Note: Descriptions are shown in the official language in which they were submitted.
CA 02471451 2004-06-17
2138-263
TEM
AN LED ILLUMINATION ENGINE USING A REFLECTOR
BACKGROUND OF THE INVENTION
Cross-reference to Related Applications:
[0001] This application claims priority to Provisional Applications Serial
Nos.
601314,091, filed August 23, 2001, and 60/324,512, filed September 26, 2001,
the
disclosures of which are incorporated by reference.
Field of Invention:
[0002] This invention relates to projection displays, and specifically to
illumination
engines for projection displays.
Description of the Related Art:
[0003] There are several major kinds of display. These displays vary
significantly
both in the amount of space they require and their cost. The most common type
of
display is the cathode ray tube (CRT) display. CRTs are inexpensive and
bright, but
require a large amount of space. Another common kind of display is the direct
view
liquid crystal display (LCD) panel. Although LCD panels with small display
areas are
relatively inexpensive, those with larger display areas may cost several times
as much
as a comparable CRT display. As a result, LCD panels are not as popular as
CRTs,
unless space is at a premium. Thus, LCD panels are often used in crowded
areas, e.g.
restaurant cashier counters. It would be desirable for an image projection
system to be
compact and inexpensive.
[0004] For larger displays, two types of displays are most prominent: plasma
display
panels and projection displays. Plasma display panels are thin, and thus
occupy only a
small amount of space. Their resolution, however, is not as high as that of a
comparable projection display. In addition, plasma displays are quite
expensive.
Plasma display panels are therefore not as popular as the other types of
displays. It
would be desirable for an image projection system to have high resolution and
be
inexpensive.
[0005] Projection displays work by shining light from an illumination engine,
such as a
white light from an arc or a filament lamp, onto an imager, such as a digital
micro-mirror
device (DMD), an LCD, or an liquid crystal on silicon (LCOS) chip. The imager
may be
CA 02471451 2004-06-17
modulated with an image signal to control its reflection and transmission
properties.
The imager may respond to the image signal by either reflecting or
transmitting the light
to create an image.
[0006] Much work has been done on projection displays using small display
imagers
such as DMD displays, LCDs, and LCOS displays. Such displays, however, require
expensive illumination engines. While these displays provide advantages for
displays
with large screens, these displays are not used as widely in displays with
small screens,
due to the high cost of the illumination engine. Therefore, there exists a
need for a
compact and low cost illumination engine that can be applied to smaller
displays, such
as those of 10" to 35". These displays could be used in, e.g_ computer
monitors and
small televisions since they will occupy a small amount of space. With the
advancement in the LED technologies, future high lumen output LEDs can have a
potential of illuminating a large screen television in the 60" range.
[0007) A color signal may be fed into the imager of the projection system in
synchronism with the colors incident on the imager such that the output
picture on the
screen will be sequentially illuminated with the three colors. The eye retains
the colors,
merging the colors and giving an impression of an overall color picture.
[0008] Arc lamps and filament lamps, which are traditionally used as sources
of
radiation in such systems, have relatively short life spans. A light emitting
diode (LED),
in contrast, may have a lifetime of 100,000 hours, which is 20 to 50 times
longer than
an arc lamp. It would be desirable to be able to use an LED, or an array of
LEDs, as a
source of illumination in an image projection system.
(0009) Fig. 1 shows an LED 1 light source for use with an embodiment of the
invention. An LED is an example of a device that produces light by electro-
luminescence. An LED may be, e.g_, a forward biased p-n junction. When an
electric
current is applied to the LED, minority carriers are injected into regions of
the crystal
where they can recombine with majority carriers, such as. in the transition
region and in
the neutral regions near the p-n junction. The carriers ernit radiation upon
recombination. In materials characterized by direct recombination, such as
e.c~. Zinc
Sulfide (ZnS), Gallium Arsenide (GaAs), Indium Antimony (InSb), Gallium
Phosphorus
2
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(GaP), and, Gallium Nitride (GaN), the radiation may include a significant
portion of
visible light. This effect may be termed injection electro-luminescence.
[0010] The LED 1 may be mounted on a substrate 2, which may be insulating and
a
good conductor of heat, such as a Beryllium Oxide (Be0) substrate. Metal
tracks 3, 5
or rails on top of the substrate 2 provide an electrical connection between
the LED 1
and the other parts of the circuit. An LED 1 may have electrodes on the top
and the
bottom. An LED 1 may be soldered to one of the metal tracks 3 on the
substrate, which
forms one contact. The other contact is formed by wire bonding 4 the electrode
on top
of the LED 1 to another metal track 5 on the substrate. In the alternative,
solder bumps
may be used for soldering to the substrate instead of wire bonding. When an
electrical
current is applied to the LED 1, radiation is emitted.
(0011] An LED will generally emit radiation having a relatively narrow range
of
bandwidths due to the intrinsic properties of the LED materials. As a result,
the output
of the LEDs will normally be colored. LEDs that emit radiation in all of the
colors from
infrared to ultraviolet are readily available. Color LEDs are customarily used
for
indicators, while white LEDs are often used for general illumination. One of
the
common usages for color LEDs is for traffic lights.
[0012] The light source in a projection system should have a small etendue. As
a
result, a good collection and condensing system is required to collect the
light from the
light source and condense the light into the target. In the case of LEDs, most
LEDs are
packed into epoxy lenses, which increase the etendue of the LED.
[0013] On the other hand, if white LEDs are used, the output is directly
compatible to
an arc lamp illumination system, but the increase in the size of the emission
area due
the application of phosphor may increase the etendue, thus reducing
brightness. Either
or both of these schemes can be used depending on the system requirements.
[0014] Radiation of different colors produced by several LEDs may be combined
to
produce other colors or a net white output. The output of several LEDs may be
combined by mixing their output in an homogenizes. In the alternative, a lens
formed of
clear epoxy 6 and a thin layer of white phosphor 7 may be applied to the top
of an LED
1 which produces blue or UV radiation to 'whiten' the rad6ation, as shown in
Fig. 2. In
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another embodiment, clear epoxy 6 may be replaced by white phosphor. For a
sequential color projection system, each color may be turned on in sequence
such that
their outputs are synchronized with an imager in a projection system. This
will produce
an overall color display.
