Note: Descriptions are shown in the official language in which they were submitted.
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ETENDUE EFFICIENT COMBINATION OF MULTIPLE LIGHT SOURCES
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims benefit of U.S. Provisional Application
No.
60/651,079 filed February 9, 2005, and the present application is a
continuation-in-part of
Application Serial No. 11/240,169 filed September 30, 2005, which is a
continuation of
Application Serial No. 10/347,522 filed January 21, 2003, now U.S. Patent No.
6,982,830,
which is a continuation of Application Serial No. 09/814,970, filed March 23,
2001, now
U.S. Patent No. 6,587,269 which claims benefit of U.S. Provisional Application
No.
60/227,312 filed August 24, 2000 and 60/246,683 filed November 8, 2000, all of
which are
incorporated by reference in their entireties.
FIELD OF THE INVENTION
[0002] The present invention relates an improved system and methodology for
providing inulti-colored illuinination without increasing the etendue of the
system.
BACKGROUND OF INVENTION
[0003] A liquid crystal display (hereafter "LCD") is a known device used to
control
the transmission of polarized light energy. The LCD may be either clear or
opaque
depending on the current applied to the LCD. Because of this functionality,
projection
systein coirunonly use an array containing numerous LCDs to form an image
source. In
particular, the projection system inputs high intensity polarized light energy
to the LCD
array (also called an imager), which selectively transmits some of the
inputted light energy
to form a projection of a desired image. Because a single LCD is relatively
small,
nuinerous LCDs can be packed together into the array, thereby forming an
imager that can
produce a high resolution image.
[0004] As suggested above, a projection system inust first polarize the light
input
to the LCD. However, light energy from a light source, such as a bulb, may
have either p-
polarization or s-polarization. Since this light input to the LCD imager must
be in one
orientation (i.e., either p-polarization or s-polarization), the LCD projector
generally uses
only half of the light energy from the light source. However, it is desirable
in projection
systeins to maximize the brightness and intensity of the light output. In
response, various
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mythologies have been developed to capture the light energy of unusable
polarization, to
convert the polarization of this captured light energy, and then to redirect
the converted
light energy toward the LD imager. These known polarization recovery
methodologies
involve creating an expanded beam of light in which the unused portion of the
light (of
undesired polarity) is sent through a half-wave plate to change the
polarization and then
recombined with the original polarized beam. Unfortunately, the implementation
of these
known methodologies requires complex, bulky systems, which usually include 2-
dimensional lens arrays and an array of polarization beain splitters.
Furthermore, the
known methodologies lose inuch of the light energy and, therefore, compromise
the
projector's goal of producing a high intensity output.
[0005] Light pipe systems have been used to separate white light into their
individual red (R), blue (B), and green (G) components using light pipes,
prisms, and beam
splitters. The reverse of such a system can be used in combining multiple
light sources
with distinct spectrum without increase in etendue. Therefore, it is desirable
to have a
systein the provides multi-colored illuinination witllout the need to increase
etendue.
SUMMARY OF THE INVENTION
[0006] In response to these needs, the present invention uses a waveguide
system
to perform the polarization recovery function in an LCD projection system. In
particular,
the present invention's waveguide polarization recovery system both polarizes
the input
light energy for use with an LCD imager and converts the polarity of unusable
light energy
to add to the illumination of the LCD imager. The compact polarization
recovery
waveguide system generally includes the following optical coinponents that are
integrated
into a single unit: (1) an input waveguide that inputs non-polarized light
energy into the
system; (2) an output waveguide that removes polarized liglit energy from the
system; (3) a
polarized beam splitter that receives the light energy from the input
waveguide and
transmits light energy of a first polarization type and reflects light energy
of a second
polarization type, and (4) a wave plate that modifies the polarization of
either the
transinitted or reflected light energy. The polarization recovery system also
generally
includes one or more miirors that are positioned as needed to direct the
transmitted and/or
reflected light energy to the output waveguide. The input and output
waveguides may be
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shaped as needed by the projection system. For example, either one or both of
the input
and output waveguides may be tapered up or down as needed to produce a desired
image.
[0007] In the waveguide polarization recovery system, the input and output
waveguides are configured to have either a substantially parallel or a
substantially
perpendicular orientation. In configurations in which the input and output
waveguides are
substantially parallel, the output waveguide directly receives light energy
transmitted by
the beam splitter. In this way, light energy enters and exits the polarization
recovery
system in substantially the same direction. Alternatively, the input and the
output
waveguides may be positioned substantially perpendicular to each other such
that the light
energy exits the polarization recovery system at a right angle from the
direction it enters.
