U.S. patent number RE42,515 [Application Number 12/831,624] was granted by the patent office on 2011-07-05 for method of manufacturing reflective mirror, illumination device, and projector.
This patent grant is currently assigned to Seiko Epson Corporation. Invention is credited to Toshiaki Hashizume.
United States Patent |
RE42,515 |
Hashizume |
July 5, 2011 |
Method of manufacturing reflective mirror, illumination device, and
projector
Abstract
A reflective mirror manufacturing method for manufacturing a
reflective mirror used in an illumination device including an arc
tube including a light-emitting portion and a reflective mirror
including a reflective surface that reflects light from the
light-emitting portion in a predetermined direction, includes: a
first step of forming a tube by heating a tube including a material
of the reflective mirror, thereafter putting the tube in a form
block, applying internal pressure with an inert gas to cause a
center portion of the tube to expand, so that part of an inner
surface of the expanded center portion includes a shape
corresponding to the reflective surface of the reflective mirror; a
second step of cutting the tube at the center portion to form a
reflective mirror member; and a third step of forming a reflective
layer on an inner surface of the reflective mirror member.
Inventors: |
Hashizume; Toshiaki (Okaya,
JP) |
Assignee: |
Seiko Epson Corporation (Tokyo,
JP)
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Family
ID: |
34191056 |
Appl.
No.: |
12/831,624 |
Filed: |
July 7, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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10916603 |
Aug 12, 2004 |
7159990 |
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Reissue of: |
11605467 |
Nov 29, 2006 |
7364311 |
Apr 29, 2008 |
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Foreign Application Priority Data
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Aug 18, 2003 [JP] |
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2003-294675 |
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Current U.S.
Class: |
353/98; 353/121;
353/99; 362/297 |
Current CPC
Class: |
H04N
9/315 (20130101); C03B 23/07 (20130101); G03B
21/2066 (20130101) |
Current International
Class: |
G03B
21/28 (20060101); G03B 21/00 (20060101) |
Field of
Search: |
;353/30,31,37,84,97,98,99,121,122 ;348/742,743,771 ;349/5,7,9
;362/295,297,298,341,346 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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A-52-22061 |
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Feb 1977 |
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JP |
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A-55-101417 |
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Aug 1980 |
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JP |
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A-59-156927 |
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Sep 1984 |
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JP |
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A-5-62595 |
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Mar 1993 |
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JP |
|
A-06-339981 |
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Dec 1994 |
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JP |
|
A-8-262437 |
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Oct 1996 |
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JP |
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A-8-281691 |
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Oct 1996 |
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JP |
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9-120067 |
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May 1997 |
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JP |
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A-9-254271 |
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Sep 1997 |
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JP |
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A-11-143378 |
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May 1999 |
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JP |
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A-2000-138005 |
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May 2000 |
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JP |
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A-2000-173313 |
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Jun 2000 |
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JP |
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A-2000-298213 |
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Oct 2000 |
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JP |
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A-2000-347293 |
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Dec 2000 |
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JP |
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A-2001-66697 |
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Mar 2001 |
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JP |
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A-2002-55393 |
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Feb 2002 |
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JP |
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A-2002-90883 |
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Mar 2002 |
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JP |
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A-2002-154837 |
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May 2002 |
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JP |
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Primary Examiner: Dowling; William C
Attorney, Agent or Firm: Oliff & Berridge, PLC
Parent Case Text
This is a Division of application Ser. No. 10/916,603 filed Aug.
12, 2004 now U.S. Pat. No. 7,159,990. The entire disclosure of the
prior application is hereby incorporated by reference in its
entirety.
Claims
What is claimed is:
1. An illumination device, comprising: an arc tube including a
light-emitting portion; a reflector including a reflective surface
that reflects light from the light-emitting portion to an
illuminated region; and an auxiliary mirror that is disposed facing
the reflector with the light-emitting portion sandwiched
therebetween, the auxiliary mirror including a reflective surface
without mold marks and which reflects part of the light emitted
from the light-emitting portion towards the light-emitting portion,
the auxiliary mirror being an auxiliary mirror manufactured by an
auxiliary mirror manufacturing method including: .[.a first step of
forming.]. .Iadd.heating .Iaddend.a tube .[.by heating a tube
including.]. .Iadd.comprising .Iaddend.a material of the auxiliary
mirror, thereafter putting the tube in a form block, applying
internal pressure with an inert gas to cause a center portion of
the tube to expand, so that part of an inner surface of the
expanded center portion includes a shape corresponding to the
reflective surface of the auxiliary mirror; .Iadd.the expanded
center portion being continuous with a part of a tube portion that
includes a shape corresponding to a fixing portion where the arc
tube is fixed to the auxiliary mirror; .Iaddend. .[.a second step
of.]. cutting the tube at the .Iadd.expanded .Iaddend.center
portion to form an auxiliary mirror member; and .[.a third step
of.]. forming a reflective layer on .[.an inner.]. .Iadd.the
reflective .Iaddend.surface of the auxiliary mirror member.
2. A projector, comprising: an illumination optical system
including the illumination device of claim 1; an electro-optical
modulation device that modulates light from the illumination
optical system in accordance with image information; and a
projection optical system that projects the light modulated by the
electro-optical modulation device.
3. The illumination device .[.of.]. .Iadd.according to
.Iaddend.claim 1, the auxiliary mirror being an auxiliary mirror
manufactured by the auxiliary mirror manufacturing method
.[.where.]. .Iadd.further including .Iaddend. .[.in the first
step,.]. .Iadd.forming .Iaddend.the tube .[.is formed.]. so that it
has a shape where two auxiliary mirror members mutually face each
other, .Iadd.when the center portion of the tube expands by
applying internal pressure with an inert gas, .Iaddend.and .[.in
the second step,.]. .Iadd.forming .Iaddend.the two auxiliary mirror
members .[.are formed.]. .Iadd.when cutting the tube at the
expanded portion.Iaddend..
