U.S. patent application number 12/831115 was filed with the patent office on 2011-01-06 for backside reflection optical display.
This patent application is currently assigned to UNI-PIXEL DISPLAYS, INC.. Invention is credited to Daniel K. Van Ostrand.
Application Number | 20110002577 12/831115 |
Document ID | / |
Family ID | 39171385 |
Filed Date | 2011-01-06 |
United States Patent
Application |
20110002577 |
Kind Code |
A1 |
Van Ostrand; Daniel K. |
January 6, 2011 |
Backside Reflection Optical Display
Abstract
The disclosure generally involves an optical (perhaps flat
panel) display utilizing backside reflection for time-multiplexed
optical shuttering. One display comprises a side-illuminated light
guide associated with conditions for total internal reflection. A
first surface of the light guide is elastomeric. Disposed against
this elastomeric surface is an active layer that selectively
deforms the elastomeric surface in locations that can correspond to
display pixels. This resulting change in the geometry of the
elastomeric surface can be sufficient to defeat the conditions for
total internal reflection. When appropriate, light is reflected by
the particular deformation and is ejected from another surface of
the light guide. In this case, each location that allows light to
exit could represent an activated display pixel. In certain
situations, color flat panel displays of varying sizes may further
implement field sequential color and time-multiplexed optical
shuttering.
Inventors: |
Van Ostrand; Daniel K.; (The
Woodlands, TX) |
Correspondence
Address: |
Rambus/Fulbright & Jaworski L.L.P.
2200 Ross Avenue, Suite 2800
Dallas
TX
75201
US
|
Assignee: |
UNI-PIXEL DISPLAYS, INC.
The Woodlands
TX
|
Family ID: |
39171385 |
Appl. No.: |
12/831115 |
Filed: |
July 6, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11524704 |
Sep 21, 2006 |
7751663 |
|
|
12831115 |
|
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Current U.S.
Class: |
385/4 |
Current CPC
Class: |
G02B 26/02 20130101;
G02B 5/02 20130101; G09G 3/3473 20130101; G02B 6/0036 20130101;
G02B 26/001 20130101 |
Class at
Publication: |
385/4 |
International
Class: |
G02F 1/295 20060101
G02F001/295 |
Claims
1. An optical component comprising: a light guide adapted to
conduct light under conditions of total internal reflection, at
least a portion of the light guide being deformable; and an active
layer, disposed on the light guide, that selectively reflects light
by deforming a first surface of the light guide such that the light
is ejected from some portion of a second surface of the light
guide.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority from U.S. patent
application Ser. No. 11/524,704, filed Sep. 21, 2006, entitled
"BACKSIDE REFLECTION OPTICAL DISPLAY," and issued Jul. 6, 2010 as
U.S. Pat. No. 7,751,663, the disclosure of which is incorporated
herein by reference.
TECHNICAL FIELD
[0002] The present disclosure generally relates to the field of
display devices and, more particularly, to an optical (perhaps flat
panel) display utilizing backside reflection.
BACKGROUND OF THE INVENTION
[0003] Certain flat panel displays exploit the principle of
frustrated total internal reflection (FTIR) to induce the emission
of light from the respective system. Such displays may be achieved
through the utilization of microelectromechanical systems or
nanoelectromechanical systems (often collectively referred to as
MEMS). For example, one representative of FTIR-based MEMS devices
may be a time multiplexed optical shuttering (TMOS) display. These
TMOS devices may each be generally able to selectively frustrate
the light undergoing total internal reflection within a (generally)
planar waveguide. When such frustration occurs, the selected region
of frustration may constitute a pixel capable of external
control.
BRIEF SUMMARY OF THE INVENTION
[0004] At a high level, this disclosure describes optical displays
incorporating or otherwise using backside reflection. More
specifically, in certain embodiments, a flat panel or other TMOS
display may present pixels that are activated by violating the
conditions for total internal reflection within a light guide or
its light guidance substrate. For example, an optical component may
include a light guide adapted to conduct light wherein at least
some portion of the light guide is deformable and an active layer
disposed on the light guide whereby the active layer selectively
reflects light by deforming a first surface of the light guide such
that light is ejected from a second surface of the light guide. In
certain situations, the deformable portion of the light guide may
be a deformable elastomer layer. The deformable elastomer layer can
then be disposed between the first surface of a light guidance
substrate of the light guide and the active layer.
[0005] In another example, an optical display comprises a light
guide adapted to conduct light under conditions of total internal
reflection, with at least a portion of the light guide being
deformable. An active layer is disposed on the light guide whereby
the active layer selectively reflects light by selectively
deforming a first surface of the light guide such that light is
ejected from a second surface of the light guide. The display also
includes a light source--potentially capable of outputting
alternating pulses of primary colored or infrared light--coupled
with the light guide.
