U.S. patent application number 11/856004 was filed with the patent office on 2009-01-08 for optical architecture.
This patent application is currently assigned to Texas Instruments Incorporated. Invention is credited to Jim Dunphy, Regis Grasser.
Application Number | 20090009995 11/856004 |
Document ID | / |
Family ID | 40221192 |
Filed Date | 2009-01-08 |
United States Patent
Application |
20090009995 |
Kind Code |
A1 |
Grasser; Regis ; et
al. |
January 8, 2009 |
OPTICAL ARCHITECTURE
Abstract
An optical beam-shaping unit comprises a fly-eye lens for
modifying light beams into modified light beams with desired
profiles. The optical beam-shaping unit is especially useful in
modifying collimated light from solid-state illuminators, such as
laser sources.
Inventors: |
Grasser; Regis; (Mountain
View, CA) ; Dunphy; Jim; (San Jose, CA) |
Correspondence
Address: |
TEXAS INSTRUMENTS INCORPORATED
P O BOX 655474, M/S 3999
DALLAS
TX
75265
US
|
Assignee: |
Texas Instruments
Incorporated
Dallas
TX
|
Family ID: |
40221192 |
Appl. No.: |
11/856004 |
Filed: |
September 14, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60947618 |
Jul 2, 2007 |
|
|
|
60953409 |
Aug 1, 2007 |
|
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Current U.S.
Class: |
362/231 ;
362/235; 362/244 |
Current CPC
Class: |
H04N 9/3129 20130101;
G02B 26/123 20130101 |
Class at
Publication: |
362/231 ;
362/235; 362/244 |
International
Class: |
F21V 5/00 20060101
F21V005/00; F21V 9/08 20060101 F21V009/08 |
Claims
1. An illumination system, comprising: an array of laser sources
capable of emitting light of substantially the same wavelength; and
a beam-shaping unit positioned for modifying the light comprising:
a fly-eye lens comprising a first array of lenslets.
2. The system of claim 1, wherein the first array of lenslets are
positioned at a front side of the fly-eye lens further comprises a
second array of lenslets at a backside of the fly-eye lens
3. The system of claim 1, further comprising: a field lens disposed
after the fly-eye lens and the array of laser sources along a
propagation path of the light.
4. The system of claim 1, wherein each laser source is associated
with at least one of the lenslets of the first array of
lenslets.
5. The system of claim 1, wherein the lenslets of the first array
are aspheric lenslets.
6. The system of claim 1, wherein the fly-eye lens is a
unidirectional fly-eye lens or a bi-directional fly-eye lens.
7. The system of claim 1, further comprising an optical diffuser
disposed on a propagation path of the light.
8. The system of claim 1, wherein the modified beam has a
substantially rectangular illumination field with a substantially
uniform intensity along a length of the illumination field.
9. The system of claim 1, further comprising a polygon having a
number of reflective facets, wherein the polygon is positioned
after the array of laser sources and the beam-shaping unit and
along a propagation path of the light.
10. The system of claim 9, further comprising: a f-theta lens
positioned between the beam-shaping unit and the polygon.
11. The system of claim 1 is in a display system that is configured
as a projector; and wherein said array of laser sources further
comprises a laser source that is capable of emitting a laser beam
having a wavelength different from said same wavelength.
12. The system of claim 11, wherein the projector is a front
projector or rear-front-projector.
13. An illumination system, comprising: an array illuminators
capable of emitting light of substantially the same wavelength; a
beam-shaping unit positioned for modifying the light comprising: a
fly-eye lens comprising a first array of lenslets.
14. The system of claim 13, wherein the illuminators are laser
sources; and wherein each laser source is associated with at least
one of the lenslets of the first array of lenslets.
15. The system of claim 13, wherein the fly-eye lens is a
unidirectional or a bi-directional fly-eye lens.
16. The system of claim 13 is in a display system that is
configured as a projector.
17. An illumination system, comprising: a light source providing
light; a beam-shaping unit positioned for modifying the light
comprising: a fly-eye lens comprising a first array of lenslets;
and a scanning-mechanism comprising a number of reflective facets
for reflecting the modified light onto a target.
18. The system of claim 17, wherein the scanning mechanism
comprises a polygon having a number of reflective facets.
19. The system of claim 18, wherein the light source comprises an
array of illuminators that are laser sources capable of emitting
light of substantially the same wavelength.
20. The system of claim 19, wherein each laser source is associated
with at least one of the lenslets of the first array of lenslets.
Description
CROSS-REFERENCE TO RELATED CASES
[0001] This US patent application claims priority under 119(e) from
co-pending U.S. provisional patent application Ser. No. 60/947,618
filed Jul. 2, 2007, attorney docket number TI-64796PS, the subject
matter being incorporated herein by reference in its entirety.
[0002] This US patent application also claims priority under 119(e)
from co-pending U.S. provisional patent application Ser. No.
60/953,409 filed Aug. 1, 2007, attorney docket number TI-64992PS,
the subject matter being incorporated herein by reference in its
entirety.
