U.S. patent application number 09/835640 was filed with the patent office on 2002-10-17 for projection display using reflective light modulators.
This patent application is currently assigned to PROKIA TECHNOLOGY CO., LTD.. Invention is credited to Chan, Sheng-Hsiung, Chuang, Fu-Ming.
Application Number | 20020149747 09/835640 |
Document ID | / |
Family ID | 25270060 |
Filed Date | 2002-10-17 |
United States Patent
Application |
20020149747 |
Kind Code |
A1 |
Chuang, Fu-Ming ; et
al. |
October 17, 2002 |
PROJECTION DISPLAY USING REFLECTIVE LIGHT MODULATORS
Abstract
In a projection display, input light is separated by a
polarization beam splitter prism into first and second color
components, and a third color component. The first and second color
components, together with a light leakage component that is
associated with the third color component, are directed by the
polarization beam splitter prism to a color synthesizing prism or a
color splitter prism set, which then separates the first and second
color components and the light leakage component so as to travel in
three different directions, respectively. The first and second
color components from the color synthesizing prism or the color
splitter prism set, and the third color component from the
polarization beam splitter prism are processed by reflective first,
second and third light modulators, respectively.
Inventors: |
Chuang, Fu-Ming; (Hsin-Chu
Hsien, TW) ; Chan, Sheng-Hsiung; (Hsin-Chu Hsien,
TW) |
Correspondence
Address: |
Stephen A. Bent
FOLEY & LARDNER
Washington Harbour
3000 K Street, N.W., Suite 500
Washington
DC
20007-5109
US
|
Assignee: |
PROKIA TECHNOLOGY CO., LTD.
|
Family ID: |
25270060 |
Appl. No.: |
09/835640 |
Filed: |
April 17, 2001 |
Current U.S.
Class: |
353/20 ;
348/E9.027; 349/9 |
Current CPC
Class: |
H04N 9/3167 20130101;
G02B 27/283 20130101; H04N 9/3105 20130101 |
Class at
Publication: |
353/20 ;
349/9 |
International
Class: |
G03B 021/14 |
Claims
We claim:
1. A projection display adapted to process an input light beam that
includes a first color component, a second color component and a
third color component, said projection display comprising: a
polarization beam splitter prism having a first side adapted to
receive the input light beam, a second side, a third side opposite
to said first side, and a fourth side opposite to said second side,
said polarization beam splitter prism being adapted to separate the
input light beam into the first and second color components, which
pass through said second side thereof, and the third color
component, a large portion of which passes through said third side
thereof, said polarization beam splitter prism further allowing a
small portion of the third color component, which serves as a light
leakage component, to pass through said second side thereof; a
color synthesizing prism disposed adjacent to said second side of
said polarization beam splitter prism, and adapted to separate the
first and second color components and the light leakage component
from said polarization beam splitter prism so as to travel in three
different directions, respectively; reflective first and second
light modulators disposed adjacent to said color synthesizing prism
so as to receive the first and second color components respectively
therefrom, said first and second light modulators modulating the
respective one of the first and second color components and
changing polarization state of the respective one of the first and
second color components when activated, said first and second light
modulators reflecting modulated first and second color components
back to said color synthesizing prism; and a reflective third light
modulator disposed adjacent to said third side of said polarization
beam splitter prism so as to receive the third color component
therefrom, said third light modulator modulating the third color
component and changing polarization state of the third color
component when activated, said third light modulator reflecting a
modulated third color component back to said polarization beam
splitter prism.
2. The projection display of claim 1, further comprising a first
light polarization selector disposed adjacent to said first side of
said polarization beam splitter prism and adapted to convert the
polarization state of the third color component, said polarization
beam splitter prism receiving the input light beam from said first
light polarization selector.
3. The projection display of claim 2, wherein said polarization
beam splitter prism receives from said color synthesizing prism the
modulated first and second color components at said second side
thereof, and receives from said third light modulator the modulated
third color component at said third side thereof.
4. The projection display of claim 3, further comprising a second
light polarization selector disposed adjacent to said fourth side
of said polarization beam splitter prism, said second light
polarization selector receiving the modulated first, second and
third color components from said fourth side of said polarization
beam splitter prism, and being adapted to convert the polarization
state of the modulated third color component.
5. The projection display of claim 4, further comprising a
polarizer disposed adjacent to said second light polarization
selector so as to receive the modulated first, second and third
color components therefrom, said polarizer being adapted to absorb
light of a first polarization state and to permit light of a second
polarization state to pass therethrough.