[0006] In a further example, an optical display comprises a light
guide adapted to conduct light under conditions of total internal
reflection where at least a portion of the light guide is
deformable. A plurality of modular active layer disposed in an
arrayed manner on a deformable surface of the light guide whereby
the modular active layer reflects light by selectively deforming a
first surface of the light guide such that light is ejected from a
second surface of the light guide. This display also includes a
light source--potentially capable of outputting alternating pulses
of primary colored or infrared light--coupled with the light
guide.
[0007] To control these example displays or components thereof,
instructions may be executed as appropriate. The instructions may
cause a light source to output alternating pulses of light through
a light guide adapted to conduct light under conditions of total
internal reflection, with at least a portion of the light guide
being deformable. The instructions may (often concurrently)
selectively apply an electrostatic field to an active layer
disposed on a first side of the light guide to deform a particular
portion of the first surface of the light guide such that the light
is ejected from a second surface of the light guide.
[0008] A method for fabricating such optical displays may include
selecting a light guide adapted to conduct light under conditions
of total internal reflection, with at least a portion of the light
guide being deformable. The method may further include coupling a
light source, capable of outputting alternating pulses of light, to
the light guide and arranging a plurality of modules on the light
guide. Each module could comprise an active layer and a driving
layer, with the active layer disposed on a first surface of the
light guide such that light is ejected from a second surface of the
light guide upon selective deformation of the active layer by the
driving layer.
[0009] The foregoing methods--as well as other disclosed example
methods--may be computer managed or implementable. For example, the
display may include processors or other control architecture that
implements some or all of the example techniques. Put another way,
some or all of these features or aspects may be further included or
implemented in respective software. Generally, such features or
aspects of these and other embodiments are set forth in the
accompanying drawings and the description below. For example, some
of these embodiments may be able to locally violate the conditions
of total internal reflection on the surface of the waveguide that
is opposite (and typically parallel) to the surface from which
light is ejected. In this case, the optical path between the viewer
and the light ejected from the display can be less obstructed,
thereby resulting in a brighter, more efficient display. Indeed, a
MEMS-based or other active layer may not be made of optically
transparent materials since it will not lie within the optical path
of the viewer. Therefore, a wider range of materials may be
considered, which can result in cost reduction. Also, this may
allow flat panel displays to be constructed of smaller modular
components of fixed cost that have a more linear cost curve. This
cost savings could make very large displays (e.g. optical display
billboards) more affordable and easier to realize.
[0010] Another advantage potentially provided by such backside
reflection could include a more parallel manufacturing or
fabrication process. For example, the described displays could be
manufactured with more independent, interchangeable parts that
benefit from a parallel manufacturing process. In other words, the
interchangeable parts may be fabricated independently and assembled
into a final product, thereby possibly reducing production costs as
well as the overall time of production. Further, interchangeable
parts can facilitate repair.
[0011] Of course, these example features are for illustration
purposes only and some or all may not be fully present (if at all)
in certain embodiments. Other features, objects, and advantages
will be apparent from the description and drawings and from the
example claims.
[0012] The foregoing has outlined rather broadly the features and
technical advantages of the present invention in order that the
detailed description of the invention that follows may be better
understood. Additional features and advantages of the invention
will be described hereinafter which form the subject of the claims
of the invention. It should be appreciated by those skilled in the
art that the conception and specific embodiment disclosed may be
readily utilized as a basis for modifying or designing other
structures for carrying out the same purposes of the present
invention. It should also be realized by those skilled in the art
that such equivalent constructions do not depart from the spirit
and scope of the invention as set forth in the appended claims. The
novel features which are believed to be characteristic of the
invention, both as to its organization and method of operation,
together with further objects and advantages will be better
understood from the following description when considered in
connection with the accompanying figures. It is to be expressly
understood, however, that each of the figures is provided for the
purpose of illustration and description only and is not intended as
a definition of the limits of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] For a more complete understanding of the present invention,
reference is now made to the following descriptions taken in
conjunction with the accompanying drawings, in which:
[0014] FIG. 1 illustrates an example display according to certain
embodiments of the present disclosure;
[0015] FIG. 2 is a more detailed illustration of a portion of the
(perhaps large scale) display in FIG. 1 showing some of the example
self-contained modules;
[0016] FIG. 3 provides a high level view of the three layers
assembled to form the portion of the display of FIG. 2;
[0017] FIGS. 4A-D are example views of the light guide described in
FIG. 3, the state of the light guide during pixel activation, and a
magnification of the situs of such pixel activation;
[0018] FIGS. 5A-B illustrate example views of the active layer
according to certain embodiments of FIG. 3;
[0019] FIGS. 6A-B illustrate example views of the driving layer
according to certain embodiments of FIG. 3;
[0020] FIGS. 7A-C illustrate example views of a portion of the
display in a quiescent state and with an activated pixel according
to certain embodiments of the present disclosure;
[0021] FIGS. 8A-B illustrate various views of another example
portion of the display comprising an anisotropic conductive film
adhesive (ACF) to activate a pixel according to certain embodiments
of the present disclosure;
[0022] FIG. 9 shows a side view of another example portion of the
display where a plurality of common conductors is disposed on the
flexible membrane according to certain embodiments of the present
disclosure;
[0023] FIGS. 10A-B illustrate various views of another example
portion of the display comprising a transparent common conductor
disposed on a deformable elastomer layer according to certain
embodiments of the present disclosure;
[0024] FIG. 11 shows a side view of another example portion of the
display where the flexible membrane is comprised of a material that
expands under an electrostatic field, such as electroactive
polymers (EAP), with an activated pixel according to certain
embodiments of the present disclosure;
[0025] FIGS. 12A-D illustrate another example portion of the
display, comprising pairs of pad electrodes disposed on a top
surface of a substrate, in the quiescent state and with a pixel
activated according to certain embodiments of the present
disclosure; and
[0026] FIGS. 13A-B illustrate an example portion of the display, in
the quiescent state and with a pixel activated respectively,
utilizing a standoff between two pixels according to certain
embodiments of the present disclosure.