[0003] This US patent application is related to US patent
application "An Optical Structure and an Imaging System Using the
Same," attorney docket number TI-65026 and "An Optical Architecture
having a Rotating Polygon for Use in Imaging Systems" to Destain,
attorney docket number TI-64796, both filed on the same day as this
application; and the subject matter of each being incorporated
herein by reference in its entirety.
TECHNICAL FIELD OF THE DISCLOSURE
[0004] The technical field of this disclosure relates to the art of
optical devices; and more particularly to the art of optical
devices and optical architectures for use in imaging systems.
BACKGROUND OF THE DISCLOSURE
[0005] In recent years, solid-state light illuminators, such as
LASERs and light-emitting-diodes (LEDs), and other narrow-banded
light illuminators capable of producing phase-coherent light, such
as wavelength specific plasma lamps, have drawn significant
attention as alternative light sources to traditional light
sources, such as arc lamps, for use in imaging systems, especially
imaging systems employing light valves each comprising an array of
individually addressable pixels, due to many advantages, such as
compact size, greater durability, longer operating life, and lower
power consumption.
[0006] Regardless of the widely embraced superior properties of
solid-state illuminators over traditional light sources, it is
however difficult to optically couple solid-state illuminators with
light valves. For example, it is difficult to generate a far-field
illumination area with uniform illumination intensity at the light
valve location using solid-state or narrow-banded light
illuminators because the illumination light from the solid-state
illuminators and most narrow-banded illuminators are highly
collimated as compared to the light from traditional
illuminators.
[0007] An approach to illuminate light valves with solid-state
illuminators, especially lasers, is to use a rotating polygonal
mirror, as set forth in US patent application "An Optical Structure
and an Imaging System Using the Same," attorney docket number
TI-65026, the subject matter of which is incorporated herein by
reference in its entirety. In a simple example, beams of color
laser light are directed to reflective facets of a rotating
polygonal mirror structure. The moving reflective facets reflect
the laser beams and generate illumination fields on the pixel array
of the light valve. By moving the illumination field across the
light valve pixel array, light valve pixels can be illuminated
sequentially. The light valve modulates the laser beams based on
the desired image; and the modulated laser beams are directed to a
screen to produce the desired image.
[0008] In order to obtain high quality images on the screen, the
illumination fields illuminating the light valve are expected to
have specific profiles, such as elongated strips along the rows (or
columns) of the pixel array; and uniform intensity distribution in
the direction perpendicular to the scanning/moving direction. The
expected profiles are not always ready for commercialized
solid-state illuminators, such as laser sources.
[0009] Single laser source often has limited output power that is
incapable of generating produced images with satisfactory
brightness. When multiple laser sources are used for providing
satisfactory output power, the multiple laser sources are often
arranged in an array for the laser sources emitting substantially
the same color light. Due to the highly collimated light beam, the
illumination field of the laser array on the light valve pixel
array is not uniform enough, resulting in poor quality images on
the screen.
[0010] Therefore, what is desired is an optical device or an
optical architecture that is capable of shaping light beams from
solid-state illuminators, especially from laser sources to generate
illumination field with pre-defined profiles.
SUMMARY
[0011] In one example, an illumination system is disclosed herein.
The system comprises: an array of laser sources capable of emitting
light of substantially the same wavelength; and a beam-shaping unit
positioned for modifying the light comprising: a fly-eye lens
comprising a first array of lenslets.
[0012] In another example, an illumination system is disclosed
herein. The system comprises: an array illuminators capable of
emitting light of substantially the same wavelength; a beam-shaping
unit positioned for modifying the light comprising: a fly-eye lens
comprising a first array of lenslets.
[0013] In yet another example, an illumination system is disclosed
herein. The system comprises: a light source providing light; a
beam-shaping unit positioned for modifying the light comprising: a
fly-eye lens comprising a first array of lenslets; and a
scanning-mechanism comprising a number of reflective facets for
reflecting the modified light onto a target.
[0014] In still yet another example, an imaging system is disclosed
herein. The system comprises: a light source providing light; a
beam-shaping unit comprising an array of unidirectional lenslets
that are optically positioned for modifying the light from the
light source; and a light valve for causing the light to propagate
toward or away from a display target so as to produce an image on
the display target.
BRIEF DESCRIPTION OF DRAWINGS
[0015] FIG. 1 schematically illustrates an exemplary display system
comprising an illumination system that is capable of illuminating
the target by causing an illumination field on the target and
moving the illumination field across the target continuously so as
to illuminate the entire image area on the target;
[0016] FIG. 2a schematically illustrates an illumination field of
the light emitting from the illuminators and before the
beam-shaping device of the display system in FIG. 1;
[0017] FIG. 2b schematically illustrates an illumination field of
the illumination light after the beam-shaping device of the display
system in FIG. 1;
[0018] FIG. 2c schematically illustrates an exemplary intensity
distribution of the illumination field on FIG. 2b along one
direction;
[0019] FIG. 2d schematically illustrates an exemplary intensity
distribution of the illumination field on FIG. 2b along another
direction;
[0020] FIG. 2e schematically demonstrates an illumination field
that is generated on the light valve of the display system in FIG.
