any of the
pillar structures illustrated in FIGS. 4A-4C. Similarly, the
diffuser layer 140 may be implemented using any of the structures
illustrated in FIGS. 5A-5D, but applied to the top of stray light
rejection layer 610, as illustrated in FIG. 6.
[0036] FIG. 7 is a perspective view illustrating functional layers
of an example rear projection display 700, in accordance with an
embodiment of the disclosure. The illustrated embodiment of display
700 includes an illumination layer 705, a display layer 710, and a
screen layer 715. Screen layer 715 may be implemented with any of
the rear projection screens described above in connection with
FIGS. 1-5, or various combinations thereof. It should be
appreciated that the rear projection screens disclosed above may
also be used in connection with other rear projection architectures
as well.
[0037] The illustrated embodiment of illumination layer 705
includes an array of illumination sources 720. The illustrated
embodiment of display layer 710 includes transmissive pixel arrays
730 separated from each other by spacing regions 735. The
illustrated embodiment of screen layer 715 is divided into regions
for displaying image portions 750 of an overall unified image. Rear
projection display 700 is made up of a plurality of pixlets, each
including an illumination source 720, transmissive pixel array 730,
and a screen region for displaying an image portion 750 all aligned
within a column through display 700.
[0038] In the illustrated embodiment, each illumination source 720
is aligned under a corresponding pixel array 730 to illuminate a
backside of the corresponding pixel array with lamp light.
Illumination sources 720 may be implemented as independent light
sources (e.g., color or monochromatic LEDs, quantum dots, etc.)
that emit light with a defined angular spread or cone to fully
illuminate their corresponding transmissive pixel array 730
residing above on display layer 710. The illumination layer 705 and
display layer 710 are separated from each other by a fixed distance
745 (e.g., 8 mm). This separation may be achieved using a
transparent intermediary (e.g., glass or plastic layers) and may
further include one or more lensing layers (including lenses,
apertures, beam confiners, etc.) to control or manipulate the
angular extent and cross-sectional shape of the lamp light emitted
from illumination sources 720. In one embodiment, an illumination
controller may be coupled to illumination sources 720 to control
their illumination intensity. Illumination layer 705 may include a
substrate upon which illumination sources 720 are disposed.
[0039] Transmissive pixel arrays 730 are disposed on the display
layer 710 and each includes an array of transmissive pixels (e.g.,
100 pixels by 100 pixels). In one embodiment, the transmissive
pixels may be implemented as backlit liquid crystal pixels. Each
transmissive pixel array 730 is an independent display array that
is separated from adjacent transmissive pixel arrays 730 by spacing
regions 735 on display layer 710. The internal spacing regions 735
that separate adjacent pixel arrays 730 from each other may be
twice the width as the perimeter spacing regions 735 that separate
a given pixel array 730 from an outer edge of display layer 710. In
one embodiment, the internal spacing regions 735 have a width of 4
mm while the perimeter spacing regions 735 have a width of 2 mm. Of
course, other dimensions may be implemented.
[0040] As illustrated, transmissive pixel arrays 730 are spaced
across display layer 710 in a matrix with spacing regions 735
separating each transmissive pixel array 730. In one embodiment,
transmissive pixel arrays 730 each represent a separate and
independent array of display pixels (e.g., backlit LCD pixels).
Spacing region 735 are significantly larger than the inter-pixel
separation between pixels of a given transmissive pixel array 730.
Spacing regions 735 provide improved flexibility for routing signal
lines or the inclusion of additional circuitry, such as a display
controller. Spacing regions 735 that reside along the exterior
perimeter of display layer 710 also provide space for a bezel trim
of display 700. The spacing regions 735 that reside along the
exterior perimeter also provide space for power and/or
communication ports.
[0041] Although FIG. 7 illustrates display layer 710 as including
six transmissive pixel arrays 730 arranged into two rows and three
columns, it should be appreciated that various implementations of
display 700 may include more or less transmissive pixel arrays 730
organized into differing combinations of rows and columns. As such,
in embodiments having a one-to-one ratio of illumination sources
720 to transmissive pixel arrays 730, the number and layout of
illumination sources 720 on illumination layer 705 may also vary.
While FIG. 7 does not illustrate intervening layers between the
three illustrated layers for the sake of clarity, it should be
appreciated that embodiments may include various intervening
optical or structural sub-layers, such as lens arrays, transparent
substrates to provide mechanical rigidity and optical offsets,
protective layers, or otherwise. Furthermore, screen layer 715 is
illustrated for simplicity as a single layer projection screen;
however, screen layer 715 may in fact be implemented using the
multi-layer projection screen 120 illustrated in FIG. 1 or
multi-layer projection screen 600 illustrated in FIG. 6.
Furthermore, collimator 115 may be disposed between screen layer
715 and display layer 710. Display layer 710 represents one
possible implementation of display panel 110 and illumination layer
705 illustrates one possible implementation of illumination source
105.
[0042] Transmissive pixel arrays 730 are switched under control of
a display controller to modulate the lamp light and project image
portions 750 onto a backside of screen layer 715. Image portions
750 collectively blend together on screen layer 715 to present a
unified image to a viewer from the viewing side of screen layer 715
that is substantially without seams. In other words, the images
created by transmissive pixel arrays 730 are magnified as they are
projected across separation 755 (e.g., 2 mm) between display layer
710 and screen layer 715. The image portions 750 are magnified
enough to extend over and cover spacing regions 735 forming a
seamless unified image. The magnification factor is dependent upon
separation 755 and the angular spread of the lamp light emitted by
illumination sources 720. In one embodiment, image portions 750 are
magnified by a factor of approximately 1.5. Not only does the
unified image cover the internal spacing regions 735, but also
covers the perimeter spacing regions 735. As such, display 700 may
be positioned adjacent to other display tiles 700 and
communicatively interlinked to form larger composite seamless
displays, in which case the unified image generated by a single
display tile becomes a sub-portion of a multi-tile unified
image.
[0043] The above description of illustrated embodiments of the
invention, including what is described in the Abstract, is not
intended to be exhaustive or to limit the invention to the precise
forms disclosed. While specific embodiments of, and examples for,
the invention are described herein for illustrative purposes,
various modifications are possible within the scope of the
invention, as those skilled in the relevant art will recognize.
[0044] These modifications can be made to the invention in light of
the above detailed description. The terms used in the following
claims should not be construed to limit the invention to the
specific embodiments disclosed in the specification. Rather, the
scope of the invention is to be determined entirely by the
following claims, which are to be construed in accordance with
established doctrines of claim interpretation.
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