U.S. patent application number 10/693594 was filed with the patent office on 2005-04-28 for high-resolution projection display system.
This patent application is currently assigned to Optical Coating Laboratory Inc., a JDS Uniphase Company, a corporation of the State of Delaware. Invention is credited to Bellis, Matthew W., Greenberg, Michael R..
Application Number | 20050088629 10/693594 |
Document ID | / |
Family ID | 34522434 |
Filed Date | 2005-04-28 |
United States Patent
Application |
20050088629 |
Kind Code |
A1 |
Greenberg, Michael R. ; et
al. |
April 28, 2005 |
HIGH-RESOLUTION PROJECTION DISPLAY SYSTEM
Abstract
An image display system uses a polarizing beam splitter to
direct light from a lamp to multiple spatial light modulators. The
spatial light modulators ("SLM") each generate an image portion,
which are stitched together on a display screen to obtain a high
resolution image. In a particular embodiment, image portions from
two conventional SLMs, each controlling about two million pixels,
are stitched together to form an image having about four million
pixels. In another embodiment, two lamps are used with four SLMs to
produce a resultant image having about eight million pixels.
Inventors: |
Greenberg, Michael R.;
(Santa Rosa, CA) ; Bellis, Matthew W.; (Santa
Rosa, CA) |
Correspondence
Address: |
ALLEN, DYER, DOPPELT, MILBRATH & GILCHRIST P.A.
1401 CITRUS CENTER 255 SOUTH ORANGE AVENUE
P.O. BOX 3791
ORLANDO
FL
32802-3791
US
|
Assignee: |
Optical Coating Laboratory Inc., a
JDS Uniphase Company, a corporation of the State of
Delaware
Santa Rosa
CA
95407
|
Family ID: |
34522434 |
Appl. No.: |
10/693594 |
Filed: |
October 24, 2003 |
Current U.S.
Class: |
353/94 ;
348/E5.141; 348/E9.012 |
Current CPC
Class: |
G03B 21/26 20130101;
H04N 9/12 20130101; H04N 5/7441 20130101 |
Class at
Publication: |
353/094 |
International
Class: |
G03B 021/26 |
Claims
1. A display system comprising; a lamp providing a lamp output; a
light integrator optically coupled to receive the lamp output from
the lamp and for providing a homogenized light output; a beam
splitter optically coupled to receive the homogenized light output
from the light integrator and configured to provide a first light
beam having a first polarization state and a second light beam
having a second polarization state; a first imager optically
coupled to receive the first light beam for Producing a first
modulated light beam, wherein the first imager is a spatial light
modulator; first projection optics optically coupled to receive the
first modulated light beam and configured to expand the first
modulated light beam to form a first display image portion; a
second imager optically coupled to receive the second light beam
and for producing a second modulated light beam, wherein the second
imager is a spatial light modulator; a second polarizing beam
splitter disposed between the polarizing beam splitter and the
first spatial light modulator; and a third polarizing beam splitter
disposed between the polarizing beam splitter and the spatial light
modulator, and second projection optics optically coupled to the
second light beam and configured to expand the second modulated
light beam to form a second display image portion, wherein the
first display image portion and the second image display portion
are combined at a margin to form a display.
2. The display system of claim 1 wherein further comprising a
half-wave retarder plate disposed between the polarizing beam
splitter and the first spatial light modulator.
3. The display system of claim 2 wherein the polarizing beam
splitter is a wire-grid polarizing beam splitter.
4. A display system comprising: a lamp providing a lamp output; a
light integrator optically coupled to the lamp output from the lamp
and providing a homogenized light output; a beam splitter optically
coupled to the homogenized light output from the light integrator
and configured to provide a first light beam and a second light
beam; a first imager optically coupled to the first light beam and
producing a first modulated light beam; first projection optics
optically coupled to the first modulated light beam and configured
to expand the first modulated light beam to form a first display
image portion; a second imager optically coupled to the second
light beam and producing a second modulated light beam; and second
projection optics optically coupled to the second light bean and
configured to expand the second modulated light beam to form a
second display image portion on the display screen, wherein the
first display image portion and the second image display portion
are combined at a margin to form a display image, wherein the beam
splitter is a polarizing beam splitter, the first light beam has a
first polarization state, and the second light beam has a second
polarization state, wherein the polarizing beam splitter is a
wire-grid polarizing beam splitter, wherein the first imager is a
first liquid-crystal-on-silicon spatial light modulator and the
second imager is a second liquid-crystal-on-silic- on spatial light
modulator, and further comprising: a half-wave retarder plate
disposed between the polarizing beam splitter and the first
liquid-crystal-on-silicon spatial light modulator; a second
polarizing beam splitter disposed between the half-wave retarder
plate and the first liquid-crystal-on-silicon spatial light
modulator; and a third polarizing beam splitter disposed between
the polarizing beam splitter and the second
liquid-crystal-on-silicon spatial light modulator.