In configurations having input and output waveguides of perpendicular
orientation, a
mirror receives the light energy transmitted by the polarized beam splitter
and redirects this
energy by 90 C toward the output waveguide.
[0008] The polarization recovery waveguide system of the present invention
combines the above-enumerated list of optical components into a single,
compact unit. In
one enbodiment, the waveguide polarization recovery system further includes
one or more
"gaps" of optically clear material positioned between the optical components
to encourage
the occurrence of total internal reflection that minimizes the loss of the
optical energy by
the system.
[0009] In the field of LED illumination, each LED generally emits a single
color.
For multi-color applications, N LEDs are used, typically N> 2. Typically, N
LEDs, e.g., 2
LEDs, are place side by side and coupled into the saine target. By varying the
output of
each LED, the desired color and brightness can be achieved. To combine color
in this
manner, the etendue of a typical illumination system inust be increased as the
area of
emission is increased. Accordingly, in accordance with an embodiment of the
present
invention, a light pipe based systein combines the colors without increasing
the etendue.
[0010] In accordance with an embodiment of the present system, a multi-colored
illumination system coinprising a beam combiner. The bealn combiner comprises
two
triangular prisms and a filter for transmitting a first light and reflecting a
second light, eacll
light having a different wavelength. The beam coinbiner combines the
transmitted first
light and the reflected light to provide a coinbined beam. Each surface of the
triangular
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prisms is polished, thereby combining the lights without increasing etendue of
the multi-
colored illumination system.
[0011] In accordance with an embodiment of the present invention, a multi-
colored
illumination systein comprises n beain combiners for combining n+l lights,
where N > 2,
each light having a different wavelength, and a low index glue or air gap
provided between
each beam combiner. Each beam combiner comprises two triangular prisms, each
surface
of the triangular prisms being polished and a filter for transmitting a
combined beain
received from a previous beam combiner and reflecting a new light from n+l
lights which
has not been previously transmitted or reflected. The beam combiner combines
the
transmitted coinbined beam and the reflected new light to provide a new
combined beam.
The new combined beam is provided to the next beam combiner if the beam
combiner is
not the last beam combiner or outputs the new combined beam if the beam
combiner is the
last beam combiner. The low index glue or air gap between each beam combiner
enables
the multi-colored illumination system to combined all of the lights without
increasing
etendue of the multi-colored illumination system.
[0012] In accordance with an embodiment of the present invention, a multi-
colored
illumination system comprises at least two LEDs, a light pipe associated with
each LED,
an X-cube and a low index glue or air gap. The two LEDs provide two lights
having two
different wavelengths. The X-cube combines the lights received from each light
pipe
associated with a LED to provide an output beam. The low index glue or air gap
is
provided between each of the light pipe and the X-cube, thereby combining the
lights
without increasing etendue of the multi-colored illumination system.
[0013] In accordance with an embodiment of the present invention, a light
engine
comprising the multi-colored illumination systein as aforesaid.
[0014] In accordance with an embodiment of the present invention, a projection
display systein comprising the light engine as aforesaid, at least one light
modulator panel
for inodulating light in accordance with a display signal; and a projection
lens for
projecting the modulated light onto a display screen.
[0015] In accordance with an embodiment of the present invention, a method for
inulti-colored illumination coinprises the steps of combining by a first beam
coinbiner a
first light transmitted by a first filter and a second light reflected by the
first filter to
provide a coinbined beazn; coinbining by a second beam combiner the coinbined
beain
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transmitted by a second filter and a third light reflected by the second
filter to provide an
output beam, each light having different wavelength; and providing a low index
glue or air
gap between the beam combiners, thereby combining the lights without
increasing etendue.