1; and used for scanning the light valve to illuminate the light
valve;
[0021] FIG. 3 schematically illustrates an exemplary optical
architecture of the beam-shaping device in FIG. 1;
[0022] FIG. 4 schematically illustrates a perspective view of an
exemplary fly-eye optical element that can be used in the optical
architecture FIG. 3;
[0023] FIG. 5a schematically illustrates a top view of another
exemplary fly-eye optical element that can be used in the optical
architecture in FIG. 3;
[0024] FIG. 5b schematically illustrates a cross-sectional view of
the fly-eye optical element in FIG. 5a;
[0025] FIG. 5c schematically illustrates a cross-sectional view of
another fly-eye optical element;
[0026] FIG. 6 schematically illustrates an exemplary display system
in which a beam-shaping device of this disclosure can be
implemented;
[0027] FIG. 7 schematically illustrates the illumination field at
the entrance of the optical architecture in FIG. 6;
[0028] FIGS. 8a and 8b schematically illustrate near-field and
far-field illumination profiles at a location between the polygonal
mirror structure and the screen in the optical architecture in FIG.
6;
[0029] FIGS. 9a and 9b schematically illustrate near-field and
far-field illumination profiles at the light valve location in the
optical architecture in FIG. 6;
[0030] FIG. 10 schematically illustrates an exemplar
rear-projection system having an optical structure of this
disclosure; and
[0031] FIG. 11 schematically illustrates an exemplary micromirror
device that can be used in the light valve of the imaging system
illustrated in FIG. 1a.
DETAILED DESCRIPTION OF SELECTED EXAMPLES
[0032] In the following, the beam-shaping optical device and
display systems using the same will be discussed with selected
examples. However, it will be appreciated by those skilled in the
art that the following discussion is for demonstration purpose, and
should not be interpreted as a limitation. Other variations within
the scope of this disclosure are also applicable. For example,
other imaging systems, such as systems for storing information of
image (e.g. 2D images or holographic images) in image storing
mediums are also applicable.
[0033] Referring to the drawings, FIG. 1 schematically illustrates
an exemplary display system employing a beam-shaping device capable
of tailoring light from the illuminators into modified light with
desired profiles. In this example, display system 100 comprises
illuminator unit 102 providing light beams, beam-shaping unit 112
for tailoring the light beams. Rotating polygon 116 comprising
reflective facets receives modified light beams, projects the
modified light beams onto light valve to generate an illumination
field, and causing the illumination field to scan the light valve
so as to illuminating the individually addressable pixels of the
light valve.
[0034] In order to provide light beams with sufficient power
corresponding to the desired brightness of produced images on the
screen, illuminator unit 102 comprises multiple solid-state
illuminators, such as lasers. The illuminators are arranged into
arrays based on the color of the light emitted by the illuminators.
Specifically, illuminators emitting light of substantially the same
color (characteristic wavelength) can be arranged in one straight
line; and illuminators emitting different color of light beams can
be arranged in separate lines, while the separate lines can be
substantially parallel. As illustrated in FIG. 1, illuminator
arrays 104, 106, and 108 each comprise illuminators emitting
substantially the same color light beam, such as red, green, blue,
white, yellow, cyan, magenta, and any desired combinations
thereof.
[0035] Each illuminator array may comprise any suitable number of
illuminators. However, it is preferred that the each array
comprises a number of illuminators such that the total output power
of the illuminators in the array satisfies the desired brightness
of the produced images on the screen.
[0036] Illumination unit 102 may comprise any suitable numbers of
arrays of illuminators with each array corresponding to a
particular color based on the desired illumination scheme for
illuminating the light valve and for producing the desired image.
For example, the illumination unit (102) may comprise illuminators
capable of emitting light of primary colors with a primary color
being defined as a color that is not a combination of other colors,
such as red, green, and blue colors. Alternatively, the
illumination unit may comprise illuminators capable of emitting
light of secondary colors with a secondary color being defined as a
color that is a combination of primary colors, such as while,
yellow, cyan, magenta, and other colors.
[0037] In one example, the illuminators of the illuminator unit
(102) can be laser sources, such as those of NECSEL.TM.
technologies from Novalux, Inc. and solid-state lasers from
Collinear Inc. and Coherent Inc. The lasers, when used in the
illuminator unit (104), are preferred to have a light power of from
50 mW or higher per color used in the system for producing the
image (e.g. the red, green, or the blue color), such as 1 W or
higher per color, and more preferably 3 W or higher per color. When
multiple laser sources are used for providing sufficient light
intensity, it is preferred, though not required, that 5 or more, 10
or more, 17 or more, 24 or more, laser sources (or independent
laser units), are used for each color light.
[0038] When the illuminators are laser sources or the like that
emit collimated light, light beams 110 from the illuminator unit
(102) has non-uniform intensity distributions, as schematically
illustrated in FIG. 2a.