6. The projection display of claim 2, wherein said first light
polarization selector includes: a first dichroic mirror adapted to
receive the first, second and third color components having a first
polarization state, said first dichroic mirror allowing said first
and second color components to pass therethrough in a first
direction, and reflecting the third color component such that the
third color components travels in a second direction transverse to
the first direction; a first reflective mirror for reflecting the
first and second color components from said first dichroic mirror
such that the first and second color components travel in a third
direction transverse to the first direction and parallel to the
second direction; a second reflective mirror for reflecting the
third color component from said first dichroic mirror such that the
third color component travels in a fourth direction transverse to
the second direction and parallel to the first direction; a second
dichroic mirror for receiving the first and second color components
from said first reflective mirror; and a half-wavelength plate
disposed between said second reflective mirror and said second
dichroic mirror, and converting the polarization state of the third
color component to a second polarization state before the third
color component reaches said second dichroic mirror; wherein the
input light beam is obtained by said polarization beam splitter
prism from said second dichroic mirror, and includes the first and
second color components having the first polarization state and
further includes the third color component having the second
polarization state.
7. A projection display adapted to process an input light beam that
includes a first color component, a second color component and a
third color component, said projection display comprising: a
polarization beam splitter prism having a first side adapted to
receive the input light beam, a second side, a third side opposite
to said first side, and a fourth side opposite to said second side,
said polarization beam splitter prism being adapted to separate the
input light beam into the first and second color components, which
pass through said second side thereof, and the third color
component, a large portion of which passes through said third side
thereof, said polarization beam splitter prism further allowing a
small portion of the third color component, which serves as a light
leakage component, to pass through said second side thereof; a
color splitter prism set disposed adjacent to said second side of
said polarization beam splitter prism, and adapted to separate the
first and second color components and the light leakage component
from said polarization beam splitter prism so as to travel in three
different directions, respectively; reflective first and second
light modulators disposed adjacent to said color splitter prism set
so as to receive the first and second color components respectively
therefrom, said first and second light modulators modulating the
respective one of the first and second color components and
changing polarization state of the respective one of the first and
second color components when activated, said first and second light
modulators reflecting modulated first and second color components
back to said color splitter prism set; and a reflective third light
modulator disposed adjacent to said third side of said polarization
beam splitter prism so as to receive the third color component
therefrom, said third light modulator modulating the third color
component and changing polarization state of the third color
component when activated, said third light modulator reflecting a
modulated third color component back to said polarization beam
splitter prism.
8. The projection display of claim 7, wherein: said color splitter
prism set includes first and second color splitter prisms, each of
which has a total reflection first side, a light splitting second
side, and a third side; said total reflection first side of said
second color splitter prism being disposed adjacent to said second
side of said polarization beam splitter prism; said light splitting
second side of said second color splitter prism being disposed
adjacent to said total reflection first side of said first color
splitter prism; said third side of said second color splitter prism
being disposed adjacent to said second light modulator; said second
color splitter prism being adapted to receive the first and second
color components and the light leakage component from said
polarization beam splitter prism at said total reflection first
side thereof, to allow the first color component and the light
leakage component to pass directly through said light splitting
second side thereof, and to reflect the second color component to
pass through said third side thereof for reception by said second
light modulator.
9. The projection display of claim 8, wherein said light splitting
second side of said first color splitter prism is disposed adjacent
to said first light modulator, said first color splitter prism
being adapted to receive the first color component and the light
leakage component from said second color splitter prism at said
total reflection first side thereof, to allow the first color
component to pass directly through said light splitting second side
thereof for reception by said first light modulator, and to reflect
the light leakage component to pass through said third side
thereof.
10. The projection display of claim 8, wherein said third side of
said first color splitter prism is disposed adjacent to said first
light modulator, said first color splitter prism being adapted to
receive the first color component and the light leakage component
from said second color splitter prism at said total reflection
first side thereof, to allow the light leakage component to pass
directly through said light splitting second side thereof, and to
reflect the first color component to pass through said third side
thereof for reception by said first light modulator.
11. The projection display of claim 8, wherein said total
reflection first side of said first color splitter prism and said
light splitting second side of said second color splitter prism
form a clearance therebetween.
12. The projection display of claim 7, further comprising a first
light polarization selector disposed adjacent to said first side of
said polarization beam splitter prism and adapted to convert the
polarization state of the third color component, said polarization
beam splitter prism receiving the input light beam from said first
light polarization selector.
13. The projection display of claim 12, wherein said polarization
beam splitter prism receives from said color splitter prism set the
modulated first and second color components at said second side
thereof, and receives from said third light modulator the modulated
third color component at said third side thereof.