5. The display system of claim 4 further comprising: a first
polarization analyzer disposed between the first
liquid-crystal-on-silicon spatial light modulator and the first
projection optics; and a second polarization analyzer disposed
between the second liquid-crystal-on-silic- on spatial light
modulator and the second projection optics.
6. The display system of claim 4 wherein the first
liquid-crystal-on-silic- on spatial light modulator is a first
analog spatial light modulator and the second
liquid-crystal-on-silicon spatial light modulator is a second
analog spatial light modulator.
7. The display system of claim 4 further comprising a trapezoidal
post projection lens fold mirror disposed between the first
liquid-crystal-on-silicon spatial light modulator and the second
liquid-crystal-on-silicon spatial light modulator, and a display
screen.
8. The display system of claim 1 wherein the first imager is a
first type of imager and the second imager is a second type of
imager different from the first type of imager.
9. The display system of claim 1 wherein the first projection
optics provide a first optical path length between the light
integrator and the first display image portion and the second
projection optics provide a second optical path length between the
light integrator and the second display image portion, the first
optical path length being essentially the same as the second
optical path length.
10. The display system of claim 1 further comprising a color wheel
disposed between the lamp and the beam splitter.
11. The display system of claim 10 wherein the color wheel is
disposed between the lamp and the light integrator.
12. The display system of claim 1 wherein the first imager
generates a first number of pixels, the second imager generates a
second number of pixels, and the display image has a third number
of pixels essentially equal to a sum of the first number of pixels
and the second number of pixels.
13. The display system of claim 12 wherein the first number of
pixels is about two million pixels and the second number of pixels
is about two million pixels, the third number of pixels being about
four million pixels.
14. The display system of claim 1 further comprising: a second lamp
providing a second lamp output; a second light integrator optically
coupled to the second lamp output from the second lamp and
providing a second homogenized light output; a second beam splitter
optically coupled to the second homogenized light output from the
second light integrator and configured to provide a third light
beam and a fourth light beam; a third imager optically coupled to
the third light beam and producing a third modulated light beam;
third projection optics configured to expand the third modulated
light image portion to form a third display image portion; a fourth
imager optically coupled to the fourth light beam and producing a
fourth modulated light beam; fourth projection optics optically
coupled to the fourth modulated light beam and configured to expand
the fourth modulated light beam to form a fourth display image
portion, wherein the first display image portion, the second
display image portion, the third display image portion, and the
fourth display image portion are combined at margins to form the
display image.
15. (canceled)
16. (canceled)
17. (canceled)
18. (canceled)
19. The display system of claim 1 further including fold mirror
optically coupled to receive light from the first and second
spatial light modulator and for folding the beam to be directed to
a display screen.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] Not applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not applicable.
REFERENCE TO MICROFICHE APPENDIX
[0003] Not applicable.
FIELD OF THE INVENTION
[0004] This invention relates generally to image display systems,
and more particularly to projection display systems using a
plurality of spatial light modulators illuminated with light from a
lamp, partial images from the spatial light modulators being
combined to form a high-resolution image on a display screen.
BACKGROUND
[0005] Projection display systems use spatial light modulators
("SLMs") to modulate light from a lamp to produce high-quality
images suitable for home theater, large-format front projectors,
such as digital cinema, projectors for business conferences, and
rear-projection television. The resolution of such systems is
related to the number of picture cells ("pixels") that the SLM
generates. The image from the SLM is magnified and projected onto a
display screen. Generally, a larger SLM will generate more pixels
than a smaller SLM with similarly sized actuator cells. Conversely,
if the size of the actuator cell is reduced, an SLM of a fixed size
can generate more pixels. However, SLMs suitable for large-format
displays might not have suitable resolution for other applications,
such as medical imaging, satellite imaging, or other display
applications requiring very high information content.