[0016] In accordance with an embodiment of the present invention, a method for
multi-colored illumination comprises the steps of combining by an X-cube at
least two
lights having two different wavelengths received from corresponding two light
pipes; and
providing a low index glue or air gap between each light pipe and the X-cube,
thereby
combining the lights without increasing etendue.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] These and other advantages of the present invention will be described
in
detail with reference to the following drawings in which like reference
numbers refer to
like elements:
[0018] Figs. 1-4 and 6-10 are scheinatic diagrams of the waveguide
polarization
recovery system in accordance with various einbodiments of the present
invention;
[0019] Fig. 5 is a schematic diagram of a compact projection device
incorporating
the polarization recovery system in accordance witll an embodiment of the
present
invention;
[0020] Fig. 11 is a schematic diagram of a light pipe comprising a 90 turn
without
an air gap or low index glue;
[0021] Fig. 12 is a schematic diagram of a light pipe comprising a 90 turn
with air
gaps or low index glue in accordance with an embodiment of the present
invention;
[0022] Fig. 13A-B are schematic diagrains of a light pipe based color system
in
accordance with an embodiment of the present invention;
[0023] Fig. 14 is a schematic diagram of a light pipe based color system in
accordance with an embodiment of the preseiit invention;
[0024] Fig. 15 is a schematic diagram of a light pipe based color system
comprising a X-cube in accordance with an einbodiment of the present
invention;
[0025] Fig. 16 is a schematic diagram of a light pipe based color systein
comprising a X-cube in accordance with an einbodiment of the present
invention;
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[0026] Fig. 17 is a schematic diagram of a light pipe based color system
comprising an array of LED sources in accordance with an embodiment of the
present
invention;
[0027] Fig. 18 is a schematic diagram of a projection system incorporating the
light
pipe system of the present invention;
[0028] Fig. 19 is a graph illustrating the peak or high intensity sections of
blue,
green and red light; and
[0029] Fig. 20 is a graph illustrating the red light formed from combining
three
different red lights having different high intensity sections.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0030] As illustrated in Figs. 1-4 and 6-10, in accordance with embodiments of
the
present invention, a compact waveguide polarization recovery system 10
comprises an
input waveguide 20, a polarizing beam splitter ("PBS") 30, a wave plate 40,
which can be
a half-wave plate, or a quarter-wave plate depending on the configuration, and
an output
waveguide 50. The waveguide polarization recovery system 10 generally fiirther
includes
mirrors 60 as needed to direct the light streain between the input and output
waveguides,
20 and 50. The following discussion first summarizes several possible
configurations for
the waveguide polarization recovery system 10 and then describes the
individual elements
in greater detail.
[0031] Figs. 1, 3, and 6 illustrate one configuration of the waveguide
polarization
recovery systein 10 in which the output light energy is substantially parallel
with the input
light energy. In this embodiment, the input waveguide 20 introduces
unpolarized input
light from a light source or LED light source at incidence to the PBS 30. The
illustrated
PBS 30 transmits p-polarized light, and so the p-polarized portion of the
input light energy
continues through in the saine direction as the initial input while the s-
polarized light is
reflected in a perpendicular direction to the initial direction of input. The
half-wave plate
40 is positioned to receive the reflected s-polarized light and convert it to
p-polarized.
Subsequently, mirror 60 redirects the converted energy from the half-wave
plate 40 back to
the initial direction of input. Both the transmitted light energy from the PBS
30 and the
converted light energy from the half-wave plate 40 are recoinbined in the
output
waveguide and mixed. AS a result, the output light energy has a unifoi7n
intensity profile
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and is polarized. It should be appreciated that an output of the opposite
polarization may
be produced through the use of a PBS 30 that only transmits s-polarized light.
[0032] Figs. 2, 4, and 7-8 illustrate an embodiment of the waveguide
polarization
recovery system 10 that has an alternative configuration in which the output
light energy is
perpendicular to the original input light energy. As in the embodiment of Fig.
1, the input
waveguide 20 introduces unpolarized input light at incidence to the PBS 30.
Furthermore,
the PBS 30 performs the same function of transmitting the p-polarized light,
and so the p-
polarized portion of the input ligla.t energy continues through in the same
direction as the
initial input while the s-polarized light is reflected in a perpendicular
direction to the initial
direction of input. However, in the configuration of Fig. 2, one mirror 60
redirects the
transmitted p-polarized portion of the input light energy by 90 toward the
output
waveguide 50. Furthermore, the reflected s-polarized light from the PBS 30
propagates
once through a quarter-wave plate 40', and a second mirror 60 then returns the
reflected
light energy to the quarter-wave plate 40' for another pass. The second pass
is also in the
direction of the output waveguide 50. Because the reflected s-polarized light
passes twice
through the quarter-wave plate 40', s-polarized light is shifted by a half-
wave to becoine p-
polarized twice wit11 the mirror as shown. Again, both p-polarized outputs
will be mixed
in the output waveguide, producing a uniform intensity output. The embodiment
of Fig. 2
requires only two optical sections: A first section formed through the
coinbination of the
input waveguide 20, the PBS 30, the quarter-wave plate 40' and a mirror 60;
and a second
section formed through the combination of the output waveguide 50 and a second
mirror
60. Therefore, the system has a simple design and a relatively low cost.
Positioning the
output light energy perpendicular to the original input light energy also has
the advantage
of allowing a more compact projection system, as described in greater detail
below.