14. The projection display of claim 13, further comprising a second
light polarization selector disposed adjacent to said fourth side
of said polarization beam splitter prism, said second light
polarization selector receiving the modulated first, second and
third color components from said polarization beam splitter prism,
and being adapted to convert the polarization state of the
modulated third color component.
15. The projection display of claim 14, further comprising a
polarizer disposed adjacent to said second light polarization
selector so as to receive the modulated first, second and third
color components therefrom, said polarizer being adapted to absorb
light of a first polarization state and to permit light of a second
polarization state to pass therethrough.
16. The projection display of claim 12, wherein said first light
polarization selector includes: a first dichroic mirror adapted to
receive the first, second and third color components having a first
polarization state, said first dichroic mirror allowing said first
and second color components to pass therethrough in a first
direction, and reflecting the third color component such that the
third color components travels in a second direction transverse to
the first direction; a first reflective mirror for reflecting the
first and second color components from said first dichroic mirror
such that the first and second color components travel in a third
direction transverse to the first direction and parallel to the
second direction; a second reflective mirror for reflecting the
third color component from said first dichroic mirror such that the
third color component travels in a fourth direction transverse to
the second direction and parallel to the first direction; a second
dichroic mirror for receiving the first and second color components
from said first reflective mirror; and a half-wavelength plate
disposed between said second reflective mirror and said second
dichroic mirror, and converting the polarization state of the third
color component to a second polarization state before the third
color component reaches said second dichroic mirror; wherein the
input light beam is obtained by said polarization beam splitter
prism from said second dichroic mirror, and includes the first and
second color components having the first polarization state and
further includes the third color component having the second
polarization state.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The invention relates to a projection display, more
particularly a single-lens projection display that utilizes
reflective light modulators.
[0003] 2. Description of the Related Art
[0004] In a conventional projection display, an input light beam,
which contains red, green and blue color components, is processed
before providing the same to a projection lens so as to generate an
output image.
[0005] Referring to FIG. 1, a conventional single-lens projection
display 1 is shown to include a first light polarization selector
11, a second light polarization selector 12, a polarization beam
splitter prism 13, a dichroic beam splitter prism 14, a first light
modulator 15, a second light modulator 16, a third light modulator
17, a polarizer 18, and a projection lens 19. An input light beam
10, which is a white light beam, is separated into first, second
and third color components 101, 102, 103, such as red, green and
blue color components, for processing by the first, second and
third light modulators 15, 16, 17, respectively.
[0006] Each of the first and second light polarization selectors
11, 12, such as the ColorSelect.TM. filter products available from
ColorLink Inc., serves to convert the polarization state of a
predetermined color 2 component, without altering the polarization
state of the other color components. In the projection display 1 of
FIG. 1, the polarization state of the third color component 103,
such as the green color component, is changed, whereas the
polarization state of the first and second color components 101,
102 remains unaltered, after the color components 101, 102, 103
pass through the first and second light polarization selectors 11,
12.
[0007] The polarization beam splitter prism 13 reflects light of a
first polarization state, such as S-polarized light, in a
transverse direction, and allows light of a second polarization
state, such as P-polarized light, to pass therethrough.
[0008] The dichroic beam splitter prism 14 is used to separate two
different color components. In the projection display 1 of FIG. 1,
the dichroic beam splitter prism 14 allows the first color
component 101 to pass directly therethrough, and reflects the
second color component 102 in a transverse direction, thereby
separating the first color component 101 from the second color
component 102.
[0009] Each of the first, second and third light modulators 15, 16,
17 is a reflective light valve, and is disposed adjacent to one of
the dichroic beam splitter prism 14 and the polarization beam
splitter prism 13 so as to receive a respective one of the first,
second and third color components 101, 102, 103 therefrom. When
activated, each of the first, second and third light modulators 15,
16, 17 modulates the respective one of the first, second and third
color components 101, 102, 103, and changes the polarization state
of the respective one of the first, second and third color
components 101, 102, 103. The first, second and third light
modulators 15, 16, 17 then reflect modulated first, second and
third color components 101, 102, 103 back to the adjacent one of
the dichroic beam splitter prism 14 and the polarization beam
splitter prism 13.
[0010] The polarizer 18 allows light of a predetermined
polarization state to pass therethrough, and absorbs light of the
other polarization state. In the projection display 1 of FIG. 1,
the polarizer 18 allows P-polarized light to pass therethrough, and
absorbs S-polarized light.