(0015] The radiation output from a plurality of LEDs may be combined to
illuminate a
screen. It is estimated that 10 to 30 LEDs of the types available in the
market today
would be needed to illuminate a screen on the order of 10" to 21 ", depending
on the
output intensity of the LEDs. As the output of the LEDs increases with the
advancement of the technology, fewer LEDs will be needed. The total output
etendue
of the LEDs should match the etendue of the imager chip. For example, a 0.25
mm2
chip emitting in a hemisphere has an etendue of approximately E = 0.25. For a
0.5"
imager chip at FI3.0, the etendue is approximately E = 6.75. Thus, if there is
no loss of
etendue from the LEDs to the imager, a total of 6.75/.25 = 27 LEDs can be
used.
[0016] At present, although LEDs with output of over 100 lumens has been
reported,
the average output from a commonly available LED is about 20 lumens. Twenty-
seven
LEDs would thus produce a total of about 540 lumens. ~fhis would be sufficient
for
smaller displays, even after considering the loss budget of various
components. LEDs
may be expected to produce more lumens as the technology advances.
(0017] The light incident on the imager may be, e_g_ filtered to produce a
color image.
Three primary colors, such as, e.,g_ red, green, and bluE:, may be fed to the
imager by,
e.g, filtering the light incident on the imager with, e.g:, a rotating color
wheel. Rotating
color wheels are comprised of, ,e.~c . red, green, and blue filters arranged
about an axis
and caused to rotate in the light. As each of the filters intersects the light
incident on
the imager, two of the colors will be filtered out white the third is
transmitted. Rotating
color wheels are simple and inexpensive, but incur losses due to the
filtering.
Furthermore, they require space for the motor. It would be desirable for a
compact
source of radiation to produce colored light with relatively low filtering
losses.
SUMMARY OF THE INVENTION
[0018] In a first embodiment, an illumination engine for a projection display
using fight
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n~dSy44~f;.2NTk: ~~...c7npgt" .~~t y.~,d.~p~ ~n.cym..:.Mau.'..x-...mau.~ -
~.... .. ..____.. . ...... ..,..._._... .... , ... ..
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emitting diodes (LEDs) includes a first reflector having a~ first and second
focal points, a
first source of electro-luminescence located proximate to the first focal
point to emit
rays of radiation in a first range of wavelengths that reflect from the first
reflector and
converge substantially at the second focal point, and a first light pipe
having an first
input end and a first output end, the first input end being located proximate
to the
second focal point to collect substantially all of the radiation and wherein
the first output
end transmits substantially aH of the radiation.
(0019] In a second embodiment, an illumination system for a projection display
using
light emitting diodes (LEDs) includes first and second sources of electro-
luminescence,
a first homogenizer having a first input end and a first output end, a second
homogenizer having a second input end and a second output end, a primary
reflector
having a first focal point and a first optical axis, a secondary reflector
having a second
focal point and a second optical axis which is placed substantially
symmetrically to a
primary reflector such that a first and second optical axes are substantially
collinear, a
third reflector having a third focal point and a third optical axis, a fourth
reflector having
a fourth focal point and a fourth optical axis which is placed substantially
symmetrically
to a third reflector such that a third and fourth optical axes are
substantially collinear.
(0020, The first source of electro-luminescence is located proximate to the
first focal
point to emit rays of radiation in a first range of wavelengths that reflect
from the
primary reflector toward the secondary reflector and substantially converge at
the
second focal point. The second source of eiectro-luminescence is located
proximate to
the third focal point to emit rays of radiation in a second range of
wavelengths that
reflect from the third reflector toward the fourth reflector and substantially
converge at
the fourth focal point. The first input end is located proximate to the second
focal point
to collect substantially all of the radiation of the first range of
wavelengths and transmit
it via the first output end, and the second input end is located proximate to
the fourth
focal point to collect substantially all of the radiation of the second range
of wavelengths
and transmit it via the second output end.
(0021 In a third embodiment, an illumination system for a projection display
using
light emitting diodes (LEDs) includes a substrate having a first side, a
platform disposed
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proximate to the first side of the substrate, a plurality of reflectors each
having a first
and second focal points disposed in the platform, each of the first and second
focal
points disposed proximate to the first side of the substrate, a plurality of
sources of
electro-luminescence disposed on the first side of the substrate, each of the
sources of
electro-luminescence disposed substantially coincident with a corresponding
one of the
first focal points to emit rays of electromagnetic radiation that reflect from
a
corresponding one of the plurality of reflectors and converges substantially
at a
corresponding one of the second focal points, a plurality of light pipes
disposed in the
substrate, each of the light pipes having an input end and an output end, each
of the
input ends disposed substantially coincident with a corresponding one of the
second
focal points to collect substantially all of the radiation, wherein each of
the output ends
transmits substantially all of the radiation emitted by a corresponding one of
the plurality
of sources.
