U.S. patent application number 10/985681 was filed with the patent office on 2005-03-24 for waveguide based light source.
This patent application is currently assigned to QUANTUM VISION, INC.. Invention is credited to Jaffe, Steven M., Jones, Michieal L., Olmsted, Brian L..
Application Number | 20050062404 10/985681 |
Document ID | / |
Family ID | 22758818 |
Filed Date | 2005-03-24 |
United States Patent
Application |
20050062404 |
Kind Code |
A1 |
Jones, Michieal L. ; et
al. |
March 24, 2005 |
Waveguide based light source
Abstract
A wave guide based light source having a phosphor film with a
large two-dimensional extent and a small thickness. The phosphor
film is excited by an excitation means.
Inventors: |
Jones, Michieal L.; (Davis,
CA) ; Jaffe, Steven M.; (Mountain View, CA) ;
Olmsted, Brian L.; (Fairport, NY) |
Correspondence
Address: |
FLIESLER MEYER, LLP
FOUR EMBARCADERO CENTER
SUITE 400
SAN FRANCISCO
CA
94111
US
|
Assignee: |
QUANTUM VISION, INC.
|
Family ID: |
22758818 |
Appl. No.: |
10/985681 |
Filed: |
November 10, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10985681 |
Nov 10, 2004 |
|
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|
09855254 |
May 15, 2001 |
|
|
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6843590 |
|
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60204645 |
May 17, 2000 |
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Current U.S.
Class: |
313/503 ;
313/485; 313/487 |
Current CPC
Class: |
H01J 63/06 20130101;
G02B 6/0003 20130101 |
Class at
Publication: |
313/503 ;
313/485; 313/487 |
International
Class: |
H05B 033/00 |
Claims
We claim:
1. An apparatus for generating light, comprising: a substrate
including a waveguide pattern thereon; a phosphor deposited upon
said substrate that forms a waveguide that matches the waveguide
pattern, said waveguide having a substantially planar shape and
further having a waveguide direction within the plane of the
waveguide and an exit region at an end of the waveguide direction;
and wherein the phosphor can receive excitation energy from an
excitation source in a direction substantially perpendicular to the
plane of the waveguide, and can generate light within the phosphor,
wherein the light travels in the waveguide direction and exits the
waveguide at the exit region.
2. The apparatus of claim 1 wherein said waveguide pattern
comprises a spiral and said waveguide direction is a spiral
direction.
3. The apparatus of claim 2 wherein said waveguide pattern
comprises multiple spirals configured about the same center.
4. The apparatus of claim 1 wherein said excitation source is an
electron beam.
5. The apparatus of claim 1 wherein said excitation source is
incident light.
6. The apparatus of claim 1 wherein said excitation source is an
alternating electric field.
7. The apparatus of claim 1 wherein at least one of the dimensions
of the waveguide is of the order of a wavelength of the generated
light.
8. The apparatus of claim 1 wherein mirrors are placed on one or
more sides of the waveguide.
9. The apparatus of claim 1 including a plurality of waveguides,
each of which are used within a display to form a display pixel at
their respective exit regions.
10. An apparatus for generating light for use in video display,
comprising: one or more substrates including a waveguide pattern or
patterns thereon; one or more phosphors deposited upon said
substrates and forming waveguides that matches the waveguide
patterns, said waveguides each having a substantially planar shape
and further having a waveguide direction within the plane of the
waveguide and an exit region at an end of the waveguide direction;
wherein the phosphors can receive excitation energy from an
excitation source in a direction substantially perpendicular to the
planes of the waveguides, and can generate light within the
phosphor, wherein the light travels in the waveguide direction and
exits the waveguide at the exit region; and wherein the output of
each waveguide is used to form a display pixel at its respective
exit region for use within a video display.
11. A method of generating light, comprising the steps of:
providing a substrate including a waveguide pattern thereon;
providing a phosphor deposited upon said substrate that forms a
waveguide that matches the waveguide pattern, said waveguide having
a substantially planar shape and further having a waveguide
direction within the plane of the waveguide and an exit region at
an end of the waveguide direction; and receiving excitation energy
at the phosphor from an excitation source in a direction
substantially perpendicular to the plane of the waveguide, and
generating light within the phosphor, wherein the light travels in
the waveguide direction and exits the waveguide at the exit
region.