[0039] Referring to FIG. 2a, the near-field of the light beams
(110) before the beam-shaping unit (112) is schematically
illustrated therein. The illumination pattern in the near-field
corresponds to the arrangement of the illuminators in the
illuminator unit (102). Light beams of the same color in the
near-field is not uniform along the illuminator array (e.g. along
the Y direction).
[0040] To modify the non-uniform light beams such that the light
beams of substantially the same color are uniform along the array
(e.g. along the Y direction), the non-uniform light beams from the
illuminator unit (102) is directed to beam-shaping unit 112, as
schematically illustrated in FIG. 1. The beam-shaping unit (112)
modifies incident light beams 110 into modified light beams 114
with a desired illumination profile, as schematically illustrated
in FIG. 2b through FIG. 2d.
[0041] FIG. 2b schematically illustrates the near-field of the
light beams after the beam-shaping unit (112). Corresponding to the
special arrangement of the illuminators, color light beams from the
illuminators in the same array are modified into a substantially
illumination strip. Specifically, color illumination field 114
comprises color strips 130, 128, 126, and blank sub-fields (e.g.
132) between color strips. Color strips 130, 128, and 126 each
extend along the direction of the illuminator array (e.g. the Y
direction). Each color strip has a desired intensity distribution
as schematically illustrated in FIG. 2c and FIG. 2d.
[0042] FIG. 2c schematically illustrates an intensity distribution
of the color strips along the Y direction (the length of the color
strips) as defined in FIG. 2a. In this example, each color strip
has a uniform intensity distribution along the length of the color
strip. Even shown in FIG. 2c that all color strips have
substantially the same maximum intensity I.sub.Y, this is one of
many possible examples. In other examples, different color strips
may have different maximum intensity along the length (Y direction)
depending upon the specific illuminators used. Regardless of
different illuminators used, each color strip preferably has a
substantially uniform intensity distribution along the length of
the color strip.
[0043] Each color strip may have any suitable intensity
distributions along the width (X direction) of the color strip,
such as uniform, Gaussian, top-hat, triangle, and random
distributions. FIG. 2d schematically illustrates an exemplary
Gaussian intensity distribution of the color strips along the width
of the color strips. In this example, all color strips have
substantially the same maximum intensity I.sub.X. In other
examples, different color strips may have different maximum
intensity along the width (X direction) depending upon the specific
illuminators used. In some examples, different color strips may
have different of intensity-distribution forms along the width of
the color strips. For example, one or more color strips may have a
random intensity distribution; while another one or more color
strips may have a uniform or a Gaussian intensity distribution
along the width of the color strips; and different color strips may
or many not have the same maximum intensity along the width.
[0044] Referring back to FIG. 1, the modified light beams (such as
that illustrated in FIG. 2b) output from beam-shaping unit can then
be used for illuminating the light valve. In one example, the
modified light beams are directed to reflective facets of rotating
polygon 116. As the polygon rotating, the reflective facets (e.g.
reflective facet 118) of the polygon moves relative to the
propagation path of the modified light beams. As a consequence, the
incident light angle (the angle between the incident light beams
and the normal direction of the reflective facet on which the light
beams are incident) changes with the rotation of the polygon. The
reflected light beams from each reflective facet change propagation
paths and sweep across a special angle (referred to as scanning
angle). By aligning the light valve (122) to the area corresponding
to the scanning angle, the reflected light beams from the polygon
are capable of moving across the light valve to sequentially
illuminating the light valve pixels. The light valve pixels being
illuminated modulate the incident light beam(s) based on image data
of the desired image to be produced. The modulated light can then
be directed towards the screen to display the desired image.
[0045] As a way of example, FIG. 2e schematically demonstrates the
movement of the illumination field (114) comprising the color
strips of FIG. 2b across the pixel array of the light valve. The
dimension of the pixel array can be characterized by width W.sub.0
and height H.sub.o. In one example, W.sub.0 can be 480 pixels or
more, 600 pixels or more, 720 pixels or more, 768 pixels or more,
1024 pixels or more, 1050 pixels or more, 1200 pixels or more, with
each pixel having a characteristic length of 200 microns or less,
150 microns or less, 100 microns or less, 50 microns or less, 20
microns or less, 14 microns or less, 8 microns or less. H.sub.0 can
be 640 pixels or more, 800 pixels or more, 1024 pixels or more,
1280 pixels or more, 1400 pixels or more, 1600 pixels or more, and
1920 pixels or more, with each pixel having a characteristic width
of 200 microns or less, 150 microns or less, 100 microns or less,
50 microns or less, 20 microns or less, 14 microns or less, 8
microns or less. In another example, H can be from 5 mm to 30 mm,
such as from 10 mm to 20 mm. The total width of the color strips
including the blank subfields (if provided) is s. s can be a value
such that the ratio of s to H.sub.0 is 1/500 or higher, such as
1/200 or higher, 1/100 or higher, 1/50 or higher, 1/20 or higher,
or 1/10 or higher, and preferably less than 1/2.