[0033] In contrast to the above-described configuration in which the wave
plate 40
modifies the light energy reflected by the PBS 30, otlier configurations for
the waveguide
polarization recovery systein 10 position the wave plate to modify the light
energy
transmitted by the PBS 30. For example, Figs. 9 and 10 illustrate
configurations in which
the half-wave plate 40 is positioned to receive light energy transmitted by
the PBS 30. In
the configuration of Fig. 9, the half-wave plate 40 is optically positioned
between a mirror
60 and the output waveguide 50. The half-wave plate 40 receives transmitted
ligllt energy
that has first been redirected by a mirror 60. Similarly, in Fig. 10, the half-
wave plate 40 is
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placed between the PBS 30 and mirror 60. In this way, the transmitted light
energy from
the PBS 30 is first repolarized before being redirected toward the output
waveguide 50.
The configurations of Figs. 9-10 are advantageous because the input light
energy only
passes through the polarization layer of the PBS 30 once, thus reducing the
loss of optical
energy in the systein 10. In contrast, the above-described configuration of
the Figs. 2, 4,
and 7-8 requires some of the input light energy to pass through the PBS 30
twice.
[0034] The various configurations of the waveguide polarization recovery
system
use the same elements, which are now described in greater detail.
[0035] The input waveguide 20 is typically an integrator that collects the
light from
a light source, such as an arc lamp, and mixes the light through inultiple
reflections to
produce a more uniform intensity profile into the waveguide polarization
recovery system
10. Likewise, the output waveguide 50 is typically an integrator that collects
the light from
the waveguide polarization recovery system 10 and mixes the light through
multiple
reflections to produce a more uniform intensity profile for illumination of
the ilnager. The
input waveguide 20 and the output waveguide 50 may be, for example, single
core optic
fibers fused bundles of optic fibers, fiber bundles, solid or hollow square or
rectangular
light pipes, or homogenizers, which can be tapered or un-tapered. In optical
projection
systems, the input waveguide 20 and the output waveguide 50 are typically
rectangular in
cross-section to correspond with the shape of the imager and the final
projected image.
The input waveguide 20 and the output waveguide 50 wave can be made from
glass,
quartz, or plastic depending on the power-handling requirement.
[0036] Either one or both of the input waveguide 20 and the output waveguide
50
can have an increasing or decreasing taper as needed for the projection
system. For
example, Fig. 3-4 and 6-10 illustrate embodiments of the waveguide
polarization recovery
system 10 in which the input waveguide 20' is a tapered rod witll the input
cross-section
matched to the area of the light source and the output cross-section related
to the
dimension of a LCD imager. The final dimensions for the input waveguide 20 may
vary as
needed to minimize stray light loss in the optical projection systein.
Similarly, Fig. 8
illustrates an ernbodiinent of the waveguide polarization recovery systein 10
in wliich the
output waveguide 50' is also tapered. Tapering of the output waveguide 50' is
advantageous because, depending on the perfonnance parameters of the PBS 30,
the wave
plate 40, and the output requirements for the projection system, polarization
recovery may
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not always be done at the same numerical aperture as the output aperture. The
performances of the PBS 30 and the wave plate 40 are better at smaller
numerical
apertures, and as a result, advantageous increases in performance are achieved
by
transforming the input light energy into a larger area with a small numerical
aperture and
then transforming the light energy back into larger numerical aperture at the
output of the
output waveguide 50'. Overall, the tapering of the input wave guide 20 and the
output
waveguide 50 can be selected to match the overall performance requirements of
the
projection system, and similarly, the input and output waveguides can be
tapered in either
direction.
[0037] The waveguide polarization recovery system 10 further includes PBS 30.
The PBS 30 is a well-known optical element that transmits ligllt energy of one
polarization
while reflecting light energy of a different polarization. Typically, the PBS
30 is a
rectangular prism of optically clear material, such as plastic or glass, that
has a polarizing
coating applied to the diagonal surface. Alternatively, the PBS 30 may be
coinposed of a
material that selectively transmit light energy depending on the polarization
of the light
energy. However, it should be appreciated that there exist numerous
alternative designs
and types of PBS, and any of these alternative PBS's may be einployed in the
waveguide
polarization recovery system 10 of the present invention. Because the PBS 30
is a well
known and commercially available item, it is not discussed further.
[0038] Another element of the waveguide polarization recovery system 10 is the
wave plate 40. The wave plate 40 is an optically transparent component that
modifies the
polarization of light energy that passes through the wave plate 40. The wave
plate 40
typically cllanges the propagating of light in one axis, thus changes the
polarization. The
wave plate 40 may be either a half-wave or quarter-wave as needed by the
specific
configuration of the waveguide polarization recovery system 10. Overall, the
wave plate
40 is a well known and coinmonly available item and will not be discussed
further.