DETAILED DESCRIPTION OF THE INVENTION
[0027] At a high level, FIG. 1 illustrates an example optical
display device 100 that may utilize backside reflection as
described herein. Generally, backside reflection indicates that the
display 100 allows for the deformation of a first surface of a
light guide such that light is ejected from a second surface of the
light guide. In other words, backside may be used to indicate any
side or other portion of the light guide apart from that emitting
the particular light. In some implementations, this display device
100 may be a flat panel display for computers, cell phones and
PDAs, televisions, automobiles, medical or diagnostic applications,
military and avionics, or in any other suitable application or
system. For example, display 100 may be implemented in a laptop (or
other handheld) computer because the potential energy-efficiency
may extend the battery life. Also, display 100 may be more sunlight
readable with higher resolution. In another example, display 100
may display images up to three times higher in resolution, thereby
enhancing diagnostic capabilities. This display 100 may also be
operable to provide a viewing angle greater than 170 degrees,
thereby giving the viewer exceptional latitude in positioning or
locating the display 100. Moreover, these displays may be bendable
(like fiber optic cable) with a radius of curvature of over 20
times the display's thickness. In such an example, display 100 may
be used in outdoor systems because of its flexibility and
ruggedness.
[0028] Generally, the present disclosure discusses an optical
display 100 that emits light by disposing guidance deforming
components (such as an active layer 300) on one surface of an
optical waveguide (or light guide) such that light is reflected or
otherwise ejected from another surface. The deformation of the
light guide frustrates total internal reflection causing light to
be ejected locally at the surface opposing some portion of each
deformation. More specifically, by selectively deforming one
surface of a light guidance substrate such that the conditions for
total internal reflection within the light guidance substrate are
locally violated, light within the light guidance substrate is
reflected at these deformations at an angle sufficient to exit the
light guide at another surface of the light guide.
[0029] As shown in FIG. 1, each of these deformations in display
100 may represent a display pixel 120. A typical display 100 could
contain an embedded matrix of over a million such pixels according
to the resolution requirements or desires of a given application.
In some cases, MEMS devices--whether microelectromechanical systems
or nanoelectromechanical systems--are disposed at the location of
each pixel 120 to selectively violate the conditions for total
internal reflection on the deformable surface of the light guide
200. For example, these example pixels can be configured as a MEMS
device using a parallel plate capacitor system that propels a
deformable membrane between two different positions and/or shapes.
One position or shape corresponds to a quiescent, inactive state
where FTIR does not occur due to inadequate proximity of the
membrane to the waveguide. The other position or shape corresponds
to an active, coupled state where FTIR does occur due to adequate
proximity. These two states correspond to off and on states for the
display pixel 120.
[0030] An aggregate MEMS-based structure may form an active layer
300 (shown in FIG. 3) that, when suitably configured, functions as
a TMOS video display capable of color generation, usually by
exploiting field sequential color and pulse width modulation (PWM)
techniques. Regardless of the particular implementation, the active
layer (300) may be disposed outside the optical path of the viewer
such that the light can ejected from the surface of the light guide
that is not the same side as each respective deformation.
Consequently, the active layer 300 does not need to be transparent
and may be comprised of cheaper or more resilient opaque materials.