4. A projector, comprising: an illumination optical system
including the illumination device of claim 3; an electro-optical
modulation device that modulates light from the illumination
optical system in accordance with image information; and a
projection optical system that projects the light modulated by the
electro-optical modulation device.
5. The illumination device .[.of.]. .Iadd.according to
.Iaddend.claim 1, the auxiliary mirror being an auxiliary mirror
disposed with an effective reflective surface in a range from a
portion of at least 40.degree. with respect to an optical axis of
the auxiliary mirror, using a light emission center of the
light-emitting portion as a reference, to an open end portion of
the auxiliary mirror.
6. A projector, including: an illumination optical system including
the illumination device of claim 5; an electro-optical modulation
device that modulates light from the illumination optical system in
accordance with image information; and a projection optical system
that projects the light modulated by the electro-optical modulation
device.
Description
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to a reflective mirror manufacturing
method, an illumination device and a projector.
2. Description of Related Art
Projectors realize image display by modulating, in accordance with
image information using a liquid crystal panel, illumination light
emitted from an illumination optical system and projecting the
modulated light onto a projection surface such as a screen.
The illumination optical system is disposed with an arc tube
including a light-emitting portion and a reflector including a
reflective surface that reflects the light from the light-emitting
portion of the arc tube in a predetermined direction. It is
preferable for the illumination device to be able to use, as
effectively as possible, the light from the arc tube.
For this reason, a parabolic reflector including a concave surface
configured by a paraboloid of revolution is conventionally used as
the reflector (e.g., see JP-A-2000-298213). FIG. 4 is a diagram
showing an example of an optical system of a projector using such a
parabolic reflector. As shown in FIG. 4, a parabolic reflector 930A
is used, and by disposing a light emission center of an arc tube
920A in the focal position of the parabolic reflector 930A, the
light emitted from the arc tube 920A can be made into substantially
parallel light. Thus, the light emitted from the arc tube can be
used effectively.
An ellipsoidal reflector including a concave surface configured by
an ellipsoid of revolution is also used as the reflector (e.g., see
JP-A-2002-90883). FIG. 5 is a diagram showing an example of an
optical system of a projector using such an ellipsoidal reflector.
As shown in FIG. 5, an ellipsoidal reflector 930B is used, and by
disposing the light emission center of an arc tube 920B in one
focal point (first focal point) of the ellipsoidal reflector 930B,
the light emitted from the arc tube 920B can be effectively focused
at another focal point (second focal point) of the ellipsoidal
reflector 930B. Thus, the light emitted from the arc tube can be
used effectively.
FIG. 6 is a diagram showing another example of an optical system of
a projector using such an ellipsoidal mirror. As shown in FIG. 6,
an ellipsoidal reflector 930C is used, and by disposing the light
emission center of an arc tube 920C in one focal point (first focal
point) of the ellipsoidal reflector 930C and disposing a
parallelizing lens 945 for making parallel the emission light from
the ellipsoidal reflector 930C, the light emitted from the arc tube
920C can be made into substantially parallel light. Thus, the light
emitted from the arc tube can be used effectively (e.g., see
JP-A-2000-347293).
Such reflectors are usually manufactured by press molding. FIG. 7
is a diagram showing a conventional reflector manufacturing method
for explanation.
In the conventional reflector manufacturing method, as shown in
FIG. 7, a reflector 930D is molded using a form block 930M disposed
with a lower mold 931 including a concave cavity, a press mold 932
disposed so as to surround the periphery of the cavity of the lower
mold 931, and a core 933 that slides the inside of a slide-use
opening of the press mold 932 towards the inside of the cavity of
the lower mold 931. Namely, a softened glass material is supplied
to the inside of the cavity of the lower mold 931, the glass
material is pressurized by sliding the core 933, and the glass
material spreads and fills the inside of the form block 930M. Thus,
reference surfaces 937 and 939 are formed by the press mold 932,
and a reflective surface 935 is formed by the core 933.
SUMMARY OF THE INVENTION
However, in this conventional reflector manufacturing method, when
the continuous production quantity increases, the surface of the
form block is abraded and the reflector material adheres to the
surface of the form block, whereby the state of the surface of the
form block deteriorates. For this reason, there have been the
problems that the characteristics of the reflective surface of the
reflector to be manufactured deteriorate, the light use efficiency
drops and the manufacturing cost rises.
Among illumination devices, there is an illumination device that
includes, in addition to an arc tube and a reflector, an auxiliary
mirror that reflects, towards the arc tube, light emitted from the
arc tube to an illuminated region (e.g., JP-A-11-143378). FIG. 8 is
a diagram showing an illumination device including such an
auxiliary mirror. As shown in FIG. 8, an auxiliary mirror 940 is
also ordinarily manufactured by press molding.
For this reason, even with respect to the auxiliary mirror 940,
when the continuous production quantity increases, the surface of
the form block is abraded and the auxiliary mirror material adheres
to the surface of the form block, whereby the state of the surface
of the form block deteriorates. For this reason, there have been
the problems that the characteristics of the reflective surface of
the auxiliary mirror to be manufactured deteriorates, the light use
efficiency drops and the manufacturing cost rises.
Thus, the present invention has been made in order to eliminate the
above-described problems, and it is an object thereof to provide a
reflective mirror manufacturing method for manufacturing a
reflective mirror such as a reflector and an auxiliary mirror, so
that even if the continuous production quantity increases, the
characteristics of the reflective surface of the reflective mirror
to be manufactured do not deteriorate, the light use efficiency
does not drop and the manufacturing cost does not rise.
It is also an object of the present invention to provide, at an
inexpensive manufacturing cost, an illumination device and a
projector including an excellent reflective mirror whose light use
efficiency is high.