[0011] In operation, when the first light polarization selector 11
receives the S-polarized white input light beam 10, the
S-polarization state of the first and second color components 101,
102, such as the red and blue color components, remains unaltered,
whereas the S-polarization state of the third color component 103,
such as the green color component, is changed to the P-polarization
state, after the first, second and third color components 101, 102,
103 pass through the first light polarization selector 11. The
polarization beam splitter prism 13 receives the S-polarized first
and second color components 101, 102 and the P-polarized third
color component 103 from the first light polarization selector 11
at a first side thereof, reflects the S-polarized first and second
color components 101, 102 in a transverse direction such that the
S-polarized first and second color components 101, 102 pass through
a second side thereof, and permits the P-polarized third color
component 103 to pass directly through a third side thereof
opposite to the first side.
[0012] The dichroic beam splitter prism 14, which is disposed
adjacent to the second side of the polarization beam splitter prism
13, receives the S-polarized first and second color components 101,
102 therefrom. The first color component 101 passes directly
through the dichroic beam splitter prism 14, whereas the second
color component 102 is reflected by the dichroic beam splitter
prism 14 in a transverse direction.
[0013] The first and second light modulators 15, 16 are disposed
adjacent to the dichroic beam splitter prism 14 so as to receive
the S-polarized first and second color components 101, 102
respectively therefrom. The first and second light modulators 15,
16 modulate the respective one of the first and second color
components 101, 102, and change the polarization state of the
respective first or second color component 101, 102 from the
S-polarization state to the P-polarization state when the first and
second light modulators 15, 16 are activated. The first and second
light modulators 15, 16 reflect the corresponding modulated color
component back to the dichroic beam splitter prism 14 for reception
by the polarization beam splitter prism 13.
[0014] The third light modulator 17 is disposed adjacent to the
third side of the polarization beam splitter prism 13 so as to
receive the P-polarized third color component 103 therefrom. The
third light modulator 17 modulates the third color component 103,
and changes the polarization state of the third color component 103
from the P-polarization state to the S-polarization state when the
third light modulator 17 is activated. The third light modulator 17
reflects the modulated S-polarized third color component 103 back
to the polarization beam splitter prism 13.
[0015] The modulated P-polarized first and second color components
101, 102 from the dichroic beam splitter prism 14 will be allowed
by the polarization beam splitter prism 13 to pass directly through
a fourth side thereof opposite to the second side for reception by
the second light polarization selector 12. The modulated
S-polarized third color component 103 from the third light
modulator 17 will be reflected by the polarization beam splitter
prism 13 in a transverse direction so as to pass through the fourth
side thereof for reception by the second light polarization
selector 12.
[0016] When the second light polarization selector 12 receives the
modulated first, second and third color components 101, 102, 103
from the polarization beam splitter prism 13, the polarization
state of the modulated P-polarized first and second color
components 101, 102 remains unaltered, whereas the polarization
state of the modulated S-polarized third color component 103 will
be changed to the P-polarization state.
[0017] The polarizer 18 permits only pure P-polarized color
components to pass therethrough, and absorbs S-polarized color
components. The modulated P-polarized first, second and third color
components 101, 102, 103 from the polarizer 18 are recombined as
they pass through the projection lens 19 for projecting a color
image on a display screen (not shown).
[0018] In the conventional projection display 1, the dichroic beam
splitter prism 14 and the polarization beam splitter prism 13
cooperate with the first and second light polarization selectors
11, 12 to separate the white input light beam 10 into the three
color components 101, 102, 103 that are modulated by the three
light modulators 15, 16, 17. However, in view of current
manufacturing constraints, the polarization beam splitter 13 does
not permit a very high transmission for P-polarized light. Thus,
when the P-polarized third color component 103 is received by the
polarization beam splitter prism 13, a small portion of the
P-polarized third color component 103 will be reflected by the
polarization beam splitter prism 13 to pass through the second side
thereof, i.e. toward the dichroic beam splitter prism 14, thus
resulting in a light leakage component 103'. This light leakage
component 103' will then be provided by the dichroic beam splitter
prism 14 to the first or second light modulator 15, 16. When the
first or second light modulator 15, 16 is inactive, the light
leakage component 103' will be reflected back to the dichroic beam
splitter prism 14, and pass through the polarization beam splitter
prism 13, the second light polarization selector 12, and the
polarizer 18 to reach the projection lens 19, thereby resulting in
a shift in the gray scale coordinate of the projected image and in
a reduction in the image contrast to adversely affect the output
quality of the projection display 1.