For example, when the "back" surface of the light guide is
actuated, light can be ejected from the "front" surface of the
light guide, as perceived by a viewer. Also, driving circuitry may
be disposed on the active layer 300 using any suitable circuit
printing techniques. Indeed, because it does not necessarily lie
within the optical path of the viewer, the active layer 300 may be
designed or fabricated as a self-contained modular unit 150 that
can contains driving circuitry as appropriate. More specifically,
as shown in FIG. 2, a rectangular array of such MEMS-based pixel
regions 150, which are often controlled by electrical/electronic
components, can be fabricated "behind" the active surface of the
planar waveguide. In this fashion, a plurality of such modular
units 150 can be arrayed or otherwise coupled to a very large light
guide 200 in such a manner that helps achieve a flat panel or other
optical display of very large dimensions, such as in an optical
billboard, highway sign, trade show signage and kiosks, and other
large scale application. Moreover, since the active layer 300 can
be fabricated independent of the light guide, its fabrication is
not dependent upon the final size of the light guide. Further,
these components may be manufactured or distributed by multiple
manufacturers and vendors without tight process control or
compatibility concerns. In other words, self contained modular
units may be fabricated at any time for multiple vendors or
distributors and subsequently arrayed on the desired light guide
during final assembly. In addition, some of these parts may be
fabricated in a manner that is substantially independent of one
another and then assembled in a final assembly process. In some
circumstances, this enables a manufacturing process that is more
parallel, perhaps using multiple manufacturers. In this embodiment,
no portion of the active layer 300 needs to be fabricated on the
light guide.
[0031] Disposed along at least one edge of the light guide 200 is a
light source 110 capable of emitting pulses of light. This light
source 110 may be operable to emit visible light, infrared, or any
other suitable light wave. For example, an infrared lamp may be
disposed next to colored lamps. The sources are chosen to emit the
primary colors of visible light to achieve the desired color gamut
of the display. Typically the sources are red, green and blue light
emitting diodes that can be temporally multiplexed to provide the
familiar color gamut known to color displays. In this example,
short bursts of red, green and blue light are emitted through the
same dot so quickly that the eye also sees them as a single color.
In this case, different durations of red, green and blue create
different shades and hues. More specifically, the duration of the
charge helps control the opening and closing of the particular
pixel. It is this duration that can determine the relative
intensity of the color. One frequency for a full cycle of such
alternations (red-green-blue) is typically 1/60 second. Thus every
second, red, green and blue are flashed into the guidance substrate
60 times each, meaning roughly 180 flashes total of all colors
combined in a second. For example, to produce a white background,
each appropriate pixel is open for the entire duration of the red,
green and blue cycles. To produce black text on the white
background, each pixel representing a letter (or portion thereof)
is closed for the entire duration of each cycle. In another
example, to produce fifty percent gray, each respective pixel is
open for 50 percent of each red, green and blue cycle. In yet
another example, to produce a blue background, each appropriate
pixel is closed during red and green cycles, but open during the
blue cycle. The shade of blue is determined by the percentage of
the blue cycle that the pixel is open (perhaps 10%=deep blue and
100%=bright blue). In short, each pixel can be left open for
different percentages of the red, green and blue cycles to produce
millions of different colors and shades of gray, a technique
commonly referred to as pulse width modulation (PWM). But it will
be understood that optical display 100 may be used for any suitable
purpose and any light and/or color may be used. For example, an
infrared light source 110 can be utilized if such an application is
appropriate. In this example, a color display 100 could be
converted to an infrared display 100 by shutting down the
red-green-blue cycle (or removing the ROB source) and coupling a
continuous infrared source to the light guide.
[0032] For a color display using time multiplexed optical
shuttering (TMOS), the light source 110 comprises a plurality of
sources capable of outputting alternating pulses of monochromatic
light, such as light emitting diodes (LEDs). To increase
distribution and mixture of tristimulus light within the light
guide 200, a linearly arrayed concatenation of LEDs may be used.
The individual LEDs may be simplex or triplex structures based, at
least in part, on an application's dimensional and power
dissipation considerations. A simplex LED is a discrete element
that emits only one primary color. A triplex LED combines all three
tristimulus primaries within a more unitary package (where the
respective junctions may even share a common reflector and potting
compound). The mounting for these linear arrays may also serve as
the primary heat sink for these power-intensive illuminating
systems.
[0033] Often, the geometry of the encapsulating structure in which
the junction is embedded helps determine the optimal separation
between the light guide 200 insertion face and the light source
110. The consequence of this physical separation is the
trigonometric restriction on the angles of incidence of light
encountering the insertion face. Moreover, Fresnel insertion losses
apply to light entering light guide 200 from the surrounding air:
maximum insertion occurs when the rays enter normal to the
insertion face, while insertion becomes increasingly attenuated for
rays at glancing angles. Typically, these issues do not arise for
architectures that actually embed the light source 110 within light
guide 200 or otherwise avoid ray transit through air prior to light
travel within light guide 200. For example, the LEDs may be
directly coupled to the light guide 200 by means of a silicone
bridge, thereby improving the range of useful angles injected into
light guide 200. The coupling of light at the interface of the
actuated active layer 300 and light guide 200 may be based on
geometric considerations involving the nature of the two surfaces
making contact. For example, Parylene (which may be prepared by
deposition on silicon wafers) may yield good optical coupling due
to reduced surface roughness and better contact intimacy. In
another example, materials that are not flat (such as latex) can
still couple well under even slight pressure, since the compliance
of the elastic material causes the latex to conform to the surface
of the light guide 200, thereby providing intimacy of contact
without benefit of an initially high surface flatness
specification. In fact, a hybridized structure where latex coating
is added onto a membrane may be used. In some cases, intimacy of
contact over a sufficiently large (>3.lamda.) area may provide a
sufficient coupling.