The present invention provides a reflective mirror manufacturing
method for manufacturing a reflective mirror used in an
illumination device including an arc tube including a
light-emitting portion and a reflective mirror including a
reflective surface that reflects light from the light-emitting
portion in a predetermined direction, the method including: a first
step of forming a tube by heating a tube comprising a material of
the reflective mirror, thereafter putting the tube in a form block,
applying internal pressure with an inert gas to cause a center
portion of the tube to expand, so that part of an inner surface of
the expanded center portion includes a shape corresponding to the
reflective surface of the reflective mirror; a second step of
cutting the tube at the center portion to form a reflective mirror
member; and a third step of forming a reflective layer on an inner
surface of the reflective mirror member.
For this reason, according to the reflective mirror manufacturing
method of the invention, a form block for forming the reflective
surface of the reflective mirror becomes unnecessary because the
tube is formed by applying internal pressure with an inert gas to
cause a center portion of the tube to expand, so that the tube has
a shape corresponding to the reflective surface of the reflective
mirror. As a result, even if the continuous production quantity of
the reflective mirror increases, the situation where the surface of
the form block is abraded and the reflective mirror material
adheres to the surface of the form block is eliminated. For this
reason, even if the continuous production quantity of the
reflective mirror increases, the situation where the state of the
surface of the form block deteriorates is eliminated, and the
situation where the characteristics of the reflective surface of
the reflective mirror to be manufactured deteriorate, the light use
efficiency drops and the manufacturing cost rises is eliminated.
Thus, it becomes possible to manufacture, at an inexpensive
manufacturing cost, an excellent reflective mirror whose light use
efficiency is high.
Also, according to the reflective mirror manufacturing method of
the invention, because internal pressure is applied with an inert
gas to cause the center portion of the tube to expand, so that a
tube is formed having a shape corresponding to the reflective
surface of the reflective mirror, the inner surface of the
reflective mirror member contacts only the inert gas. Thus, a
smooth reflective surface whose surface roughness is extremely
small can be obtained as the reflective surface of the reflective
mirror.
For this reason, according to the reflective mirror manufacturing
method of the invention, it becomes possible to manufacture, at an
inexpensive manufacturing cost, a smooth reflective mirror whose
surface roughness is extremely small and whose light use efficiency
is high.
Also, according to the reflective mirror manufacturing method of
the invention, because that which contacts the form block is the
outer surface of the reflective mirror member, affects such as mold
marks do not appear in the reflective surface of the reflective
mirror. Thus, there is also the effect that a reflective mirror
having characteristics that are stable from the initial manufacture
to the end of the mold life can be manufactured.
In the reflective mirror manufacturing method of the invention, it
is preferable that in the first step, the tube is molded to have a
shape where two reflective mirror members mutually face each other,
and in the second step, the two reflective mirror members are
formed.
By configuring the invention in this manner, it becomes possible to
form two reflective mirrors from one tube, and it becomes possible
to further reduce the manufacturing cost of the reflective
mirror.
In this case, it is also easy to make the two reflective mirrors
have exactly the same shape, so that in this case, it becomes
possible to further reduce the manufacturing cost.
In the reflective mirror manufacturing method of the invention, it
is preferable for the reflective mirror to be a reflective mirror
disposed with an effective reflective surface in a range from a
portion of at least 40.degree. with respect to an optical axis of
the reflective mirror, using a light emission center of the
light-emitting portion as a reference, to an open end portion of
the reflective mirror.
Usually, arc tubes such as high-pressure mercury lamps and metal
halide lamps include a light distribution characteristic such that
the brightness of the light emitted in a range of 40.degree. to
140.degree. with respect to an extension-direction axis of seal
portions extending from both ends of the arc tube becomes
relatively high. Also, in illumination devices, usually the optical
axis of the reflective mirror, such as a reflector or auxiliary
mirror, coincides with the extension-direction axis of the seal
portions of the arc tube. For this reason, according to the
reflective mirror manufacturing method of the invention, because a
reflective mirror is manufactured that has an effective reflective
surface in a range from a portion of at least 40.degree. with
respect to the optical axis of the reflective mirror, using the
light emission center of the light-emitting portion as a reference,
to an open end portion of the reflective mirror, the reflective
mirror can be made into a reflective mirror having a reflectance
characteristic matching the light distribution characteristic of
the arc tube, and the use efficiency of the light emitted from the
arc tube can be raised.
The invention also provides an illumination device including an arc
tube including a light-emitting portion and a reflector that
reflects light from the light-emitting portion to an illuminated
region, wherein the reflector is a reflective mirror manufactured
by the reflective mirror manufacturing method of the invention.
For this reason, according to the illumination device of the
invention, as described above, the illumination device is
inexpensive and has a light use efficiency that is high because the
illumination device includes the reflector that is inexpensive and
has a light use efficiency that is high.
The invention also provides an illumination device including an arc
tube including a light-emitting portion, a reflector that reflects
light from the light-emitting portion to an illuminated region, and
an auxiliary mirror that is disposed facing the reflector with the
light-emitting portion sandwiched therebetween and which reflects
part of the light emitted from the light-emitting portion towards
the light-emitting portion, wherein the auxiliary mirror is a
reflective mirror manufactured by the reflective mirror
manufacturing method of the invention.
For this reason, according to the illumination device of the
invention, as described above, the illumination device is
inexpensive and has a light use efficiency that is high because the
illumination device includes the auxiliary mirror that is
inexpensive and has a light use efficiency that is high.
In the illumination device of the invention, in addition to the
auxiliary mirror, it is preferable for the reflector to also be a
reflective mirror manufactured by the reflective mirror
manufacturing method of the invention.
By configuring the invention in this manner, as described above, in
addition to including the auxiliary mirror that is inexpensive and
has a light use efficiency that is high, the illumination device is
even more inexpensive and has a higher light use efficiency because
it includes a reflector that is inexpensive and has a light use
efficiency that is high.
The invention also provides a projector including: an illumination
optical system including the illumination device of the invention;
an electro-optical modulation device that modulates light from the
illumination optical system in accordance with image information;
and a projection optical system that projects the light modulated
by the electro-optical modulation device.