[0006] A viewer typically sits relatively far back from a
large-format display screen, where the viewer's eye smooths the
pixellated image. Unfortunately, the resolution acceptable for
large-screen displays might not be suitable for high-resolution
displays, where the viewer is relatively close to the displayed
image and a higher information density is desired. One technique to
provide a high-resolution image is to provide SLMs with more
actuator cells, either by making a larger SLM chip or by reducing
the size of the actuator cells. Unfortunately, both approaches
adversely affect yield-per-wafer and cost.
[0007] Multiple SLMs have been used in image display systems for
various reasons. One technique overlays images from multiple SLMs
to increase the brightness of the resultant image. Another
technique interleaves images from multiple SLMs that control
different colors of light operating at a reduced duty cycle (e.g.
50% duty cycle when using two SLMs). Using multiple SLMs allows the
use of slower SLMs to achieve a higher apparent refresh rate, but
does not increase the resolution of the display.
SUMMARY OF THE INVENTION
[0008] The present invention enables high-resolution image display
systems. In some embodiments, a single lamp is used. The lamp
output is homogenized in a light integrator, which provides a
homogenized light output. The homogenized light output is split
into first and second light beams with a beam splitter. A first
imager optically coupled to the first light beam produces a first
modulated light beam that is optically coupled to first projection
optics. The projection optics expand the first modulated light beam
to form a first display image portion on a display screen. A second
imager optically coupled to the second light beam produces a second
modulated light beam that is optically coupled to second projection
optics. The second projection optics expand the second modulated
light beam to form a second display image portion on the display
screen. The first display image portion and the second display
image portion are combined at a margin to form a display image. An
optional fold mirror(s) is used to enable a more compact projection
system.
[0009] In a particular embodiment, the beam splitter is a
polarizing beam splitter and the imagers are LCoS SLMs. The first
light beam from the polarizing beam splitter has a first
polarization state and the second light beam from the polarizing
beam splitter has a second polarization state. A half-wave retarder
plate in the path of the first light beam rotates the polarization
state to operate in conjunction with the LCoS SLM. Thus, the full
output of the lamp is utilized without polarization recovery, and
resolution of the display image is enhanced.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1A is a simplified diagram of a monochrome image
display system according to an embodiment of the present
invention.
[0011] FIG. 1B is a simplified side view of a portion of the image
display system of FIG. 1A illustrating the relationship of the fold
mirror to a display screen.
[0012] FIG. 2 is a simplified diagram of a color image display
system according to another embodiment of the present
invention.
[0013] FIG. 3 is simplified diagram of a multi-lamp stitched image
display system according to an embodiment of the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0014] I. Introduction
[0015] A projected image is formed from partial images produced by
a plurality of SLMs. The modulated light from the each SLM forms a
portion of the projected image, and the portions are combined
("stitched") to form a high-resolution image on a display screen.
For example, image portions from two SLMs, each having two million
pixels, are stitched together to form a projected image having
about four million pixels.
[0016] In one embodiment, liquid-crystal on silicon ("LCoS") SLMs
are used. LCoS SLMs modulate polarized light by reflection. In
conventional image display systems, unpolarized light from the lamp
is filtered with a pre-polarizer and light having the undesired
polarization state is discarded, reducing brightness.
Alternatively, light having the undesired polarization state is
converted to light of the desired polarization state and is
provided to a LCoS SLM. Such techniques are known as polarization
conversion/recovery systems, but increase the complexity, cost,
size, and weight of the display system.
[0017] In an embodiment of the present invention, unpolarized light
from a lamp is split into two polarization states using a
polarizing beam splitter ("PBS"). Light having the first
polarization state is directed to a first SLM, and light having the
second polarization state is directed at a second SLM. The SLM can
be a LCoS SLM or other type of SLM, such a digital mirror display
("DMD") having a plurality of separately actuated micromirrors, or
a transmissive SLM. The present invention enables the full output
of the lamp to be utilized without resorting to polarization
recovery or conversion schemes. Similarly, a single set of
homogenizing optics, and in some embodiments relay optics, are
shared by multiple SLMs.