[0039] The waveguide polarization recovery systein 10 may further include one
or
more mirror 60 as needed to direct the light energy through the waveguide
polarization
recovery systein 10. While mirrors are commonly known to be metal-coated glass
surfaces
or polished metal, the inirrors 60 should not be limited to this common
definition for the
purpose of this invention. Instead, mirrors 60 should be considered any
optical coinponent
capable of reflecting or redirecting liglit energy. For exainple, mirrors 60
may be replaced
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with a light pipe, e.g., a prism or light pipes having a turn, e.g., 90 turn,
(collectively
referred to herein as a prism), that use the angle of incidence to capture and
redirect light
energy. For example, Figs. 9 and 10 illustrate a waveguide polarization
recovery system
that has a prism to guide or redirect light energy transmitted by the PBS 30
toward the
output waveguide 50. For systems with small numerical apertures, total
internal reflection
at the prism can be used, and as a result, the coating is not necessary.
[0040] In another preferred embodiment of the present invention, illustrated
in
Figs. 6-10, the waveguide polarization recovery system 10 further includes one
or more
optically clear area, low index glue, or "gaps" 70, between the other optical
eleinents
(collectively referred to herein as the gap). The gaps 70 may be pockets of
air left between
the optical components. The gap 70 can also be filled with low index epoxy or
other
transparent material such that the total internal reflection still occurs, but
the assembly of
the components will be simplified. For example, Fig. 6 illustrates a
configuration having
gap 70 between the input waveguide 20 and the PBS 30. This gap 70 ensures that
light
energy reflected by the diagonal PBS 30 is turned by 90 toward the quarter-
wave plate 40'
because total internal reflection from the interface between the PBS 30 and
the gap 70
prevents the light energy from returning instead to the input waveguide 20 and
exiting as a
loss. The waveguide polarization recovery systein 10 in Fig. 6 also has other
gaps 70 to
promote total internal reflection between the different optical elements.
Similarly, Fig. 7
illustrates a waveguide polarization recovery system 10 in which gaps 70 have
been added
to a polarization recovery system with a tapered input waveguide 20 and
perpendicularly
configured output waveguide 50 illustrated in Fig. 4. Again these gaps 70
increase the
efficiency by encouraging total internal reflection between the optical
components. As
illustrated in Figs. 6-7, the gaps 70, while increasing the efficiency of the
system, cause the
waveguide polarization recovery system 10 to become more complex with an
increased
number of discrete parts.
[0041] In the above-described configurations of Fig. 9-10, the gaps 70 further
serve
the purpose of improving the performance of the prism 60' that serves as a
mirror to direct
the light energy toward the output waveguide 50. In particular, the gap 70 is
needed
between the PBS 30 and the prism 60' such that the light reflected from the
hypotenuse of
the prism 60', baclc toward the PBS 30, hits this interface of the gap 70 and
is internally
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reflected toward the output waveguide 50. In this way, efficiency of the
system is
improved by minimizing loss.
[0042] The performance advantages of the gaps 70 may be further increased
through the use of anti-reflection coating on botlz surfaces such that the
transmitted light
suffers minimal loss.
[0043] Fig. 5 illustrates a projector 100 that employs the waveguide
polarization
recovery system 10. The projector 100 consists of a light collecting system
110, which is
this illustrated example has two paraboloid reflectors and a retro-reflector
that increase the
output by reflecting the light from a light source 120 back into itself. The
arc of the light
source 120 is placed at a focus of the first paraboloid reflector and the
proximal end of the
input waveguide 20 is at the focus of the second paraboloid reflector. It
should be
appreciated that this light collection system 110 is provided merely for
illustration, and
many other ligllt collection systems are known and may be used. Likewise, the
light
source 120 may be an arc lamp, such as xenon, metal-halide lainp, HID, or
mercury lamps,
or a filainent lamp, such as a halogen lamp, provided that the system is
modified to
accommodate the non-opaque filaments of the lamp.
[0044] Within the illustrated projector 100, the input waveguide 20 is a
tapered
light pipe that is designed to match the light input collected from the light
collecting
system 110 to the optical needs of an LCD imager 150. As described above in
Fig. 4, the
light output of the input waveguide 20 is polarized by the PBS 30 and the
other
polarization is recovered by the quarter-wave plate 40'. The output waveguide
50 then
directs the polarized optical energy toward the LCD imager 150. In this case,
the light
output in the output waveguide 50 is then incident into a second PBS 130 whose
orientation is matched to the polarization of the incident light to minimize
the loss. A
color wheel 140, or other type of color section systein, and the reflective
LCD imager 150
create the projected image by the projection lenses 160 in a traditional
manner. As shown
in Fig. 5, the number of optical elements is minimal and, as the result, the
cost for the
projector is relatively low.