For this reason, according to the projector of the invention, as
described above, the projector is inexpensive and has a light use
efficiency that is high because the projector is disposed with the
illumination device that is inexpensive and has a light use
efficiency that is high.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1 are diagrams for describing a reflector manufacturing
method pertaining to a first embodiment.
FIGS. 2 are diagrams for describing an auxiliary mirror
manufacturing method pertaining to a second embodiment.
FIG. 3 is a diagram showing an optical system of a projector
pertaining to a third embodiment.
FIG. 4 is a diagram showing an example of an optical system of a
projector using a parabolic reflector.
FIG. 5 is a diagram showing an example of an optical system of a
projector using an ellipsoidal reflector.
FIG. 6 is a diagram showing another example of an optical system of
a projector using an ellipsoidal reflector.
FIG. 7 is a diagram showing a conventional reflector manufacturing
method for explanation.
FIG. 8 is a diagram showing an illumination device including an
auxiliary mirror.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
A reflective mirror manufacturing method, an illumination device
and a projector of the present invention will be described below on
the basis of embodiments shown in the drawings.
First Embodiment
A first embodiment will be described using a reflector
manufacturing method as an example of the reflective mirror
manufacturing method of the invention.
FIGS. 1 are diagrams for describing the reflector manufacturing
method pertaining to the first embodiment. FIG. 1(a) is a diagram
for describing a reflector manufacturing method (press molding)
pertaining to a comparative example, and FIGS. 1(b) are diagrams
for describing the reflector manufacturing method (gas pressure
molding) pertaining to the first embodiment.
As shown in FIG. 1(a), the reflector manufacturing method (press
molding) pertaining to the comparative example includes the step of
conducting press molding in a state where a reflector material W1
is put between an upper mold MU30 and a lower mold ML30 having
desired shapes. For this reason, according to the reflector
manufacturing method pertaining to the comparative example, a
high-precision reflector can be relatively easily manufactured
using the high-precision upper mold MU30.
However, in the reflector manufacturing method pertaining to the
comparative example, when the continuous production quantity
increases, the surface of the upper mold MU30 is abraded and the
reflector material W1 adheres to the surface of the upper mold
MU30, whereby the state of the surface of the upper mold MU30
deteriorates. For this reason, there have been the problems that
the characteristics of the reflective surface of the reflector to
be manufactured deteriorate and the light use efficiency drops.
The reflector manufacturing method (gas pressure molding)
pertaining to the first embodiment includes: a first step of
heating part of a tube T1 comprising a reflector material as shown
in FIG. 1(b-1), thereafter putting the tube T1 in a form block M30,
applying internal pressure with an inert gas to cause the center
portion of the tube T1 to expand as shown in FIG. 1 (b-2) so that
part of the expanded inner surface includes a shape corresponding
to the reflective surface of the reflector to be manufactured; a
second step (not shown) of cutting the tube T1 at the center
portion and both ends to form a reflector member; and a third step
(not shown) of forming a reflective layer by forming a derivative
multilayer film such as TiO.sub.2 and SiO.sub.2 on the inner
surface of the reflector material by vapor deposition, sputtering
or CVD.
For this reason, according to the reflector manufacturing method
pertaining to the first embodiment, because internal pressure is
applied with an inert gas to cause the center portion of the tube
to expand, so that a tube is formed having a shape corresponding to
the reflective surface of the reflector, a form block for forming
the reflective surface of the reflector becomes unnecessary. As a
result, even if the continuous production quantity of the reflector
increases, the situation where the surface of the form block is
abraded and the reflector material adheres to the surface of the
form block is eliminated. For this reason, even if the continuous
production quantity of the reflector increases, the situation where
the state of the surface of the form block deteriorates is
eliminated, and the situation where the characteristics of the
reflective surface of the reflective mirror to be manufactured
deteriorate, the light use efficiency drops and the manufacturing
cost rises is eliminated. Thus, it becomes possible to manufacture,
at an inexpensive manufacturing cost, an excellent reflective
mirror whose light use efficiency is high.
Also, according to the reflector manufacturing method pertaining to
the first embodiment, because internal pressure is applied with an
inert gas to cause the center portion of the tube to expand, so
that a tube is formed having a shape corresponding to the
reflective surface of the reflector, the inner surface of the
reflector member contacts only the inert gas. Thus, a smooth
reflective surface whose surface roughness is extremely small can
be obtained as the reflective surface of the reflector.
For this reason, according to the reflector manufacturing method
pertaining to the first embodiment, it becomes possible to
manufacture, at an inexpensive manufacturing cost, a smooth
reflector whose surface roughness is extremely small and whose
light use efficiency is high.
Also, according to the reflector manufacturing method pertaining to
the first embodiment, because that which contacts the form block is
the outer surface of the reflector material, affects such as mold
marks do not appear in the reflective surface of the reflector.
Thus, there is also the effect that a reflector having
characteristics that are stable from the initial manufacture to the
end of the mold life can be manufactured.
In the reflector manufacturing method pertaining to the first
embodiment, in the first step, as shown in FIG. 1(b-2), the tube T1
is molded to have a shape where two reflector members mutually face
each other, and in the second step, the two reflector members are
formed (not shown).
For this reason, it becomes possible to form two reflectors with
the same shape from one tube T1, and it becomes possible to further
reduce the manufacturing cost of the reflector.
In the reflector manufacturing method pertaining to the first
embodiment, the reflector is a reflector disposed with an effective
reflective surface in a range from a portion of at least 40.degree.
with respect to the optical axis of the reflector, using the light
emission center of a light-emitting portion as a reference, to an
open end portion of the reflector.