[0022] In a fourth embodiment, a method for using light emitting diodes (LEDs)
in a
projection display is performed by positioning a source of electro-luminescent
radiation
at a first focal point of a reflector, producing rays of radiation by the
source, reflecting
the rays of radiation by the reflector toward a second focal point of the
reflector,
converging the rays of radiation at the second focal point, positioning a
light pipe having
an input end and output end so the input end is substantially proximate to the
second
focal point, collecting the rays of radiation at the input end, passing the
rays of radiation
through the light pipe, and outputting rays of radiation from the output end
of the fight
pipe.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0023] In Fig. 1 is shown a schematic diagram of a LED chip mounted on a
substrate
for use with an embodiment of the invention;
In Fig. 2 is shown a schematic diagram of a white LED, with the chip mounted
on
a substrate and covered with transparent epoxy and a Layer of phosphor for use
with an
embodiment of the invention;
In Fig. 3 is shown an illumination engine according to a first embodiment of
the
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invention;
In Fig. 4 is shown an illumination engine according to a second embodiment of
the invention;
In Fig. 5 is shown a waveguide for use with the first or the second embodiment
of
the invention;
In Fig. 6 is shown a fiber optic for use with the first or the second
embodiment of
the invention;
In Fig. 7 is shown a condenser lens and an image projection system for use
with
the first or the second embodiment of the invention;
1n Fig. 8 is shown an illumination engine according to a third embodiment of
the
invention;
In Fig. 9 is shown an illumination engine according to a fourth embodiment of
the
invention;
In Fig. 10 is shown an homagenizer for use with the third or the fourth
embodiment of the invention;
In Fig. 11 is shown a waveguide for use with the third or the fourth
embodiment
of the invention;
In Fig. 12 is shown a fiber optic for use with the third or the fourth
embodiment of
the invention;
!n Fig. 13 is shown a condenser lens and an image projection system for use
with the third or the fourth embodiment of the invention;
In Fig. 14 is shown an illumination engine according to a fifth embodiment of
the
invention;
In Fig. 15 is shown an illumination engine according to a sixth embodiment of
the
invention;
in Fig. 16 is shown an homogenizes for use with the fifth or the sixth
embodiment
of the invention;
In Fig. 17 is shown a waveguide for use with the fifth or the sixth embodiment
of
the invention;
In Fig. 18 is shown a fiber optic for use with the fifth or the sixth
embodiment of
7
.~ . . ,~ ~ :~,..,, n ,~y, .~ ..,...~. _.. . .__. ._ _.._ ...._ __ _. . . _ .
.___. ..____...__ ..
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the invention;
In Fig. 19 is shown a condenser lens and an image projection system for use
with the fifth or the sixth embodiment of the invention;
In Fig. 20 is shown an illumination system according to a seventh embodiment
of
the invention;
In Fig. 21 is shown an illumination system according to an eighth embodiment
of
the invention;
In Fig. 22 is shown an homogenizer for use with the seventh or the eighth
embodiment of the invention;
In Fig. 23 is shown a waveguide for use with the seventh or the eighth
embodiment of the invention;
In Fig. 24 is shown a fiber optic for use with the seventh or the eighth
embodiment of the invention;
1n Fig. 25 is shown a condenser lens and an image projection system for use
with the seventh or the eighth embodiment of the invention;
In Fig. 26 is shown a straight and a tapered homogenizer for use with an
embodiment of the invention;
In Fig. 27 is shown various cross-sections of light pipes for use with an
embodiment of the invention;
In Fig. 28 is shown various configurations of waveguides for use with an
embodiment of the invention;
fn Fig. 29 is shown various cross-sections of waveguides for use with an
embodiment of the invention;
In Fig. 30 is shown various cross-sections of homogenizers for use with an
embodiment of the invention; and
In Fig. 31 is shown an illumination system according to the seventh or eighth
embodiment of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0024] In Fig. 3 is shown an illumination engine 300 according to a first
embodiment
of the invention. A first source of electro-luminescence 302 is disposed
proximate to a
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first focal point 304 of a first reflector 306 to emit rays of radiation 308
in a first range of
wavelengths 318 that reflect from first reflector 306 and converge
substantially at a
second focal point 310 of first reflector 306. A first light pipe 312 having
an first input
end 314 located proximate to second focal point 310 to collect substantially
all of
radiation 308, and a first output end 31f through which substantially all of
radiation 308
is transmitted.
(0025] First source of electro-luminescence 302 may be, e.~., source of
injection
electro-luminescence, such as a forward-biased p-n junction, or a fight-
emitting diode.
Radiation 308 may be, e.~c . recombination radiation. First output end 316 may
be, e.~,lc ..
substantially convex. First range of wavelengths 318 may be, e.g_ white
radiation,
infrared radiation, red radiation, orange radiation, yellow radiation, green
radiation, blue
radiation, indigo radiation, violet radiation, and ultraviolet radiation. The
LED may be
placed at a first focus of the reflector while a target is placed at a second
focus of the
reflector. The target may be, e.g_ a tapered light pipe (TLP). A reflector may
provide a
magnification of 1:1 such that the etendue of the LED emission is preserved at
the input
of the output TLP.
[0026] In one embodiment, first source of electro-luminescence 302 includes a
conversion layer 320, which may be made of, e.~c . phosphor, converts
radiation 308 to
produce substantially white radiation. Conversion layer 320 may be, e.~c . a
first layer of
substantially clear epoxy 322 and a second layer of substantially white
phosphor 324,
or a single layer of white phosphor. In another embodiment, the electro-
luminescence
302 does not have a phosphor conversion layer 320 or clear epoxy 322.
[0027] First light pipe 312 may be, e.g_ a tapered light pipe or a straight
light pipe, as
shown in Fig. 26. A cross-section of first light pipe 312 may be, e.g, a
rectangle, a
circle, a triangle, a rhombus, a trapezoid, a pentagon, a hexagon, or an
octagon, as
shown in Fig. 27.
[0028] First reflector 306 may be, e,g_ at least a portion of a substantially
ellipsoidal
surface of revolution, at least a portion of a substantially toroidal surface
of revolution,
at feast a portion of a substantially spheroidal surface of revolution, or at
least a portion
of a substantially dual-paraboloidal surface of revolution.
9
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[0029] For the case of the toroidal and spherical surface of revolutions, one
focal
point may be defined as a first point chosen close to a center of curvature
and a second
point having the best image of the first point. The two points may be, e.~.c .
substantially
equidistant from the center of curvature and on opposite sides of the center
of
curvature. For the case of the dual paraboloidal surface of revolution, the
two focal
points correspond to a focal point of each paraboloidal surface of revolution.
[0030] In one embodiment, first reflector 306 has a coating that reflects only
a pre-
specified portion of the electromagnetic radiation spectrum, such as, e.~c .
visible light
radiation, a pre-specified band of radiation, or a specific color of
radiation.