[0034] FIG. 3 provides a high level view of the three layers
assembled to form one portion of the display. The light guide 200,
active layer 300, and driving layer 400 can all be manufactured
separately and in parallel. Each of the three layers can be
assembled together at the end of the production process to yield a
completed display 100. In fact, each layer may not be manufactured
to the same planar dimensions, which can be varied for each part to
optimize cost and performance criteria. For example, since the
drive circuit 422 for the driving layer 400 can be printed on the
back of the substrate 420, the driving layer 400 when combined with
an active layer 300 can function as a self-contained modular unit
150.
[0035] FIG. 4A shows the light guide 200, often comprising a
generally planar light guidance substrate 201. The light guidance
substrate 201 is normally manufactured using an optically
transparent material of high refractive index such as glass or
plastic. For example, high quality optical glasses may be used. In
another example, certain polymer substrates may be selected because
of lower densities (and a corresponding lower weight per screen),
lower cost, and superior mechanical robustness. More specifically,
light guide substrate 201 may also be fabricated using any number
of other polycarbonates with sufficient clarity, perfluoropolymers
configured to achieve some parity with optical glass, hollow
waveguides, or any other suitable materials or components. FIG. 4A
further depicts a light ray 105 injected into the light guide 200
from the light source 110 and channeled within the light guide 200
via total internal reflection. More specifically, light entering
the light guidance substrate 201 from the light source 110 is
refracted such that the incident light experiences total internal
reflection within the light guidance substrate 201. In some cases,
the side surfaces of the light guide may be mirrored 204 to prevent
light from escaping at the edges. The light guidance substrate 201
is composed of a rigid, transparent material of optical quality. In
this illustrated embodiment, a deformable elastomer layer 202 is
disposed upon a first surface of the light guidance substrate 201.
The deformable elastomer layer 202 is normally optically
transparent and its index of refraction is sufficiently matched to
the index of refraction of the light guidance substrate 201 so that
there is no substantial optical boundary between the deformable
elastomer layer 202 and the light guidance substrate 201. In many
cases, the two structures function as a single light guide 200 such
that conditions for total internal reflection may exist within the
entire structure. The light guide 200 is designed to channel or
guide light received from the light source 110 under conditions
that satisfy total internal reflection. For example, the light
guide 200 may have mirrored surfaces 204 on sides against which a
light source 110 is not disposed, which may help minimize optical
losses.
[0036] FIG. 4B shows an alternative embodiment of a light guide
200. In this situation, the illustrated portion of light guidance
substrate 201 is comprised of a deformable elastomer of high
refractive index. Accordingly, there may be no need for a
deformable elastomer layer to be disposed upon the light guidance
substrate 201. Any surface of the light guide 200 is thus capable
of undergoing selective local deformation.
[0037] FIG. 4C shows the state of the light guide 200 during pixel
activation. Prior to pixel activation, the light rays 105 within
the light guide 200 typically do not strike either large surface of
the light guide 200 at an angle of incidence great enough to
overcome total internal reflection. The deformable elastomer layer
202 has been pushed upward at the surface by the active portion of
the flexible membrane 110 (not shown) resulting in a deformation.
The light rays 105 within the light guide 200 contact the boundary
of the deformable elastomer layer 202 at the situs of the
deformation. That light is reflected at an angle sufficient to exit
the light guide 200 at the surface opposite to the deformation,
which is normally the so-called front or viewable surface of the
display 100.
[0038] FIG. 4D shows a magnified view of the light guide 200 near
the situs of pixel activation. The scale is exaggerated to more
clearly show the features. In embodiments that include a coating of
small asperities 314 disposed on the surface of the common
conductor 312, these asperities ensure multiple reflection points
within the pixel area to maximize light output. These reflection
points are caused when the surface of the deformable elastomer
layer 202 is not smoothly deformed. The small 314 asperities cause
multiple surface deformations across the entire pixel area as
opposed to only a single global deformation for each pixel.
[0039] The selective deformation of a first surface of the light
guide 200 results in light being locally ejected from a second
surface of the light guide 200. Every component required to
activate the pixel, in relation to the viewer, lies behind the
surface from which light is reflected out of the light guide 200.
