U.S. patent application number 11/096032 was filed with the patent office on 2006-10-05 for visual display with electro-optical individual pixel addressing architecture.
Invention is credited to David L. Patton, Frank Pincelli, John P. Spoonhower.
Application Number | 20060222288 11/096032 |
Document ID | / |
Family ID | 37018972 |
Filed Date | 2006-10-05 |
United States Patent
Application |
20060222288 |
Kind Code |
A1 |
Spoonhower; John P. ; et
al. |
October 5, 2006 |
VISUAL DISPLAY WITH ELECTRO-OPTICAL INDIVIDUAL PIXEL ADDRESSING
ARCHITECTURE
Abstract
A display device and method of operating the display device. The
display device comprising a support substrate, a plurality of light
emitting light emitting resonators placed in a matrix on the
support substrate forming a plurality of rows and columns of the
light emitting resonators, a plurality of light waveguides
positioned on the substrate such that each of the light emitting
resonators is associated with an electro-coupling region with
respect with to one of the plurality of light waveguides, a
deflection mechanism for causing relative movement between a
portion of at least one of the plurality of light waveguides and
the associated light emitting resonator so as to individually
control when each of the light emitting resonator is in the
electro-coupling region, and a light source associated with each of
the plurality of light waveguides for transmitting a light along
the plurality of light waveguides for selectively activating each
of the light emitting resonators when positioned within the
electro-coupling region.
Inventors: |
Spoonhower; John P.;
(Webster, NY) ; Patton; David L.; (Webster,
NY) ; Pincelli; Frank; (Rochester, NY) |
Correspondence
Address: |
Pamela R. Crocker;Patent Legal Staff
Eastman Kodak Company
343 State Street
Rochester
NY
14650-2201
US
|
Family ID: |
37018972 |
Appl. No.: |
11/096032 |
Filed: |
March 31, 2005 |
Current U.S.
Class: |
385/16 ;
385/15 |
Current CPC
Class: |
G09G 3/3473 20130101;
G09G 2310/02 20130101; G02B 26/02 20130101; G02B 6/12007 20130101;
G09G 2360/142 20130101; G09F 9/372 20130101 |
Class at
Publication: |
385/016 ;
385/015 |
International
Class: |
G02B 6/35 20060101
G02B006/35; G02B 6/26 20060101 G02B006/26 |
Claims
1. A display device, comprising: a. a support substrate; b. a
plurality of light emitting resonators placed in a matrix on said
support substrate forming a plurality of rows and columns of said
light emitting resonators; c. a plurality of light waveguides
positioned on said substrate such that each of said light emitting
resonators is associated with an electro-coupling region with
respect with to one of said plurality of light waveguides; d. a
deflection mechanism for causing relative movement between a
portion of at least one of said plurality of light waveguides and
said associated light emitting resonator so as to individual
control when each of said light emitting resonator is in said
electro-coupling region, said deflection mechanism comprises pairs
of electrodes associated with each of said plurality of light
emitting resonators and an triggering electrode associated with
each of said pairs of electrodes for selecting deflecting a portion
of said waveguide associated with one of said plurality of light
emitting resonators whereby when a voltage is applied across said
pair of electrodes and said triggering electrodes associated with
said selected resonator that field is produced which caused said at
least one waveguide to move into said electro-coupling region; and
e. a light source associated with each of said plurality of light
waveguides for transmitting a light along said plurality of light
waveguides for selectively activating each of said light emitting
resonators when positioned within said electro-coupling region.
2. A display device according to claim 1 wherein said light source
comprises an infrared light source.
3. A display device according to claim 2 wherein said infrared
light source comprises a laser infrared light source.
4. A display device according to claim 1 wherein said light source
comprises a light emitting diode.
5. A display device according to claim 1 wherein said plurality of
light emitting resonators comprises light emitting resonators.
6. A display device according to claim 5 wherein said light
emitting resonators have a roughened surface.
7. A display device according to claim 6 wherein said light
emitting resonators comprises an upconverting phosphor.
8. A display device according to claim 6 wherein an emissive
coating is provided over said roughened surface.
9. A display device according to claim 1 wherein an overcoat is
provided over said plurality of light emitting resonators and light
waveguides.
10. (canceled)
11. A display device according to claim 1 wherein a control
mechanism is provided for controlling the amount of voltage across
said pair of electrodes and said triggering electrodes for
controlling the distance in which said at least one waveguide moves
into said electro-coupling region so as to control the amount of
emission from said associated light emitting resonator.
12. A display device according to claim 1 wherein said plurality of
light emitting resonator are grouped into sets wherein in each of
said light emitting resonators emit a different color.
13. A display device according to claim 1 wherein at least one of
said plurality of light emitting resonators have a ring shaped.
14. A display device according to claim 1 wherein at least one said
plurality of light emitting resonators is disc shaped.
