U.S. patent application number 09/230084 was filed with the patent office on 2001-12-20 for optical modulation element and projection display device.
Invention is credited to FUJIMORI, MOTOYUKI, HABA, SHINJI, HASHIZUME, TOSHIAKI.
Application Number | 20010052963 09/230084 |
Document ID | / |
Family ID | 26465293 |
Filed Date | 2001-12-20 |
United States Patent
Application |
20010052963 |
Kind Code |
A1 |
HASHIZUME, TOSHIAKI ; et
al. |
December 20, 2001 |
OPTICAL MODULATION ELEMENT AND PROJECTION DISPLAY DEVICE
Abstract
Liquid crystal modulation elements 925R, 925G and 925B are
arranged so that light outgoing surfaces 9252R, 9252G and 9252B
thereof face light incident surfaces 911R, 911G and 911b of a color
synthesizing prism 910. Transparent plates 970R, 970G and 970B are
bonded to the light outgoing surfaces 9252R, 9252G and 9252B of the
liquid crystal modulation elements 925R, 925G, and 925B. For this
reason, adhesion of dust to the light outgoing surfaces 9252R,
9252G and 9252B of the liquid crystal modulation elements 925R,
925G and 925B can be prevented. Further, it is possible to prevent
light reflection at the interface surface between the light
outgoing surfaces 9252R, 9252G and 9252B and air due to the
difference in refractive index therebetween. This allows a
high-quality image to be projected without deteriorating the
switching characteristic of the liquid crystal modulation elements
925R, 925G and 925B while preventing dirt from adhering to the
light outgoing surfaces 9252R, 9252G and 9252B of the liquid
crystal modulation elements 925R, 925G and 925B.
Inventors: |
HASHIZUME, TOSHIAKI;
(OKAYA-SHI, JP) ; HABA, SHINJI; (SHIUJIRI-SHI,
JP) ; FUJIMORI, MOTOYUKI; (SUWA-SHI, JP) |
Correspondence
Address: |
OLIFF & BERRIDGE
PO BOX 19928
ALEXANDRIA
VA
22320
|
Family ID: |
26465293 |
Appl. No.: |
09/230084 |
Filed: |
January 19, 1999 |
PCT Filed: |
May 19, 1998 |
PCT NO: |
PCT/JP98/02201 |
Current U.S.
Class: |
353/30 ;
348/E9.027 |
Current CPC
Class: |
H04N 9/3141 20130101;
H04N 9/3105 20130101; G03B 21/006 20130101 |
Class at
Publication: |
353/30 |
International
Class: |
G03B 021/26 |
Foreign Application Data
Date |
Code |
Application Number |
May 20, 1997 |
JP |
9-130093 |
Dec 1, 1997 |
JP |
9-330619 |
Claims
1. An optical modulation element for modulating a light flux
emitted from a light source according to image information, wherein
a transparent plate is provided on at least one surface thereof,
and the space between the transparent plate and said optical
modulation element is shielded from the outside by a
dust-preventing member.
2. The optical modulation element according to claim 1, wherein
said dust-preventing member is formed of resin containing glass
fiber.
3. The optical modulation element according to claim 1, wherein
said dust-preventing member is made of metal.
4. The optical modulation element according to claims 1 to 3,
wherein a polarizer is bonded to said transparent plate.
5. The optical modulation element according to claims 1 to 3,
wherein at least one surface of said transparent plate is coated
with a surface-active agent, or treated for electrostatic
protection.
6. A projection display device having an optical modulation element
for modulating a light flux emitted from a light source according
to image information, and projection means for enlarging and
projecting the light modulated by said optical modulation element
onto a projection plane, wherein a transparent plate is provided on
the side of a light outgoing surface of said optical modulation
element, and a space between said transparent plate and the light
outgoing surface of said optical modulation element is shielded
from the outside by a dust-preventing member.
7. The projection display device according to claim 6, wherein said
dust-preventing member has a frame body for holding said optical
modulation element, said transparent plate and said spacer, and a
light outgoing-side outer frame detachably fixed to the light
outgoing side of said frame body, said frame body includes a
contact surface for the light incident surface contacting a part of
the light incident surface of said optical modulation element, a
contact surface for the optical modulation element side surface
contacting the side surface of said optical modulation element and
a contact surface for the transparent plate side surface contacting
the side surface of said transparent plate, and said light
outgoing-side outer frame includes a pressure surface that can
press a part of the light outgoing surface of said transparent
plate towards said frame body.
8. The projection display device according to claim 7, wherein said
frame body has a guide surface formed thereon for putting a roller
on the light outgoing surface of said optical modulation element
and moving said roller in one direction.
9. The projection display device according to any one of claims 6
to 8, wherein an antireflection film is provided on the surface of
said transparent plate.
10. The projection display device according to any one of claims 6
to 9, wherein said optical modulation element is the transmissive
optical modulation element, and a light incident-side transparent
plate is provided on the side of the light incident surface of said
transmissive optical modulation element.
11. The projection display device according to claim 10, wherein a
space between said light incident-side transparent plate and the
light incident surface of said transmissive optical modulation
element is cut off from the outside by said dust-preventing
member.
12. The projection display device according to claim 11, including
a light incident-side outer frame to be detachably fixed to the
light incident side of said frame body, wherein said light
incident-side outer frame includes a pressure surface that can
press a part of the light incident surface of said light
incident-side transparent plate towards said frame body, and said
frame body includes a contact surface for the light outgoing
surface contacting a part of the light outgoing surface of said
light incident-side transparent plate, and a contact surface for
the transparent plate contacting the side surface of said light
incident-side transparent plate.
13. The projection display device according to claim 12, wherein
said light incident-side outer frame and said light outgoing-side
outer frame are formed into the same shape and include engaging
pawls extending along side surface of said frame body, said frame
body includes engaging projections corresponding to said engaging
pawls, respectively, and the respective engaging projections are
formed at the positions shifted in a direction perpendicular to the
thickness direction of said frame body.
14. The optical modulation element according to claim 6, wherein
said dust-preventing member is formed of resin containing glass
fiber.
15. The optical modulation element according to claim 6, wherein
said dust-preventing member is made of metal.
16. The optical modulation element according to claims 6 to 13,
wherein a polarizer is bonded to said transparent plate.
17. The optical modulation element according to claims 6 to 13,
wherein at least one surface of said transparent plate is coated
with a surface-active agent, or treated for electrostatic
protection.
18. A projection display device for separating a light flux emitted
from a light source into a plurality of color light fluxes,
modulating the color light fluxes according to image information
through an optical modulation element, synthesizing the color light
fluxes modulated by said optical modulation element by color
synthesizing means, and enlarging and projecting light synthesized
by said color synthesizing means onto a projection surface through
projection means, said projection display device including: a
transparent plate provided on the side of a light outgoing surface
of said optical modulation element, a dust-preventing member for
holding said transparent plate and said optical modulation element,
and shielding the space between said transparent plate and the
light outgoing surface of said optical modulation element from the
outside, a fixed frame plate fixed on the light incident surface of
said color synthesizing means, and an intermediate frame plate
removably fixed to said fixed frame plate, wherein said
dust-preventing member is fixed to said intermediate frame
plate.
19. The projection display device according to claim 18 including
positioning means for positioning said optical modulation element
by defining the mounting position of said dust-preventing
member.
20. The projection display device according to claim 18, wherein
said optical modulation element is the transmissive optical
modulation element, said transparent plate is also provided on the
side of the light incident surface of said transmissive optical
modulation element, said transparent plate is also held by said
dust-preventing member, and the space between said transparent
plate and the light incident surface of said transparent plate
optical modulation element is shielded from the outside by said
dust-preventing member.
21. The projection display device according to claims 18 to 20,
wherein a polarizer is provided on said light incident surface of
said color synthesizing means, and the bonded surface of said fixed
frame plate to said light incident surface is not completely
covered with said polarizer.
22. The projection display device according to claims 18 to 21,
wherein at least one surface of said transparent plate is coated
with a surface-active agent, or treated for electrostatic
protection.
23. The projection display device according to claims 18 to 21,
wherein a polarizer is bonded to said transparent plate.
24. The projection display device according to claims 18 to 23,
wherein said dust-preventing member is formed of resin containing
glass fiber.
25. The projection display device according to claims 18 to 23,
wherein said dust-preventing member is made of metal.
Description
TECHNICAL FIELD
[0001] The present invention relates to an optical modulation
element and a projection display device. More particularly, the
present invention relates to a layout structure of optical elements
on the periphery of an optical modulation element that modulates a
light flux according to image information.
BACKGROUND ART
[0002] A projection display device basically consists of a light
source lamp unit, an optical unit for optically processing a light
flux emitted from the light source lamp unit so as to synthesize a
color image corresponding to image information, a projection lens
unit for enlarging and projecting the synthesized light flux onto a
screen, a power supply unit, and a circuit substrate on which a
control circuit and the like are mounted.
[0003] FIG. 17 schematically shows the construction of the optical
unit and the projection lens unit of the above-mentioned
components. As shown in this drawing, an optical system of an
optical unit 9a includes a lamp body 81 serving as a light source,
a color separation optical system 924 for separating a light flux W
emitted from the lamp body 81 into respective color light fluxes R,
G and B of the primary colors of red (R), green (G) and blue (B),
three sheets of liquid crystal modulation elements 925R, 925G and
925B for modulating the separated respective color light fluxes
according to image information, and a color synthesizing prism 910
in the shape of a prism with a square cross section to synthesize
the modulated color light fluxes. The light flux W emitted from the
lamp body 81 is separated into respective color light fluxes R, G
and B by the color separation optical system 924 including various
types of dichroic mirrors, and the red and green light fluxes R and
G of the respective color light fluxes are emitted from outgoing
sections provided in the color separation optical system 924
towards corresponding liquid crystal modulation elements 925R and
925G. The blue light flux B is guided to the corresponding liquid
crystal modulation element 925B via a light guide system 927, and
is emitted from an outgoing section provided in the light guide
system 927 towards the corresponding liquid crystal modulation
element 925B.