[0046] In one example, the color strips can be equally spaced. The
total width s can be substantially equal to the height H.sub.0 of
the pixel array. For N color strips that are equally spaced with
blank sub-fields, the total width s of the N sub-fields and the
blank sub-fields is preferably H.sub.0.times.(1-(1/2.times.N)) with
H.sub.o. A blank sub-field between two consecutive color strips may
be designed to provide a time period during which light valve
pixels of a display system can be updated. In particular, the size
(width) of a blank sub-field can be determined based on the minimum
update (state-switching) time period of light valve pixels.
[0047] It is noted that FIG. 2a through FIG. 2e illustrate only one
of many possible configurations. Other configurations are also
applicable. For example, the illumination field (114) may comprise
any suitable numbers of color strips and blank fields; and the
illumination field may also comprise multiple color strips of the
same color. In one example, the illumination field may comprise
color strips of R-G-B, R-G-B-W, R-R-G-G-B-B, R-R-G-G-B-B-W,
R-G-B-Y-C-M, R-G-B-Y-C-M-W, with R, G, B, W, Y, C, and M
respectively representing red, green, blue, white, yellow, cyan,
and magenta colors. Blank sub-fields can be distributed between
colored sub-fields in any desired ways if provided.
[0048] The beam-shaping unit (112) in FIG. 1 can be implemented in
many ways. In one example, the beam-shaping unit can employ a
fly-eye lens, as schematically illustrated in FIG. 3.
[0049] Referring to FIG. 3, beam-shaping unit 112 comprises fly-eye
lens 134 and field lens 140. The front side lenslets (136) is
distanced L.sub.1 from the backside lenslets in the fly-eye lens.
The field lens (140) is disposed such that target (e.g. pixel array
of the light valve) is substantially at a focal plane of the field
lens (140); and the focal length of the field lens (140) is
L.sub.2.
[0050] The fly-eye lens (134) can be a unidirectional lenticular
array, which corresponds to the fact that homogenization of the
light beams from each illuminator array is expected along the
length (length of the array). FIG. 4 schematically illustrates a
perspective view of the front side of the unidirectional fly-eye
lens (134).
[0051] Referring to FIG. 4, front side 136 of the fly-eye lens
comprises an array of lenslets arranged along the Y direction; and
each lenslet uniformly extends along the X direction so as to
uniformly homogenize the incident light beams in the Y direction,
while substantially maintain the illumination profile of the
incident light in the X direction. The uniformity can be further
improved by selecting aspheric lenslets so as to avoid spherical
aberration caused non-uniformities. In particular, low power
lenslets, which exhibit low spherical aberration, can be
employed.
[0052] The total number of lenslets in each front and back sides of
the fly-eye lens is preferably (though not required) equal to or
larger than the number of illuminators in each illuminator array.
For example, the number of lenslets of the front side (or the
backside) can be equal to or larger than K.times.N, wherein K is an
integer equal to or larger than 1, such as a number between 5 and
10; and N is the number of illuminators in each illuminator array,
or can be the maximum number of illuminators in an illuminator
array when the illuminator arrays have different numbers of
illuminators.
[0053] The center-to-center distance between adjacent lenslet is
defined as pitch of the lenslet, P.sub.lens. The lenslet pitch
P.sub.lens is preferably (though not required) equal to or smaller
than P.sub.illum/K, wherein P.sub.illum is the center-to-center
distance between adjacent illuminators in each illuminator array
(referred to as the pitch of an illuminator array), or the minimum
pitch of the illuminator arrays. With this configuration, each
illuminator can be associated with at least one lenslet in
substantially the same way.
[0054] The distance G.sub.lens between adjacent illuminator arrays
can be selected based on the desired size (e.g. width) of the
blank-field between the color strips, such as black-field 132
between color strips 130 and 128 as illustrated in FIG. 2b.
[0055] It is noted that FIG. 4 is for demonstration purpose, and
should not be interpreted as a limitation. Even though 8 lenslets
are illustrated corresponding to 8 illuminators in each illuminator
array, this is only an example. In many other configurations, the
front/back side of the fly-eye lens each may have any suitable
number of lenslets corresponding to the numbers(s) of the
illuminators in the illuminator arrays, as discussed above. The
illuminator arrays can be arrayed such that illuminators of the
same position in different arrays are aligned along a straight line
(e.g. along the X direction), as illustrated in FIG. 4. In other
examples, the illuminator arrays can be arranged in many other
suitable ways, in which instances, the lenslets of the fly-eye lens
can be extended according to the arrangements of the illuminator
arrays.