12. The method of claim 11 wherein said waveguide pattern comprises
a spiral and said waveguide direction is a spiral direction.
13. The method of claim 12 wherein said waveguide pattern comprises
multiple spirals configured about the same center.
14. The method of claim 11 wherein said excitation source is an
electron beam.
15. The method of claim 11 wherein said excitation source is
incident light.
16. The method of claim 11 wherein said excitation source is an
alternating electric field.
17. The method of claim 11 wherein at least one of the dimensions
of the waveguide is of the order of a wavelength of the generated
light.
18. The method of claim 11 wherein mirrors are placed on one or
more sides of the waveguide.
19. The method of claim 11 including a plurality of waveguides,
each of which are used within a display to form a display pixel at
their respective exit regions.
Description
[0001] This application is a continuation application of U.S.
application Ser. No. 09/855,254, filed May 15, 2001, now U.S.
patent application Publication No. 2003/0044160, Published Mar. 6,
2003 (QVIS-01057US1), which claims priority to Provisional Patent
Application, S/C No. 60/204,645 filed May 17, 2000
(QVIS-01057US0).
FIELD OF THE INVENTION
[0002] The present invention relates to a light source comprising a
phosphor film and a method of concentrating the emitted light.
BACKGROUND OF THE INVENTION
[0003] High brightness light sources are needed for many
applications including optical fiber illumination and image
projection. In optical fiber illumination, particularly for
telecommunications applications, light-emitting diodes (LEDs), and
semiconductor diode lasers are the dominant light sources as
described in the article of Hecht, which is attached hereto and
incorporated herein by reference (see Hecht, Jeff, Back to Basics:
Fiber-optic Light Sources, Laser Focus World, January 2000). The
output power density of LEDs is generally too low for most fiber
illumination applications. Semiconductor diode lasers have many
favorable characteristics for fiber illumination. Inexpensive diode
lasers are readily available in red or near-infrared wavelengths.
However, semiconductor diode lasers suitable for many other
applications are either not available or very expensive to
produce.
[0004] For a variety of reasons, lasers and LEDs are rarely used as
light sources for image projection. The primary reason is the high
cost of lasers and LEDs capable of producing the high total outputs
needed, especially one to several watts of blue light. In addition,
coherent light sources such as lasers can produce artifacts in many
projection applications. For these reasons the dominant light
source for projection is the arc lamp.
[0005] Arc lamps are capable of the brightness and total luminous
output required for almost any projection need. Indeed arc lamps
are partially responsible for the great success of the movie
industry in the 20th century. However, arc lamps are considered too
expensive for use in many consumer devices. In addition, the wide
spread use of arc lamps in consumer devices would pose a new set of
safety problems.
[0006] In an issued U.S. Pat. No. 5,469,018, which is incorporated
herein by reference, a Resonant Microcavity Display was disclosed.
A resonant microcavity display is a light source incorporating a
thin film phosphor embedded in a microcavity resonator. The
microcavity resonator consists of an active region surrounded by
reflectors. The dimensions are chosen such that a resonant standing
wave or traveling wave is produced by the reflectors. The methods
described lead to the emission of strong and controlled radiative
modes. This is in contrast to a bare thin film phosphor (which is
not provided in a microcavity) which generates strong emission into
waveguide modes (i.e., the emissions travel along the material),
but only weak and diffuse radiative emissions (i.e., for example
perpendicular to the material).
[0007] A light source is formed by coupling an excitation source to
the microcavity structure. The phosphor inside the microcavity may
be excited through several means including bombardment by
externally generated electrons (cathodoluminescence), excitation by
electrodes placed across the active layer to create an electric
field (electroluminescence) or excitation using photons
(photoluminescence).
[0008] Phosphors in general are restricted in the power density of
excitation and emission due to multiple causes. Phosphors are
typically insulating materials with relatively low thermal
conductivities. In addition, many phosphors exhibit relatively long
emission times which limit the number of photons each luminescence
center may produce in a given time. Due to these restrictions,
phosphors may rarely be excited at levels greater than 1 W per
square cm resulting in a emission level rarely greater than 100 MW
per square cm. For these reasons phosphor based devices have been
difficult to utilize in high brightness applications such as fiber
illumination or film projection.