[0031] In Fig. 4 is shown an illumination engine 400 according to a second
embodiment of the invention. In the second embodime~at, first reflector 402 is
composed of a first primary reflector 404 having a first optical axis 406 and
a first focal
point 412, and a first secondary reflector 408 having a second optical axis
410 and a
second focal point 414. First secondary reflector 408 may be placed
substantially
symmetrically to first primary reflector 404 such that first and second
optical axes 406,
410 are substantially collinear.
[0032] First primary and first secondary reflectors 404, 408 may be, a _gr at
least a
portion of a substantially paraboloidal surface of revolution. In one
embodiment, first
primary reflector 404 comprises at least a portion of a substantially
ellipsoidal surface of
revolution, and first secondary reflector 408 comprises at least a portion of
a
substantially hyperboloidal surface of revolution. In another embodiment,
first primary
reflector 404 comprises at least a portion of a substantially hyperboloidal
surface of
revolution, and first secondary reflector 408 comprises at least a portion of
a
substantially ellipsoidal surtace of revolution.
[0033] In Fig. 5 is shown an illumination engine 500 according to the first or
the
second embodiment of the invention with a waveguide 502 disposed substantially
proximate to output end 504. Waveguide 502 may be, e.~c . a single core optic
fiber, a
fiber bundle, a fused fiber bundle, a polygonal rod, or a hollow reflective
light pipe, as
shown in Fig. 28.
[0034] In one embodiment, a first etendue 506 is associated with output end
504,
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CA 02471451 2004-06-17
white a second etendue 508 is associated with waveguide 502, such that first
etendue
506 is substantially equal to second etendue 508. A cross-section of waveguide
502
may be, e.g_. a circle, or a polygon, as shown in Fig. 29. In another
embodiment,
waveguide 502 may be a tapered waveguide. Waveguide 502 may be made of, e.g_
quartz, glass, plastic, or acrylic.
[0035] In Fig. 6 is shown an illumination engine 600 according to the first or
the
second embodiment of the invention with a fiber optic 602 disposed
substantially
proximate to output end 604. Fiber optic 602 may be illuminated by radiation
606
transmitted at output end 604 of first light pipe 608, the fiber optic 602
releasing the
collected and condensed radiation to provide for illumination at a desired
location 610.
[0036] In one embodiment, a first etendue 612 is associated with output end
604,
while a second etendue 614 is associated with fiber optic 602, such that first
etendue
612 is substantially equal to second etendue 614.
[0037] In Fig. 7 is shown an illumination engine 700 according to the first or
the
second embodiment of the invention with a condenser fens 702 disposed
substantially
proximate to output end 704 and an image projection system 714 disposed
substantially proximate to an output side of condenser lens 702. Projection
system 714
may display an image 712 being illuminated by the radiation 706 transmitted at
output
end 704 of first light pipe 708.
[0038] In one embodiment, a first etendue 716 is associated with output end
704,
while a second etendue 718 is associated with condenser lens 702, such that
first
etendue 716 is substantially equal to second etendue 718.
[0039] In Fig. 8 is shown an illumination engine 800 according to a third
embodiment
of the invention. In the third embodiment, a second and third sources of
electro-
luminescence 802, 804 are added to the first embodiment. A second reflector
806
having a third and fourth focal points 808, 810 is arranged so that second and
third
sources of electro-luminescence 802, 804 are located proximate to third focal
point 808
to emit rays of radiation in a second and third ranges of wavelengths 812, 814
that
reflect from second reflector 806 and substantially converge at fourth focal
point 810.
[0040] A second light pipe 816 having a second input and output ends 818, 820
is
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arranged such that second input end 818 is located proximate to fourth focal
point 810
to collect substantially all of radiation of second and third ranges of
wavelengths 812,
814. First and second output ends 820, 822 transmit substantially all of
radiation of
first, second and third ranges of wavelengths 824, 812, 814. 1n one
embodiment,
second output end 820 is substantially convex. In one embodiment, first,
second and
third ranges 824, 812, 814 are substantially incongruent. In another
embodiment, first,
second and third ranges 824, 812, 814 are combined to produce a fourth range
of
wavelengths 826.
[0041] In another embodiment, second and third sources of electro-luminescence
802, 804 emit radiation substantially sequentially. Second and third sources
of electro-
luminescence 802, 804 may be, e.~c . sources of injection electro-
luminescence, such as
forward-biased p-n junctions, or light-emitting diodes. In one embodiment,
second and
third ranges 812, 814 comprise recombination radiation. Second range of
wavelengths
812 may be, e.,g_ white radiation, infrared radiation, red radiation, orange
radiation,
yellow radiation, green radiation, blue radiation, indigo radiation, violet
radiation, and
ultraviolet radiation. Third range of wavelengths 814 may be, e.~c . white
radiation,
infrared radiation, red radiation, orange radiation, yellow radiation, green
radiation, blue
radiation, indigo radiation, violet radiation, and ultraviolet radiation.
(0042] Second light pipe 816 may be, e.g_ a tapered light pipe or a straight
light pipe,
as shown in Fig. 26. A cross-section of second light pipe 816 may be, e.~c . a
rectangle,
a circle, a triangle, a rhombus, a trapezoid, a pentagon, <~ hexagon, or an
octagon, as
shown in Fig. 27. Second reflector 806 may be, e..~Lc . at least a portion of
a substantially
ellipsoidal surfaceof revolution, at least a portion of a substantially
toroidal surface of
revolution, at least a portion of a substantially spheroidal surface of
revolution, or at
least a portion of a substantially dual paraboloidal surface of revolution. In
one
embodiment, second reflector 806 has a coating that reflects only a pre-
specified
portion of the elecfiromagnetic radiation spectrum, such as, e.~c . visible
light radiation, a
pre-specified band of radiation, or a specific color of radiation.