[0056] The front side and backside are disposed in the fly-eye lens
such that the front side and the backside are substantially images
to each other; and the lenslets of the front side (backside) are
substantially at the focal planes of the lenslets of the backside
(front side), as illustrated in FIG. 3. Referring again to FIG. 3,
each lenslet in the front side corresponds to a lenslet on the
backside. The distance L.sub.1 between the front side and the
backside, and the field lens (140) can be arranged such that the
magnification (defined as ratio of L.sub.2/L.sub.1) of the fly-eye
architecture in FIG. 3 is equal to or larger than 2, such as 3 or
more, 5 or more, 10 or more, such as from 10 to 30. Larger
magnification can be of great importance in minimizing divergence
of the color strips, for example, divergence along the width of the
color strips.
[0057] Incident light beams converging at the front lenslets, such
as lenslet 148a, are directed to the corresponding lenslet (148b)
at the backside; and are collimated as parallel light beams after
the lenslets at the backside of the fly-eye lens. The collimated
light beams pass through field lens 140; and are converged at the
pixel array of light valve 146.
[0058] Collimated light beams incident to the lenslets at the front
side, such light beams incident to lenslet 150a, are converged to
the corresponding lenslets at the backside, such as lenslet 150b.
The lenslets (e.g. lenslet 150b) pass the light beams to the field
lens (140) that expands the light beams into an illumination strip
on the light valve (146) with the illumination strip corresponding
to the desired color strip. As a consequence, the fly-eye lens
integrates incident light beams at the light valve; and forms a
homogenized illumination strip (color strip) at the light valve
with the desired profile.
[0059] When illuminators are lasers or the like, the light beams
emitted thereof are phase-coherent, which may cause unwanted
diffraction, interference fringes, and/or speckle noises. The
unwanted diffraction, interference fringes, and/or speckle noises
can degrade line uniformity; and are desired to be minimized or
eliminated.
[0060] Speckle noises can be minimized or eliminated using a
movable optical diffuser (e.g. diffuser 142 in FIG. 3). The optical
diffuser can be any suitable optical diffusers, such as surface
optical diffusers, bulk optical diffusers, and engineered optical
diffusers. The optical diffuser can be moved along many suitable
directions, and more preferably along the direction of the
illumination strip where the uniform intensity distribution is
desired, such as along the length of the illumination strip. The
movement preferably has a frequency equal to or higher than the
flick frequency of viewer's eyes such that the movement is not
perceptible by viewer's eyes. Other moving frequencies lower than
the flick frequencies are also applicable; while prevent from being
observed by viewer's eyes. This arises from the fact that the
illumination field on the light valve moves across the light valve
pixel array; and such movement can reduce or eliminate the speckles
or unwanted artifacts caused by the movements of the optical
diffuser.
[0061] Diffractive patterns, such as interference fringes, may
exist. This is due to the fact that light beams from single
illuminator may pass propagates along different paths (e.g. passing
through different lenslets of the fly-eye); and converging at one
location. The interference fringes can be eliminated or reduced by
adding a bi-directional feature to the fly-eye lens, as
schematically illustrated in FIG. 5a and FIG. 5b.
[0062] Referring to FIG. 5a, a top view of a bi-directional fly-eye
lens is illustrated. Fly-eye lens 154 in this example can be the
same as the fly-eye lens 136 in FIG. 4 except that each lenslet
extends in the X direction to form a two-dimensional structure,
instead of a one-dimensional straight line as illustrated in FIG.
4. The two dimensional structure of each lenslet in the X-Y plane
can be any suitable forms, such as smooth and continuous curves and
zigzagged line-segments. It is preferred, though not required, that
the lenslets are substantially parallel, regardless the different
structures.
[0063] A cross-sectional view of the fly-eye lens is schematically
illustrated in FIG. 5b. Referring to FIG. 5b, the lenslets in the
Y-Z plane each have an aspheric profile; and the curved top
surfaces of the lenslets can be continuous. In other examples, the
curved top surfaces of the lenslets can be interconnected by other
features, such as a flat segment, as schematically illustrated in
FIG. 5c.
[0064] Examples of the beam-shaping unit as discussed above can be
implemented in a wide range of systems and in many ways. As an
example, a light beam-shaping unit can be implemented in a display
system; while the display system can be configured as a
front-screen projector, a rear-screen projector, a rear-projection
TV, or many other imaging systems. FIG. 6 schematically illustrates
a display system that employs a beam-shaping unit as discussed
above.
[0065] Referring to FIG. 6, the display system comprises
illuminator unit 102, beam-shaping unit 112, optical element 157
that can be an f-theta lens comprising lenses 158 and 160, rotating
polygonal mirror 116 that comprises a number of reflective facets
(e.g. reflective facet 118), optical diffuser 142, optical elements
164 and 172, a dichroic filter stack that comprises dichroic
filters 166, 168, and 170, and light valve 122 that comprises an
array of individually addressable pixels.
[0066] The illuminator unit (102) comprises illuminator arrays as
discussed above with reference to FIG. 1. In this example, the
illuminator unit (102) comprises laser sources capable of emitting
red, green, and blue laser light beams. Laser sources emitting
substantially the same color light beams are arranged in a line
(array); and different lines of illuminators are arranged in
parallel. In other examples, the illuminator unit may comprise any
suitable illuminators. For example, the illuminator unit may
comprise illuminators capable of emitting red (R)--green (G)--blue
(B) light beams, R-G-B-white (W) light beams, R-R-G-G-B-B with
multiple illuminator arrays emitting the same color light beams,
R-R-G-G-B-B-W, R-G-B-Y (yellow)-C (cyan)-M (magenta),
R-G-B-Y-C-M-W.