[0018] II. Exemplary Display Systems
[0019] FIG. 1A is a simplified diagram of a monochrome image
display system 10 according to an embodiment of the present
invention. A lamp 12 having an arc 14 or filament and a reflector
16 provides unpolarized light 18 to a light integrator 20,
typically through a condenser lens 22. The arc 14 generates
non-uniform light, and the light integrator converts the
non-uniform light from the arc 14 into a homogenized light beam 26.
Examples of light integrators include light rods and light tunnels,
and are recirculating (recycling) or non-recirculating in
alternative embodiments.
[0020] A lens 28 couples the homogenized light beam 26 from the
light integrator 20 to a wire-grid PBS 30, which reflects light
having a first polarization state 32 and transmits light having a
second polarization state 34. Alternatively, a thin-film PBS or
other PBS is used. Alternatively, a 50/50 non-polarizing beam
splitter is used; however, a PBS enables efficient use of the lamp
output, and a wire-grid PBS enables a wide spectral band and good
cone illumination, and hence is particularly desirable. The
wire-grid PBS splits the light from the lamp 12 into two separate
light beams, which are then directed to two SLMs 42, 48. It is
desirable to position the wire-grid PBS 30 in a telecentric optical
space to maintain color uniformity across the projected image.
[0021] Light of the first polarization state 32 is reflected to an
optional fold mirror 36, which reflects the light to a half-wave
retarder plate 38. The half-wave retarder plate rotates the light
from the first polarization state to the second polarization state,
which is passed through another wire-grid PBS 40 to a LCoS SLM 42.
Light falling on a pixel of a LCoS SLM in the dark state is
unmodified and is reflected back through the PBS 40. Light falling
on a pixel of a LCoS SLM in the bright state rotates the incident
polarized light 90.degree.. The rotated light 43 is reflected by
the PBS 40 through an optional polarization analyzer 51 to
projection optics 60. Imaging off the wire-grid PBS 40 in
reflection (rather than imaging the transmitted beam) provides a
higher quality image, but an alternative image display system
images the light transmitted through the wire-grid PBS. The
polarization analyzer is basically an absorptive filter that
removes light of the undesired polarization state to improve the
contrast of the projected image. The optional fold mirrors keep the
light path from the lamp to the display screen 56 contained within
a compact spatial envelope, which is particularly desirable for
rear-projection image display systems.
[0022] Light of the second polarization state 34 is transmitted to
optional fold mirrors 44, 46, and then through a wire-grid PBS 47
to another LCoS SLM 48. A pixel of the LCoS SLM in the dark state
is unmodified and is reflected back through the PBS 47. A pixel of
the LCoS SLM in the bright state rotates the incident polarized
light 90.degree. to the complimentary polarization state. The
rotated light 50 is coupled to the PBS 47, which reflects the
rotated light 50 through an optional polarization analyzer 52 to
projection optics 54.
[0023] The projection optics 54 expand the image from the SLM 48 to
form a first contiguous (i.e. continuous two-dimensional) display
image portion 58A on a first portion of an optional fold mirror 56.
Similarly, the image from the other SLM 42 is expanded by second
projection optics 60 to form a second contiguous display image
portion 58B on a second portion of the fold mirror 56. Light from
the projection optics, represented as arrows 55A, 55B is reflected
off the fold mirror 56 to a display screen (see FIG. 1B, ref. num.
61). The reflected light is represented by arrows 59A, 59B. It is
understood that representation of the image portions using arrows
is for simplicity of illustration, in particular, that the
projection optics 54, 60 provide fields of illumination.
[0024] The first 58A and second 58B image portions are combined on
the display screen at a margin essentially equivalent to the margin
57 between the image portions on the fold mirror 56. In a
particular embodiment, the fold mirror 56 is trapezoidal to account
for the expanding footprint of the image portions from the
projection optics, which increases with increased distance from the
projection optics. The image portions combine on the display screen
to form a display image with approximately the combined number of
pixels as are contained in the first 42 and second 48 SLMs. In many
cases, the first and second SLM will be identical, but this is not
required. Similarly, it is not required that the first and second
SLM be of the same type. For example, a first SLM could be a LCoS
SLM, and the second SLM could be a transmissive liquid-crystal
light valve or digital mirror display. LCoS SLMs are particularly
desirable for use in high-resolution monochrome display systems
because they can be controlled to provide a gray-scale output. An
analog LCoS device produces a gray-scale output according to the
amplitude of the control input signal, and a digital LCoS device
produces a gray-scale output by modulating pulse width of the
control input signal.