[0004] As shown in FIGS. 17(B) and 17(C) in enlargement, in the
optical unit 9a, polarizers 960R, 960G and 960B are respectively
arranged on the side of incident surfaces of the liquid crystal
modulation elements 925R, 925G and 925B so that they unify the
planes of polarization of the respective color light fluxes to be
incident on the liquid crystal modulation elements 925R, 925G and
925B. In addition, polarizers 961R, 961G and 961B are respectively
arranged on the side of outgoing surfaces of the liquid crystal
modulation elements 925R, 925G and 925B so that they unify the
planes of polarization of the modulated color fluxes to be incident
on the color synthesizing prism 910. The actions of these
polarizers allow an enlarged image excellent in contrast to be
projected onto the surface of a screen 10. Of the two polarizers
that sandwich the liquid crystal modulation elements 925R, 925G and
925B, the polarizers 961R, 961G and 961B positioned on the side of
the outgoing surfaces of the liquid crystal modulation elements
925R, 925G and 925B are bonded to the light outgoing surfaces of
the liquid crystal modulation elements.
[0005] Incidentally, as the liquid crystal modulation elements
925R, 925G and 925B, an active matrix-type liquid crystal device is
generally used, in which pixels arranged in the form of a matrix
are controlled by a switching element.
[0006] Here, in order to improve the contrast of an image enlarged
and projected onto the screen 10, it is effective to bond a
polarizer, which has high selection properties with respect to
polarized light, to the light outgoing surface of each of the
liquid crystal modulation elements 925R, 925G and 925B. However,
such a polarizer having high selection properties absorbs much
light and therefore, generates much heat. Inside the projection
display device mentioned above, an air flow is formed as shown in
FIG. 17(C) and cools the polarizer. However, since the polarizer is
directly attached to the light outgoing surface of the liquid
crystal modulation element, heat is apt to be transmitted to the
liquid crystal modulation element, and to thereby increase the
temperature of the liquid crystal modulation element. This increase
in temperature deteriorates the optical properties of a liquid
crystal panel, and the image contrast.
[0007] Thus, it may be possible to arrange the polarizer apart from
the light outgoing surface of the liquid crystal modulation
element. However, if the polarizer is simply arranged apart from
the light outgoing surface, there is a fear that the switching
element in the liquid crystal modulation element may malfunction
due to a light beam reflected by the light outgoing surface of the
liquid crystal modulation element. In addition, there is a fear
that dust or the like may be caused by an air flow formed inside
the projection display device to adhere to the light outgoing
surface of the liquid crystal modulation element, and it may make
high-quality image projection impossible.
[0008] In view of the above-described points, an object of the
present invention is to provide an optical modulation element and a
projection display device that achieve high-quality image
projection by preventing dust from adhering to the light outgoing
surface of the optical modulation element without deteriorating the
switching characteristic of the optical modulation element.
DISCLOSURE OF INVENTION
[0009] In order to achieve the above-described object, there is
provided an optical modulation element for modulating a light flux
emitted from a light source according to image information, wherein
a transparent plate is provided on at least one surface thereof,
and the space between the transparent plate and the optical
modulation element is shielded from the outside by a
dust-preventing member.
[0010] In such an optical modulation element, heat generated by a
polarizer to be transmitted to the optical modulation element can
be further reduced. In addition, since the space between the
transparent plate and the optical modulation element is shielded
from the outside by the dust-preventing member, dust does not enter
the space. For this reason, negative effects, such as the light
flux emitted from the optical modulation element being scattered by
dust, can be solved.
[0011] The dust-preventing member may preferably be formed of resin
containing glass fiber. In this case, it is possible to restrict
linear expansion, to prevent movement of the optical modulation
element, and to maintain a constant temperature and a uniform
in-plane temperature distribution of the optical modulation
element.
[0012] On the other hand, the dust-preventing member may be made of
metal. This makes it possible to improve the heat dissipation
effect. In particular, when a polarizer is bonded to the
transparent plate, it is preferable that the dust-preventing member
be made of metal because heat is generated with the absorption of
light by the polarizer.
[0013] In the optical modulation element of the present invention,
it is also possible to bond the polarizer to the transparent plate.
This prevents dust from entering between the polarizer and the
transparent plate. For this reason, negative effects, such as the
light flux emitted from the optical modulation element being
scattered by dust, can be prevented more effectively.
[0014] In addition, in the optical modulation element of the
present invention, at least one surface of the transparent plate
may preferably be coated with a surface-active agent, or treated
for electrostatic protection. This makes it possible to prevent
dust from adhering to the transparent plate.
[0015] A projection display device of the present invention may be
constructed in which a transparent plate is provided on the side of
a light outgoing surface of the optical modulation element, and the
space between the transparent plate and the light outgoing surface
of the optical modulation element is shielded from the outside by a
dust-preventing member.
[0016] When the polarizer is arranged on the side of the light
outgoing surface of the transparent plate, since the transparent
plate and an air layer exist between the optical modulation element
and the polarizer, heat generated by a polarizer to be transmitted
to the optical modulation element can be further reduced. In
addition, since the space between the transparent plate and the
optical modulation element is shielded from the outside by the
dust-preventing member, dust does not enter the space. For this
reason, bad effects, such as the light flux emitted from the
optical modulation element being scattered by dust, can be
solved.
[0017] As the dust-preventing member, a member having a frame body
for holding the optical modulation element and the transparent
plate, and a light outgoing-side outer frame detachably fixed to
the light outgoing side of the frame body may be used. In the case
of using such a dust-preventing member, the frame body may be
provided with a light incident contact surface which contacts a
part of the light incident surface of the optical modulation
element, an optical modulation element side contact surface which
contacts the side surface of the optical modulation element, and a
transparent plate side contact surface which contacts the side
surface of the transparent plate. In addition, the light
outgoing-side outer frame may be provided with a pressure surface
that can press a part of the light outgoing surface of the
transparent plate towards the frame body.
[0018] This allows the optical modulation element to come into
contact with the light incident contact surface and the optical
modulation element contact surface provided on the frame body,
thereby being arranged in a predetermined position on the frame
body. In addition, the position of the transparent plate relative
to the frame body and the optical modulation element is defined by
the the transparent plate contact surface and a spacer provided on
the frame body. Therefore, if the light outgoing-side outer frame,
is fixed to the frame body after the optical modulation element,
spacer and transparent plate have been superposed in this order,
the light outgoing surface of the transparent plate is pressed by
the pressure surface of the light outgoing-side outer frame towards
the frame body side, so that the optical modulation element, spacer
and transparent plate can be held by the frame body and the light
outgoing-side outer frame, and at the same time, arrangement
thereof in relation to one another can be maintained.
[0019] If the optical modulation element, the transparent plate and
the like are fixed to the frame body using an adhesive, replacement
thereof requires much labor. For example, after the optical
modulation element and the transparent plate are separated from the
frame body, a step of cleaning the adhesive adhering thereto is
required.
[0020] In contrast, if the dust-preventing member such as described
above is used, the light outgoing-side outer frame may merely be
removed at the time of replacement of components, so that
operability of rework can be improved.
[0021] It is desirable that a guide surface for putting a roller on
the light outgoing surface of the optical modulation element and
moving the roller in one direction is provided on the frame body.
An antireflection film (AR film) may be bonded to the light
outgoing surface of the optical modulation element for the purpose
of improving the light utilizing efficiency. In such a case, if the
roller is moved along the guide surface with the AR film placed on
the light outgoing surface of the optical modulation element, the
AR film can be easily bonded to the light outgoing surface of the
optical modulation element.
[0022] In addition, since the guide surface is formed and the
roller can be easily moved, it is easy to eliminate air bubbles
generated between the light outgoing surface of the optical
modulation element and the AR film. When replacing the AR film to
which dust is adhered, the light outgoing-side outer frame is
removed from the frame body and the transparent plate and the
spacer are removed from the frame body. Thereafter, the AR film to
which dust is adhered is separated from the light outgoing surface
of the optical modulation element, and a new AR film is bonded with
the use of the guide surface as described above while moving the
roller. After the renewal of the AR film, the spacer and the
transparent plate are superposed on the optical modulation element
and the light outgoing-side outer frame is fixed to the frame body.
The AR film can be easily renewed by using the dust-preventing
member having the frame body on which the guide surface is
formed.
[0023] In such a projection display device of the present
invention, at least one surface of the transparent plate may be
coated with an antireflection film, whereby light reflected from
the transparent plate to the optical modulation element can be
eliminated as described above, and switching characteristic of the
optical modulation element can be maintained more excellently.
[0024] As the optical modulation element, either of transmissive or
reflective optical modulation element may be used. When the
transmissive optical modulation element is used, the transparent
plate (light incident-side transparent plate) may desirably be
provided not only on the side of the light outgoing surface, but
also on the side of the light incident surface thereof and further,
the space between the transparent plate provided on the side of the
light incident surface and the light incident surface of the
optical modulation element may desirably be shielded from the
outside by the dust-preventing member.
[0025] When the transmissive optical modulation element is used and
the transparent plate is provided on the side of the light incident
surface thereof, a bonded light outgoing surface contacting a part
of the light outgoing surface of the transparent plate on the side
of the light incident surface and a transparent side contact
surface contacting the side surface of the light incident-side
transparent plate may be provided on the frame body of the
dust-preventing member. In addition, a light incident-side outer
frame detachably fixed to the light incident side of the frame body
may be provided, and a pressure surface that can press the light
incident surface of the light incident-side transparent plate
towards the frame body may be provided on the light incident-side
outer frame. This allows the light incident-side transparent plate
to be held on the side of the light incident surface of the optical
modulation element without using an adhesive. In addition, the
transparent plate can be easily replaced by only removing the light
incident-side outer frame from the frame body.
[0026] When the light incident-side outer frame and the light
outgoing-side outer frame are formed of the same shape, engaging
pawls extending along the side surface of the frame body are formed
on the respective outer frames, and engaging projections each
corresponding to the engaging pawls are formed on the frame body,
the positions of the respective engaging projections formed on the
frame body may desirably be shifted in the direction perpendicular
to the thickness direction of the frame body. It is difficult to
form a frame body on which the positions of the respective engaging
projections match in the thickness direction of the frame body by
upper and lower dies. However, the frame body can be easily formed
as in a conventional manner by using the frame body as described
above. In addition, since the light incident-side outer frame and
the light outgoing-side outer frame have the same shape,
commonality of components can be achieved.
[0027] The dust-preventing member may preferably be formed of resin
containing glass fiber. In this case, it is possible to restrict
linear expansion, to prevent movement of the optical modulation
element, and to maintain a constant temperature and a uniform
in-plane temperature distribution of the optical modulation
element.
[0028] On the other hand, if the dust-preventing member is made of
metal, it is possible to improve the heat dissipation effect. In
particular, when a polarizer is bonded to the transparent plate, it
is preferable that a mounting frame plate be made of metal because
heat is generated with the absorption of light by the
polarizer.