[0043] In Fig. 9 is shown an illumination engine 900 according to a fourth
embodiment of the invention. In the fourth embodiment, second reflector 902 is
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CA 02471451 2004-06-17
composed of a second primary reflector 904 having a first optical axis 906 and
a third
focal point 912, and a second secondary reflector 908 having a second optical
axis 910
and a fourth focal point 914. Second secondary reflector 908 may be placed
substantially symmetrically to second primary reflector 904 such that first
and second
optical axes 906, 910 are substantially collinear.
[0044] Second primary and second secondary reflectors 904, 908 may be, e.~c .
at
least a portion of a substantially paraboloidal surface of revolution. In one
embodiment,
second primary reflector 904 comprises at least a portion of a substantially
ellipsoidal
surface of revolution, and second secondary reflector 908 comprises at least a
portion
of a substantially hyperboloidal surface of revolution. In another embodiment,
second
primary reflector 904 comprises at least a portion of a substantially
hyperboloidal
surface of revolution, and second secondary reflector 9U8 comprises at least a
portion
of a substantially ellipsoidal surface of revolution.
[0045] In Fig. 10 is shown an illumination engine 1000 according to the third
or the
fourth embodiment of the invention with a homogenizes 1002 disposed
substantially
proximate to first and second output ends 1004 and 1010.
[0046] In one embodiment, a first etendue 1006 is associated with first and
second
output ends 1004 and 1010, while a second etendue 1008 is associated with
homogenizes 1002, such that first etendue 1006 is substantially equal to
second
etendue 1008. A cross-section of homogenizes 1002 may be, ,e.~c . a circle, or
a
polygon, as shown in Fig. 30. In another embodiment, homogenizes 1002 may be a
tapered waveguide. Homogenizes 1002 may be made of , e.~c . quartz, glass,
plastic, or
acrylic.
[0047] In Fig. 11 is shown an illumination engine 1100 according to the third
or the
fourth embodiment of the invention with a waveguide 1102 disposed
substantially
proximate to first and second output ends 1104 and 111 U. Waveguide 1102 may
be,
e_g_ a single core optic fiber, a fiber bundle, a fused fiber bundle, a
polygonal rod, or a
hollow reflective light pipe, as shown in Fig. 28.
[0048] In one embodiment, a first etendue 1106 is associated with first and
second
output ends 1104 and 1110, while a second etendue 1108 is associated with
13
CA 02471451 2004-06-17
waveguide 1102, such that first etendue 1106 is substantially equal to second
etendue
1108. A cross-section of waveguide 1102 may be, e.~..c . a circle, or a
polygon, as shown
in Fig. 29. In another embodiment, waveguide 1102 may be a tapered waveguide.
Waveguide 1102 may be made of, e.g: quartz, glass, plastic, or acrylic.
[0049] In Fig. 12 is shown an illumination engine 1200 according to the third
or the
fourth embodiment of the invention with a fiber optic 1202 disposed
substantially
proximate to first and second output ends 1204 and 1210. Fiber optic 1202 may
be
illuminated by radiation 1206 transmitted at first and second output ends 1204
and
1210, the fiber optic 1202 releasing the collected and condensed radiation to
provide
for illumination at a desired location 1210.
[0050] In one embodiment, a first etendue 1212 is associated with first and
second
output ends 1204 and 1210, while a second etendue 1214 is associated with
fiber optic
1202, such that first etendue 1212 is substantially equal to second etendue
1214.
[0051] In Fig. 13 is shown an illumination engine 1300 according to the third
or the
fourth embodiment of the invention with a condenser lens 1302 disposed
substantially
proximate to first and second output ends 1304 and 1310 and an image
projection
system 1314 disposed substantially proximate to an output side of condenser
lens
1302. Projection system 1314 may display an image 1312 being illuminated by
the
radiation 1306 transmitted at first and second output ends 1304 and 1310.
[0052, In one embodiment, a first etendue 1316 is associated with first and
second
output ends 1304 and 1310, while a second etendue 1318 is associated with
condenser
fens 1302, such that first etendue 1316 is substantially equal to second
etendue 1318.
[0053] In Fig. 14 is shown an array of reflectors according to a fifth
embodiment of the
invention. fn the fifth embodiment, a second and third sources of electro-
luminescence
1402, 1404 are added to the first embodiment. A second reflector 1406 having a
third
and fourth focal points 1408, 1410 is arranged so that second source of
electro-
luminescence 1402 is located proximate to third focal point 1408 to emit rays
of
radiation in a second range of wavelengths 1412 that reflect from second
reflector 1406
and substantially converge at fourth focal point 1410. A second light pipe
1414 having
a second input and output ends 1416, 1418 is arranged such that second input
end
14
CA 02471451 2004-06-17
1416 is located proximate to fourth focal point 1410 to collect substantially
all of
radiation of second range of wavelengths 1412.
[0054] A third reflector 1420 having a fifth and sixth focal points 1422, 1424
is
arranged so that third source of electro-luminescence 1404 is located
proximate to fifth
focal point 1422 to emit rays of radiation in a third range of wavelengths
1426 that
reflect from third reflector 1420 and substantially converge at sixth focal
point 1424. A
third light pipe 1428 having a third input and output ends 1430, 1432 is
arranged such
that third input end 1430 is located proximate to fifth focal point 1422 to
collect
substantially all of radiation of third range of wavelengths 1426. First,
second and third
output ends 1434, 1418, 1432 transmit substantially all of radiation of first,
second and
third ranges of wavelengths 1436, 1412, 1426. In one embodiment, second and
third
output ends 1418, 1432 are substantially convex. fn one embodiment, first,
second and
third ranges 1436, 1412, 1426 are substantially incongruent. In another
embodiment,
first, second and third ranges 1436, 1412, 1426 are combined to produce a
fourth
range of wavelengths 1438.
[00551 In another embodiment, first, second and third .sources of electro-
luminescence 1402, 1404, 1440 emit radiation substantially sequentially.