Usually, arc tubes such as high-pressure mercury lamps and metal
halide lamps include a light distribution characteristic such that
the brightness of the light emitted in a range of 40.degree. to
140.degree. with respect to an extension-direction axis of seal
portions extending from both ends of the arc tube becomes
relatively high. Also, in illumination devices, usually the optical
axis of the reflector coincides with the extension-direction axis
of the seal portions of the arc tube. For this reason, according to
the reflector manufacturing method pertaining to the first
embodiment, because a reflector is manufactured that has an
effective reflective surface in a range from a portion of at least
40.degree. with respect to the optical axis of the reflector, using
the light emission center of a light-emitting portion as a
reference, to an open end portion of the reflector, the reflector
can be made into a reflector having a reflectance characteristic
matching the light distribution characteristic of the arc tube, and
the use efficiency of the light emitted from the arc tube can be
raised.
Hard glass and quartz glass are suitable as the material of the
tube T1. Among these, quartz glass is particularly suitable. This
is because the coefficient of thermal expansion is low, and
therefore internal warps do not remain, so that annealing is not
necessary.
In the reflector manufacturing method pertaining to the first
embodiment, an excellent reflective surface is obtained and the
inner surface of the reflector can always maintain a high
reflectance because the inner surface of the glass tube excellently
managed by the mold at the time of removal ordinarily becomes a
departure shape.
In this manner, according to the reflector manufacturing method
pertaining to the first embodiment, it becomes possible to
manufacture, at an inexpensive manufacturing cost, a smooth
reflector whose surface roughness is extremely small and whose
light use efficiency is high.
For this reason, by using, in an illumination device or projector,
the reflector manufactured by the reflector manufacturing method
pertaining to the first embodiment, it becomes possible to
manufacture, at an inexpensive manufacturing cost, an excellent
illumination device and projector whose light use efficiency is
high.
Second Embodiment
A second embodiment will be described using an auxiliary mirror
manufacturing method as an example of the reflective mirror
manufacturing method of the invention.
FIGS. 2 are diagrams for describing the auxiliary mirror
manufacturing method pertaining to the second embodiment. FIG. 2(a)
is diagram for describing an auxiliary mirror manufacturing method
(press molding) pertaining to a comparative example, and FIGS. 2(b)
are diagrams for describing the auxiliary mirror manufacturing
method (gas pressure molding) pertaining to the second
embodiment.
As shown in FIG. 2(a), the auxiliary mirror manufacturing method
(press molding) pertaining to the comparative example includes the
step of conducting press molding in a state where an auxiliary
mirror material W2 is put between an upper mold MU40 and a lower
mold ML40 having desired shapes. For this reason, according to the
auxiliary mirror manufacturing method pertaining to the comparative
example, a high-precision auxiliary mirror can be relatively easily
manufactured using the high-precision upper mold MU40.
However, in the auxiliary mirror manufacturing method pertaining to
the comparative example, when the continuous production quantity
increases, the surface of the upper mold MU40 is abraded and the
auxiliary mirror material W2 adheres to the surface of the upper
mold MU40, whereby the state of the surface of the upper mold MU40
deteriorates. For this reason, there have been the problems that
the characteristics of the reflective surface of the auxiliary
mirror to be manufactured deteriorate and the light use efficiency
drops.
The auxiliary mirror manufacturing method (gas pressure molding)
pertaining to the second embodiment includes: a first step of
heating part of a tube T2 comprising quartz glass, which is an
auxiliary mirror material, as shown in FIG. 2(b-1), thereafter
putting the tube T2 in a form block M40, applying internal pressure
with an inert gas to cause the center portion of the tube T2 to
expand as shown in FIG. 2(b-2) so that part of the expanded inner
surface includes a shape corresponding to the reflective surface of
the auxiliary mirror to be manufactured; a second step of cutting
the tube T2 at the center portion and both ends to form an
auxiliary mirror member as shown in FIG. 2(b-3); and a third step
(not shown) of forming a reflective layer by forming a derivative
multilayer film such as TiO.sub.2 and SiO.sub.2 on the inner
surface of the auxiliary mirror member by vapor deposition,
sputtering or CVD.
FIG. 2(b-4) is a diagram where the auxiliary mirror manufactured by
the auxiliary mirror manufacturing method pertaining to the second
embodiment is fixed to an arc tube using an adhesive. A ceramic
adhesive that can withstand high temperatures is used as the
adhesive.
For this reason, according to the auxiliary mirror manufacturing
method pertaining to the second embodiment, because internal
pressure is applied with an inert gas to cause the center portion
of the tube to expand, so that a tube is formed having a shape
corresponding to the reflective surface of the auxiliary mirror, a
form block for forming the reflective surface of the auxiliary
mirror becomes unnecessary. As a result, even if the continuous
production quantity of the auxiliary mirror increases, the
situation where the surface of the form block is abraded and the
auxiliary mirror material adheres to the surface of the form block
is eliminated. For this reason, even if the continuous production
quantity of the auxiliary mirror increases, the situation where the
state of the surface of the form block deteriorates is eliminated,
and the situation where the characteristics of the reflective
surface of the auxiliary mirror to be manufactured deteriorate, the
light use efficiency drops and the manufacturing cost rises is
eliminated. Thus, it becomes possible to manufacture, at an
inexpensive manufacturing cost, an excellent auxiliary mirror whose
light use efficiency is high.
Also, according to the auxiliary mirror manufacturing method
pertaining to the second embodiment, because internal pressure is
applied with an inert gas to cause the center portion of the tube
to expand, so that a tube is formed having a shape corresponding to
the reflective surface of the auxiliary mirror, the inner surface
of the auxiliary mirror member contacts only the inert gas. Thus, a
smooth reflective surface whose surface roughness is extremely
small can be obtained as the reflective surface of the auxiliary
mirror.
For this reason, according to the auxiliary mirror manufacturing
method pertaining to the second embodiment, it becomes possible to
manufacture, at an inexpensive manufacturing cost, a smooth
auxiliary mirror whose surface roughness is extremely small and
whose light use efficiency is high.
Also, according to the auxiliary mirror manufacturing method
pertaining to the second embodiment, because that which contacts
the form block is the outer surface of the auxiliary mirror member,
affects such as mold marks do not appear in the reflective surface
of the auxiliary member. Thus, there is also the effect that an
auxiliary mirror having characteristics that are stable from the
initial manufacture to the end of the mold life can be
manufactured.