[0029] In the above-described projection display device of the
present invention, it is also possible to bond the polarizer to the
transparent plate. This prevents dust from entering between the
polarizer and the transparent plate. For this reason, negative
effects, such as the light flux emitted from the optical modulation
element being scattered by dust, can be prevented more
effectively.
[0030] In addition, in the above-described projection display
device of the present invention, at least one surface of the
transparent plate may preferably be coated with a surface-active
agent, or treated for electrostatic protection. This makes it
possible to prevent dust from adhering to the transparent
plate.
[0031] Furthermore, the projection display device of the present
invention adopts a construction such as a projection display device
for separating a light flux emitted from a light source into a
plurality of color light fluxes, modulating respective color light
fluxes according to image information through an optical modulation
element, synthesizing respective color light fluxes modulated by
the optical modulation element by a color synthesizing means, and
enlarging and projecting light synthesized by the color
synthesizing means onto a projection surface through projection
means, the projection display device including: a transparent plate
provided on the side of a light outgoing surface of the optical
modulation element, a dust-preventing member for holding the
transparent plate and the optical modulation element and for
shielding the space between the transparent plate and the light
outgoing surface of the optical modulation element from the
outside, a fixed frame plate fixed on the light incident surface of
the color synthesizing means, and an intermediate frame plate
removably fixed to the fixed frame plate, wherein the
dust-preventing member is fixed to the intermediate frame plate. By
the projection display device having this construction, the heat
generated by the polarizer to be transmitted to the optical
modulation element can be further reduced, and bad effects such
that the light flux emitted from the optical modulation element is
scattered by dust can be avoided. In addition to this, since it is
not necessary to mount the optical modulation element to the color
synthesizing means side by directly touching the optical modulation
element, it is also possible to prevent the optical modulation
element from interfering with other parts and to prevent it from
being broken or chipped.
[0032] In the projection display device of the present invention
having this construction, it is convenient to provide positioning
means for positioning the optical modulation element by defining
the mounting position of the dust-preventing member because the
mounting positions of the dust-preventing member and the optical
modulation element can be defined at the same time by this
positioning means.
[0033] In the projection display device having this construction,
when the transmissive optical modulation element is used, it is
desirable to provide the transparent plate not only on the side of
the light outgoing surface but also on the side of the light
incident surface, as mentioned above. It is also desirable that the
space between the transparent plate provided on the light incident
surface side and the light incident surface of the optical
modulation element is shielded from the outside by the
dust-preventing member.
[0034] Here, there may be a case where the polarizer is fixed to
the light incident surface of the color synthesizing means. In such
a case, if the peripheral portion of the polarizer is completely
superposed on the bonded surface of the fixed frame plate, there is
a fear that the bonding strength decreases or the polarizer is
separated. In order to assuredly avoid such a problem, it may be
preferable to form the fixed frame plate so that only a part of the
bonded surface is superposed on the peripheral portion of the
polarizer. That is, it may be preferable that the bonded surface of
the fixed frame plate to the light incident surface is not
completely covered with the polarizer.
[0035] The surface of the transparent plate may be coated with a
surface-active agent, or treated for electrostatic protection. In
this case, it is difficult for dust to adhere to the surface of the
transparent plate, and it is possible to prevent dust from adhering
effectively.
[0036] When a polarizer is bonded to the transparent plate, since
it is possible to prevent dust from entering between the optical
modulation element and the polarizer, the polarization condition of
light is not disturbed by dust. In addition, when a black image is
displayed, a spot on the black image corresponding to the adhering
dust can be prevented from being displayed as a white blank, and
display quality can be improved.
[0037] When the above-described dust-preventing member is formed of
resin containing glass fiber, it is possible to restrict linear
expansion, to prevent moving of the optical modulation element, and
to maintain a constant temperature and a uniform in-plane
temperature distribution of the optical modulation element.
[0038] On the other hand, if the dust-preventing member is made of
metal, it is possible to improve the heat dissipation effect. In
particular, when a polarizer is bonded to the transparent plate, it
is preferable that the dust-preventing member be made of metal
because heat is generated with the absorption of light by the
polarizer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0039] FIG. 1 is a perspective view showing an external shape of a
projection display device to which the present invention is
applied.
[0040] FIG. 2 is a schematic plan structural view showing the
internal construction of the projection display device shown in
FIG. 1.
[0041] FIG. 3 is a schematic sectional structural view taken along
the line A-A of FIG. 2.
[0042] FIG. 4 is a schematic plan structural view showing only an
optical unit and a projection lens unit.
[0043] FIG. 5 is a schematic structural view showing an optical
system incorporated into the optical unit.
[0044] FIG. 6 is an enlarged view of the surroundings of a liquid
crystal modulation element of a projection display device according
to an embodiment 1 of the present invention.
[0045] FIG. 7 is a schematic sectional structural view of a
dust-preventing member.
[0046] FIG. 8 is a schematic plan structural view of the
dust-preventing member when viewed from the light incident
side.
[0047] FIG. 9 is a schematic plan structural view of the
dust-preventing member when viewed from the light outgoing
side.
[0048] FIG. 10(A) is an exploded perspective view showing a state
in which the dust-preventing member is attached to a light incident
surface of a color synthesizing prism, and
[0049] FIG. 10(B) is an illustration showing a large and small
relationship between a fixed frame plate and a polarizer.
[0050] FIG. 11 is an exploded perspective view of an example of a
dust-preventing member different from the dust-preventing member
shown in FIG. 7.
[0051] FIG. 12(A) is a schematic sectional structural view of the
dust-preventing member shown in FIG. 11 when cut along an XZ plane,
and
[0052] FIG. 12(B) is a schematic sectional structural view of the
dust-preventing member shown in FIG. 11 when cut by a YZ plane.
[0053] FIG. 13 is an illustration showing a state in which a roller
moves on a light outgoing surface of a liquid crystal modulation
element.
[0054] FIG. 14 is a plan view showing the engagement between
engaging pawls and engaging projections.
[0055] FIG. 15 is an exploded perspective view showing a state in
which the dust-preventing member shown in FIG. 11 is attached to
the color synthesizing prism.
[0056] FIG. 16 is a schematic structural view of the surroundings
of a liquid crystal modulation element of a projection display
device according to an embodiment 2 of the present invention.
[0057] FIG. 17 is a schematic structural view of an optical system
incorporated into an optical unit of a conventional projection
display device.
BEST MODE FOR CARRYING OUT THE INVENTION
[0058] <Embodiment 1>
[0059] An example of a projection display device to which the
present invention is applied will be described below with reference
to the drawings. The projection display device of this embodiment
separates a light flux emitted from a light source lamp unit into
light fluxes of three primary colors of red (R), green (G) and blue
(B), and these color light fluxes are modulated in correspondence
to image information through liquid crystal modulation elements,
and modulated light fluxes of respective colors are synthesized and
displayed in enlargement onto a screen through a projection lens
unit.
[0060] FIG. 1 shows an external appearance of the projection
display device of this embodiment. As shown in FIG. 1, a projection
display device 1 of this embodiment has an outer casing 2 in the
shape of a rectangular parallelepiped. The outer casing 2 basically
consists of an upper casing 3, a lower casing 4 and a front casing
5 for defining the front of the device. The leading end of a
projection lens unit 6 protrudes from the center of the front
casing 5.
[0061] FIG. 2 shows the respective arrangement of components inside
the outer casing 2 of the projection display device 1, and FIG. 3
shows a cross section taken along the line A A of FIG. 2. As shown
in these drawings, inside the outer casing 2, a power supply unit 7
is arranged on the rear end of the inside of the outer casing 2. A
light source lamp unit 8 is arranged at position adjacent to and
offset from the power supply unit 7 towards the front side of the
device. An optical unit 9 is arranged in front of the light source
lamp unit 8. A base end of the projection unit 6 is positioned at
the front center of the optical unit 9.
[0062] On the other hand, an interface substrate 11 having an
input-output interface circuit mounted thereon is arranged on a
side of the optical unit 9 so that it extends towards the front and
rear directions of the device, and a video substrate 12 having a
video signal processing circuit mounted thereon is arranged in
parallel to therewith. Furthermore, a control substrate 13 for
controlling the drive of the device is arranged above the light
source lamp unit 8 and the optical unit 9. Speakers 14R and 14L are
arranged at the right and left front corners of the device,
respectively.
[0063] A suction fan 15A for cooling is arranged on the center
upper side of the optical unit 9, and a circulating fan 15B for
forming a circulating stream for cooling is arranged on the center
bottom side of the optical unit 9. In addition, an exhaust fan 16
is arranged on a side of the device, which is the rear side of the
light source lamp unit 8. Furthermore, an auxiliary cooling fan 17
for sucking a cooling air stream from the suction fan 15A into the
power supply unit 7 is arranged at a position in the power supply
unit 7 opposed to the ends of the substrates 11 and 12.
[0064] A floppy-disk drive unit 18 is arranged directly above the
power supply unit 7 on the left side of the device.
[0065] The light source lamp unit 8 includes a light source lamp
80, and a lamp housing 83 containing therein the light source lamp
80. The light source lamp 80 includes a lamp body 81 such as a
halogen lamp, a xenon lamp, or a metal halide lamp, and a reflector
82 including a reflecting surface that is parabolic in cross
section, and it can reflect divergent light from the lamp body 81
so that the light emerges towards the optical unit 9 almost along
an optical axis.
[0066] FIG. 4 shows only the optical unit 9 and the projection lens
unit 6. As shown in this drawing, in the optical unit 9, optical
elements other than a color synthesizing prism 910 are vertically
sandwiched and held between the upper and lower light guides 901
and 902. The upper light guide 901 and the lower light guide 902
are fixed by fixing screws on the sides of the upper casing 3 and
the lower casing 4, respectively.
[0067] In addition, these upper and lower light guide plates 901
and 902 are similarly fixed on the sides of the color synthesizing
prism 910 by fixing screws. The color synthesizing prism 910 is
fixed by fixing screws on the rear of a thick head plate 903 formed
of a die-casting plate. The base end of the projection lens unit 6
is similarly fixed on the front of the head plate 903 by fixing
screws.