15. A method for controlling visible light emitting from a display
device having plurality of light emitting resonators placed in a
pattern forming a plurality of rows and columns and a plurality of
wave light guides positioned so that each of said light emitting
resonators is positioned adjacent one of said plurality of wave
light guides; comprising the steps of: a. providing a light source
associated with each of said plurality of light waveguides for
transmitting a light along said associated light waveguide; b.
providing deflection mechanism for causing selective individual
relative movement between a portion of at least one of said
plurality of light waveguides and one of said associated light
emitting resonator so as to selectively control when each of said
light emitting resonator is in said electro-coupling region; and c.
selectively controlling emission of visible light from said
plurality of light emitting resonators by controlling said
deflection mechanism and light source such that when said light
emitting resonator in said electro-coupling region and a light is
transmitted along said associated light waveguide said emission of
visible light will occur; and d. a control mechanism is provided
for controlling the amount of voltage across said pair of
electrodes and said triggering electrodes so as to control the
distance in which said at least one waveguide moves into said
electro-coupling region so as to control the amount of emission
from said associated light emitting resonator.
16. The method according to claim 15 wherein deflection mechanism
for causing relative movement comprises pairs of electrodes
associated with each of said plurality of light emitting resonators
and an triggering electrode associated with each of said pairs of
electrodes for selecting deflecting a portion of said waveguide
associated with one of said plurality of light emitting resonators
whereby when a voltage is applied across said pair of electrodes
and said triggering electrodes associated with said selected
resonator that field is produced which caused said at least one
waveguide to move into said electro-coupling region.
17. The method according to claim 15 wherein said light source
comprises an infrared light source.
18. The method according to claim 17 wherein said infrared light
source comprises a laser infrared light source.
19. The method according to claim 15 wherein said light source
comprises a light emitting diode.
20. (canceled)
21. The method according to claim 15 wherein said plurality of
light emitting resonator are grouped into sets wherein in each of
said light emitting resonators emit a different color.
22. The method according to claim 15 wherein at least one of said
plurality of light emitting resonators have a ring shaped.
23. The method according to claim 15 wherein at least one said
plurality of light emitting resonators is disc shaped.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] U.S. Ser. No. ______, filed concurrently herewith, of John
P. Spoonhower, and David Lynn Patton entitled "Visual Display With
Electro-Optical Addressing Architecture", Atty. Docket No.
88841/F-P;
[0002] U.S. Ser. No. ______, filed concurrently herewith, of John
P. Spoonhower and David Lynn Patton, entitled "Polarized Light
Emitting Source With An Electro-Optical Addressing Architecture",
Atty. Docket No. 89582/F--P; and
[0003] U.S. Ser. No. ______, filed concurrently herewith, of John
P. Spoonhower, and David Lynn Patton entitled "Placement Of
Lumiphores Within A Light Emitting Resonator In A Visual Display
With Electro-Optical Addressing Architecture", Atty. Docket No.
89705/F-P.
FIELD OF THE INVENTION
[0004] A flat panel visible display wherein optical waveguides and
other thin film structures are used to distribute (address)
excitation light to a patterned array of visible light emitting
pixels.
BACKGROUND OF THE INVENTION
[0005] A flat panel display system is based on the generation of
photo-luminescence within a light cavity structure. Optical power
is delivered to the light emissive pixels in a controlled fashion
through the use of optical waveguides and a novel addressing scheme
employing Micro-Electro-Mechanical Systems (MEMS) devices. The
energy efficiency of the display results from employing efficient,
innovative photo-luminescent species in the emissive pixels and
from an optical cavity architecture, which enhances the excitation
processes operating inside the pixel. The present system is thin,
light weight, power efficient and cost competitive to produce when
compared to existing technologies. Further advantages realized by
the present system include high readability in varying lighting
conditions; high color gamut; viewing angle independence, size
scalability without brightness and color quality sacrifice, rugged
solid-state construction, vibration insensitivity and size
independence. The present invention has potential applications in
military, personal computing and digital HDTV systems, multi-media,
medical and broadband imaging displays and large-screen display
systems. Defense applications may range from full-color,
high-resolution, see-through binocular displays to 60-inch diagonal
digital command center displays. The new display system employs the
physical phenomena of photo-luminescence in a flat-panel display
system.
[0006] Previously, Newsome disclosed the use of upconverting
phosphors and optical matrix addressing scheme to produce a visible
display in U.S. Pat. No. 6,028,977. Upconverting phosphors are
excited by infrared light; this method of visible light generation
is typically less efficient than downconversion (luminescent)
methods like direct fluorescence or phosphorescence, to produce
visible light. Furthermore, the present invention differs from the
prior art in that a different addressing scheme is employed to
activate light emission from a particular emissive pixel. The
method and device disclosed herein does not require that two
optical waveguides intersect at each light emissive pixel.