[0045] It should be appreciated that the waveguide polarization recovery
system 10
inay be used in other types of projection systeins. For example, the projector
may also use
two or three imagers 150 to define the projected image. The imager 150 inay
also be a
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reflective display using liquid crystal on silicon ("LCOS") technology, or any
other type of
systems that requires polarized systems.
[0046] Turning now to Fig. 11, there are illustrated light pipes 20, 50 with a
turn,
e.g., 90 turn, without an air gap or low index glue, and various light paths
inside the light
pipes. Some high angle light will be lost, thus reducing the efficiency of the
light pipe
system. In accordance witli an embodiment of the present invention, the light
pipe system
200 comprises light pipes 20, 50 comprising air gaps or low index glue 70 as
shown in Fig.
12. The light, e.g., light paths (a) and (c), that are lost in Fig. 11 are
recaptured by total
internal reflection and collected by the output light pipe 50 of the light
pipe system 200.
[0047] In accordance with an embodiment of the present invention, as shown in
Fig. 13A, the color system 300 comprises beam combiners 310, 320, air gaps or
low index
glue 70 and three light sources, namely, red (R), green (G), and blue (B).
Each light input
is coupled directly or indirectly through a light pipe or lens system 200 (not
shown but
such as one shown in Fig. 12), into the color system 300. Each beam combiner
comprises
a filter and two prisms or beam splitters, preferably triangular prisms with
all of the
surfaces polished. The first beain combiner 310 with filter A transmits red
light (R) and
reflects green light (G). It is appreciated that the filter A is controlled,
tuned or selected to
transmit red light (R) and reflect green light (G). The red light (R) from the
input is
transmitted by the first combiner 310 and the green light (G) from the other
face of the first
combiner 310 is reflected. The reflected green light (G) combines with the
transmitted red
light (R) and exit together out of the same face of the combiner 310. The
combined
red/green light (R, G) then enters the second combiner 320 with a filter B,
which transmits
the red and green light (R, G), and reflects the blue light (B). It is
appreciated that the filter
B is controlled, tuned or selected to transmit red and green light (R, G) and
reflect the blue
light (B). As a result, the red/green light will continue to pass through the
second
combiner 320 and the blue light (B) from the blue input is reflected by the
second
combiner 320. The reflected blue light (B) coinbines with the transmitted red
and green
light (R, G) and the combined light (R, G, B) exit the color system 300
together. It is
appreciated that the output intensity and color are controlled by the ainount
of each color
light inputted into the color systein 300. Additionally, it is appreciated
that the placement
of liglit source is arbitrary and depends on the application of the color
systein 300. That is,
instead of green light (G) being inputted to the first beam combiner 310, the
blue light (B)
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can be inputted to the first beam combiner 310 provided that the filter A is
now tuned to
reflect blue light (B) instead of green light (G). The output beain of the
color system 300 of
the present invention occupies the same cross-section area of an individual
input beam,
thus preserving the same etendue of a single light source. The efficient
coupling of the
light is accomplished by providing an air gap or low index glue 70 between the
various
optical components, such the beam combiners 310, 320. In accordance with an
aspect of
the present invention, the combined output beam of the color system 300 of the
present
invention can be used for fiber optic illuminations or for projection display
applications,
e.g., a light engine for a projection display system.
[0048] In accordance with an embodiment of the present invention, as shown in
Fig. 13B, the color system 300 comprises a beam combiner 310 and two light
sources,
namely, red (R) and green (G). Each light input is coupled directly or
indirectly through a
light pipe or lens systein 200 (not shown but such as one shown in Fig. 12),
into the color
system 300. Each beam combiner comprises a filter and two prisins or beam
splitters,
preferably triangular prisms with all of the surfaces polished. The beam
combiner 310
with filter A transmits red light (R) anc? reflects green light (G). It is
appreciated that the
filter A is controlled, tuned or selected to transmit red light (R) and
reflect green ligllt (G).
The red light (R) from the input is transmitted by the first combiner 310 aild
the green light
(G) from the other face of the first combiner 310 is reflected. The reflected
green light (G)
combines with the transmitted red light (R) and exit together out of the saine
face of the
combiner 310. It is appreciated that the output intensity and color are
controlled by the
ainount of each color light inputted into the color system 300. Additionally,
it is
appreciated that the placement of light source is arbitrary and depends on the
application of
the color system 300. That is, instead of green light (G) being inputted to
the beam
combiner 310, the blue light (B) can be inputted to the beam combiner 310
provided that
the filter A is now tuned to reflect blue light (B) instead of green light
(G). The output
beam of the color system 300 of the present invention occupies the same cross-
section area
of an individual input beain, thus preserving the saine etendue of a single
light source. The
efficient coupling of the ligllt is accoinplished by the reflective polished
surfaces of the
triangular prisms. In accordance with an aspect of the present invention, the
combined
output beam of the color system 300 of the present invention can be used for
fiber optic
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illuminations or for projection display applications, e.g., a light engine for
a projection
display system.