Except for any protective coatings used in commercial applications,
the optical path between the viewer and the point at which light is
ejected from the light guide 200 is relatively unobstructed. More
specifically, there may be no transparent conductors, thin film
transistors, cladding layers, and such to cause loss. Furthermore,
there is no need for the materials in the active layer 300 or
driving layer 400 to be optically transparent. In fact, the common
conductor 312 is often dark in color and non-reflective. This
enables the substrate 420 to be made of an opaque material such as
a wafer or printed circuit board. The drive circuit 422 can be
disposed on the back of the substrate 420 using common, low-cost
circuit board manufacturing techniques.
[0040] FIG. 5A shows the active layer 300 of the display. The words
top and bottom are used herein only in reference to the orientation
of the figures as shown. The active layer 300 is comprised of a
flexible membrane 310. In the preferred embodiment, the flexible
membrane 310 is composed of a material or device that changes
position and/or shape in response to an applied electrostatic field
and in a manner that is well-suited to external control. Such
materials include electro-active polymers like polyvinylidine
difluoride (PVDF), metallized piezoelectric films and a wide range
of MEMS devices that can produce the required localized dimensional
change. This disclosure contemplates other embodiments of selective
localized activation or deformation well-suited to external control
that respond to electrostatic, electromagnetic, electrochemical or
thermal stimuli.
[0041] Pixel conductors 311 are patterned on the bottom surface of
the flexible membrane 310. An opaque common conductor 312 is
disposed on the top surface of the flexible membrane 310. The
common conductor 312 is typically non-reflective so that light is
not coupled into the active layer 300 when it comes into contact
with the light guide 200. The surface of the common conductor 312
is preferably black in color to improve the contrast ratio of the
emitted light, since that is what the viewer sees when the pixel is
off. The surface of the common conductor 312 may be coated with a
layer of small asperities 314, such as glass beads. A through-hole
conductor 313 extends from common conductor 312 on the top of the
flexible membrane 310 to the bottom surface for the purpose of
providing a contact point for the common conductor and the driving
layer 400 shown in FIG. 6. FIG. 5B shows a bottom view of the
active layer 300. Pixel conductors 311 are patterned on the bottom
of the flexible membrane 310 at each situs where a display pixel is
located.
[0042] FIG. 6A shows the driving layer 400. The driving layer 400
is comprised of a substrate 420, such as a silicon wafer, flex
circuit, or printed circuit board. The driving layer 400 may be
controlled by a processor or other control architecture (such as a
video converter and field sequential color converter) that executes
instructions and manipulates data to perform the operations of
display 100. These control components may include, for example, a
central processing unit (CPU), an application specific integrated
circuit (ASIC) or a field-programmable gate array (FPGA). The
display 100 could behave as a large dynamic RAM chip and be driven
directly by video RAM in one-to-one correlation under an extremely
rapid refresh regimen. In some systems, converters could be
utilized with the present invention to permit compatibility with
conventional television or with high definition television (HDTV).
Moreover, the control components may collectively or individually
execute software operable to manage the various layers and display
components. For example, these instructions may be written or
described in any appropriate computer language including C, C++,
assembler, PerI, any suitable scripting language, or any
combination thereof. Regardless of the particular implementation,
"software" may include software, firmware, wired or programmed
hardware, or any combination thereof as appropriate.
[0043] Returning to the illustrated embodiment, driving layer 400
may include a drive circuit 422 that can be placed on the bottom
side of the substrate 420. In the illustrated example, a plurality
of pad electrodes 421 is disposed on the top surface of the
substrate 420. Each pad electrode 421 is disposed on the substrate
420 such that each pad electrode 421 can correspond to a pixel
conductor 311 on the active layer 300. When the active layer 300 is
brought into contact with the driving layer 400, each pad electrode
421 comes into contact with its corresponding pixel conductor 311
making an electrical connection. The through-hole conductor 313
will come into contact with a pad electrode 421 that drives the
common conductor 312. The thickness of the pad electrodes 421 and
any adhesive are typically sufficient to provide a standoff between
the driving layer 400 and the active layer 300. FIG. 6B shows a top
view of the driving layer 400.
[0044] FIG. 7A shows the three layers (light guide 200, active
layer 300 and driving layer 400) assembled to form any portion of
display 100, such as module 150. The active layer 300 is disposed
such that the common conductor 312 is brought into close proximity
to (but normally not in contact with) the surface of the deformable
elastomer layer 202 of the light guide 200. With regard to the
example shown of FIG. 4B, either surface of the light guidance
substrate 201 may be brought into close proximity with the active
layer 300. Put another way, the "bottom" or the "top" of the light
guidance substrate 201 may be immaterial in the long dimension. In
some embodiments, the driving layer 400 is affixed to the active
layer 300 such that the pad electrodes 421 line up with the pixel
conductors 311. FIGS. 7B-C illustrate various materials that buckle
or bulge under the influence of an electrostatic field, though
materials that exhibit similar behavior under the influence of
other stimuli may also be utilized.