Moreover, according to the auxiliary mirror manufacturing method
pertaining to the second embodiment, there are the effects that the
rate at which the reflection light from the reflector is blocked
can be minimized and the light use efficiency can be further raised
because the auxiliary mirror can be formed extremely thinly. There
is also the effect that the molding of the portion fixing the
auxiliary mirror to the arc tube also becomes easy.
In the auxiliary mirror manufacturing method pertaining to the
second embodiment, in the first step, as shown in FIG. 2(b-2) and
FIG. 2(b-3), the tube T2 is molded to have a shape where two
auxiliary mirror members mutually face each other, and in the
second step, two auxiliary mirror members 42 are formed.
For this reason, it becomes possible to form two auxiliary mirrors
40 with the same shape from one tube T2, and it becomes possible to
further reduce the manufacturing cost of the auxiliary mirror.
In the auxiliary mirror manufacturing method pertaining to the
second embodiment, the auxiliary mirror is an auxiliary mirror
disposed with an effective reflective surface in a range from a
portion of at least 40.degree. with respect to the optical axis of
the auxiliary member, using the light emission center of a
light-emitting portion as a reference, to an open end portion of
the auxiliary mirror.
Usually, arc tubes such as high-pressure mercury lamps and metal
halide lamps include a light distribution characteristic such that
the brightness of the light emitted in a range of 40.degree. to
140.degree. with respect to an extension-direction axis of seal
portions extending from both ends of the arc tube becomes
relatively high. Also, in illumination devices, usually the optical
axis of the reflector coincides with the extension-direction axis
of the seal portions of the arc tube. For this reason, according to
the auxiliary mirror manufacturing method pertaining to the second
embodiment, because an auxiliary mirror is manufactured that has an
effective reflective surface in a range from a portion of at least
40.degree. with respect to the optical axis of the auxiliary
mirror, using the light emission center of a light-emitting portion
as a reference, to an open end portion of the auxiliary mirror, the
auxiliary mirror can be made into an auxiliary mirror having a
reflectance characteristic matching the light distribution
characteristic of the arc tube, and the use efficiency of the light
emitted from the arc tube can be raised.
Hard glass and quartz glass are suitable as the material of the
tube T2. Among these, quartz glass is particularly suitable. This
is because the coefficient of thermal expansion is low, and
therefore internal warps do not remain, so that annealing is not
necessary.
In the auxiliary mirror manufacturing method pertaining to the
second embodiment, an excellent reflective surface is obtained and
the inner surface of the auxiliary mirror can always maintain a
high reflectance because the inner surface of the glass tube
excellently managed by the mold at the time of removal ordinarily
becomes a departure shape.
In this manner, according to the auxiliary mirror manufacturing
method pertaining to the second embodiment, it becomes possible to
manufacture, at an inexpensive manufacturing cost, a smooth
auxiliary mirror whose surface roughness is extremely small and
whose light use efficiency is high.
For this reason, by using, in an illumination device or projector,
the auxiliary mirror manufactured by the auxiliary mirror
manufacturing method pertaining to the second embodiment, it
becomes possible to manufacture, at an inexpensive manufacturing
cost, an excellent illumination device and projector whose light
use efficiency is high.
Third Embodiment
In order to describe the effects when the reflective mirror
manufactured by the reflective mirror manufacturing method of the
invention is used in an illumination device and projector, a third
embodiment will be described using, as an example, a case where the
reflector manufactured by the reflector manufacturing method
pertaining to the first embodiment is used in a projector.
FIG. 3 is a diagram showing an optical system of a projector
pertaining to the third embodiment.
A projector 100 pertaining to the third embodiment is an optical
device where light beams emitted from a light source are modulated
in accordance with image information to form an optical image, and
the optical image is enlarged and projected onto a screen SCR.
The projector 100 pertaining to the third embodiment includes an
optical system that is basically the same as the optical system of
a conventional projector 900A shown in FIG. 4. Namely, as shown in
FIG. 3, the projector 100 pertaining to the third embodiment is
disposed with an illumination optical system 101, a color light
separation optical system 200, a relay optical system 240, an
optical device 250 and a projection optical system 420.
The illumination optical system 101 is disposed with an
illumination device 10A and an integrator optical system 60.
The illumination device 10A is disposed with a reflector 30A
manufactured by the reflector manufacturing method pertaining to
the first embodiment and an arc tube 20 including a light emission
center at a focal position of the reflector 30A.
The arc tube 20 includes a tube and seal portions that extend at
both sides of the tube. The tube is made of quartz glass formed in
a spherical shape and includes a pair of electrodes disposed inside
the tube, with the inside of the tube being filled with mercury, a
noble gas and a small amount of halogen.
The pair of electrodes inside the tube of the arc tube 20 is for
forming an arc image. When a voltage is applied to the pair of
electrodes, a potential difference arises between the electrodes, a
discharge arises, and an arc image is generated.
Here, various kinds of arc tubes that emit light at a high
brightness can be used as the arc tube. For example, a metal halide
lamp, a high-pressure mercury lamp and a super high-pressure
mercury lamp can be used.
The reflector 30A includes a concave surface that aligns and emits,
in a constant direction, the light emitted from the arc tube 20.
The concave surface of the reflector 30A is formed as a cold mirror
that reflects visible light and transmits infrared light. The
optical axis of the reflector 30A coincides with an optical axis
30ax that is the central axis of the light beams emitted from the
illumination device 10A.
As described above, the illumination device 10A includes the arc
tube 20, which includes a light-emitting portion, and the reflector
30A, which reflects the light from the light-emitting portion to an
illuminated region, and the reflector 30A is a reflector
manufactured by the reflector manufacturing method pertaining to
the first embodiment. For this reason, as described above, the
illumination device is inexpensive and has a light use efficiency
that is high because the illumination device includes the reflector
that is inexpensive and has a light use efficiency that is
high.