[0068] FIG. 5 shows a schematic construction of an optical system
incorporated into the projection display device 1 of this
embodiment. The optical system in the projection display device 1
of this embodiment adopts a light source lamp 80, which is a
component of the light source lamp unit 8, and a uniform
illumination optical system 923 consisting of integrator lenses 921
and 922, which are uniform illumination optical elements. The
projection display device 1 includes a color separation optical
system 924 for separating a light flux W emitted form the uniform
illumination optical system 923 into red (R), green (G) and blue
(B), three sheets of liquid crystal modulation elements 925R, 925G
and 925B for modulating the respective color light fluxes R, G and
B, the color synthesizing prism 910 serving as a color synthesizing
optical system for synthesizing the modulated color light fluxes,
and a light guide system 927 for guiding the synthesized light
fluxes to the liquid crystal modulation element 925B corresponding
to the blue light flux B in the projection lens unit 6 that
enlarges and projects the synthesized color light fluxes onto the
surface of the screen 10.
[0069] The uniform illumination optical system 923 includes a
reflecting mirror 931 so as to bend an optical axis 1a of outgoing
light from the uniform illumination optical system 923 at the right
angle towards the front of the device. The integrator lenses 921
and 922 are arranged in the state of being perpendicular to each
other with this reflecting mirror 931 sandwiched therebetween.
[0070] Light emitted from the light source lamp 80 is projected as
a secondary source image through the integrator lens 921 onto the
incident surface of each of the lenses constituting the integrator
lens 922, so that an object to be illuminated is irradiated using
the outgoing light from the integrator lens 922.
[0071] The color separation optical system 924 consists of a
blue-green reflecting dichroic mirror 941, a green reflecting
dichroic mirror 942 and a reflecting mirror 943. First, the blue
light flux B and the green light flux G contained in the light flux
W are reflected at right angles by the blue-green reflecting
dichroic mirror 941, and directed towards the green reflecting
dichroic mirror 942.
[0072] The red light flux R passes through this mirror 941, and is
reflected at right angles by the rear reflecting mirror 943 located
behind, and emitted from an outgoing section 944 for the red light
flux R to the side of the prism unit 910. Next, only green light
flux G of the blue and green light fluxes B and G reflected by the
mirror 941 is reflected at right angles by the green reflecting
dichroic mirror 942, and is emitted from an outgoing section 945
for the green light flux G to the side of the color synthesizing
optical system. The blue light flux B passing through this mirror
942 is emitted from an outgoing section 946 for the blue light flux
B to a side of the light guide system 927. In this embodiment, all
the distances between the outgoing section for the light flux W of
the uniform illumination optical element and the outgoing sections
944, 945 and 946 for the color light fluxes of the respective color
separation optical system 924 are equally set.
[0073] Condenser lenses 951 and 952 are arranged on the outgoing
sides of the outgoing sections 944 and 945 of the red and green
light fluxes R and G in the color separation optical system 942,
respectively. Therefore, the red and green light fluxes R and G
emitted from the outgoing sections respectively are incident on
these condenser lenses 951 and 952, where they are collimated.
[0074] The thus collimated red and green light fluxes R and G are
incident on the liquid crystal modulation elements 925R and 925G to
be modulated, and given image information corresponding thereto.
That is, these light valves are subjected to switching control by
non-illustrated driving means according to image information,
whereby each color light passing therethrough is modulated. As such
driving means, well-known means may be used unchanged.
[0075] On the other hand, the blue light flux B is guided to the
corresponding liquid crystal modulation element 925B through the
light guide system 927, where it is similarly modulated according
to the image information. In the light valves of this embodiment,
for example, a poly-silicon TFT may be used as a switching
element.
[0076] The light guide system 927 consists of a condenser lens 954
arranged on the outgoing side of the outgoing section 946 for the
blue light flux B, an incident-side reflecting mirror 971, an
outgoing-side reflecting mirror 972, an intermediate lens 973
arranged between these reflecting mirrors, and a condenser lens 953
arranged upstream of the liquid crystal modulation element 925B.
The blue light flux B of the color light fluxes has the longest
optical path lengths, that is, the distances between a light source
lamp 805 and each of the liquid crystal panels, and therefore, the
amount of light of the blue light flux B to be lost is the largest.
However, the light loss can be restricted by interposing the light
guide system 927 therebetween.
[0077] Next, the respective color light fluxes R, G and B modulated
passing through the respective liquid crystal modulation elements
925R, 925G and 925B are incident on the color synthesizing prism
910, where they are synthesized. A color image synthesized by the
color synthesizing prism 910 is enlarged and projected through the
projection lens unit 6 onto the surface of the screen 10 located at
a predetermined position.
[0078] FIG. 6 schematically shows a construction of the
surroundings of the liquid crystal modulation elements.
[0079] As shown in FIG. 6, in this embodiment, transparent plates
962R, 962G, 962B, 963R, 963G and 963B made of plastic or glass are
provided between dust-preventing members 965R, 965G and 965B on the
side of the light incident surfaces and on the side of the light
outgoing surfaces of the liquid crystal modulation elements 925R,
925G and 925B, respectively, which are plane-opposed to light
incident surfaces 911R, 911G and 911B of the color synthesizing
prism 910 at a predetermined distance. Spaces between the
transparent plates 962R, 962G, 962B, 963R, 963G and 963B and the
liquid crystal modulation elements 925R, 925G and 925B are shielded
from the outside by the dust-preventing members 965R, 965B and
965B. For this reason, since dust does not enter between the
transparent plates 962R, 962G, 962B, 963R, 963G and 963B and the
liquid crystal modulation elements 925R, 925G and 925B, the
respective color light fluxes can be prevented from being scattered
by the dust. In addition, the light outgoing surfaces of the liquid
crystal modulation elements 925R, 925G and 925B are coated with
light antireflection thin films, thereby preventing the
aforementioned malfunction of the liquid crystal modulation
elements 925R, 925G and 925B due to the return light described
above.
[0080] The incident and outgoing surfaces of the transparent plates
963R, 963G and 963B are also coated with light antireflection thin
films.
[0081] Incident-side polarizers 960R, 960G and 960B are arranged at
a predetermined distance from the light incident surfaces of the
transparent plates 962R, 962G and 962B, and outgoing-side
polarizers 961R, 961G and 961B are bonded to the light incident
surfaces 911R, 911G and 911B of the color synthesizing prism 910,
respectively.
[0082] In the thus constructed projection display device, since the
incident-side polarizers 960R, 960G and 960B and the outgoing-side
polarizers 961R, 961G and 961B are provided apart from the light
incident surfaces and light outgoing surfaces of the liquid crystal
modulation elements 925R, 925G and 925B, and the transparent plates
962R, 962G and 962B, 963R, 963G and 963B and air are provided
between the incident-side polarizers 960R, 960G and 960B, the
outgoing-side polarizers 961R, 961G and 961B and the liquid crystal
modulation elements 925R, 925G and 925B, it is possible to prevent
heat generated by the incident-side polarizers 960R, 960G and 960B
and the outgoing-side polarizers 961R, 961G and 961B from being
transmitted to the liquid crystal modulation elements 925R, 925G
and 925B. In addition, since the light outgoing surfaces of the
liquid crystal modulation elements 925R, 925G and 925B are
protected by the transparent plates 963R, 963G and 963B, and the
transparent plates 963R, 963G and 963B are apart from the light
outgoing surfaces of the liquid crystal modulation elements 925R,
925G and 925B, it is possible to prevent heat generated by the
outgoing-side polarizers 961R, 961G and 961B from being transmitted
to the liquid crystal modulation elements 925R, 925G and 925B. This
makes it possible to restrict the increase in temperature of the
liquid crystal modulation elements 925R, 925G and 925B and to
prevent the deterioration of optical properties thereof.
[0083] In addition, since the liquid crystal modulation elements
925R, 925G and 925B and the outgoing-side polarizers 961R, 961G and
961B are apart from each other, the light emitted from the liquid
crystal modulation elements 925R, 925G and 925B is widely spread,
and the light can be received by a wide area. For this reason, it
is possible to decrease the heat generated by the polarizers 961R,
961G and 961B per unit area, and to permit easy heat dissipation.
In particular, it is effective to arrange a michrolens array, which
gathers light onto each pixel of the liquid crystal modulation
elements, on the side of the light incident surfaces of the liquid
crystal modulation elements 925R, 925G and 925B because the light
can spread more widely.
[0084] Furthermore, in the projection display device of this
embodiment, since the transparent plates 962R, 962G and 962B are
bonded to the side of the light incident surfaces of the liquid
crystal modulation elements 925R, 925G and 925B, it is possible to
prevent dust from adhering to the light incident surfaces of the
liquid crystal modulation elements 925R, 925G and 925B.
[0085] Incidentally, the outgoing-side polarizers 961R, 961G and
961B may surely be bonded to the transparent plates 963R, 963G and
963B without being bonded to the light incident surfaces 911R, 911G
and 911B of the color synthesizing prism 910. In this case, it is
possible to prevent dust from entering between the liquid crystal
modulation elements 925R, 925G and 925B and the polarizers 961R,
961G and 961B, and to thereby prevent the polarization condition of
light from being disturbed by dust. In addition, when a black image
is displayed, its portion corresponding to the adhering dust can be
prevented from being displayed as a white blank, and the display
quality can be improved.
[0086] In addition, the outgoing-side polarizers 961R, 961G and
961B may surely be independently arranged between the transparent
plates 962R, 962G, 962B and the color synthesizing prism 910.
[0087] Further, the surfaces of such transparent plates 962R, 962G,
962B, 963R, 963G and 963B may be coated with a surface-active agent
(surfactant), or treated for electrostatic protection. This makes
it difficult for dust to adhere to the surfaces of the transparent
plates 962R, 962G, 962B, 963R, 963G and 963B, so that adhesion of
the dust can be prevented more effectively.
[0088] Incidentally, the polarizers include two types of
polarizers, a reflective polarizer and an absorptive polarizer. The
reflective polarizer transmits one of two types of linearly
polarized light, and reflects the other linearly polarized light.
In addition, the absorptive polarizer transmits one of two types of
linearly polarized light and absorbs the other linearly polarized
light. The polarizers 960R, 960G, 960B, 961R, 961G and 961B may be
either reflective or transmissive.
[0089] The structure of the dust-preventing members 965R, 965G and
965B will now be described in detail. Incidentally, since the
respective dust-preventing members 965R, 965G and 965B have the
same construction, only the dust-preventing member 965R will be
described on behalf thereof. In addition, in the following
explanation, three directions perpendicular to one another are
referred to as the X-axis direction (lateral direction), the Y-axis
direction (vertical direction) and the Z-axis direction (direction
parallel to the optical axis) for convenience. FIG. 7 shows a
schematic sectional construction of the dust-preventing member
965R. In addition, FIG. 8 shows a schematic plan construction of
the dust-preventing member 965R when viewed from the side of the
light incident surface, and FIG. 9 shows a schematic plan
construction when viewed from the side of the light outgoing
surface.