SUMMARY OF THE INVENTION
[0019] Therefore, the main object of the present invention is to
provide a projection display that utilizes reflective light
modulators and that is capable of overcoming the aforesaid light
leakage drawback of the prior art to enhance both contrast and
output image quality.
[0020] According to one aspect of the present invention, a
projection display is adapted to process an input light beam that
includes a first color component, a second color component and a
third color component, and comprises:
[0021] a polarization beam splitter prism having a first side
adapted to receive the input light beam, a second side, a third
side opposite to the first side, and a fourth side opposite to the
second side, the polarization beam splitter prism being adapted to
separate the input light beam into the first and second color
components, which pass through the second side thereof, and the
third color component, a large portion of which passes through the
third side thereof, the polarization beam splitter prism further
allowing a small portion of the third color component, which serves
as a light leakage component, to pass through the second side
thereof;
[0022] a color synthesizing prism disposed adjacent to the second
side of the polarization beam splitter prism, and adapted to
separate the first and second color components and the light
leakage component from the polarization beam splitter prism so as
to travel in three different directions, respectively;
[0023] reflective first and second light modulators disposed
adjacent to the color synthesizing prism so as to receive the first
and second color components respectively therefrom, the first and
second light modulators modulating the respective one of the first
and second color components and changing polarization state of the
respective one of the first and second color components when
activated, the first and second light modulators reflecting
modulated first and second color components back to the color
synthesizing prism; and
[0024] a reflective third light modulator disposed adjacent to the
third side of the polarization beam splitter prism so as to receive
the third color component therefrom, the third light modulator
modulating the third color component and changing polarization
state of the third color component when activated, the third light
modulator reflecting a modulated third color component back to the
polarization beam splitter prism.
[0025] According to another aspect of the present invention, a
projection display is adapted to process an input light beam that
includes a first color component, a second color component and a
third color component, and comprises:
[0026] a polarization beam splitter prism having a first side
adapted to receive the input light beam, a second side, a third
side opposite to the first side, and a fourth side opposite to the
second side, the polarization beam splitter prism being adapted to
separate the input light beam into the first and second color
components, which pass through the second side thereof, and the
third color component, a large portion of which passes through the
third side thereof, the polarization beam splitter prism further
allowing a small portion of the third color component, which serves
as a light leakage component, to pass through the second side
thereof;
[0027] a color splitter prism set disposed adjacent to the second
side of the polarization beam splitter prism, and adapted to
separate the first and second color components and the light
leakage component from the polarization beam splitter prism so as
to travel in three different directions, respectively;
[0028] reflective first and second light modulators disposed
adjacent to the color splitter prism set so as to receive the first
and second color components respectively therefrom, the first and
second light modulators modulating the respective one of the first
and second color components and changing polarization state of the
respective one of the first and second color components when
activated, the first and second light modulators reflecting
modulated first and second color components back to the color
splitter prism set; and
[0029] a reflective third light modulator disposed adjacent to the
third side of the polarization beam splitter prism so as to receive
the third color component therefrom, the third light modulator
modulating the third color component and changing polarization
state of the third color component when activated, the third light
modulator reflecting a modulated third color component back to the
polarization beam splitter prism.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] Other features and advantages of the present invention will
become apparent in the following detailed description of the
preferred embodiments with reference to the accompanying drawings,
of which:
[0031] FIG. 1 is a schematic view showing a conventional
single-lens projection display;
[0032] FIG. 2 is a schematic view showing the first preferred
embodiment of a projection display according to the present
invention;
[0033] FIG. 3 is a schematic view showing the second preferred
embodiment of a projection display according to the present
invention;
[0034] FIG. 4 is a schematic view showing the third preferred
embodiment of a projection display according to the present
invention;
[0035] FIG. 5 is a schematic view showing a first light
polarization selector for the projection display of this
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0036] Referring to FIG. 2, the first preferred embodiment of a
projection display 2 according to the present invention is shown to
include a first light polarization selector 21, a second light
polarization selector 22, a polarization beam splitter prism 23, a
polarizer 24, a color synthesizing prism 25, a first light
modulator 26, a second light modulator 27, a third light modulator
28, and a projection lens (not shown). A white input light beam 3
contains S-polarized first, second and third color components 31S,
32S, 33S, such as red, green and blue color components, that are to
be modulated by the first, second and third light modulators 26,
27, 28, respectively.