Furthermore, novel optical cavity structures, in the form of
optical light emitting resonators, are disclosed for the emissive
pixels in the present invention.
[0007] Additionally, in US Patent Application Publication No.
US2002/0003928A1, Bischel et al. discloses a number of structures
for coupling light from the optical waveguide to a radiating pixel
element. The use of reflective structures to redirect some of the
excitation energy to the emissive medium is disclosed. In the
present invention, we disclose the use of novel optical cavity
structures, in the form of ring or disk resonators, the resonators
themselves modified to affect the emission of visible light.
[0008] The use of such resonators further allows for a novel method
of control of the emission intensity, through the use of
Micro-Electro-Mechanical Systems (MEMS) devices to alter the degree
of power coupling between the light power delivering waveguide and
the emissive resonator pixel. Such means have been disclosed in
control of the power coupling to opto-electronic filters for
telecommunications applications. In this case, the control function
is used to tune the filter. Control over the power coupling is
described in "A MEMS-Actuated Tunable Microdisk Resonator", by
Ming-Chang M. Lee and Ming C. Wu, paper MC3, 2003 IEEE/LEOS
International Conference on Optical MEMS, 18-21 Aug. 2003.
SUMMARY OF THE INVENTION
[0009] In accordance with one aspect of the present invention there
is provided a display device, comprising:
[0010] a. a support substrate;
[0011] b. a plurality of light emitting resonators placed in a
matrix on the support substrate forming a plurality of rows and
columns of the light emitting resonators;
[0012] c. a plurality of light waveguides positioned on the
substrate such that each of the light emitting resonators is
associated with an electro-coupling region with respect with to one
of the plurality of light waveguides;
[0013] d. a deflection mechanism for causing relative movement
between a portion of at least one of the plurality of light
waveguides and the associated light emitting resonator so as to
individually control when each of the light emitting resonator is
in the electro-coupling region; and
[0014] e. a light source associated with each of the plurality of
light waveguides for transmitting a light along the plurality of
light waveguides for selectively activating each of the light
emitting resonators when positioned within the electro-coupling
region.
[0015] In accordance with another aspect of the present invention
there is provided a method for controlling visible light emitting
from a display device having plurality of light emitting resonators
placed in a pattern forming a plurality of rows and columns and a
plurality of wave light guides positioned so that each of the light
emitting resonators is positioned adjacent one of the plurality of
wave light guides; comprising the steps of:
[0016] a. providing a light source associated with each of the
plurality of light waveguides for transmitting a light along the
associated light waveguide;
[0017] b. providing deflection mechanism for causing selective
individual relative movement between a portion of at least one of
the plurality of light waveguides and one of the associated light
emitting resonator so as to selectively control when each of the
light emitting resonator is in the electro-coupling region;
[0018] c. selectively controlling emission of visible light from
the plurality of light emitting resonators by controlling the
deflection mechanism and light source such that when the light
emitting resonator in the electro-coupling region and a light is
transmitted along the associated light waveguide the emission of
visible light will occur.
[0019] These and other aspects, objects, features and advantages of
the present invention will be more clearly understood and
appreciated from a review of the following detailed description of
the preferred embodiments and appended claims and by reference to
the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The above and other objects, features, and advantages of the
present invention will become more apparent when taken in
conjunction with the following description and drawings wherein
identical reference numerals have been used, where possible, to
designate identical features that are common to the figures, and
wherein:
[0021] FIG. 1 is a schematic top view of an optical flat panel
display made in accordance with the present invention;
[0022] FIG. 2 is an enlarged top plan view of the light emitting
resonators for the display of FIG. 1 made in accordance with the
present invention;
[0023] FIG. 3 is enlarged top plan views of the red light, green
light and blue light emitting resonators for a color display 1 made
in accordance with the present invention;
[0024] FIG. 4 is an enlarged cross-sectional view of the optical
waveguide as taken along line 4-4 of FIG. 3;
[0025] FIG. 5 is an enlarged cross-sectional schematic view of the
optical waveguide showing the electrode geometry and electrostatic
forces;
[0026] FIG. 6 is an enlarged perspective view of a portion of the
display of FIG. 1 showing a single ring resonator; single
associated optical waveguide and electrodes;
[0027] FIGS. 7A, B and C are enlarged cross-sectional view of the
display of FIG. 6 taken along line 7-7 of FIG. 6, which shows the
location of a MEMS device used to control the pixel intensity at
various intensity positions;
[0028] FIG. 8 is an enlarged cross-sectional view of the waveguide
and resonator elements showing an alternative embodiment for the
light-emissive resonator, and
[0029] FIG. 9 is an enlarged top plan view showing an alternative
resonator embodiment in the form of a disk.