SUMMARY OF THE INVENTION
[0009] An embodiment of the present invention consists of a
relatively large area of phosphor film excited through, by way of
example only, conventional broad area means. The device may be many
square centimeters in extent allowing for high power excitation and
emission. The embodiment is formed such that a substantial amount
of the light emitted by the phosphor is confined to one or more
guided modes with a very small cross section. These guided modes
exit the device through one or more regions of similarly small
cross section resulting in extremely high brightness.
[0010] Other objects and advantages of the present invention will
become apparent to those skilled in the art from the following
detailed description of the preferred embodiments, when read in
light of the accompanying drawings.
BRIEF DESCRIPTION OF THE FIGURES
[0011] FIG. 1 illustrates an embodiment of a spiral shaped dual
waveguide structures of the invention.
[0012] FIG. 2 illustrates a cross-sectional view of the embodiment
of the dual waveguide structure of FIG. 1.
[0013] FIG. 3 illustrates a cross-sectional view of another
embodiment of a dual wave guide structure with a conducting
layer.
[0014] FIG. 4 illustrates a cross-section of yet another dual wave
guide structure with a separate wave guide structure located
adjacent to the phosphor layer.
[0015] FIG. 5 is a side view of one of the dual wave guide channel
of FIG. 4.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0016] In the preferred embodiment the construction of the device
is such that the guided modes have two dimensions which are of the
order of a wavelength of light. One of these dimensions is given by
the thickness 12, 14 of the thin film layer 16, 18 involved. This
small dimension or thickness 12 can be formed by in-plane
patterning.
[0017] The other in-plane dimension 20, 22 is sufficiently long in
extent to produce a total area which may be many square
centimeters. This one long dimension 20, 22 may consist of spirals
or parallel lines so that a circular, rectangle, or other simple
shape or surface area is substantially filled allowing for
efficient broad area excitation.
[0018] The emitted light travels along the spirals or parallel
lines and exits the device through "openings" approximately the
same size as the small dimensions 12, 18 of the waveguide. FIG. 1
illustrates this spiral waveguide and is similar in appearance to a
coiled garden hose.
[0019] In the simplest embodiment, a spiral is formed on a low
index buffer layer or a low index substrate 24, 26 using standard
techniques common in the semiconductor or holographic optics
industry (see Digital Optics Corporation Standard Program dated
Oct. 19, 1994 attached hereto and incorporated by reference). As
illustrated in FIG. 2, an example of a spiral embodiment consists
of two parallel intertwined channels 24, 26, one recessed below the
other by a depth greater than the thickness of the waveguide to be
formed. In the preferred embodiment, the depth and width of these
features shall be of the order of a wavelength of the light to be
emitted.
[0020] A higher index phosphor layer 16, 18 is deposited onto this
substrate 24, 26 using any appropriate technique of thin film
growth including but not limited to sputtering or evaporation. This
layer may consist of a wide range of phosphors (e.g. sulfides,
oxides, silicates, oxysulfides, and aluminates) most commonly
activated with transition metals, rare earths or color centers. The
deposited phosphor layer matches the relief pattern of the
underlying structure so that two spiral waveguides are formed. One
waveguide spiral 18 is elevated with a low index mesa underneath
and air, another gas, or a vacuum, on the sides and above. The
other waveguide spiral 16 is recessed with low index underneath,
low index mesas on either side and air, another gas or a vacuum,
above. In other embodiments, a specific high-index waveguide layer
may be grown and this layer followed by a layer of phosphor which
is formed so as to optically couple to the waveguide layer.
[0021] The guided modes may be confined strictly to the phosphor or
may reside primarily in a separate waveguide adjacent to the
phosphor layer with a mechanism for coupling guided modes of the
phosphor layer to modes of the waveguide structure.