First, second
and third sources of electro-luminescence 1402, 1404, 1440 may be, e.~c .
sources of
injection electro-luminescence, such as forward-biased p-n junctions, or light-
emitting
diodes. In one embodiment, first, second and third ranges 1436, 1412, 1426
comprise
recombination radiation. Second range of wavelengths '1412 may be, e.~.Lc .
white
radiation, infrared radiation, red radiation, orange radiation, yellow
radiation, green
radiation, blue radiation, indigo radiation, violet radiation, and ultraviolet
radiation. Third
range of wavelengths 1426 may be, e.g_ white radiation, infrared radiation,
red
radiation, orange radiation, yellow radiation, green radiation, blue
radiation, indigo
radiation, violet radiation, and ultraviolet radiation.
[0056] Second and third light pipes 1414, 1428 may be, e.g_ a tapered light
pipe or a
straight fight pipe, as shown in Fig. 26. A cross-section of second and third
light pipes
1414, 1428 may be, e.g_ a rectangle, a circle, a triangle, a rhombus, a
trapezoid, a
pentagon, a hexagon, or an octagon, as shown in Fig. 27.
CA 02471451 2004-06-17
[0057] Second and third reflectors 1406, 1420 may be, e.g_ at least a portion
of a
substantially ellipsoidal surface of revolution, at least a portion of a
substantially toroidal
surface of revolution, at least a portion of a substantially spheroidal
surface of
revolution, or at least a portion of a substantially dual parabofoidal surface
of revolution.
In one embadiment, second and third reflectors 1406, 1420 have a coating that
reflects
only a pre-specified portion of the electromagnetic radiation spectrum, such
as, e.g_
visible light radiation, a pre-specified band of radiation, or a specific
color of radiation.
[0058] In Fig. 15 is shown an illumination engine 1500 according to a sixth
embodiment of the invention. In the sixth embodiment, second reflector 1502 is
composed of a second primary reflector 1504 having a optical axis 1506 and a
third
focal point 1512, and a second secondary reflector 1508 having a second
optical axis
1510 and a fourth focal point 1514. Second secondary reflector 1508 may be
placed
substantially symmetrically to second primary reflector 1504 such that first
and second
optical axes 1506, 1510 are substantially collinear.
[0059] Second primary and second secondary reflectors 1504, 1508 may be, e.~c
. at
least a portion of a substantially paraboloidal surface of revolution. In one
embodiment,
second primary reflector 1504 comprises at least a portion of a substantially
ellipsoidal
surface of revolution, and second secondary reflector 1508 comprises at least
a portion
of a substantially hyperboloidal surface of revolution. In another embodiment,
second
primary reflector 1504 comprises at least a portion of a substantially
hyperboloidal
surface of revolution, and second secondary reflector 1508 comprises at feast
a portion
of a substantially ellipsoidal surface of revolution.
[0060] Third reflector 1516 is composed of a third primary reflector 1518
having a first
optical axis 1520 and a fifth focal point 1522, and a third secondary
reflector 1524
having a second optical axis 1526 and a sixth focal point 1528. Third
secondary
reflector 1524 may be placed substantially symmetrically to third primary
reflector 1518
such that first and second optical axes 1520, 1526 are substantiaNy collinear.
[0061] Third primary and third secondary reflectors 1518, 1524 may be, e.~c .
at least a
portion of a substantially paraboloidal surface of revolution. In one
embodiment, third
primary reflector 1518 comprises at least a portion of a substantially
ellipsoidal surface
16
CA 02471451 2004-06-17
of revolution, and third secondary reflector 1524 comprises at least a portion
of a
substantially hyperboloidal surface of revolution. In another embodiment,
third primary
reflector 1518 comprises at least a portion of a substantially hyperboloidal
surface of
revolution, and third secondary reflector 1524 comprises at least a portion of
a
substantially ellipsoidal surface of revolution.
[0062] In Fig. 16 is shown an illumination engine 1600 according to the fifth
or the
sixth embodiment of the invention with a homogenizes 1602 disposed
substantially
proximate to first, second and third output ends 1604, 1606 and 1608.
[0063] In one embodiment, a first etendue 1610 is associated with first,
second and
third output ends 1604, 1606 and 1608, while a second etendue 1612 is
associated
with homogenizes 1602, such that first etendue 1610 is substantially equal to
second
etendue 1612. A cross-section of homogenizes 1602 may be, e.~c . a circle, or
a
polygon, as shown in Fig. 30. In another embodiment, homogenizes 1602 may be,
e.g,
a straight or a tapered homogenizes. Homogenizes 1602 may be made of, e.g_
quartz,
glass, plastic, or acrylic.
[0064] In Fig. 17 is shown an illumination engine 1700 according to the fifth
or the
sixth embodiment of the invention with a waveguide 1702 disposed substantially
proximate to first, second and third output ends 1704, 1 i'06 and 1708.
Waveguide
9 702 may be, e.g: a single core optic fiber, a fiber bundle, a fused fiber
bundle, a
polygonal rod, or a hollow reflective light pipe, as shown in Fig. 17.
[0065] In one embodiment, a first etendue 1710 is associated with first,
second and
third output ends 1704, 1706 and 1708, while a second etendue 1712 is
associated
with waveguide 1702, such that first etendue 1710 is substantially equal to
second
etendue 1712. A cross-section of waveguide 1702 may be, e.~c . a circle, or a
polygon,
as shown in Fig. 29. In another embodiment, waveguide 1702 may be a tapered
waveguide. Waveguide 1702 may be made of, e.~c . quartz, glass, plastic, or
acrylic.
[0066] In Fig. 18 is shown an illumination engine 1800 according to the fifth
or the
sixth embodiment of the invention with a fiber optic 1802 disposed
substantially
proximate to first, second and third output ends 1804, 1806 and 1808. Fiber
optic 1802
may be illuminated by radiation 1816 transmitted at first, second and third
output ends
17
CA 02471451 2004-06-17
1804, 1806 and 1808, the fiber optic 1802 releasing they collected and
condensed
radiation 1816 to provide for illumination at a desired location 1818.
[0067] In one embodiment, a first etendue 1812 is associated with first,
second and
third output ends 1804, 1806 and 1808, while a second etendue 1814 is
associated
with fiber optic 1802, such that first etendue 1812 is substantially equal to
second
etendue 1814.