DETAILED DESCRIPTION OF THE INVENTION
[0030] Referring to FIGS. 1-2 there is illustrated a
photo-luminescent display 5 system made in accordance with the
present invention. The display system functions by converting
excitation light to emitted, visible light. In the embodiment
illustrated each pixel 10 in display 5 is comprised of one or more
sub-pixels; sub-pixels are typically comprised of a red sub-pixel
11, a green sub-pixel 12, and a blue sub-pixel 13, as shown in FIG.
3. Colors other than red, green, and blue are caused by the
admixture of these primary colors; thus controlling the intensity
of the individual sub-pixels adjusts both the brightness and color
of a pixel 10. Those skilled in the art understand that other
primary color selections are possible and will lead to a full color
display. Color generation in the display is a consequence of the
mixing of multiple-wavelength light emissions by the viewer. This
mixing is accomplished by the viewer's integration of spatially
distinct, differing wavelength light emissions from separate
sub-pixels that are below the spatial resolution limit of the
viewer's eye. Typically a color display has red, green, and blue
separate and distinct sub-pixels, comprising a single variable
color pixel. Monochrome displays may be produced by the use of a
single color pixel 10 or sub-pixel (11,12, 13), or by constructing
a single pixel capable of emitting "white" light. The spectral
characteristics of a monochrome display pixel will be determined by
the choice of lumiphore or combination of lumiphores. White light
generation can be accomplished through the use of multiple doping
schemes for the light emitting resonator 30 as described by Hatwar
and Young in U.S. Pat. No. 6,727,644 B2. Photo-luminescence is used
to produce the separate wavelength emission from each pixel (or
subpixel) element. The photo-luminescence may be a result of a
number of physically different processes including, multi-step,
photonic up-conversion processes and the subsequent radiative
emission process, direct optical absorption and the subsequent
radiative emission process, or optical absorption followed by one
or more energy transfer steps, and finally, the subsequent
radiative emission process. Use of combinations of these processes
may also be considered to be within the scope of this
invention.
[0031] Referring now to FIGS. 1 and 2, FIG. 1 is schematic top view
of an optical flat panel display 5 made in accordance with the
present invention and FIG. 2 is and enlarged top view of a portion
of FIG. 1. The display 5 contains an array 7 of light emitters
comprised of a matrix of pixels 10 each having a light emitting
resonator 30 (shown in FIG. 3) located at each intersection of an
optical row waveguide 25 and rows 23 comprising triggering
electrodes 24.sub.1-n and column electrodes 28. A power source 22
is used to activate the light source array 15. The light source
array 15 provides optical power or light 20, used to excite the
photo-luminescent process in each pixel 10. Typical light source
array elements 17 may be diode lasers, infrared laser, light
emitting diodes (LEDs), and the like. These may be coherent or
incoherent light sources. There may be a one-to-one correspondence
between the light source array element 17, and an optical row
waveguide 25, or alternatively, there may be a single light source
array element 17 multiplexed onto a number of optical row
waveguides 25, through the use of an optical switch to redirect the
light 20 output from the single light source array element 17.
[0032] A principal component of the photo-luminescent flat panel
display system 5 is the optical row waveguide 25, also known as a
dielectric waveguide. Two key functions are provided by the
waveguides 25. They confine and guide the optical power to the
pixel 10. Several channel waveguide structures have been
illustrated in US patent Application U.S. Pat. No. 6,028,977. The
optical waveguides must be restricted to TM and TE propagation
modes. TM and TE mode means that optical field orientation is
perpendicular to the direction of propagation. Dielectric
waveguides confining the optical signal in this manner are called
channel waveguides. The buried channel and embedded strip guides
are applicable to the proposed display technology. Each waveguide
consists of a combination of cladding and core layer. These layers
are fabricated on either a glass-based or polymer-based substrate.
The core has a refractive index greater than the cladding layer.
The core guides the optical power past the resonator in the absence
of power coupling. With the appropriate adjustment of the distance
between the optical row waveguide 25 and the light emitting
resonator 30, power is coupled into the light emitting resonator
30. At the light emitting resonator 30 the coupled optical light
power drives the resonator materials into a luminescent state. The
waveguides 25 and resonators 30 can be fabricated using a variety
of conventional techniques including microelectronic techniques
like lithography. These methods are described, for example, in
"High-Finesse Laterally Coupled Single-Mode Benzocyclobutene
Microring Resonators" by W.-Y. Chen, R. Grover, T. A. Ibrahim, V.
Van, W. N. Herman, and P.-T. Ho, IEEE Photonics Technology Letters,
16(2), p. 470. Other low-cost techniques for the fabrication of
polymer waveguides can be used such as imprinting, and the like.
Nano-imprinting methods have been described in "Polymer Microring
Resonators Fabricated By Nanoimprint Technique" by Chung-yen Chao
and L. Jay Gao, J. Vac. Sci. Technol. B 20(6), p. 2862.