[0045] More particularly, FIG. 7B illustrates a material that
expands predominantly in the horizontal direction (causing the
flexible membrane 310 to buckle), while FIG. 7C illustrates a
material that expands predominantly in the vertical direction
(causing the flexible membrane 310 to bulge). FIG. 7B shows a
display with an activated pixel. In the preferred embodiment, a
pixel is activated by placing an electrostatic potential between
the common conductor 312 and the pixel conductor 311 corresponding
to the pixel that is to be activated. The flexible membrane 310
changes shape in a desired manner in response to the applied
electrostatic field. This causes an upward local deformation of the
flexible membrane 310 at the situs of the pixel being activated. As
the flexible membrane 310 pushes upward, it contacts the deformable
elastomer layer 202 of the light guide 200. The deformable
elastomer layer 202 is mechanically pushed upward in a
corresponding manner. This changes the geometry of the deformable
elastomer layer 202, defeating the conditions for total internal
reflection within the light guide 200. The deformation shown in
FIG. 8 is more typical of a material that expands predominantly in
the horizontal direction, causing the flexible membrane 310 to
buckle. FIG. 7C shows the deformation of a material that expands
predominantly in vertical direction, causing the flexible membrane
310 to bulge. An optional non-conductive shim 725 may be disposed
between the substrate 420 and the pixel conductor 311 to further
control the deformation of the flexible membrane 310. The
non-conductive shim forces the flexible membrane 310 to bulge or
buckle in the direction of the light guide 200 and not back toward
the driving layer.
[0046] FIG. 8A shows another embodiment of the portion of the
display 100, such as a module 150. In this case, anisotropic
conductive film adhesive (ACF) 850 is used to selectively activate
a particular pixel. ACF 850 can be a thermoset epoxy system that is
generally conductive in one dimension and non-conductive in others.
An ACF layer of any suitable thickness is disposed between the
active layer 300 and the driving layer 400. The pixel is activated
by means of a pixel electrode 851 and the excitation of ACF 850
that lies directly above it. The dimensions of pixel electrode 851
are often matched to the size of a display pixel. Pixel conductors
311 may not be necessary since their electrical function has been
replaced by the layer of ACF 850.
[0047] FIG. 8B shows the activation of a pixel shown in FIG. 8A
slightly magnified. In this case, pixel activation is achieved via
a conductive path with an electrical connection between the ACF 850
and the pixel electrode 851. Accordingly, ACF 850 is conductive
only in the vertical direction and in the region bounded by the
horizontally planar dimensions of the pixel electrode 851. This
electrical connection creates a parallel plate capacitor between
the shaded regions of ACF 850 and the common conductor 312 (except
in the region where the through hole conductor 313 connects the ACF
850 to the common conductor 312). Upon charging, Coulomb attraction
sets up an electrostatic field across the capacitor that deforms
the flexible membrane 310.
[0048] FIG. 9 shows another embodiment of the portion of the
display 100, such as a module 150. In this example, the common
conductor 312 on top of the flexible membrane 310 in FIG. 3 is
replaced with individual pixel conductors 940. This similarly
creates a localized parallel plate capacitor at the situs of each
pixel. Each individual pixel conductor 940 is connected to the
driving layer 400 by means of a through-hole conductor 313.
Additional pad conductors 421 are added to the substrate 420 of the
driving layer to electrically connect each through-hole conductor
313.
[0049] FIG. 10A shows another embodiment of the portion of the
display 100, such as a module 150, wherein a transparent common
conductor 1001 is disposed on the deformable elastomer layer 202.
The transparent common conductor 1001 can be made from a material
such as indium tin oxide. An individual pixel conductor 940 is
disposed on top of the flexible membrane 310 and electrically
connected to the substrate 420 by means of a through-hole conductor
313 and pad conductor 421. The individual pixel conductors 940 may
have a coating of small asperities 314 on the top surface. A
parallel plate capacitor is set up between the transparent common
conductor 1001 and each individual pixel conductor 940. When the
light guidance substrate 201 is deformable, as in FIG. 4B, this
alternative embodiment can be realized by disposing the transparent
common conductor on the top surface of the light guidance substrate
201. Two factors for consideration may be the thickness of the
light guidance substrate 201 and the concomitant voltage required
to activate the pixel. Often as thickness increases, so does the
voltage required to activate the pixel.
[0050] FIG. 10B shows the embodiment in FIG. 10A where the pixel
120 is activated by electrostatic attraction. hen a charge is
placed on individual pixel conductor 940, it is drawn by Coulomb
attraction toward the transparent common conductor 1001. The
activated individual pixel conductor 940 presses upward into the
deformable elastomer layer 202 creating a localized deformation at
the situs of the pixel. Light reflects off of this deformation and
is ejected from the light guidance substrate 201.