[0037] Each of the first and second light polarization selectors
21, 22, such as the ColorSelect.TM. filter products available from
ColorLink Inc., serves to convert the polarization state of a
predetermined color component, without altering the polarization
state of the other color components. In the projection display 2 of
this embodiment, the polarization state of the third color
component 33, such as the green color component, is changed,
whereas the polarization state of the first and second color
components 31, 32, such as the red and blue color components,
remains unaltered, after the color components 31, 32, 33 pass
through the first and second light polarization selectors 21,
22.
[0038] The polarization beam splitter prism 23 reflects light of a
first polarization state, such as S-polarized light, in a
transverse direction, and allows light of a second polarization
state, such as P-polarized light, to pass therethrough. In the
embodiment of FIG. 2, the polarization beam splitter prism 23 has a
first side disposed adjacent to the first light polarization
selector 21, a second side disposed adjacent to the color
synthesizing prism 25, a third side opposite to the first side and
disposed adjacent to the third light modulator 28, and a fourth
side opposite to the second side and disposed adjacent to the
second light polarization selector 22. In view of the
characteristics of the polarization beam splitter prism 23, when
the P-polarized third color component 33P is received by the
polarization beam splitter prism 23 from the first light
polarization selector 21, a small portion of the P-polarized third
color component 33P will be reflected by the polarization beam
splitter prism 23 to pass through the second side thereof, i.e.
toward the color synthesizing prism 25, thus resulting in a light
leakage component 33P'.
[0039] The polarizer 24, which is disposed adjacent to the second
light polarization selector 22, allows light of a predetermined
polarization state to pass therethrough, and absorbs light of the
other polarization state. In the present embodiment, the polarizer
24 allows P-polarized light to pass therethrough, and absorbs
S-polarized light.
[0040] The color synthesizing prism 25 receives the S-polarized
first and second color components 31S, 32S and the light leakage
component 33P' from the polarization beam splitter prism 23. In the
present embodiment, the color synthesizing prism 25 reflects the
S-polarized first and second color components 31S, 32S in opposing
transverse directions, and allows the light leakage component 33P'
to pass directly therethrough.
[0041] Each of the first, second and third light modulators 26, 27,
28 is a reflective light valve, and is disposed adjacent to one of
the color synthesizing prism 25 and the polarization beam splitter
prism 23 so as to receive a respective one of the first, second and
third color components 31, 32, 33 therefrom. In this embodiment,
the first and second light modulators 26, 27 are disposed adjacent
to opposite sides of the color synthesizing prism 25, whereas the
third light modulator 28 is disposed adjacent to the third side of
the polarization beam splitter prism 23. When activated, each of
the first, second and third light modulators 26, 27, 28 modulates
the respective one of the first, second and third color components
31, 32, 33, and changes the polarization state of the respective
one of the first, second and third color components 31, 32, 33. The
first, second and third light modulators 26, 27, 28 then reflect
modulated first, second and third color components 31, 32, 33 back
to the adjacent one of the color synthesizing prism 25 and the
polarization beam splitter prism 23.
[0042] In operation, when the first light polarization selector 21
receives the S-polarized white input light beam 3, the
S-polarization state of the first and second color components 31S,
32S remains unaltered, whereas the polarization state of the third
color component 33S is changed to the P-polarization state, after
the first, second and third color components 31S, 32S, 33S pass
through the first light polarization selector 21. The polarization
beam splitter prism 23 receives the S-polarized first and second
color components 31S, 32S and the P-polarized third color component
33P from the first light polarization selector 21 at the first side
thereof, reflects the S-polarized first and second color components
31S, 32S in a transverse direction such that the S-polarized first
and second color components 31S, 32S pass through the second side
thereof toward the color synthesizing prism 25, permits a large
portion of the P-polarized third color component 33P to pass
directly through the third side thereof toward the third light
modulator 28, and reflects a small portion of the P-polarized third
color component 33P, i.e. the light leakage component 33P', in the
transverse direction so as to pass through the second side
thereof.
[0043] The color synthesizing prism 25 receives the S-polarized
first and second color components 31S, 32S and the light leakage
component 33P' from the polarization beam splitter prism 23. The
color synthesizing prism 25 reflects the S-polarized first color
component 31S in a first transverse direction for reception by the
first light modulator 26, and further reflects the S-polarized
second color component 32S in a second transverse direction for
reception by the second light modulator 27. The color synthesizing
prism 25 permits the light leakage component 33P' to pass directly
therethrough, thereby preventing the light leakage component 33P'
from reaching the projection lens (not shown). A shift in the gray
scale coordinate of the projected image can thus be avoided to
enhance both the image contrast and the output quality of the
projection display 2.