Photobleaching Of Polymeric Materials As A Fabrication Method has
been described by Joyce K. S. Poon, Yanyi Huang, George T. Paloczi,
and Amnon Yariv, in "Wide-Range Tuning Of Polymer Microring
Resonators By The Photobleaching Of CLD-1 Chromophores" by, Optics
Letters 29(22), p. 2584. This is an effective method for post
fabrication treatment of optical micro-resonators. A wide variety
of polymer materials are useful in this and similar applications.
Theses can include fluorinated polymers, polymethylacrylate, liquid
crystal polymers, and conductive polymers such as polyethylene
dioxythiophene, polyvinyl alcohol, and the like. These materials
and additionally those in the class of liquid crystal polymers are
suitable for this application (see "Liquid Crystal Polymer (LCP)
for MEMs", by X. Wang et. al., J. Micromech. MicroEng, 13, (2003),
p. 628-633.) This list is not intended to be all inclusive of the
materials that may be employed for this application.
[0033] Excitation of the light emitting resonator 30 (shown in FIG.
3) by the row waveguide 25 under the control of the column voltage
source 18 row and column 28 individual triggering electrodes
24.sub.1-n respectively causes the light emitting resonator 30 to
emit visible light. The excitation of the light emitting resonator
30 is caused by optical pumping action of the light 20 shown in
FIG. 1 from a row light source array element 17 through the row
waveguide 25 and controlling voltage to the row 28 and triggering
electrodes 24.sub.1-n and controller 19 from a column voltage
source 18. The excitation process is a coordinated row-column,
electrically activated, optical pumping process called
electro-optical addressing. Those skilled in the art know that the
roles of columns and rows are fully interchangeable without
affecting the performance of this display 5.
[0034] Now referring to FIG. 3, electro-optical addressing is
defined as a method for controlling an array 7 (not shown) of light
emitting resonators 30 that form the optical flat panel display 5
(see FIG. 1). In FIG. 2, a pixel 10 comprised of 3 sub-pixels, 11,
12, and 13 is shown. In electro-optical addressing, the selection
of a particular pixel that appears to be light emitting is
accomplished by the specific combination of excitation of light in
a particular optical row waveguide 25, and voltage applied to a
selected individual light emitting resonators 30.
[0035] The light emitting resonator 30 is excited into a
photo-luminescent state through the absorption of light 20 as a
result of the close proximity to the row waveguides 25. The physics
of the coupling of energy between the resonator 30 and the optical
row waveguide 25 is well known in the art. It is known to depend
critically upon the optical path length between the row waveguide
25 and the light emitting resonator 30; it can therefore be
controlled by the distance (h, shown in FIGS. 7A and 7B) separating
the two structures or by various methods of controlling the index
of refraction. Typical methods for control of the index of
refraction include heat, light, and electrical means; these are
well known. These methods correspond respectively to the
thermo-optic, photorefractive, and electro-optic methods. The
invention disclosed herein makes use of control of the distance
parameter via a MEMS device to control the energy coupling, and
thus affect the intensity of photo-luminescent light generated in
the pixel 10. In an example, the light emitting resonator 30 is
composed of a light transmissive material but incorporating (doped
with) a light emitting photo-luminescent species. The base material
(the material excluding the photo-luminescent species or dopant)
for the light emitting resonator may be the same or different from
the optical row waveguide 25 material. Typical base materials can
include glasses, semiconductors, or polymers.
[0036] Photo-luminescent species or dopants can include various
fluorophores, or phosphors including up-converting phosphors. The
selection of a particular dopant or dopants will primarily
determine the emission spectrum of a particular light emitting
resonator 30. These lumiphores (fluorophores or phosphors) may be
inorganic materials or organic materials. The light emitting
resonator 30 can include a combination of dopants that cause it to
respond to the electro-optic addressing by emitting visible
radiation. Dopant or dopants include the rare earth and transition
metal ions either singly or in combinations, organic dyes, light
emitting polymers, or materials used to make Organic Light Emitting
Diodes (OLEDs). Additionally, lumiphores can include such highly
luminescent materials such as inorganic chemical quantum dots, such
as nano-sized CdSe or CdTe, or organic nano-structured materials
such as the fluorescent silica-based nanoparticles disclosed in
U.S. Patent Application Publication US 2004/0101822 A1 by Wiesner
and Ow. The use of such materials is known in the art to produce
highly luminescent materials. Single rare earth dopants that can be
used are erbium (Er), holmium, thulium, praseodymium, neodymium
(Nd) and ytterbium. Some rare-earth co-dopant combinations include
ytterbium: erbium, ytterbium: thulium and thulium: praseodymium.