[0051] FIG. 11 shows another embodiment of the portion of the
display 100, such as a module 150, wherein the deformable elastomer
layer 202 is comprised of a material that expands under the
influence of an electrostatic field, such as electroactive polymers
(EAP). A transparent common conductor 1001 is disposed on the
deformable elastomer layer 202. The need for a flexible membrane is
eliminated. The pixel conductors 940 are disposed on the top
surface of the substrate 420. This can occasionally be done rather
inexpensively using, for example, traditional circuit board
printing. The top of each individual pixel conductor 940 may be
coated with small asperities 314. A parallel plate capacitor is set
up between the transparent common conductor 1001 and each pixel
conductor 940. A pixel is activated by placing a charge on the
pixel conductor 940. An electrostatic field is set up between the
transparent common conductor 1001 and the individual pixel
conductor 940. Under the influence of this field, the deformable
elastomer layer 202 composed of EAP expands downward, pressing
against the pixel conductor 940 and the small asperities 314 that
coat its surface. This creates a localized deformation at the situs
of the pixel. Light reflects off of this deformation and is ejected
from the light guidance substrate 201.
[0052] FIGS. 12A-D show another embodiment of the portion of the
display 100, such as a module 150. In the illustrated embodiment,
pairs of pad electrodes 621 and 622 are disposed on the top surface
of a substrate 420. Comb-like coplanar pixel conductors 511 and 512
are also disposed in an interdigitated manner on the "bottom"
surface of the flexible membrane 310. Disposing a common conductor
in another plane may not be necessary to actuate the flexible
membrane 310. Each pixel conductor 511 and 512 comprises an
electrical pole. The active layer 500 and the driving layer 600 are
disposed so that the pad electrodes 621 make electrical contact
with the pixel conductors 511 and pad electrodes 622 make
electrical contact with the pixel conductors 512. The flexible
membrane 310 is composed of a material that expands under the
influence of an electric field, such as EAP. The desired pixel 120
is activated by placing an electric potential between pixel
conductor 511 and pixel conductor 512. This causes the flexible
membrane 310 to expand, which in turn causes it to buckle upward.
The flexible membrane 310 presses into the deformable elastomer
layer 202 forming a deformation at the situs of the pixel, as shown
in FIG. 12D. Small asperities 314 may be disposed on the top
surface of the flexible membrane to provide multiple reflection
points. The top surface of the flexible membrane is normally opaque
and non-reflective to provide adequate contrast.
[0053] FIGS. 13A-B illustrate an example portion of the display, in
the quiescent state and with a pixel activated respectively,
utilizing a standoff 1034 between two pixels according to certain
embodiments of the present disclosure. Standoff 1304 may comprise
any suitable materials such as, for example, silicone, parylene or
polyethylene terephthalate. Generally, use of this standoff 1304
between pixels may help mitigate pixel cross talk, which may occur
when light is ejected from a pixel 1302 unintentionally due to
actuation of an adjacent pixel 1301. Specifically, in some cases,
the active layer 300 may bend sharply upward at the margin of a
given pixel area, so that it is in full contact with the light
guide within the area of the pixel 1301 and not in contact in the
surrounding areas outside the particular pixel. Such sharpness of
this bending is typically a material property. Thus, to prevent the
selectively deformed portion of the active layer 300 from coming
into contact with the light guide 200 in the area of an adjacent
pixel, the effective size of the pixel can be reduced (or the space
between pixels 1303 must be increased). Further, the use of the
standoff 1304 between pixels helps enable a "sharper" deformation
in the active layer 300, thereby possibly reducing the unused space
between pixels 1303. In certain embodiments, the light guide 200
may couple into the standoff 1304 when they come into contact, as
depicted by light ray 107, upon pixel activation. This can
introduce noise into the display and may reduce the contrast ratio
of the display. But, in certain cases, light may not effectively
couple into a material that has a surface roughness exceeding 100
nanometers, as shown at 1305. Accordingly, if the surface of the
standoff that contacts the light guide has a roughness greater than
100 nanometers, then light from the light guide 200 may not follow
the path of light ray 107 and noise further reduced.
[0054] It will be understood that many of the preceding figures are
not drawn to scale in an effort to aid the reader. Further, the
preceding description discusses example techniques. But this
disclosure contemplates using any suitable technique for performing
these and other similar tasks. Accordingly, many of the steps may
take place simultaneously and/or in different orders than as shown.
Moreover, manufacturers or other parties may use methods with
additional steps, fewer steps, and/or different steps, so long as
the methods remain appropriate. While various embodiments have been
described, it will be understood that various modifications may be
made without departing from the spirit and scope of the disclosure.
For example, while the terms "bottom" and "top" have been used to
more easily describe the display, the display may be oriented in
any suitable direction. Indeed, a particular deformable surface of
the light guide may not be directly opposite (or parallel to) the
surface emitting the light as appropriate. Accordingly, other
embodiments are within the scope of the following claims.
* * * * *