[0090] As shown in these drawings, the transparent plate 962R is
arranged on the light incident surface of the liquid crystal
modulation element 925R through a spacer 21, and the transparent
plate 963R is arranged on the light outgoing surface through a
spacer 22. In this embodiment, the liquid crystal modulation
element 925R, and transparent plates 962R and 963R are maintained
in such an arrangement by the dust-preventing member 965R.
[0091] The dust-preventing member 965R includes first and second
outer frames 51 and 52 for clamping the liquid crystal modulation
element 925R and transparent plates 962R and 963R, and an
intermediate frame 53 for shielding the space between the light
outgoing surface of the liquid crystal modulation element 925R and
the transparent plate 963R, and the space between the light
incident surface of the liquid crystal modulation element 925R and
the transparent plate 962R from the outside. The liquid crystal
modulation element 925R, transparent plates 962R and 963R are held
between the first and second outer frames 51 and 52.
[0092] The first outer frame 51 includes a rectangular opening 51a
for light transmission, and a peripheral wall 51b having a uniform
thickness on the periphery thereof. The second outer frame 52 also
includes a rectangular opening 52a for light transmission, and a
peripheral wall 52b having a uniform thickness on the periphery
thereof. The vertical (vertical direction Y) length of the second
outer frame 52 is set longer than the transparent plate 963R, and
shorter than the first outer frame 51.
[0093] The intermediate frame 53 is a rectangular frame, and is
provided to surround the outer periphery of the liquid crystal
modulation element 925R, and transparent plates 962R and 963R.
Engaging projections 53a are formed at respective left and right
positions on the side surface of this intermediate frame 53. In
contrast, the engaging holes 51lc capable of fitting therein these
engaging projections 53a are formed on the side surface of the
first outer frame 51 at positions corresponding to the engaging
projections 53a.
[0094] Engage projections 53b are also formed at respective left
and right positions on the side surface of this intermediate frame
53. In contrast, the engaging holes 52c capable of fitting in these
engaging projections 53b are formed on the side surface of the
second outer frame 52 at positions corresponding to the engaging
projections 53b.
[0095] Therefore, if the first outer frame 51 is pressed into the
intermediate frame 53 so that each of the engaging projections 53a
are inserted into respective engaging holes 51c from the outside of
the transparent plate 962R provided on the side of the light
incident surface of the liquid crystal modulation element 925R, and
if the second outer frame 52 is pressed into the intermediate frame
53 so that each of the engaging projections 53b are inserted into
each of the engaging holes 52c from the outside of the transparent
plate 963R provided on the side of the light outgoing surface of
the liquid crystal modulation element 925R, the liquid crystal
modulation element 925R, the transparent plates 962R and 963R are
held by the dust-preventing member 965R.
[0096] In addition, the space between the light incident surface of
the liquid crystal modulation element 925R and the transparent
plate 962R, and the space between the light outgoing surface of the
liquid crystal modulation element 925 R and the transparent plate
963R are shielded from the outside. Incidentally, a flexible cable
9253R for wiring extends upward from the dust-preventing member
965R.
[0097] In this case, if the dust-preventing member 965R is made of
resin containing glass fiber, such as FRP, it is possible to
restrict linear expansion, to prevent the shift of the
dust-preventing member 965R, and to maintain a constant temperature
and a uniform in-plane temperature of the dust-preventing member
965R.
[0098] On the other hand, if the dust-preventing member is made of
metal, it is possible to improve the heat dissipation effect. In
particular, when light-absorptive polarizer is bonded to the
transparent plate, the heat caused by light being absorbed by the
polarizer can be efficiently radiated.
[0099] FIG. 10(A) illustrates a state in which the dust-preventing
member 965R holding the liquid crystal modulation element 925R, and
the transparent plates 962R and 963R is attached to the light
incident surface 9llR of the color synthesizing prism 910. An
attachment structure for attaching the dust-preventing member 965R
to the light incident surface 911R of the color synthesizing prism
910 will be described with reference to this drawing.
[0100] As shown in FIG. 10(A), the dust-preventing member 965R
holding the liquid crystal modulation element 925R and the like is
fixed to a fixed frame plate 54 to be fixedly bonded to the light
incident surface 911R of the color synthesizing prism 910.
Incidentally, a red filter 23 is bonded to the light incident
surface 911R of the color synthesizing prism 910 of this
embodiment, and the polarizer 961R is fixed to the surface of the
red filter 23.
[0101] An intermediate frame plate 55 is a rectangular frame that
is formed in almost the same or a larger size of the first outer
frame 51 of the dust-preventing member 965R, and includes a
rectangular opening 55a for light transmission. The intermediate
frame plate 55 has engaging projections 55d that extend
perpendicularly from the surface of the frame plate at the four
corners of the rectangular opening 55a thereof. In contrast, the
dust-preventing member 965R has engaging holes 51d formed at
positions corresponding to the engaging projections 55d, into which
the engaging projections 55d can be inserted.
[0102] In this embodiment, the engaging holes 51d are formed by
through holes that are formed in the first outer frame 51 and the
intermediate frame 53 of the dust-preventing member 965R.
Therefore, when the respective engaging holes of the
dust-preventing member 965R and the respective engaging projections
of the intermediate frame plate 55 are aligned and overlaid one on
another, the respective engaging projections 55d are inserted in
the respective engaging holes 51d, whereby a temporarily attached
state is formed.
[0103] On the other hand, the fixed frame plate 54 is also a
rectangular frame plate having a rectangular opening 54a for light
transmission. In addition, the rectangular opening 54a formed in
the fixed frame plate 54 is formed smaller than the light incident
surface of the polarizer 961R. The fixed frame plate 54 is fixed to
the red filter 23 provided on the light incident surface 911R of
the color synthesizing prism 910 with an adhesive.
[0104] At this time, if the bonded surface 54e of the fixed frame
plate 54 is completely covered with the polarizer 961R, there is a
fear that the bonding strength decreases and the polarizer 961R is
separated. In this embodiment, however, as shown in FIG. 10(B),
since the bonded surface 54e of the fixed frame plate 54 is not
completely covered with the polarizer 961R, there is an extremely
little possibility of a decrease in bonding strength and separation
of the polarizer 961R.
[0105] Returning to FIG. 10(A), the fixed frame plate 54 has screw
holes 54c at both ends of its upper frame section and at the
widthwise center of its lower frame section. The intermediate frame
plate 55 also has screw holes 55c corresponding to the three screw
holes 54c. By inserting flat-head screws 56 for fastening into the
corresponding screw holes 54c and 55c, the intermediate frame plate
55 is fixed to the fixed frame plate 54. Incidentally, in this
embodiment, the intermediate frame plate 55 is fixed to the fixed
frame plate 54 by the three screws 56. The number of screws is not
limited and may be four or more, and two or less. In general, as
the number of screws decreases, the number of steps of fastening
the screws decreases, and manufacturing is facilitated.
[0106] Here, the fixed frame plate 54 has engaging projections 54b
at the right and left corners of its lower frame section, and the
intermediate frame plate 55 has engaging holes 55b at the right and
left corners of its lower frame section corresponding to the two
engaging projections 54b. Therefore, when being fixed with the
screws 56, the intermediate frame plate 55 can be temporarily fixed
to the fixed frame plate 54 by pressing the intermediate frame
plate 55 towards the fixed frame plate 54 while aligning the
engaging holes 55b of the intermediate frame plate 55 with the
engaging projections 54b of the fixed frame plate 54. This makes it
possible to further improve the positioning accuracy of both the
frame plates.
[0107] The projection display device of this embodiment includes
positioning means for positioning the dust-preventing member 965R
to the intermediate frame plate 55 that is fixed to the fixed frame
plate 54. This positioning means includes two wedges 57. Wedge
guide surfaces 5le to 51g, against which inclined surfaces 57a of
the wedges 57 abut, are formed on the vertical centers of the right
and left side surfaces of the dust-preventing member 965R. When the
dust-preventing member 965R is temporarily attached to the
intermediate frame plate 55, wedge insertion grooves are formed
between the wedge guide surfaces 51e and the frame sections of the
intermediate frame plate 55 facing the wedge guide surfaces
51e.
[0108] Therefore, after the dust-preventing member 965R has been
temporarily attached to the intermediate frame plate 55, the two
wedges 57 are struck in the right and left sides of the
dust-preventing member 965R, and the amount of the wedges 57 to be
pressed in is adjusted, whereby the position of the dust-preventing
member 965R is defined, and the liquid crystal modulation element
925R held by the dust-preventing member 965R can be positioned.
[0109] A description will now be given of a procedure of attaching
the dust-preventing member 965R to the light incident surface 911R
of the color synthesizing prism 910. First, the dust-preventing
member 965R by which the liquid crystal modulation element 925R and
the transparent plates 962R and 963R are held is prepared. In
addition, the color synthesizing prism 910 having the light
incident surface 911R to which the polarizer 961R is fixed through
the red filter 23 is prepared. Next, the fixed frame plate 54 is
positioned and fixedly bonded to the red filter 23 that is fixed to
the light incident surface 911R of the color synthesizing prism
910. An ultraviolet-curing adhesive or the like may be used as an
adhesive.
[0110] Then, the intermediate frame plate 55 is positioned on the
surface of the fixed frame plate 54 that is fixedly bonded, and the
intermediate frame plate 55 is fastened by the three flat-head
screws 56. Thereafter, the dust-preventing member 965R by which the
liquid crystal modulation element 925R and the like are held is
positioned on the intermediate frame plate 55, and is temporarily
attached thereto. That is, the engaging projection 55d of the
intermediate frame plate 55 is aligned with the engaging hole 51d
of the dust-preventing member 965R, and the dust-preventing member
965R is pressed towards the intermediate frame plate 55 in this
state. Incidentally, if the fixed frame plate 54 and the
intermediate frame plate 54 are combined in advance by screws 56
before fixedly bonding the fixed frame plate 54 to the color
synthesizing prism 910, the accuracy of position can be easily
obtained.
[0111] Thereafter, the liquid crystal modulation element 925R is
positioned onto the light incident surface 911R of the color
synthesizing prism 910 using the wedges 57 as the positioning
means. That is, the two wedges 57 are inserted between the
dust-preventing member 965R and the intermediate frame plate 55
that are temporarily attached, along the wedge guide surface 51e
formed on the dust-preventing member 965R. Then, the alignment and
focusing of the liquid crystal modulation element 925R are adjusted
by controlling the amount of insertion of the wedges 57.