Single transition metal dopants are chromium (Cr), thallium (Tl),
manganese (Mn), vanadium (V), iron (Fe), cobalt (Co) and nickel
(Ni). Other transition metal co-dopant combinations include Cr:Nd
and Cr:Er. The up-conversion process has been demonstrated in
several transparent fluoride crystals and glasses doped with a
variety of rare-earth ions. In particular, CaF.sub.2 doped with
Er.sup.3+. In this instance, infrared upconversion of the Er3+ ion
can be caused to emit two different colors: red (650 nm) and green
(550 nm). The emission of the system is spontaneous and isotropic
with respect to direction. Organic fluorophores can include dyes
such as Rhodamine B, and the like. Such dyes are well known having
been applied to the fabrication of organic dye lasers for many
years. The preferred organic material for the light emitting
resonator 30 is a small-molecular weight organic host-dopant
combination typically deposited by high-vacuum thermal evaporation.
It is also preferred that the host materials used in the present
invention are selected such that they have sufficient absorption of
the excitation light 20 and are able to transfer a large percentage
of their excitation energy to a dopant material via Forster energy
transfer. Those skilled in the art are familiar with the concept of
Forster energy transfer, which involves a radiationless transfer of
energy between the host and dopant molecules. An example of a
useful host-dopant combination for red-emitting lasers is aluminum
tris(8-hydroxyquinoline) (Alq) as the host and
[4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl--
9-enyl)-4H-pyran] (DCJTB) as the dopant (at a volume fraction of
1%). Other host-dopant combinations can be used for other
wavelength emissions. For example, in the green a useful
combination is Alq as the host and
[110-(2-benzothiazolyl)-2,3,6,7-tetrahydro-1,1,7,7-tetramethyl-1-
H,5H,1H-[1]Benzopyrano[6,7,8-ij]quinolizin-11-one] (C545T) as the
dopant (at a volume fraction of 0.5%). Other organic light emitting
materials can be polymeric substances, e.g., polyphenylenevinylene
derivatives, dialkoxy-polyphenylenevinylenes, poly-para-phenylene
derivatives, and polyfluorene derivatives, as taught by Wolk et al.
in commonly assigned U.S. Pat. No. 6,194,119 B1 and references
therein.
[0037] Electro-optical addressing employs the optical row waveguide
25 to deliver light 20 to a selected light emitting resonator 30.
The light emitting resonator 30 is the basic building block of the
optical flat panel display 5. Referring again to FIG. 3 an enlarged
top view of a red light 41, green light 42 and blue light 43 light
emitting resonator 30 respectively, is illustrated. Using the red
light 41, green light 42 and blue light 43 light emitting
resonators to create red 11, green 12, and blue 13 pixels, a full
color optical flat panel display 5 can be formed. The wavelength of
the emission of the red, green and blue (41-43) light is controlled
by the type of material used in forming the light emitting
resonators 30. Selection of a particular pixel 10 or sub-pixel
(11-13) is based upon the use of a MEMS device to alter the
distance and affect the degree of power transfer of light 20 to the
light emitting resonator 30. Note that in each instance, light 20
is directed within an appropriate optical row waveguide 25 to
excite a particular light emitting resonator 30. Through the
combination of excitation specific optical row waveguide with light
20 and excitation of a specific MEMS device, controlled by
energizing one of the triggering electrodes 24.sub.1-n and one of
the rows 28, a particular pixel 10 (subpixel) is excited. The light
emitting resonator 30 may take the form of a micro-ring or a
micro-disk. These forms are shown in FIGS. 3, and 9, respectively.
Note that in order for the light emitting resonator 30 to produce
sufficient light to be viewable, the resonator 30 must be
fabricated in a manner so that it is "leaky"; there are a number of
methods to accomplish this lowering of the cavity Q, including but
not limited to increasing the surface roughness of the resonator
cavity surface. Additionally, one could lower the refractive index
of the material comprising the light emitting resonator 30.
[0038] The substrate or support 45 (see FIG. 4) can be constructed
of either a silicon, glass or a polymer-based substrate material. A
number of glass and polymer substrate materials are either
commercially available or readily fabricated for this application.
Such glass materials include: silicates, germanium oxide, zirconium
fluoride, barium fluoride, strontium fluoride, lithium fluoride,
and yttrium aluminum garnet glasses. A schematic of an enlarged
cross-sectional view of the optical flat panel display 5 taken
along the line 4-4 of FIG. 3 is shown in FIG. 4. The individual
triggering electrodes 24.sub.1-n and column electrodes 28 are not
shown for simplicity. On a substrate 45 is formed a layer 35
containing the optical row waveguide 25 and the light emitting
resonator. For such a buried-channel waveguide structure it is
imperative that the refractive index of optical row waveguide 25
(the core) be greater than the surrounding materials, in this
instance the layer 35. The layer 35 acts as the cladding region in
this embodiment. An optional layer 32 is shown, this may be of a
relatively lower index material in order to better optically
isolate the optical row waveguide 25. A top layer 52 is provided on
the top surface 47 of layer 35 for protection of the underlying
structures. In the case of FIG. 4 the entire structure is shown
surrounded by air 55.