[0044] The first and second light modulators 26, 27 receive the
S-polarized first and second color components 31S, 32S from the
color synthesizing prism 25, modulate the respective one of the
S-polarized first and second color components 31S, 32S, and change
the polarization state of the respective one of the first and
second color components 31S, 32S from the S-polarization state to
the P-polarization state when the first and second light modulators
26, 27 are activated. The first and second light modulators 26, 27
then reflect the corresponding modulated P-polarized color
component 31P, 32P back to the color synthesizing prism 25 for
reception by the polarization beam splitter prism 23.
[0045] The third light modulator 28 receives the P-polarized third
color component 33P from the polarization beam splitter prism 23,
modulates the P-polarized third color component 33P, and changes
the polarization state of the third color component 33P from the
P-polarization state to the S-polarization state when the third
light modulator 28 is activated. The third light modulator 28
reflects the modulated S-polarized third color component 33S back
to the polarization beam splitter prism 23.
[0046] The modulated P-polarized first and second color components
31P, 32P from the color synthesizing prism 25 will be allowed by
the polarization beam splitter prism 23 to pass directly through
the fourth side thereof for reception by the second light
polarization selector 22. The modulated S-polarized third color
component 33S from the third light modulator 28 will be reflected
by the polarization beam splitter prism 23 in a transverse
direction so as to pass through the fourth side thereof for
reception by the second light polarization selector 22.
[0047] When the second light polarization selector 22 receives the
modulated first, second and third color components 31P, 32P, 33S
from the polarization beam splitter prism 23, the polarization
state of the modulated P-polarized first and second color
components 31P, 32P remains unaltered, whereas the polarization
state of the modulated S-polarized third color component 33S will
be changed to the P-polarization state.
[0048] The polarizer 24 permits only pure P-polarized color
components to pass therethrough, and absorbs S-polarized color
components. The modulated P-polarized first, second and third color
components 31P, 32P, 33P from the polarizer 24 are recombined as
they pass through the projection lens (not shown) for projecting a
color image on a display screen (not shown)
[0049] Referring to FIG. 3, the second preferred embodiment of a
projection display 4 according to the present invention is shown to
include a first light polarization selector 41, a second light
polarization selector 42, a polarization beam splitter prism 43, a
polarizer 44, a first light modulator 46, a second light modulator
47, a third light modulator 48, and a projection lens (not shown).
However, unlike the first preferred embodiment, which uses a color
synthesizing prism 25, the projection display 4 of this embodiment
additionally includes a color splitter prism set formed from first
and second color splitter prisms 451, 452. The first color splitter
prism 451 has a first side formed as a total reflection interface
456, a second side formed as a light splitting interface 457 and
disposed adjacent to the first light modulator 46, and a third
side. The second color splitter prism 452 has a first side formed
as a total reflection interface 454 and disposed adjacent to the
second side of the polarization beam splitter prism 43, a second
side formed as a light splitting interface 455 and disposed
adjacent to the total reflection interface 456 of the first color
splitter prism 451, and a third side disposed adjacent to the
second light modulator 47. The light splitting interface 455 of the
second color splitter prism 452 cooperates with the total
reflection interface 456 of the first color splitter prism 451 to
form a clearance 453 therebetween.
[0050] In use, when the second color splitter prism 452 receives
the second color component 52 from the polarization beam splitter
prism 43 at the total reflection interface 454 thereof, the second
color component 52 is subsequently reflected entirely back to the
total reflection interface 454 by the second light splitting
interface 455 so as to pass through the third side of the second
color splitter prism 452 for reception by the second light
modulator 47. When activated, the second light modulator 47
modulates the second color component 52, and changes the
polarization state of the second color component 52. The second
light modulator 47 then reflects the modulated second color
component 52 back to the second color splitter prism 452 for
reception by the polarization beam splitter prism 43.
[0051] On the other hand, when the second color splitter prism 452
receives the first color component 51 from the polarization beam
splitter prism 43 at the total reflection interface 454 thereof,
the first color component 51 will be allowed to pass directly
through the light splitting interface 455 for reception by the
first color splitter prism 451 at the total reflection interface
456 of the latter. The first color splitter prism 451 allows the
first color component 51 to pass directly through the light
splitting interface 457 for reception by the first light modulator
46. When activated, the first light modulator 46 modulates the
first color component 51, and changes the polarization state of the
first color component 51. The first light modulator 46 then
reflects the modulated first color component 51 back to the first
color splitter prism 451 for passage through the second color
splitter prism 452 prior to reception by the polarization beam
splitter prism 43.