[0068] In Fig. 19 is shown an illumination engine 1900 according to the fifth
or the
sixth embodiment of the invention with a condenser lens 1902 disposed
substantially
proximate to first, second and third output ends 1904, 1906 and 1908 and an
image
projection system 1910 disposed substantially proximate to an output side of
condenser
lens 1902. Projection system 1910 may display an image 1912 being illuminated
by the
radiation 1914 transmitted at first, second and third output ends 1904, 1906
and 1908.
[0069] In one embodiment, a first etendue 1918 is associated with first,
second and
third output ends 1904, 1906 and 1908, while a second ~etendue 1920 is
associated
with condenser lens 1902, such that first etendue 1918 is substantially equal
to second
etendue 1920.
[0070] In a preferred embodiment, sequential color will be used with a single
imager
chip. In this case, red, green, and blue LEDs will be turned on and off
sequentially, and
the color signal will be fed into the imager of the projection system 1910 in
synchronism
with the LEDs such that the output picture on the screen will be sequentially
illuminated
with the three colors. The retention of the eye will merge the colors and give
an overall
color picture. This has an effect that is similar to the sequential color
system using color
wheels. In that case, the lamp emits white light and the color is generated by
the
rotation of the color wheel, which introduces loss in the system and increase
the size of
the system.
[0071] The output from a homogenizer may then be used by the projection system
to
project the image onto the screen. The small power dissipation of the LED
array and its
long lifetime make this a very suitable light source for projection displays.
[0072] In Fig. 20 is shown an illumination system according to a seventh
embodiment
of the invention. In the seventh embodiment a platform 2.002 is disposed
proximate to
18
CA 02471451 2004-06-17
a first side 2004 of a substrate 2006. Substrate 2006 maybe formed
substantially of,
e..g, beryllium oxide (Be0). A plurality of reflectors 2008, each having a
first and second
focal points 2010, 2012, are disposed in platform 2002, with each of first and
second
focal points 2010, 2012 disposed proximate to first side 2004 of substrate
2006. The
reflectors may, e.g_ be made individually and assembled together, or more
preferably,
made into a common platform by machining or glass molding. A proper reflector
coating such as, e.~Lc.. a cold coating can be deposited into the platform.
[0073] A plurality of sources of eiectro-luminescence 2014 are disposed on
first side
2004 of substrate 2006. Each of sources of electro-luminescence 2014 are
disposed
substantially coincident with a corresponding one of first focal points 2010
to emit rays
of electromagnetic radiation 2016 that reflect from a corresponding one of
plurality of
reflectors 2008 and converge substantially at a corresponding one of second
focal
points 2012. Reflectors 2008 may be, e..g_ elliptical, spherical, toroidal, or
dual-
paraboloid reflectors. In one embodiment, the plurality of sources of electro-
luminescence 2014 is between ten and thirty. In another embodiment, the
plurality of
sources of electro-luminescence 2014 are arranged in tvvo-dimensional array
such as,
e.g_ 2 by 2, 2 by 3, 3 by 3, 3 by 4, etc., and in general m by n, where m and
n are
integers. The output face 2002 of the light pipe can be square or rectangular
or other
shapes as shown in Figure 27.
[0074] A plurality of light pipes 2018, each having an input end 2020 and an
output
end 2022, are disposed in substrate 2006, with each of input ends 2020
disposed
substantially coincident with a corresponding one of second focal points 2012
to collect
substantially all of radiation 2016 from a corresponding one of sources of
electro-
luminescence 2014. Each of output ends 2022 then transmits substantially all
of
radiation 2016 emitted by a corresponding one of plurality of sources 2014.
[0075] Holes are made in substrate 2006 for light pipes 2018 such that the
sources of
efectro-luminescence 2014 and input ends 2020 are matched to the corresponding
foci
of the reflectors. The tapering of light pipes 2018 provides a transformation
of the high
numerical aperture (NA) at the input to a lower NA at the oufpufi. Also, for
best
performance, the outputs of light pipes 2018 are made such that they occupy
the space
19
CA 02471451 2004-06-17
at the output plane without gaps. This allows the smallest etendue at the
output for
further coupling of light. When the platform and substrate are assembled
together, it
becomes a compact illumination unit as shown in Fig. 31. The output ends of
the light
pipes may be made convex for, e.~c . more efficient transformation of NA. A
homogenizer 2202 may be added to mix the light input, as shown in Fig. 22, as
well as
a power source 2204. Homogenizer 2202 can be straight or tapered, either
larger or
smaller, to fit the particular application. The mixing of light homogenizes
the spatial
uniformity, and also the color when colored LEDs are used, e.g. red, green,
and blue.
[0076] 1n one embodiment, a first etendue 2206 is associated with plurality of
output
ends 2022, while a second etendue 2208 is associated with homogenizer 2202,
such
that first etendue 2206 is substantially equal to second etendue 2208. A cross-
section
of homogenizer 2202 may be, e.g_ a circle, or a polygon, as shown in Fig. 30.
In
another embodiment, homogenizer 2202 may be, e.g_ a straight or a tapered
homogenizer, as shown in Fig. 26. Homogenizer 2202 may be made of, e.~c .
quartz,
glass, plastic, or acrylic.
[0077] Sources of electro-luminescence 2014 may be, e.g_ sources of injection
electro-luminescence, such as a forward-biased p-n junction, or a light-
emitting diode.
Radiation 2016 may be, e.g_, recombination radiation. Output ends 2022 may be,
e,g:,
substantially convex. Sources of electro-luminescence 2014 may each, e.g_
output a
range of wavelengths 2024 which may be, e.g,; white racliation, infrared
radiation, red
radiation, orange radiation, yellow radiation, green radiation, blue
radiation, indigo
radiation, violet radiation, and ultraviolet radiation.