[0025] Those of ordinary skill in the art will appreciate that the
image display system shown in FIG. 1A is merely exemplary. Several
other topologies are possible, and various combinations of fold
mirrors are alternatively used. It is generally desirable that the
optical path lengths between the output of the light integrator 20
and SLMs 42, 48 are similar in the two sub-image paths to permit
common relay optics to be used in both paths. The image display
system enables a high-resolution projection display image to be
stitched from partial images generated by conventional SLMs using a
single lamp and light integrator. The number of pixels in the
display image is essentially the sum of the pixels modulated by the
first and second SLMs. The display image (formed from display image
portions 58A+58B) is shown as being divided into right- and
left-hand portions, but could be divided into upper and lower
portions. Generally, the form factor of an image portion is
equivalent to the form factor of the associated SLM, which is
typically rectangular. Using a single lamp in combination with a
single light integrator and PBS enables efficient utilization of
the light from the lamp, and results in lower power consumption and
heat generation for a given display brightness compared to display
systems that "dump" unwanted light.
[0026] FIG. 1B is a simplified side view of a portion of the image
display system of FIG. 1A illustrating the relationship of the fold
mirror 56 to a display screen 61. Light from the projection optics
54 is reflected off the fold mirror 56 to the display screen
61.
[0027] FIG. 2 is a simplified diagram of a color image display 60
system according to another embodiment of the present invention. A
color wheel 62 between the light integrator 20 and the lamp 12
transmits a selected color(s) of light to the light integrator. A
color wheel motor 64 rotates the color wheel 62 to sequentially
present different colored filters between the lamp 12 and the light
integrator 20. Alternatively, a color wheel is located after the
output of the light integrator 20. In a further embodiment, a color
wheel located after the output of a recirculating light integrator
has dichroic color filter segments that transmit a colored light
beam to a beam splitter 30', such as a pre-polarizer, for
separation into first and second colored light beams.
[0028] The first and second light beams have complimentary
polarization states and are coupled to the SLMs ("imagers"). The
non-selected color(s) are optionally reflected back into the light
integrator to be recycled, thus increasing color light output
efficiency. In a particular embodiment the dichroic color filter
segments are logarithmic spiral color filter segments that generate
scrolling color bands. It is generally desirable that the imagers
operate sufficiently fast to permit sequential color operation at
frame rates sufficient to eliminate color break-up or other color
artifacts in the displayed image.
[0029] FIG. 3 is simplified diagram of a multi-lamp image display
system 100 according to an embodiment of the present invention. The
multi-lamp image display system 100 has a first lamp 12A whose
output is homogenized by a first light integrator 20A and is split
by a first polarizing beam splitter 30A, and a second lamp 12B
whose output is homogenized by a second light integrator 20B and is
split by a second polarizing beam splitter 30B. The light from the
two lamps 12A, 12B are coupled to imagers 42A, 48B, 42A, 48B.
[0030] The resulting displayed image, which is made up of four
image portions 58A, 58B, 58C, 58D stitched together at margins 157,
157' has a resolution essentially equal to the sum of pixels
generated by the imagers 42A, 42B, 48A, 48B. The fold mirror 156 is
typically rectangular, but this is not required, and reflects the
image portions to a display screen (not shown). Alternatively,
multiple fold mirrors are used. In a particular embodiment each
imager generates about two million pixels and the displayed image
has about eight million pixels. Additional lamps, light
integrators, imagers, and projection optics may be combined to
further increase the number of pixels in the displayed image.
[0031] While the invention has been described above in terms of
various specific embodiments, the invention may be embodied in
other specific forms without departing from the spirit of the
invention. Thus, the embodiments described above illustrate the
invention, but are not restrictive of the invention, which is
indicated by the following claims. All modifications and
equivalents that come within the meaning and range of the claims
are included within their scope.
* * * * *