The integrator optical system 60 is an optical system that
separates the light beams emitted from the illumination device 10A
into plural partial light beams to equalize the in-plane
illuminance of the illumination region. The integrator optical
system 60 is disposed with a first lens array 950, a second lens
array 960, a polarization conversion element 970, a superposition
lens 980 and a reflective mirror 955. An infrared reflective filter
80 is disposed on the optical path between the illumination device
10A and the first lens array 950.
The first lens array 950 includes a function as a light beam
separation optical element that separates the light beams emitted
from the illumination device 10A into plural partial light beams,
and is disposed with plural small lenses arranged in a matrix in a
plane intersecting the optical axis 30ax that is the central axis
of the light beams emitted from the illumination device 10A.
The second lens array 960 is an optical element that focuses the
plural partial light beams separated by the first lens array 950,
and similar to the first lens array 950, includes a configuration
disposed with plural small lenses arranged in a matrix in a plane
intersecting the optical axis 30ax.
The polarization conversion element 970 is a polarization
conversion element that emits, as substantially one kind of
linearly polarized light whose polarization direction has been
aligned, the polarization direction of the partial light beams
separated by the first lens array 950.
Although it is not shown, the polarization conversion element 970
is disposed with a configuration where polarization separation
films and reflection films disposed at an inclination with respect
to the optical axis 30ax are alternately arranged. The polarization
separation films transmit the polarized light beams of one of
P-polarized light beams and S-polarized light beams included in the
partial light beams, and reflect the other polarized light beams.
The other reflected polarized light beams are bent by the
reflective films and emitted in the emission direction of the other
polarized light beams, i.e., in the direction along the optical
axis 30ax. The polarization of either of the emitted polarized
light beams is converted by a phase difference plate disposed in
the light beam emission plane of the polarization conversion
element 970. By using the polarization conversion element 970, the
use efficiency of the light source light used by the optical device
250 can be raised because the light beams emitted from the
illumination device 10A can be aligned into polarized light beams
of substantially one direction.
The superposition lens 980 is an optical element that focuses the
plural partial light beams passing through the first lens array
950, the second lens array 960 and the polarization conversion
element 970, and superposes the plural partial light beams onto an
image forming region of three later-described liquid crystal
devices of the optical device 250.
The light emitted from the illumination optical system 101 is
emitted to the color separation optical system 200 and separated
into color light of the three colors of red (R), green (G) and blue
(B) in the color light separation optical system 200.
The color separation optical system 200 is disposed with two
dichroic mirrors 210 and 212 and a reflective mirror 220, and
includes the function of using the dichroic mirrors 210 and 211 to
separate, into color light of the three colors of red (R), green
(G) and blue (B), the plural partial light beams emitted from the
integrator optical system 60.
The dichroic mirrors 210 and 212 are optical elements where a
wavelength selection film that reflects light beams of a
predetermined wavelength region and transmits light beams of
another wavelength region are formed on a substrate. Additionally,
the dichroic mirror 210 disposed in the former stage of the optical
path is a mirror that transmits infrared light and reflects other
color light. Also, the dichroic mirror 212 disposed in the latter
stage of the optical path is a mirror that reflects green light and
transmits blue light.
The relay optical system 240 is disposed with an incident-side lens
262, a relay lens 264 and reflective mirrors 252 and 254, and
includes the function of guiding, to the optical device 250, the
blue light transmitted through the dichroic mirror 212 configuring
the color separation optical system 200. The reason the relay
optical system 240 is disposed in the optical path of the blue
light is to prevent a drop in the use efficiency of the light
resulting from diffusion of the light, because the optical path
length of the blue light is longer than the optical path lengths of
the other color light. Although the projector 100 pertaining to the
third embodiment is configured in this manner because the optical
path length of the blue light is long, a configuration is also
conceivable where the optical path length of the red light is
lengthened and the relay optical system 240 is used in the optical
path of the red light.
After the red light separated by the dichroic mirror 210 is bent by
the reflective mirror 220, it is supplied to the optical device 250
via a field lens. Also, the green light separated by the dichroic
mirror 212 is supplied to the optical device 250 as is via a field
lens. Moreover, the blue light is focused and bent by the lenses
262 and 264 and the reflective mirrors 252 and 254 configuring the
relay optical system 240, and is supplied to the optical device 250
via a field lens. The field lenses disposed in the former stage of
the optical path of each color light of the optical device 250 are
disposed in order to convert, to light beams substantially parallel
to the optical axis 30ax, the partial light beams emitted from the
illumination optical system 101.
The separated color light is modulated in correspondence to image
information in liquid crystal devices 300R, 300G and 300B.
The optical device 250 forms a color image by modulating the
incident light beams in accordance with image information. The
optical device 250 is disposed with the liquid crystal devices
300R, 300G and 300B (the liquid crystal device for the red light is
300R, the liquid crystal device for the green light is 300G, and
the liquid crystal device for the blue light is 300B) and a cross
dichroic prism 400. Here, each of the liquid crystal devices 300R,
300G and 300B is configured by a liquid crystal panel corresponding
to an electro-optical modulation device of the invention and
polarization plates disposed at the light-incident surface side and
the light-emission surface side of the liquid crystal panel. Light
modulation of each color light made incident is conducted by the
incident-side polarization plates, the liquid crystal panels and
the emission-side polarization plates.
The liquid crystal panels are panels where liquid crystal, which is
an electro-optical substance, is sealed in a pair of transparent
glass substrates. For example, a polysilicon TFT is used as a
switching element to modulate, in accordance with an applied image
signal, the polarization direction of the polarized light beams
emitted from the incident-side polarization plates.
The color light beams modulated in the liquid crystal devices 300R,
300G and 300B are synthesized by the cross dichroic prism 400.