[0022] FIG. 4 depicts a dual wave guide structure 40 which includes
a phosphor wave guide structure 42 and a separate wave guide
structure 44 adjacent thereto. In a preferred embodiment, the
separate wave guide structure 44 is comprised of a fiber optics
wave guide structure. It is to be understood that the fiber optics
wave guide structure can be made with substantially fewer
impurities than the phosphor wave guide structure. Accordingly, the
fiber optics wave guide structure 44 can transmit light much longer
distances due to the fact that the absorption problems which may be
present with the phosphor of that structure are not present with
the fiber optic wave guide structure. The phosphor wave guide
structure is coupled to the fiber optics wave guide structure by
ramps or reflectors such as the aluminum reflectors as previously
discussed and as depicted in FIG. 5. In FIG. 5 the deflector is
identified by number 46. It is to be understood that in this
embodiment, the phosphor wave guide structures 42 can be composed
of a multiplicity of discrete segments each with a transition or
ramp to the fiber optics wave guide structure 44. This can increase
light output should the phosphor wave guide structure 42 absorb
light to a high degree. In this situation the phosphor wave guide
structure 42 and in particular each spiral would be divided into
many segments, each with a ramp 46 which would direct the generated
light to the, preferably continuous, fiber optics wave guide
structure.
[0023] In the preferred embodiment FIG. 3, a buffer layer 28, 30 of
low index material is deposited onto the phosphor followed by a
conducting layer 32 and 34, such as for example an aluminum layer.
The buffer layer is between the phosphor layer and the conducting
layer since although the aluminum conducting layer is principally
reflective, it does absorb light, reducing the efficiency of the
embodiment. This embodiment allows the structure to form an anode
for electron beam excitation from the top side. This e-beam
excitation may consist of a broad area cathode as is used in vacuum
fluorescent displays or field-emission displays (FEDs), or a
conventional CRT operated as a flood gun. Appropriate means may be
provided for excitation by other mechanisms.
[0024] The inner and outer ends of each spiral may be terminated
with tapers or ramps as part of the substrate patterned structure
or may be cleaved or otherwise formed after growth. Alternatively
an aluminum taper at a 45.degree. angle or other appropriate angle
can reflect light generated in a phosphorous spiral, for example, a
fiber optic wave guide as described below. These outputs from the
taper or ramp termination may be combined using standard waveguide
or fiber optics couplers or may be utilized separately. Fiber
optics can be made with reflection high purity in comparison to
phosphor layer, and thus light generated in the phosphor layer can
be transferred to the fiber optics for substantially loss free
communication to a desired location. In other embodiments, other
techniques for coupling the light from the waveguides such as
wavelength selective gratings may be used. With such gratings, each
light frequency bounces off the grating at a different angle and
thus the light can be appropriately separated. Thus the grating can
be used to couple light output to other structures, such as other
wave guide structures.
[0025] It is to be understood that QED principles can be used to
enhance the generation of light for the wave guide structure.
[0026] Industrial Applicability:
[0027] A light source for telecommunications applications may be
created by combining the thin film light source with an appropriate
modulator utilizing electro-absorption, electro-optic or other
effects. The waveguide formed may be specifically designed to allow
coupling to a telecommunications fiber. The wide range of phosphors
available allows for the generation of light at many different
wavelengths, in particular erbium doped phosphors may be used to
generate light within the low absorption band of silica fibers near
1.5 micrometer. Other phosphors may be used to generate light
within the low dispersion band near 1.3 micrometers.
[0028] A high intensity light source coupled to a fiber optic may
be utilized for a variety of medical applications including
invasive surgery. In particular phosphors may be selected for the
specific purposes of activating photosensitive compounds, or for
interaction with specific tissues, cell types or chemicals.
[0029] The high brightness light source of the preferred embodiment
may be utilized as an illumination source for an electronic
projection display. Separate red, green, and blue sources may be
formed and coupled to image forming devices such as liquid crystal
arrays or digital micromirror arrays. Through modulation of the
excitation source or external modulation of the generated light,
separate color sources may be rapidly switched allowing use in a
single chip digital micromirror projector. An array of small light
sources may be formed through patterning so that separate light
sources are available for each pixel element of an image forming
device. That is to say that each pixel can include a spiral of a
phosphor material much as shown in FIGS. 1, 2. If a pixel were one
hundred microns across, the spiral would be one hundred microns
across. An e-beam could be a source of energy used to excite
selected pixels. Each spiral could have a taper, ramp or reflector
to reflect the generated light perpendicular to that plane of the
coil and selectively illuminate each pixel. If an addressable
excitation source such as a raster scanned CRT or an FED is
utilized, this array of small light sources may be utilized to form
a display without the imposition of an additional image forming
device. Additionally it is to be understood that flood lamps could
be used with this technology.
[0030] It is to be understood that other embodiments of the
invention can be developed and fall within the spirit and scope of
the invention and claims.
* * * * *