[0039] Integrated semiconductor waveguide optics and microcavities
have raised considerable interest for a wide range of applications,
particularly for telecommunications applications. The invention
disclosed herein applies this technology to electronic displays. As
stated previously, the energy exchange between cavities and
waveguides is strongly dependent on the spatial distance.
Controlling the distance between waveguides and microcavities is a
practical method to manipulate the power coupling and hence the
brightness of a pixel 10 or sub-pixel (11-13).
[0040] An ideal resonator or cavity has characteristics of high
quality factor (which is the ratio of stored energy to energy loss
per cycle) and small mode volume. Dielectric micro-sphere and
micro-toroid resonators have demonstrated high quality factors.
Micro-cavities possess potential to construct optical resonators
with high quality factor and ultra-small mode volume due to high
index-contrast confinement. Small mode volume enables small pixel
10 or sub-pixel (11-13) dimensions, consistent with the
requirements of a high resolution display. A MEMS device structure
for affecting the amount of light 20 coupled into a light emitting
resonator 30 is shown in FIG. 5. FIG. 5 is an enlarged
cross-sectional view of the optical waveguide showing the electrode
geometry, field lines 46, and resulting downward electrostatic
force 44 for affecting the power coupling change. MEMS actuators
using electrostatic forces in this instance, move a waveguide to
change the distance h, shown in FIG. 7A between a resonator and the
optical row waveguide 25, resulting in a wide tunable range of
power coupling ratio by several orders of magnitude which is
difficult to achieve by other methods. Based on this mechanism, the
micro-disk/waveguide system can be dynamically operated in the
under-coupled, critically-coupled and over-coupled condition.
[0041] In high-Q micro-resonators, varying the gap spacing or
distance h, between the waveguide and the micro-disk or micro-ring
resonator by simply a fraction of a micron leads to a very
significant change in the power transfer to the light emitting
resonator 30 from the optical row waveguide 25. FIG. 6 is an
enlarged perspective view of the display of FIG. 1 showing a light
emitting ring resonator 30; optical waveguide 25, and triggering
electrodes 24.sub.1-n and 28. As shown in FIG. 6, a suspended
waveguide is placed in close proximity to the micro-ring or
micro-toroid light emitting resonator 30. The initial gap (not
shown) (.about.1 .mu.m wide) is large so there is no coupling
between the waveguide and the resonator. Referring to FIG. 6, the
suspended optical row waveguide 25 can be pulled towards the micro
ring resonator by four electrostatic gap-closing actuators, the
electrodes 23 and 28. Therefore, the coupling coefficient can be
varied by applied voltage. For high index-contrast waveguides, the
coupling coefficient is very sensitive to the critical distance.
1-um displacement can achieve a wide tuning range in power coupling
ratio, which is more than five orders of magnitude. Typically, the
radius of micro-ring resonator is 10 .mu.m and the width of
waveguide is 0.7 .mu.m. But these sizes may vary depending upon the
display type and application. In FIG. 6 the optical waveguide 25 is
shown displaced downward so as to affect a maximum power transfer
to the light emitting resonator 30.
[0042] FIG. 7A is an enlarged cross-sectional view of the display
of FIG. 6, which shows the location of a MEMS device used to
control the pixel intensity. The area surrounding the optical row
waveguide 25 and the light emitting ring resonator 30 has been
etched back to expose the top surfaces 48 to air 55. The optical
row waveguide 25 is aligned to the edge of the light emitting
resonator 30 and vertically displaced to preclude a high degree of
coupling. The waveguide 25 is electrically grounded and actuated by
a pair of triggering electrodes 24.sub.1-n associated with a single
resonator 30 and electrode 28, which forms an electro-coupling
region 58. Due to the electrostatic force, the waveguide is pulled
downward toward the light emitting resonator 30, resulting in the
decreased gap-spacing, h. The optical row waveguide 25 is shown in
the rest position d in FIG. 7A. In FIG. 7A, the distance between
the optical row waveguide 25 and the light emitting ring resonator
30 is large; coupling of light into the light emitting resonator 30
is precluded and there is no light emission from the pixel.