[0049] In accordance with an embodiment of the present invention, each input
light
source (R, G or B) in Fig. 13A-B is a LED light source coupled to a straight
or tapered
light pipe 330, as shown in Fig. 14. Although a tapered up light pipe 330 is
shown in Fig.
14, it is appreciated that a tapered down light pipe 330 can be also utilized.
As shown in
Fig. 17, it is appreciated that the light sources can be a plurality of LED
lights sources or
arrays of LED light sources Il - I,,, each providing light with different
color or wavelength
where n--> 2. Optionally, a light source Io can be provided as an input to the
beam combiner
BC1 which transmits the light from the light source Io to the next beam
coiubiner BC2.
Light or light energy from each light source Ij is reflected by the
corresponding beam
combiner BCj comprising a filter Fj matching the wavelength of the light from
the
corresponding light source Ij. The reflected light Ij combines with the
transmitted light Io
... Ij_1 and the combined light Io ... Ij then enters the next beam combiner
BCj-,-1. Finally
the combined light Io ... Iõ exits the beam combiner BCõ and enters the
straight, tapered up
or tapered down output light pipe 430 Although not shown, eacli light source
can be
coupled to a straight, tapered up or tapered down light pipe 330 as shown in
Fig. 14.
[0050] When enhanced or better color is required by a particular application
of the
present invention, a plurality of LEDs whicll generate various colors can be
used so that a
large area is covered in the color coordinate space. In a projection display
system, a 6-
colored system has been known to provide more vivid and saturated colors. In
accordance
with an embodiment of the present invention, a n-colored projection display
system
comprises a n different LED light sources (I1 ... Iõ) providing n different
colored light or
lights with n different wavelengths, as shown in Fig. 17. The filter Fj is
controlled, tuned
or selected to matcli the wavelength %j of the LED light source Ij such that
it reflects only
light having wavelength %j.
[0051] In accordance with an exemplary einbodiment of the present invention,
the
brightness of the output light can be controlled and increased with
appropriate selection of
the filters and light sources to provide a inore vivid and intense colors. For
example, each
filter Fj can be controlled, tuned or selected to filter out the low-intensity
portion of the
light or light energy from the corresponding light or LED source, thereby
propagating only
high-intensity portion of the light and resulting in a brighter output beam.
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[0052] In accordance with an exemplary embodiment of the present invention, as
shown in Fig. 20, multiple LED light sources can be used to enhance a single
color, e.g.,
red. Typically, as shown in Fig. 19, each light has a high-intensity section,
e.g., the red
light has a high-intensity section XR and the blue light has a high-intensity
section %$. For
example, three different red lights Rl, R2 and R3 respectively having high-
intensity sections
XR1, Xp2 and XR3 are combined to form a single high-intensity red light to be
inputted into
the X-cube 410 or the beam combiner 310, 320 or BCi. The corresponding filters
FR1, FR2
and FR3 respectively filter out the low-intensity sections of the red lights
Rl, R2 and R3.
[0053] In accordance with an embodiment of the present invention, as shown in
Figs. 15 and 16, the color system 400 comprises a X-cube color combiner 410
(or X-cube
410) for combining beams of light without increasing the etendue of the color
system 400.
Each light source (Fig. 16) or a LED light source (Fig. 15) is coupled to a
straight, tapered
up or tapered down light pipe 420. The red light (R) from the red light source
or red LED
liglit source enters the X-cube 410 from a first input face of the X-cube 410
via the
straight, tapered up or tapered down light pipe 420. The red light (R) is
transmitted by the
X-cube 410 and exits out of the output face of the X-cube 410 and into a
straight, tapered
up or tapered down output light pipe 430. The green light (G) from the green
light source
or the green LED light source enters the X-cube 410 from a second input face
of the X-
cube 410 via the straight, tapered up or down light pipe 420. The X-cube 410
reflects the
green light (G). The reflected green light (G) combines with the transmitted
red light (R)
and exit together out of the saine output face of the X-cube 410 and into the
straight,
tapered up or tapered down output light pipe 430. The blue light (B) from the
blue light
source or the blue LED light source enters from a third input face of the X-
cube 410 via the
straight, tapered up or tapered down light pipe 420. The X-cube reflects the
blue light (B).