[0078] Each of plurality of light pipes 2018 may be, e.~c . a tapered light
pipe or a
straight light pipe, as shown in Fig. 26. A cross-section of each of plurality
of light pipes
2018 may be, e.c,~. a rectangle, a circle, a triangle, a rhombus, a trapezoid,
a pentagon,
a hexagon, or an octagon, as shown in Fig. 27.
(0079] Each of plurality of reflectors 2008 may be, erlc ., at least a portion
of a
substantially ellipsoidal surface of revolution, at least a portion of a
substantially toroidal
surface of revolution, at least a portion of a substantially spheroidal
surface of
revolution, or at least a portion of a substantially dual paraboloidal surface
of revolution.
CA 02471451 2004-06-17
In one embodiment, each of plurality of reflectors 2008 has a coating that
reflects only
a pre-specified portion of the electromagnetic radiation spectrum, such as,
e.g_. visible
light radiation, a pre-specified band of radiation, or a specific color of
radiation.
[0080] In Fig. 21 is shown a plurality of reflectors for use with an eighth
embodiment
of the invention. In the eighth embodiment, each of plurality of reflectors
2108
comprises a primary reflector 2124 having a first optical axis 2126 and a
secondary
reflector 2128 having a second optical axis 2130. Each of secondary reflectors
2128 is
placed substantially symmetrically to a corresponding one of primary
reflectors 2124
such that first and second optical axes 2126, 2130 are substantially
collinear. Each of
first focal points 2010 is a focal point of a corresponding one of primary
reflectors 2124
and each of second focal points 2012 is a focal point of a corresponding one
of
secondary reflectors 2128.
[0081] Primary reflector and secondary reflector 2124, 2128 may be, e.g_ at
least a
portion of a substantially paraboloidal surface of revolution. In one
embodiment,
primary reflector 2124 comprises at least a portion of a substantially
ellipsoidal surface
of revolution, and secondary reflector 2128 comprises at feast a portion of a
substantially hyperboloidal surface of revolutian. 1n another embodiment
primary
reflector 2124 comprises at least a portion of a substantially hyperboloidal
surface of
revolution, and secondary reflector 2128 comprises at least a portion of a
substantially
ellipsoidal surface of revolution. Of course, primary reflector and secondary
reflector
2124, 2128 may be, e.~c . a single reflector, which may beg, e.g_ at least a
portion of a
substantially ellipsoidal surface of revolution, at least a portion of a
substantially toroidal
surface of revolution, at least a portion of a substantially spheroidal
surface of
revolution, or at least a portion of a substantially dual paraboloidal surface
of revolution
[0082] In Fig. 23 is shown an illumination engine 2300 according to the
seventh or the
eighth embodiment of the invention with a waveguide 2302 disposed
substantially
proximate to plurality of output ends 2304. Waveguide 2302 may be, e.~.c . a
single core
optic fiber, a fiber bundle, a fused fiber bundle, a polygonal rod, or a
hollow reflective
light pipe, as shown in Fig. 28.
[0083] In one embodiment, a first etendue 2306 is associated with plurality of
output
21
,..n~..~su.~m..;wn~~m m .,y.mmja»,...,xsm."e.:aaro..,em,..,..rvFrfrT.Pamr-
~.yeah..~-a~tawcal~"'=t~wf~s~,~p~s~''~.s°marmaaF.~:~mm~-.m,.,.,,....-.
:H.,..~~,v",~: ".,a...........--.._~,.__ .. .....
CA 02471451 2004-06-17
ends 2304, while a second etendue 2308 is associated with homogenizer 2302,
such
that first etendue 2306 is substantially equal to second etendue 2308. A cross-
section
of waveguide 2302 may be, e:g: a circle, or a polygon, as shown in Fig. 29. In
another
embodiment, waveguide 2302 may be a tapered waveguide. ~Illaveguide 2302 may
be
made of, e.g_, quartz, glass, plastic, or acrylic.
[0084] In Fig. 24 is shown an illumination engine 2400 according to the
seventh or the
eighth embodiment of the invention with a fiber optic 2402 disposed
substantially
proximate to plurality of output ends 2404. Fiber optic 2402 may be
illuminated by
radiation 2416 transmitted at plurality of output ends 2404, the fiber optic
2402
releasing the collected and condensed radiation 2416 to provide for
illumination at a
desired location 2418.
[0085] In one embodiment, a first etendue 2406 is associated with plurality of
output
ends 2404, while a second etendue 2408 is associated with fiber optic 2402,
such that
first etendue 2406 is substantially equal to second etendue 2408.
[0086] In Fig. 25 is shown an illumination engine 2500 according to the
seventh or the
eighth embodiment of the invention with a condenser lens 2502 disposed
substantially
proximate to plurality of output ends 2504 and an image projection system 2510
disposed substantially proximate to an output side of condenser lens 2502.
Projection
system 2510 may display an image 2512 being illuminated by the radiation 2514
transmitted at plurality of output ends 2504. An additional light pipe may be
placed
between the plurality of output ends 2504 and the condenser lens 2502 for
improved
uniformity of the output.
[0087] In one embodiment, a first etendue 2518 is associated with plurality of
output
ends 2504, while a second etendue 2520 is associated ~nrith condenser lens
2502, such
that first etendue 2518 is substantially equal to second et:endue 2520.
[0088] In a tenth embodiment of the invention, a method of illumination
comprises the
steps of i) positioning a source of electro-luminescent radiation at a first
focal point of a
reflector, ii) producing rays of radiation by the source, iii) reflecting the
rays of radiation
by the reflector toward a second focal point of the reflector, iv) converging
the rays of
radiation at second focal point, v) positioning a fight pipe having an input
end and
22
CA 02471451 2004-06-17
output end so the input end is substantially proximate to the second focal
point, vi)
collecting the rays of radiation at the input end, vii) passing the rays of
radiation through
the light pipe, and vii) outputting the rays of radiation from the output end
of the light
pipe.
(0089] While the invention has been described in detail above, the invention
is not
intended to be limited to the specific embodiments as described. It is evident
that those
skilled in the art may now make numerous uses and modifications of and
departures
from the specific embodiments described herein without departing from the
inventive
concepts.
23