[0112] When the positioning is completed, these wedges 57 are
fixedly bonded with an adhesive to the dust-preventing member 965R
and the intermediate frame plate 55 that are the members to be
positioned. As the adhesive used in this case, an
ultraviolet-curing adhesive can also be used.
[0113] The positioning operation and the fixedly bonding operation
of the above wedges 57 will now be described in more detail
following the sequence of steps.
[0114] First, a focal surface of the liquid crystal modulation
element 925R is adjusted into a focal surface of the projection
lens unit 6 using a specific adjustment device. In this state, as
mentioned above, the ultraviolet-curing adhesive is filled into the
gap formed when the engaging projection 55d of the intermediate
frame plate 55 is inserted into the engaging hole 51d of the
dust-preventing member 965R, and cured by radiation of
ultraviolet-ray to effect temporarily fixing.
[0115] Then, by the intermediate frame plate 55 and the wedge guide
surfaces 51e provided on the dust-preventing member 965R, the
ultraviolet-curing adhesive is irradiated with ultraviolet-ray from
the exposed end surfaces of the wedges 57 to effect bonding and
actual fixing. Similarly, focusing and pixel-matching between the
liquid crystal modulation elements 925R and 925B are adjusted with
reference to the liquid crystal modulation element 925G that is
arranged in the center of the liquid crystal modulation elements
925R, 925G and 925B so as to effect the temporarily fixing and the
actual fixing.
[0116] Incidentally, since the temporarily fixing is effected by a
setting adjustment device with the color synthesizing prism 910 and
the projection lens 6 attached to the head plate 903, it is
possible to adjust optimally in accordance with characteristics of
individual components. In addition, the dust-preventing member 965R
is chucked in the adjustment device with reference to the external
shape of the first outer frame 51.
[0117] Since the attachment structure of the dust-preventing
members 965G and 965B holding the liquid crystal modulation
elements 925G and 925B other than the liquid crystal modulation
element 925R to the color synthesizing prism 910 is the same as
that of the dust-preventing member 965R, a description thereof will
be omitted.
[0118] When the dust-preventing member 965R is attached to the
color synthesizing prism 910 as described above, the following
effects can be obtained.
[0119] Firstly, since the peripheral portion of the liquid crystal
modulation element 925R is protected by the dust-preventing member
965R, it is not necessary to directly touch the liquid crystal
modulation element 925R so as to attach it to the color
synthesizing prism 910. Therefore, it is possible to prevent the
liquid crystal modulation element 925R from abutting against other
portions and to prevent it from being broken or chipped. In
addition, since the surroundings of the liquid crystal modulation
element 925R are covered with the dust-preventing member 965R, it
is possible to cut off external light, and to prevent the
malfunction of the liquid crystal modulation 925R due to the
external light.
[0120] Secondly, the dust-preventing member 965R holding the liquid
crystal modulation element 925R is detachably fastened by screws to
the light incident surface 911R of the color synthesizing prism 910
through the intermediate frame plate 55. Therefore, for example,
when the liquid crystal modulation element 925R becomes defective,
it can be replaced by a simple operation of removing the screws 56.
In addition, since the liquid crystal modulation element 925R is
not directly fixedly bonded to the color synthesizing prism 910,
the color synthesizing prism 910 is not damaged at the time of the
replacement, and expensive components can be used most
efficiently.
[0121] Thirdly, the dust-preventing member 965R holding the liquid
crystal modulation element 925R can be temporarily attached to the
intermediate frame plate 55. After forming this temporarily
attached state, the liquid crystal modulation element 925R and the
light incident surface 911R of the color synthesizing prism 910 can
be positioned using the wedges 57. Since the temporarily attached
state can be formed as described above, the positioning operation
using the wedges 57 can be easily performed in a separate step,
thus contributing to an improvement of the cycling time of the
equipment.
[0122] In general, the wedges 57 made of glass can be used.
However, when the dust-preventing member 965R is formed of resin,
since it has a high thermal expansion coefficient as compared with
glass, the wedges 57 may tend to be separated from the frame plate
due to the difference in thermal expansion, and may be broken by a
change in temperature. In order to avoid these matters, it is
desirable that the wedges 57 be formed of resin of the acrylic
group or the like. In addition, the wedges 57 can be molded by
being formed of an acrylic material, so that the cost thereof can
be substantially reduced as compared with a glass material.
Incidentally, by using materials that transmit ultraviolet-ray as
the material of the wedges 57, a ultraviolet-curing adhesive of
little increase in temperature and of short curing time can be used
as the adhesive for fixedly bonding the wedges 57.
[0123] In addition, the wedge guide surfaces 51e are formed on the
dust-preventing member 965R, whereby the upper end surfaces 51f and
51g are formed on upper and lower portions thereof, and the wedges
57 are guided by these three surfaces. That is, when the adhesive
is filled into the portions and the wedges 57 are inserted
thereinto, the wedges 57 are automatically moved to the inside
while being guided by these three surfaces due to the surface
tension of the adhesive. Therefore, the wedges 57 become resistant
to disturbance encountered in steps, and can be easily
attached.
[0124] While the adhesive is used when the dust-preventing member
965R is temporarily fixed to the intermediate frame plate 55,
soldering or the like may be used instead of the adhesive. When the
dust-preventing member 965R and the like are made of resin, a
substance having a metallic member bonded to the joint thereof, or
a substance having a metalized layer formed on the joint thereof
may be used.
[0125] The above-described dust-preventing member 965R,
intermediate frame plate 55 and fixed frame plate 54 can be formed
of thermosetting resin into which glass fiber or calcium carbonate
is mixed. When such a resin material is used, the thermal expansion
coefficient thereof becomes close to that of glass as compared with
a common resin material. For this reason, pixel displacements and
the like due to thermal deformation can be avoided in the state
where they are bonded to the color synthesizing prism 910.
[0126] While the ultraviolet-curing adhesive can be used as the
adhesive for fixedly bonding the fixed frame plate 54 to the color
synthesizing prism 910 as described above, it may be desirably
coated with a base-processing material in order to increase bonding
properties. That is, in the color synthesizing prism 910, the
incident surface 911R of the red light flux faces the incident
surface 911B of the blue light flux as described above. Since the
blue light flux has a short wavelength, a part thereof may be
transmitted through a reflecting film of the color synthesizing
prism 910 to reach the opposite incident surface 911R of the red
light flux. If such backlight is incident on the liquid crystal
modulation element 925R, a malfunction may be caused. In this
embodiment, since the red filter 23 is provided on the incident
surface 911R of the red light flux, it is possible to cut off such
a backlight, and to thereby prevent the malfunction of the liquid
crystal modulation element 925R due to the backlight.
[0127] The filter is attached only to the incident surface 911R of
the red light flux because of the largest influence of the
backlight of the blue light flux. This, however, does not apply to
a case in which the influence of the backlight of other light
fluxes is large. The filter may be provided on another surface, or
filters may be provided on a plurality of surfaces.
[0128] However, the presence of such a filter blocks ultraviolet
rays at the time of fixedly bonding, whereby a portion lacking in
ultraviolet-ray radiation is generated in the ultraviolet-curing
adhesive for fixedly bonding the fixed frame plate 54 to the
incident surfaces 911R, 911G and 911B of the color synthesizing
prism 910. In order to avoid the negative effects so as to
assuredly fixedly bond the fixed frame plate 54 to the incident
surface 911R, it is desirable that these bonded surfaces are coated
with the base-processing material and that an anaerobic type
adhesive is used together with the ultraviolet-curing adhesive. Of
course, the incident surface having no such filter may be treated
for a similar process.
[0129] While the use of the ultraviolet-curing adhesive is
described above, other adhesives may be used. For example, when a
hot-melt type adhesive is used to fixedly bond the fixed frame
plate 54 and the wedges 57, there is no need to consider the above
problem arising from the filter.
[0130] In addition, in this embodiment, the fixed frame plate 54
and the intermediate frame plate 55 are flat. As described with
reference to FIG. 3, the fan 15B is arranged below the color
synthesizing prism 910, and cooling air flows from bottom to top.
In order to prevent this flow from being disturbed, it is desirable
to arrange straightening vanes above the fan 15B. Since the fixed
frame plate 54 and the intermediate frame plate 5 are flat, the
straightening vanes can be mounted at a position directly below the
liquid crystal modulation element 925R and hence, cooling air can
flow effectively from bottom to top. Further, since these frame
plates have a simple shape, parts can be easily utilized, and the
accuracy of the parts is thereby improved.
[0131] In addition to this, the two wedges 57 are used for
positioning, and they are fixedly bonded to the vertical centers of
the right and left sides of the dust-preventing member 965R and the
intermediate frame plate 55. If the wedges 57 are fixedly bonded at
inadequate positions, there is a fear that excessive stress
concentration is caused in the components by thermal deformation of
the dust-preventing member 965R, the intermediate frame plate 55,
or the wedges 57. In addition, this may cause the wedges 57 to
separate from the dust-preventing member 965R or the intermediate
frame plate 55.
[0132] As described above, however, since the wedges 57 are fixedly
bonded to the centers of the right and left sides, the
dust-preventing member 965R and the intermediate frame plate 55 are
free to thermally deform in the vertical direction, centered on the
wedges 57. Therefore, the degree to which the thermal deformation
of these frame plates is restrained is low, so that negative
effects, such as undesired stress concentration and separation of
wedges, can be avoided.
[0133] Further, as apparent from FIG. 10(A), each of the wedges 57
in this embodiment has two blind holes 57c formed on its rear
surface 57b. These blind holes 57c, in chucking the wedges 57 with
a jig, function as engaging portions for chucking. The formation of
such blind holes 57c permits easy chucking and therefore, handling
thereof becomes easy.
[0134] In this embodiment, the blind holes 57c for engagement in
chucking are formed on the rear side of the wedges 57. The engaging
portions for chucking may be formed on other members. For example,
engaging portions for chucking, such as blind holes, may be formed
on the outer surface of the dust-preventing member 965R.
[0135] A modification of the dust-preventing member 965R will now
be described. FIG. 11 is an exploded perspective view of a
modification of the dust-preventing member 965R. FIG. 12(A) is a
schematic sectional structural view of a dust-preventing member
1965R when cut along an XZ plane, and FIG. 12(B) is a schematic
sectional structural view of the dust-preventing member 1965R shown
in FIG. 11 when cut along a YZ plane.