[0067] The light valve pixels can be any suitable pixels, such as
reflective and deflectable micromirror devices and
liquid-crystal-on-silicon (LCOS) cells, examples of which will be
discussed afterwards with reference to FIG. 11.
[0068] Rotating polygonal mirror 116 comprises a number N of
reflective facets that can be specular or non-specular reflective,
wherein N is an integer larger than 2. The polygonal mirror is
aligned to the color light beams such that, when rotating along a
rotation axis passing through the major axis (center) of the
polygon, the reflective facets sequentially intercept the light
beams and reflecting the light beams onto the light valve. For
simplicity purpose, only one reflective facet 118 is illustrated,
but the polygonal mirror may have any suitable number of reflective
facets, as discussed above. It is noted that the reflective
polygonal mirror can comprise any desired materials. For example,
the reflective polygonal mirror can comprise a plastic material
with the surfaces coated by a light reflective material, such as
aluminum, gold, silver, or many other suitable materials. For
moving/rotating the polygonal mirror, the polygonal mirror can be
mounted to a driving mechanism, such as a motor.
[0069] Light beams from the illuminator unit (102) pass through
beam-shaping unit 112. The beam-shaping unit modifies the light
beams into modified light beams 114 that may comprise red, green,
and blue color light beams 126, 128, and 130, respectively. FIG. 7
schematically illustrates the near-field illumination pattern of
the modified light beams after the beam-shaping unit, such as at
plane at plane 156.
[0070] Referring to FIG. 7, the near-field illumination pattern
comprises illumination fields 126, 128, and 130 respectively
corresponding to the light emitted from illuminator arrays.
[0071] Referring again to FIG. 6, the illumination light beams
(126, 128, and 130) are incident to a reflective facet, such as
facet 118, of rotating polygonal mirror 116 through f-theta lenses
157 that comprises lens 158 and 160. The light beams (126, 128, and
130) respectively generate illumination fields (e.g. color strips)
on the reflective facet (118).
[0072] The illumination fields (e.g. color strips) on the
reflective facet (118) are spatially separated as illustrated in
FIG. 6. The light beams are then reflected by the reflective facet;
and passes through the f-theta lens (157). The near field and far
field illumination pattern of the reflected light beams after the
f-theta lenses (157) at plane 162 are schematically illustrated in
FIG. 8a and FIG. 8b.
[0073] Referring to FIG. 8a, illumination fields 126a, 128a, and
130a correspond to the illumination fields 126, 128, and 130 in
FIG. 7, respectively. However, the illumination fields 126, 128,
and 130 in FIG. 7 are spatially static; while illumination fields
126a, 128a, and 130a in FIG. 8a are spatially moving during to the
rotation of the reflective facet of the rotating polygonal
mirror.
[0074] Referring to FIG. 8b, the far-field illumination pattern of
the reflected light from the facet of the polygonal mirror
comprises circular illumination fields 190, 192, and 194
corresponding to the near field illumination fields 126a, 128a, and
130a, respectively. The far field illumination fields 190, 192, and
194 are spatially separated.
[0075] Referring again to FIG. 6, the reflected light after f-theta
lenses 154 and 156 is directed to movable diffuser 142. The movable
diffuser can be any suitable optical diffusers, such as bulk- or
surface engineered optical diffusers for spreading each color light
so as to substantially fill the pupil of the projection optical
element at far field. The movement of the optical diffuser can be
accomplished by attaching the optical diffuser to a moving
mechanism that is capable of rotating and/or vibrating the optical
diffuser.
[0076] The reflected light after the optical diffuser (142) is
projected to a stack of dichroic filters 166, 168, and 170 through
relay optical element 164; wherein the stack of dichroic filters is
substantially disposed at the far field of relay optical element
164. The stack of dichroic filters comprises dichroic filters
corresponding to the wavelengths (colors) of the light beams. For
example, when red, green, and blue color light beams are used, the
dichroic filters can be red, green, and blue dichroic filters. In
another example, one of the dichroic filters can be replaced by a
folding mirror, such as a specular or non-specular folding mirror.
The dichroic filters are disposed such that the reflected light of
different colors from the dichroic filters are overlapped at far
field, such as at the location of the screen, on which the
modulated light from the light valve (174) are projected. An
exemplary far field illumination pattern of the reflected light
after the stack of dichroic filters is schematically illustrated in
FIG. 9b.
[0077] Referring to FIG. 9b, the far-field illumination pattern,
such as the illumination pattern at the pupil of the projection
lens that projects the modulated light from the light valve, is
substantially a uniform field 188.