[0052] Like the previous embodiment, the polarization beam splitter
prism 43 permits a large portion of the third color component 53 to
pass directly through the third side thereof toward the third light
modulator 48 for processing in the manner described beforehand. A
small portion of the third color component 53, i.e. the light
leakage component 53', is reflected by the polarization beam
splitter prism 43 in the transverse direction so as to be received
by the second color splitter prism 452 at the total reflection
interface 454 of the latter. The second color splitter prism 452
permits the light leakage component 53' to pass directly through
the color splitting interface 455 thereof for reception by the
first color splitter prism 451 at the total reflection interface
456. The light leakage component 53' is reflected entirely by the
color splitting interface 457 back to the total reflection
interface 456, which then reflects the same to pass through the
third side of the first color splitter prism 451, thereby
preventing the light leakage component 53' from reaching the
projection lens (not shown). Stability in the gray scale coordinate
of the projected image can thus be ensured to enhance both the
image contrast and the output quality of the projection display
4.
[0053] The modulated first, second and third color components 51,
52, 53 will be directed by the polarization beam splitter prism 43
to pass in sequence through the second light polarization selector
42, the polarizer 44, and the projection lens (not shown) for
projecting a color image on a display screen (not shown).
[0054] FIG. 4 illustrates the third preferred embodiment of a
projection display 6 according to the present invention, which is a
modification of the second preferred embodiment. Like the
embodiment of FIG. 3, a color splitter prism set includes first and
second color splitter prisms 63, 64 that have a clearance 62 formed
therebetween. However, unlike the previous embodiment, the first
color splitter prism 63 has a first side formed as a total
reflection interface 631 adjacent to the second color splitter
prism 64, a second side formed as a light splitting interface 632,
and a third side disposed adjacent to the first light modulator
65.
[0055] When the first color component 71 passes through the second
color splitter prism 64 for reception by the first color splitter
prism 63 at the total reflection interface 631 thereof, the first
color component 71 will be reflected entirely by the color
splitting interface 632 back to the total reflection interface 631,
which then reflects the same to pass through the third side of the
first color splitter prism 63 for processing by the first light
modulator 65. On the other hand, the small portion of the third
color component 73, i.e. the light leakage component 73', that is
reflected by the polarization beam splitter prism 61 and that
passes through the second color splitter prism 64, will be allowed
by the first color splitter prism 63 to pass through the total
reflection interface 631 and the light splitting interface 632,
thereby preventing the light leakage component 73' from reaching
the projection lens (not shown) of the projection display 6.
[0056] It has thus been shown that, with the inclusion of a color
synthesizing prism or a color splitter prism set, the light leakage
component that is attributed to the third color component can be
prevented from reaching the projection lens so as to ensure
stability in the gray scale coordinate of the projected image and
to thereby enhance both the image contrast and the output quality
of the projection display.
[0057] FIG. 5 illustrates a first light polarization selector that
is suitable for use in any one of the projection displays of FIGS.
2, 3 and 4. As shown, a first dichroic mirror 91 receives
S-polarization first, second and third color components Rs, Bs, Gs.
The first dichroic mirror 91 allows the first and second color
components Rs, Bs to pass therethrough in a first direction, and
reflects the third color component Gs such that the third color
components Gs travels in a second direction transverse to the first
direction. A first reflective mirror 92 reflects the first and
second color components Rs, Bs from the first dichroic mirror 91
such that the first and second color components Rs, Bs travel in a
third direction transverse to the first direction and parallel to
the second direction. A second reflective mirror 93 reflects the
third color component Gs from the first dichroic mirror 91 such
that the third color component Gs travels in a fourth direction
transverse to the second direction and parallel to the first
direction. A second dichroic mirror 94 receives the first and
second color components Rs, Bs from the first reflective mirror 92.
A half-wavelength plate 95 is disposed between the second
reflective mirror 93 and the second dichroic mirror 94 and converts
the polarization state of the third color component from
S-polarization to P-polarization before the third color component
reaches the second dichroic mirror 94. As such, the input light
beam can be obtained by the polarization beam splitter prism of the
projection display from the second dichroic mirror 94 of the first
light polarization selector, and includes the S-polarization first
and second color components Rs, Bs and the P-polarization third
color component Gp.
[0058] While the present invention has been described in connection
with what is considered the most practical and preferred
embodiments, it is understood that this invention is not limited to
the disclosed embodiments but is intended to cover various
arrangements included within the spirit and scope of the broadest
interpretation so as to encompass all such modifications and
equivalent arrangements.
* * * * *