[0136] As shown in these drawings, the dust-preventing member 1965R
holds the liquid crystal modulation element 925R and the
transparent plates 962R and 963R. The dust-preventing member 1965R
has an intermediate frame 30, a second outer frame 31 serving as a
light outgoing side outer frame that is detachably fixed to the
light outgoing side of the intermediate frame 30, a first outer
frame 32 serving as a light incident side outer frame that is
detachably fixed to the light incident side of the intermediate
frame 30, and a spacer 33 arranged between the liquid crystal
modulation element 925R and the transparent plate 963R. The liquid
crystal modulation element 925R and the transparent plate 963R are
held between the intermediate frame 30 and the second outer frame
31, and the transparent plate 962R is held between the intermediate
frame 30 and the first outer frame 32.
[0137] The liquid crystal modulation element 925R has a lower step
surface 9254R at its end portion of the light incident surface. A
flexible cable 9253R for wiring extends from above the liquid
crystal modulation element 925R.
[0138] The intermediate frame 30 is a rectangular frame, and has a
lower step surface 303 at its inside edge portion on the light
outgoing surface side of the frame portion. The step surface 9254R
of the liquid crystal modulation element 925R is in contact with a
surface 302 on the light outgoing side of the frame portion, and an
edge portion of the higher light outgoing surface of the liquid
crystal modulation element 925R is in contact with the step surface
303 that is formed on the intermediate frame 30. That is, contact
surfaces 302 and 303 for the light incident surface that are in
contact with a part of the light outgoing surface of the liquid
crystal modulation element 925R are formed on the light outgoing
side of the intermediate frame 30.
[0139] In addition, a pair of length-side wall portions 304
extending along the length-side side surfaces of the liquid crystal
modulation element 925R and a pair of width-side wall portions 305
extending along the width-side side surfaces of the liquid crystal
modulation element 925R are formed on the outer end of the frame
portion of the intermediate frame 30. The length-side wall portions
304 extend to the positions where the leading ends thereof are
equal to the light outgoing surface of the liquid crystal
modulation element 925R. These length-side wall portions 304 are
opposed to the length-side side surfaces of the liquid crystal
modulation element 925R at a predetermined distance.
[0140] The leading ends of the width-side wall portions 305 extend
to the width-side side surfaces of the transparent plate 936R
across the width-side side surfaces of the liquid crystal
modulation element 925R. A contact surface 306 for the light valve
side surface contacting the width-side side surface of the liquid
crystal modulation element 925R, and a contact surface 307 for the
transparent plate side surface contacting the width-side side
surfaces of the transparent 963R are formed on the width-side wall
portions 305. In this embodiment, the contact surface 306 for the
light valve side surface and the contact surface 307 for use in the
transparent plate side surface are formed on the same plane.
[0141] The spacer 33 is a rectangular frame having a constant
thickness. The lengthwise size of the spacer 33 is set
substantially equal to that of the liquid crystal modulation
element 925R, and the width-side side surfaces of the spacer 33 are
in contact with the contact surface 307 for the transparent plate
side surface (the contact surface 306 for the light valve side
surface). Projections 331 extending towards the light incident side
are formed on the length-side frame portions of the spacer 33. The
projections 331 are inserted between the length-side side surfaces
of the liquid crystal modulation element 925R and the length-side
wall portions 304 formed on the intermediate frame 30.
[0142] In addition, projections 332 extending towards the light
outgoing side are formed on the length-side frame portion of the
spacer 33. The transparent plate 963R is held by the projections
332 from the vertical direction (the Y direction).
[0143] The second outer frame 31 is a rectangular frame having the
constant thickness thinner than the spacer 33. The overall surface
of the light incident side of the frame portion of the outer frame
31 is a pressure surface 311 for pressing the light outgoing
surface of the transparent plate 963R towards the intermediate
frame 30. In addition, the second outer frame 31 has engaging pawls
312 formed on four corners thereof that extend along the side
surfaces of the width-side frame portion of the intermediate frame
30. In contrast, the intermediate frame 30 has engaging projections
341 formed at the positions corresponding to the engaging pawls 312
that can engage with the engaging pawls 312.
[0144] A procedure of assembling the liquid crystal modulation
element 925R, the spacer 33, the transparent plate 963R and the
second outer frame 31 onto the intermediate frame 30 will now be
described.
[0145] First, the liquid crystal modulation element 925R is
inserted between a pair of width-side wall portions 305 formed on
the intermediate frame 30. At this time, the liquid crystal
modulation element 925R is inserted so that the edge portion of the
light incident surface of the liquid crystal modulation element
925R abuts against the step surface (light incident-side contact
surface) 303 of the intermediate frame 30. This allows the liquid
crystal modulation element 925R to be arranged at a predetermined
position on the intermediate frame 30 by the contact surfaces 302
and 303 for the light incident surface and the contact surface 306
for the light valve side surfaces. In this state, as shown in FIG.
13(A), the width-side wall portions 305 extend towards the light
outgoing side across the width-side side surfaces of the liquid
crystal modulation element 925R. On the other hand, as shown in
FIG. 13(B), the leading ends of the length-side wall portions 304
and the light outgoing surface of the liquid crystal modulation
element 925R are positioned on substantially the same plane. In
this state, the liquid crystal modulation element 925R is not
completely fixed to the intermediate frame 30, and can be easily
removed.
[0146] Next, the spacer 33 is superposed on the light incident
surface of the liquid crystal modulation element 925R along the
width-side wall portions 305 of the intermediate frame 30. At this
time, if the projections 331 formed on the spacer 33 are to be
inserted between the length-side side surfaces of the liquid
crystal modulation element 925R and the length-side wall portions
304 of the intermediate frame 30, the spacer 33 is arranged at a
predetermined position on the light outgoing surface of the liquid
crystal modulation element 925R.
[0147] Then, the transparent plate 963R is superposed on the spacer
33 along the width-side wall portions 305 of the intermediate frame
30. At this time, if the transparent plate 963R is to be positioned
between the projections 332 formed on the spacer 33, the
transparent plate 963R is arranged on a predetermined position, so
that the alignment of the intermediate frame 30, the liquid crystal
modulation element 925R, the spacer 33 and the transparent plate
963R in relation to one another is defined. When the transparent
plate 963R is merely superposed on the spacer 33, they are not
completely fixed to the intermediate frame 30, and can be removed
at any time.
[0148] After that, the second outer frame 31 is attached to the
intermediate frame 30 in such a manner that the engaging pawls 312
formed on the second outer frame 31 engage with the engaging
projections 341 formed on the intermediate frame 30. This allows
the light outgoing surface of the transparent plate 963R to be
pressed towards the intermediate frame 30 by the pressure surface
311 of the second outer frame 31, so that all of the transparent
plate 963R, spacer 33 and liquid crystal modulation element 925R
are pressed from the light outgoing side onto the intermediate
frame 30. Consequently, the liquid crystal modulation element 925R,
the spacer 33 and the transparent plate 963R are held between the
intermediate frame 30 and the second outer frame 31, and the
alignment relation thereof is maintained.
[0149] The structure of the light incident side of the intermediate
frame 30 will now be described. The intermediate frame 30 includes
a wall portion 308 extending along the side surfaces on the
periphery of the transparent plate 962R on the light incident side
thereof, and a contact surface 309 for the light outgoing surface
that is in contact with the edge portion of the light outgoing
surface of the transparent plate 962R. A contact surface 310 for
the transparent plate side surface that is in contact with the side
surface of the transparent plate 962R is formed on the wall portion
309.
[0150] The first outer frame 32 is of an identical shape with the
outer frame 31 on the light incident side. That is, the first outer
frame 32 is a rectangular frame having a constant thickness thinner
than the spacer 33. The overall surface on the light outgoing side
of the frame portion of the first outer frame 32 is a pressure
surface 321 for pressing the light incident surface of the
transparent plate 962R to the intermediate frame 30. In addition,
the first outer frame 31 has engaging pawls 322 formed on four
corners thereof that extend in the thickness direction of the
width-side frame portion of the intermediate frame 30. In contrast,
the intermediate frame 30 has engaging projections 342 formed at
the positions corresponding to the engaging pawls 322 that can
engage with the engaging pawls 322.
[0151] Therefore, when the transparent plate 962R is fitted to a
portion enclosed by the wall portion 308 formed on the intermediate
frame 30, the edge portion of the light incident surface of the
transparent plate 962R strikes the contact surface 309 for the
light outgoing surface of the intermediate frame 30. In addition,
the peripheral side surfaces of the transparent plate 962R abut
against the contact surface 309 for the transparent plate side
surface formed on the wall portion 308. This allows the transparent
plate 962R to be arranged at a predetermined position on the
intermediate frame 30, and a space from the light incident surface
of the liquid crystal modulation element 925R is maintained. In
this state, the transparent plate 962R is not completely fixed to
the intermediate frame 30, and can be easily removed.
[0152] In this state, when the first outer frame 31 is fitted to
the intermediate frame 30 so that the engaging pawls 322 formed on
the first outer frame 32 engage with the engaging projections 342
formed on the intermediate frame 30, the transparent plate 962R is
pressed by the pressure surface 321 of the first outer frame 32,
and the transparent plate 962R is held between the intermediate
frame 30 and the first outer frame 32. In addition, the space
between the light incident surface of the liquid crystal modulation
element 925R and the transparent plate 962 is shielded from the
outside by the wall portion 308 formed on the intermediate frame
30.
[0153] When the liquid crystal modulation element 925R, and the
transparent plates 962R and 963R are held by such a dust-preventing
member 1965R, operability of rework such as replacement of
components can be improved. That is, if the liquid crystal
modulation element 925R and the transparent plates 962R and 963R
are fixed to the intermediate frame 30 with an adhesion or the
like, a step for cleaning the adhesive adhering to the components
(the liquid crystal modulation element 925R and the transparent
plates 962R and 963R) is required in the case of replacement
thereof after separating them from the intermediate frame 30.
However, if the above dust-preventing member 1965R is used,
components can be easily replaced because the components such as
the liquid crystal modulation element 925R and the like can be
easily removed by removing the second outer frame 31 and first
outer frame 32 at the time of replacement of components.
[0154] In the state where the liquid crystal modulation element
925R is arranged on the intermediate frame 30, while the leading
ends of the length-side wall portions 304 formed on the
intermediate frame 30 and the light outgoing surface of the liquid
crystal modulation element 925R are positioned on substantially the
same plane, the width-side wall portions 305 extend to the light
outgoing side across the light outgoing surface of the liquid
crystal modulation element 925R, as shown in FIGS. 13(A) and (B).