[0078] Referring again to FIG. 6, the reflected light after the
stack of dichroic filters is incident onto the light valve (122)
through relay lens 172. At the light valve, the reflected light
from the stack of dichroic filters forms the desired illumination
fields, as schematically illustrated in FIG. 9a.
[0079] The generated illumination fields as illustrated in FIG. 9
move along the desired direction (e.g. along the column) across the
light valve pixels so as to sequentially illuminating the light
valve pixels. The light valve pixels modulate the illumination
light in each illumination field according to image data (e.g.
bitplane data) associated with the desired image to be produced on
the screen. The modulated light from the light valve pixels is then
projected to the screen of the system to present the desired
image.
[0080] It is noted that relay lenses 164 and 172 can be of great
importance in improving image quality. This arises from the fact
that the illumination fields generated by the light beams of
different colors on each reflective facet are spatially separated,
thereby are not telecentric. On the other hand, in order to obtain
a high duty cycle on the polygonal mirror, it is expected that each
illumination field generated by a color light has a small angular
divergence. The above two problems together may cause a non-uniform
pupil filling of the projection lens that is often provided for
projecting the modulated light from the light valve onto the screen
of the display system. This problem can be solved by the relay lens
(164 and 172), as well as a moving diffuser and a stack of dichroic
filters.
[0081] With the above optical architecture, the illumination light
of different colors from the illuminators can be projected to the
light valve simultaneously, which in turn allows for the
illuminators being operated continuously. Because all light from
the illuminators can arrive at the screen simultaneously with
substantially no light being blocked, the brightness of the
produced images on the screen can be significantly larger than that
in existing display systems wherein light of different colors are
sequentially incident to the light valve and only one color light
is incident to the light valve at a time.
[0082] As a way of example, FIG. 10 schematically illustrates an
exemplary rear-projection system, such as a rear-projection TV that
employs an optical architecture as discussed above.
[0083] Referring to FIG. 10, the rear-projection system (190)
comprises block unit 144 for providing illumination light. The
block unit (144) can be the same as that discussed above with
reference to FIG. 6. The illumination light from the block unit 144
is incident to light valve 174 and illuminates the pixels of the
light valve (174) in a way as discussed above with reference to
FIG. 6. The light valve pixels modulate the incident light
according to image data (e.g. bitplane data) derived from the
desired image to be produced. The modulated light is then directed
to a folding mirror (192) through optical element 196 that spreads
the modulated light from the light valve across the reflecting area
of the folding mirror (192). The folding mirror projects the
modulated light onto a translucent screen (194) so as to present
the desired image on the translucent screen.
[0084] As discussed above, the light valve may comprise any
suitable type of pixels, one of which is reflective and deflectable
micromirror devices. FIG. 11 schematically illustrates an exemplary
reflective and deflectable micromirror device.
[0085] Referring to FIG. 11, the micromirror device comprises
substrate layer 222 in which substrate 224 is provided. Substrate
224 can be any suitable substrates, such as semiconductor
substrates, on which electronic circuits (e.g. circuits 226) can be
formed for controlling the state of the micromirror device.
[0086] Formed on substrate layer 222 can be electrode pad layer 216
that comprises electrode pad 218 and other features, such as
electronic connection pad 220 that electrically connects the
underlying electronic circuits to the above deformable hinge and
mirror plate. Hinge layer 206 is formed on the electrode pad layer
(216). The hinge layer comprises deformable hinge 208 (e.g. a
torsion hinge) held by hinge arm 210 that is supported above the
substrate by hinge arm posts. Raised addressing electrodes, such as
electrode 212 is formed in the hinge layer (206) for
electrostatically deflecting the above mirror plate. Other
features, such as stopper 214a and 214b each being a spring tip,
can be formed in the hinge layer (206). Mirror plate layer 202,
which comprises reflective mirror plate 204 attached to the
deformable hinge by a mirror post, is formed on the hinge layer
(206).
[0087] FIG. 11 schematically illustrates one of many possible
micromirror devices. In other examples, the micromirror device may
comprise a light transmissive substrate, such as glass, quartz, and
sapphire, and a semiconductor substrate formed thereon an
electronic circuit. The light transmissive substrate and the
semiconductor substrate are disposed proximate to each other
leaving a vertical gap therebetween. A reflective mirror plate is
formed and disposed within the gap between the light transmissive
and semiconductor substrates. In another example, the reflective
mirror plate can be in the same plane of the light transmissive
substrate and derived from the light transmissive substrate.
[0088] It will be appreciated by those of skill in the art that a
new and useful optical architecture having an optical scanning
mechanism for causing an illumination field on a target and moving
the illumination field across the target has been described herein.
In view of the many possible embodiments, however, it should be
recognized that the embodiments described herein with respect to
the drawing figures are meant to be illustrative only and should
not be taken as limiting the scope of what is claimed. Those of
skill in the art will recognize that the illustrated embodiments
can be modified in arrangement and detail. Therefore, the devices
and methods as described herein contemplate all such embodiments as
may come within the scope of the following claims and equivalents
thereof.
* * * * *