[0043] Initially, in the absence of the application of the control
voltage, the optical row waveguide 25 is separated from the light
emitting resonator by a distance significantly greater than the
critical distance "h.sub.c" 31 (see FIG. 7C) and hence there is no
light emission from the light emitting resonator 30. In FIG. 7B,
the vertical distance d' is shown where there exists a degree of
coupling between the optical row waveguide 25 and the light
emitting ring resonator 30, and hence light emission from the pixel
occurs. By varying the distance d', the intensity of the light
emission from the pixel can be varied in a controllable manner. In
FIG. 7C, the distance d'' is shown that corresponds to the
displacement of the optical row waveguide 25 necessary to place the
optical row waveguide 25 at the critical coupling distance h.sub.c
and thereby optimize power coupling. This configuration will
produce the maximum emitted light intensity from the pixel. Note
that light emitting resonator is shown with a roughened surface 60;
this will be discussed below. The optical row waveguide can be
fabricated from silicon appropriately doped to provide electrical
conductivity. Alternatively, the optical row waveguide can be
fabricated from other optically transparent conductive materials
such as polymers that meet the optical index of refraction
requirement disclosed above.
[0044] In the embodiment shown in FIG. 7C, the light emitting
resonator 30 is shown spaced the critical distance 31, h.sub.c from
the optical row waveguide 25. Excitation light 20 is emitted from
top roughened surface 60 of the light emitting resonator 30, which
causes the light emitting resonator to leak light and become
visible to a viewer. As shown in FIG. 7C, a light emitting layer 49
is placed within the light emitting resonator. This layer 49
contains photo-luminescent species or lumiphores 65 that absorb the
pump or excitation light 20 and via the luminescence processes
discussed above, produce the visible light directed to the viewer.
The wavelength of the light produced in the emitting layer 49 is
determined by the material composition as previously disclosed. The
light emitting layer 49 may be formed on the top surface of the
light emitting resonator 30 as well as placed within the internal
structure of the light emitting resonator as is shown in FIG. 7C.
FIG. 7C shows the emitting layer 49 displaced vertically from the
bottom surface 39 of light emitting resonator 30.
[0045] FIG. 8 is an enlarged cross-sectional view of the resonator
elements showing an alternative embodiment for the light-emissive
resonator 30. In this embodiment the lumiphores 65 are shown
uniformly distributed within the light emitting resonator 30.
[0046] FIG. 9 is an enlarged top plan view showing an alternative
resonator embodiment in the form of a disk. The critical distance
"h.sub.c" 31 is shown as well as the light emitting disk 67
resonator. A number of structures have been demonstrated for the
resonator element including ring, disk, elliptical and racetrack or
oval structures. The coupling of optical power into such structures
is well known to those skilled in the art. The use of such
structures as light emitting resonators is considered within the
scope of this invention.
[0047] The present invention allows for the individual addressing
of individual pixel elements, such as resonators 30. The individual
allows for an improved performance of the device. The individual
addressing of the pixel elements of the present invention allows
quicker refreshing rates as only those resonators that need
changing are accessed thereby minimizing the potential for
flickering of the display image. In addition, individually
addressing the resonators 30, the possibility of activating
undesired resonators is minimized. While the present application
has shown one way of individually addressing the electrodes
associated with a single pixel element, any suitable technique may
be utilized.
[0048] The invention has been described with reference to a
preferred embodiment; however, it will be appreciated that
variations and modifications can be affected by a person of
ordinary skill in the art without departing from the scope of the
invention. In particular, it is well known in the art that the
optical row waveguide 25 can be placed adjacent to the light
emitting resonator 30 in the same horizontal plane, and tuned for
power transfer by affecting a lateral, that is in-plane or
horizontal displacement, rather than the vertical displacements
depicted above. Additionally, it may be advantageous to place the
optical row waveguide 25 above the light emitting resonator 30
adjacent to the periphery of the light emitting resonator 30. In
this latter case the electro-coupling region 58 would be placed
vertically above the edge of the light emitting resonator 30 and
power transfer affected by a vertical displacement of the optical
row waveguide 25 relative to the top surface of the light emitting
resonator 30. Many other such variations are possible and
considered within the scope of this invention.
[0049] It is to be understood that further modification made be
made without departing from the present invention, the present
invention be defined by the claims set forth herein.
PARTS LIST
[0050] 5 display [0051] 7 array [0052] 10 pixel [0053] 11 red
sub-pixel [0054] 12 green sub-pixel [0055] 13 blue sub-pixel [0056]
15 light source array [0057] 17 light source array element [0058]
18 column voltage source [0059] 19 multiplex controller [0060] 20
light [0061] 22 power source [0062] 23 row electrodes [0063] 24
triggering electrodes [0064] 25 row waveguide [0065] 28 column
electrodes [0066] 30 light emitting resonator [0067] 31 critical
distance [0068] 32 optional layer [0069] 35 layer [0070] 39 bottom
surface of light emitting resonator [0071] 41 red light [0072] 42
green light [0073] 43 blue light [0074] 44 force [0075] 45
substrate/support [0076] 46 field lines [0077] 47 top surface
[0078] 48 top surface [0079] 49 emitting layer [0080] 52 top layer
[0081] 55 air [0082] 58 electro-coupling region [0083] 60 roughened
surface [0084] 65 lumiphores [0085] 67 light emitting resonator
disk
* * * * *