Therefore, a roller 40 is put on the light outgoing surface of the
liquid crystal modulation element 925R, and the roller 40 can be
moved in one direction (the Y direction) by using the transparent
plate-side contact surfaces 307 formed on the width-side wall
portion 305 as guide surfaces.
[0155] An antireflection film (AR film) may be bonded to the light
outgoing surface of the liquid crystal modulation element for the
purpose of improving the light utilizing use efficiency. In this
case, the AR film is placed on the light outgoing surface of the
liquid crystal modulation element 925R and the roller 40 is moved
in one direction as described above, whereby the AR film can be
easily bonded to the light outgoing surface. In addition, since the
roller 40 can be moved in one direction, the roller 40 can be
easily moved, and air bubbles generated between the light outgoing
surface and the AR film can be effectively eliminated.
[0156] Furthermore, when replacing the AR film to which dust is
adhered, first, the second outer frame 31 is removed from the
intermediate frame 30, and the transparent plate 963R and the
spacer 33 are removed from the intermediate frame 30. After that,
the AR film to which dust is adhered is separated from the light
outgoing surface of the liquid crystal modulation element 925R and
a new AR film is bonded with the above-described procedure. After
the renewal of the AR film, the spacer 33 and the transparent plate
963R are superposed on the liquid crystal modulation element 925R,
and the second outer frame 31 is fixed to the intermediate frame
30. This allows a renewal operation of the AR film to be completed.
By using the intermediate frame 30 including the guide surfaces
(the contact surface for the transparent plate 307, in this
embodiment), the renewal operation of the AR film to the light
outgoing surface of the liquid crystal modulation element 925 can
be also easily performed.
[0157] FIG. 14 illustrates the engagement between the engaging
pawls 312 and 322 and the engaging projections 341 and 342. As
shown in this drawing, the engaging pawls 312 and 322 formed on the
outer frames 31 and 32 have rectangular openings 313 and 323,
respectively. Engaging projections 341 and 342 corresponding to the
engaging pawls 312 and 322 are formed so that they are engaged with
the rectangular openings 313 and 323 of the engaging pawls 312 and
322, and are located at positions shifted in the direction
perpendicular (the X direction) to the thickness direction (the Z
direction) of the intermediate frame 30.
[0158] Since it is difficult to form the intermediate frame on
which the positions of match in the thickness direction of the
respective engaging projections 341 and 342 using upper and lower
frames, the engaging projections to be formed on the intermediate
frame should be shifted in the direction perpendicular to the
thickness direction using the first and second outer frames having
different shapes. However, if an engagement mechanism in this
embodiment is adopted, the intermediate frame can be easily formed
and at the same time, commonality of components can be achieved by
forming the first outer frame 32 and the second outer frame 31 into
the same shape.
[0159] The structure for attaching the dust-preventing member 1965R
to the light incident surface 911R of the color synthesizing prism
910 is the same as that of the aforementioned dust-preventing
member 965R. That is, as shown in FIG. 15, the dust-preventing
member 1965R is fixed to the fixed frame plate 54 that is fixedly
bonded to the light incident surface 911R of the color synthesizing
prism 910. In addition, since the procedures of attaching the
dust-preventing member 1965R to the color synthesizing prism 910
using the intermediate frame plate 55 and the fixed frame plate 54,
and actions and effects thereof are the same as those of the
dust-preventing member 965R, a description thereof will be
omitted.
[0160] <Embodiment 2>
[0161] While the projection display device using a transmissive
liquid crystal modulation element as the liquid crystal modulation
element has been described in the embodiment 1, the present
invention can be applied to a projection display device that uses a
reflective liquid crystal modulation element as the liquid crystal
modulation element. An example of a projection display device to
which a reflective liquid crystal modulation element is adopted
will be shown below.
[0162] FIG. 16 is a schematic structural view of the surroundings
of light valves in the projection display device of this
embodiment. In FIG. 16, the projection display device includes a
blue reflecting dichroic mirror 2941 and a red reflecting dichroic
mirror 2942 that reflect illumination light emitted from a light
source lamp unit 8. A blue light flux B contained in a light flux W
is reflected at right angles by the blue reflecting dichroic mirror
2941 and then, is further reflected at right angles by a reflecting
mirror 2971, and is incident on a first polarization beam splitter
2900B provided adjacent to a dichroic prism 2910.
[0163] This polarization beam splitter 2900B is formed of a prism
having an s-polarized light flux-reflecting plane 2901B that is
formed of a polarized light separation film for reflecting an
s-polarized light flux and transmitting a p-polarized light flux.
The polarization beam splitter 2900B bends an s-polarized light
component of the blue light flux into 90.degree. by the s-polarized
light flux-reflecting plane 2901B, and allows the s-polarized light
component to be incident on a light incident and outgoing surface
of a reflective liquid crystal modulation element 2925B that is
opposing one side of the polarization beam splitter 2900B.
[0164] Then, only a p-polarized light of the blue light flux, which
is modulated by the liquid crystal modulation element 2925B and
transmitted through the s-polarized light flux-reflecting plane
2901B, is emitted from the same light incident and outgoing surface
to the dichroic prism 2910. Incidentally, a transparent plate 2963B
is arranged on the side of the light incident and outgoing surface
of the liquid crystal modulation element 2925B through a
dust-preventing member 2965B.
[0165] On the other hand, a red light flux R and a green light flux
G are first reflected at right angles by the red-green reflecting
dichroic mirror 2942, and then further reflected at right angles by
a reflecting mirror 2972.
[0166] After being transmitted through a green reflecting dichroic
mirror 2941, the red light flux R is incident on a second
polarization beam splitter 2900R that is provided on an opposite
side to the first polarization beam splitter 2900B across the
dichroic prism 2910. The second polarization beam splitter 2900R is
formed of a prism having an s-polarized light flux-reflecting plane
2901R that is formed of a polarized light separation film for
reflecting an s-polarized light flux and transmitting a p-polarized
light flux.
[0167] The second polarization beam splitter 2900R bends an
s-polarized light component of the red light flux into 90.degree.
by the s-polarized light flux-reflecting plane 2901B, and allows
the s-polarized light component to be incident on a light incident
and outgoing surface of a reflective liquid crystal modulation
element 2925R that is opposing one side of the polarization beam
splitter 2900R.
[0168] Then, only p-polarized light of the red light flux, which is
modulated by the liquid crystal modulation element 2925R and
transmitted through the s-polarized light flux-reflecting plane
2901R, is emitted from the same light incident and outgoing surface
to the dichroic prism 2910. Incidentally, a transparent plate 2963R
is arranged on the light incident side and outgoing surface side of
the liquid crystal modulation element 2925R through a
dust-preventing member 2965R.
[0169] After being reflected by a green reflecting dichroic mirror
2943, the green light flux G is incident on a third polarization
beam splitter 2900G that is provided on one side of the dichroic
prism 2910. The third polarization beam splitter 2900G is formed of
a prism having an s-polarized light flux-reflecting plane 2901G
that is formed of a polarized light separation film for reflecting
an s-polarized light flux and transmitting a p-polarized light
flux. This polarization beam splitter 2900G bends an spolarized
light component of the green light flux into 90.degree. by the
s-polarized light flux-reflecting plane 2901G, and allows the
s-polarized light component to be incident on a light incident and
outgoing surface of a reflective liquid crystal modulation element
2925G that is opposing one side of the polarization beam splitter
2900G.
[0170] Then, only p-polarized light of the green light flux, which
is modulated by the liquid crystal modulation element 2925G and
transmitted through the s-polarized light flux-reflecting plane
2901G, is emitted from the same light incident and outgoing surface
to the dichroic prism 2910. Incidentally, a transparent plate 2963G
is arranged on the light incident side and outgoing surface side of
the liquid crystal modulation element 2925G through a
dust-preventing member 2965G.
[0171] As described above, the light fluxes B, R and G modulated
through the respective liquid crystal modulation elements 2925B,
2925R and 2925G are incident on the dichroic prism 2910, where they
are synthesized. The synthesized color image is enlarged and
projected through a projection lens unit 6 onto a screen that is
placed at a predetermined position.
[0172] In such a projection display device using the reflective
liquid crystal modulations 2925R, 2925G and 2925B, since light
outgoing surfaces of the reflective liquid crystal modulation
elements 2925R, 2925G and 2925B are protected by the transparent
plates 2963R, 2963G and 2963B, the heat generated by the
outgoing-side polarizers 961R, 961G and 961B can be prevented from
being transmitted to the liquid crystal modulation elements 925R,
925G and 925B. This makes it possible to restrict the increase in
temperature of the liquid crystal modulation elements 925R, 925G
and 925B and to prevent the deterioration of the optical properties
thereof.
[0173] In addition, since the liquid crystal modulation elements
925R, 925G and 925B and the outgoing-side polarizers 961R, 961G and
961B are apart from each other, the light emitted from the liquid
crystal modulation elements 925R, 925G and 925B widely spread, and
the polarizers 961R, 961G and 961B can receive the light in a wide
area. For this reason, it is possible to decrease the heat
generated by the polarizers 961R, 961G and 961B per unit area, and
to permit easy heat dissipation. In particular, it is effective to
arrange a microlens array, which gathers light onto each pixel of
the liquid crystal modulation element, on the light incident
surface of the liquid crystal modulation elements 925R, 925G and
925B because the light can spread more widely.
[0174] Furthermore, the surfaces of such transparent plates 2963R,
2963G and 2963B may be coated with a surface-active agent
(surfactant), or treated for electrostatic protection. Since this
makes it difficult for dust to adhere to the surfaces of the
transparent plates 2963R, 2963G and 2963B, the adhesion of dust can
be prevented more effectively.
[0175] <Other Embodiments>
[0176] While the projection display device having three liquid
crystal modulation elements for modulating three color lights,
respectively, is described in the above embodiments, a projection
display device to which the present invention is applied is not
limited to the above-described device, for example, it may use only
a single liquid crystal modulation element. In addition, the
projection display devices are divided into two types, a front type
that performs projection from the side on which the screen is
observed, and a rear type that performs projection from the side
opposite to the screen observing side, and the present invention is
applicable to either of the types.
INDUSTRIAL APPLICABILITY
[0177] The present invention can be utilized as a projection
display device that optically processes a light flux emitted from a
light source and enlarges and projects an image onto a projection
plane, such as a video projector having liquid crystal modulation
elements.
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