The reflected blue light (B) coinbines with the transmitted red light (R) and
the reflected
green light (G), and exit together out of the same output face of the X-cube
410 and into
the straight, tapered up or tapered down output light pipe 430. The light
pipes 420, 430
can be, for exainple, single core optic fibers fused bundles of optic fibers,
fiber bundles,
solid or liollow square or rectangular light pipes, or homogeiiizers, which
can be tapered
up, tapered down or un-tapered. It is appreciated that the output intensity
and color are
controlled by the amount of each color liglit inputted by the corresponding
light source or
LED liglit source into the color systein 400. Additionally, it is appreciated
that the
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placement of light source is arbitrary and depends on the application of the
color system
400. That is, instead of green light (G) being inputted to the second input
face of the X-
cube 410, the red light (R) can be inputted to the second input face of the X-
cube 410. The
output beam of the color system 400 of the present invention occupies the same
cross-
section area of an individual input beam, thus preserving the same etendue of
a single light
source. The efficient coupling of the light is accomplished by providing an
air gap or low
index glue 70 between the various optical components, such as X-cube and the
straight,
tapered up or tapered down light pipes 420, 430. In accordance with an aspect
of the
present invention, the combined output beam of the color system 400 of the
present
invention can be used for fiber optic illuminations or for projection display
applications,
e.g., a light engine for a projection display system.
[0054] In accordance with an aspect of the present invention, the efficient
coupling
of the light is accomplished by providing an air gap or low index glue 70
between the
various optical components, such as light pipes 20, 50, 330, prisms and beam
combiners
310, 320, BCl - BC11. These air gaps or low index glue 70 provide total
internal reflections
for angled light to be reflected back in+o the color systein 300 whicli would
otherwise be
lost, thereby minimizing or eliminating loss of light or light energy.
[0055] One of ordinary skill in the art would appreciate that other
configurations
that follows the same concept of this invention can be created with different
set of filters
and positions of the light source. The sequence of two or n colors can be
varied. The entry
point of the colored LEDs can also be varied.
[0056] In accordance with an embodiment of the present invention, a method for
multi-colored illuinination comprises the steps of combining by a first beam
combiner 310
a first light (R) transmitted by a first filter A and a second light (G)
reflected by the first
filter A to provide a combined beam; combining by a second beam combiner 320
the
coinbined beam transmitted by a second filter B and a third light (B)
reflected by the
second filter B to provide an output beam, each light having different
wavelengtll; and
providing a low index glue or air gap 70 between the beam combiners 310, 320,
thereby
combining the liglits without increasing etendue.
[0057] In accordance with an einbodiinent of the present invention, a method
for
multi-colored illuinination comprises the steps of combining by an X-cube 410
at least two
liglits having two different wavelengtlis received from corresponding two
light pipes 330;
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and providing a low index glue or air gap 70 between each light pipe 330 and
the X-cube
410, thereby combining the lights without increasing etendue.
[0058] Turning now to Fig. 17, in accordance with am embodiment of the present
invention, there is illustrated a schematic diagram of the light projection
system
incorporating the light pipe based color system of the present invention. The
output from
the LED light source 510, e.g., any of the color systems described herein, is
inputted into
the projection engine 520 (e.g., digital light processing (DLP), liquid
crystal on silicon
(LCOS), high temperature poly-silicon (HTPs), and the like) which creates the
projected
image by the projection lens 530 in a traditional manner. In accordance with
an aspect of
the present invention, the projection engine 520 comprises at least one
modulator panel for
modulating light in accordance with a display signal and the projection lens
530 projects
the modulated light onto a display screen.
[0059] For fiber optics application where the fibers are usually round, the
system
can also be implemented using round prisms and filters.
[0060] Although solid tapered light pipes 330, 420, 430 are shown in Figs. 14,
15
and 17, other coupling configurations including coinpound parabolic
concentrators
(CPC's), lenses, solid or hollow CPC or light pipes, and any other imaging or
non-imaging
systems can be used. In accordance with an embodiment of the present
invention, the
tapered light pipe has a lensed output surface. In accordance with an
embodiment of the
present invention, the input of the light pipe is also shaped to increase the
coupling
efficiency from the LED light source.
[0061] While the present invention has been particularly described with
respect to
the illustrated embodiment, it will be appreciated that various a
[0062] Iterations, modifications and adaptations may be made based on the
present
disclosure, and are intended to be within the scope of the present invention.
It is intended
that the appended claims be interpreted as including the embodiments discussed
above,
those various alternatives, which have been described, and all equivalents
thereto.
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