The cross dichroic prism 400 is an optical element that forms a
color image by synthesizing optical images modulated per color
light emitted from the emission-side polarization plates. The cross
dichroic prism 400 has a substantially square shape in plan view
where four right-angled prisms are adhered together, and derivative
multilayer films are formed at the substantially X-shaped interface
where the right-angled prisms are adhered together. One of the
substantially X-shaped derivative multilayer films reflects red
light, and the other derivative multilayer film reflects blue
light. The red light and the blue light are bent by these
derivative multilayer films and aligned with the traveling
direction of the green light, whereby the light beams of the three
colors are synthesized.
The color image synthesized by the cross dichroic prism 400 is
enlarged and projected onto the screen SCR by the projection
optical system 420. Thus, an image is displayed on the screen
SCR.
As described above, the projector 100 pertaining to the third
embodiment is disposed with the illumination optical system 101
including the illumination device 10A, the liquid crystal devices
300R, 300G and 300B that modulate the light from the illumination
optical system 101 in accordance with image information, and the
projection optical system 420 that projects the light modulated by
the liquid crystal devices 300R, 300G and 300B.
For this reason, according to the projector 100 pertaining to the
third embodiment, as described above, the projector is inexpensive
and has a light use efficiency that is high because the projector
100 is disposed with the illumination device 10A that is
inexpensive and has a light use efficiency that is high.
The projector 100 pertaining to the third embodiment used the
illumination optical system 101 disposed with the integrator
optical system 60 and the illumination device 10A including the
reflector 30A manufactured by the reflector manufacturing method
pertaining to the first embodiment, but the projector 100 can also
use an illumination optical system 901B disposed with an
illumination device 910B including an ellipsoidal reflector 930B
including a concave surface configured by an ellipsoid of
revolution as shown in FIG. 5 and an integrator optical system
including an integrator rod 990. In a case where the illumination
optical system 901B is used in the projector, similar to the case
of the projector 100 pertaining to the third embodiment, the
projector can be configured to be an inexpensive projector and have
a light use efficiency that is high by using, in lieu of the
ellipsoidal reflector 930B, the reflector manufactured by the
reflector manufacturing method pertaining to the first
embodiment.
Also, the projector 100 pertaining to the third embodiment used the
illumination device 10A including the reflector 30A manufactured by
the reflector manufacturing method pertaining to the first
embodiment, but the projector can also use an illumination device
910E including an auxiliary mirror 940 and an ellipsoidal reflector
930E including a concave surface configured by an ellipsoid of
revolution as shown in FIG. 8. In a case where the illumination
device 910E is used in the projector, similar to the case of the
projector 100 pertaining to the third embodiment, the projector can
be configured to be an inexpensive projector and have a light use
efficiency that is high by using, in lieu of the auxiliary mirror
940, the auxiliary mirror 40 (see FIG. 2(b-4)) manufactured by the
auxiliary mirror manufacturing method pertaining to the second
embodiment. In this case, the projector can be configured to be an
inexpensive projector and have a light use efficiency that is high
by using, in lieu of the ellipsoidal reflector 910E, the reflector
manufactured by the reflector manufacturing method pertaining to
the first embodiment. In an illumination device including such an
auxiliary mirror, because the light emitted to the illuminated
region from the light-emitting portion of the arc tube is reflected
towards the reflector by the auxiliary mirror, it is not necessary
to set the size of the reflector to a size that covers the
illuminated region end portion of the arc tube, and the reflector
can be made compact. As a result, the illumination device can be
made compact.
A reflective mirror manufacturing method, an illumination device
and a projector of the invention have been described on the basis
of the preceding embodiments, but the present invention is not
limited to these embodiments. It is possible to implement the
invention in various kinds of modes within a range that does not
deviate from the gist thereof. For example, the following
modifications are also possible.
The illumination device described in the first embodiment is an
illumination device including the reflector manufactured by gas
pressure molding, and the illumination device described in the
second embodiment is an illumination device including an auxiliary
mirror manufactured by gas pressure molding, but the invention is
not limited thereto. The illumination device of the invention may
also be an illumination device including, in addition to an
auxiliary mirror manufactured by gas pressure molding, a reflector
manufactured by gas pressure molding.
In the preceding embodiments, an illumination device disposed with
the reflector manufactured by the reflector manufacturing method
pertaining to the first embodiment and/or the auxiliary mirror
manufactured by the auxiliary mirror manufacturing method
pertaining to the second embodiment was disposed in a projector,
but the invention is not limited thereto. The illumination device
may also be disposed in another optical device.
In the projector pertaining to the third embodiment, a case was
described where an illumination device disposed with the reflector
manufactured by the reflector manufacturing method pertaining to
the first embodiment and/or the auxiliary mirror manufactured by
the auxiliary mirror manufacturing method pertaining to the second
embodiment was used in a front type projector that projects a
projection image from the observing side, but the invention is also
applicable to a rear type projector that projects a projection
image from the side opposite from the observing side.
In the projector pertaining to the third embodiment, a projector
using the three liquid crystal devices 300R, 300G and 300B was
described as an example, but the invention is also applicable to a
projector disposed with one, two, or four or more liquid crystal
devices.
In the projector pertaining to the third embodiment, a case was
described where the illumination device of the invention was
applied to a transmissive type reflector, but it is also possible
to apply the invention to a reflective type projector. Here,
"transmissive type" means a type where an electro-optical
modulation device serving as light modulating means transmits
light, such as in a transmissive type liquid crystal device, and
"reflective type" means a type where an electro-optical modulation
device serving as light modulating means reflects light, such as in
a reflective type liquid crystal device. Even in a case where the
invention is applied to a reflective type projector, effects that
are substantially the same as those of a transmissive type
projector can be obtained.
The projector pertaining to the third embodiment used the liquid
crystal devices 300R, 300G and 300B as electro-optical modulation
devices, but the invention is not limited thereto. It suffices as
long as the electro-optical modulation device is one that usually
modulates incident light in accordance with image information, and
a micromirror type optical modulation device may be used. For
example, a DMD (digital micromirror device) (trademark of Texas
Instruments) can be used as the micromirror type optical modulation
device.
* * * * *