A projector includes a light source, an illumination optical system, and a color separating optical system. The color separating optical includes a dichroic mirror which reflects a first color light component of an illumination light through a first optical path by a reflection angle and transmits a second light component through a second optical path; a first mirror which bends the first optical path by a first bent angle; and a second mirror which bends the second optical path by a second bent angle. The reflection angle, the first bent angle, and the second bent angle are arranged to provide a predetermined difference between the length of the first optical path and the length of the second optical path, and the predetermined difference corresponding to a difference between focal distances of a superimposing optical element corresponding to the first and second light components.
1. A projector comprising:
a light source that emits light;
an illumination optical system that includes a superimposing optical element capable of performing superimposition illumination and that uniformizes the light emitted from the light source to form illumination light, the superimposing optical element having a first focal distance corresponding to a first color light component and a second focal distance corresponding to a second color light component, the first and second focal distances are not identical;
a color separating optical system that includes:
a dichroic mirror which reflects the first color light component of the illumination light through a first optical path by a reflection angle and transmits a second color light component through the second optical path,
a first mirror which bends the first optical path by a first bent angle, and
a second mirror which bends the second optical path by a second bent angle;
light modulating devices that are illuminated by the first and second color light components emitted from the color separating optical system and form color optical images;
a combining optical system that combines the color optical images; and
a projection optical system that projects an image combined by the combining optical system,
the reflection angle, the first bent angle, and the second bent angle being arranged to provide a predetermined difference between the length of the first optical path and the length of the second optical path,
the predetermined difference corresponding to a difference between the first focal distance of the superimposing optical element and the second focal distance of the superimposing optical element.
2. The projector according to claim 1 , wherein
the superimposing optical element is composed of a single lens, and
when a main wavelength of the first color light component passing through the first optical path and main wavelengths of the second color light component passing through the second optical path are used as reference wavelengths, the length of the first optical path is L a , the length of the second optical path is L b , the refractive index of the single lens with respect to the main wavelength of the first color light component is n λa , the refractive index of the single lens with respect to the main wavelengths of the second color light component is n λb , a curvature radius of an incident surface of the single lens is r 1 , a curvature radius of an emission surface of the single lens is r 2 , and the thickness of the single lens is d, the color separating optical system substantially satisfies the following Expression related to a difference L a −L b :
L
a
-
L
b
=
f
a
-
f
b
,
where
1
f
a
=
(
n
λ
a
-
1
)
(
1
r
1
-
1
r
2
)
+
(
n
λ
a
-
1
)
2
d
n
λ
b
r
1
r
2
,
and
1
f
b
=
(
n
λ
b
-
1
)
(
1
r
1
-
1
r
2
)
+
(
n
λ
b
-
1
)
2
d
n
λ
b
r
1
r
2
.
3. The projector according to claim 1 , wherein the illumination optical system includes a pair of fly-eye lenses.
4. The projector according to claim 1 , wherein the first optical path and the second optical path are arranged perpendicular to each other with respect to the combining optical system.
5. The projector according to claim 1 , wherein,
in the illumination optical system, an optical axis up to the second mirror is perpendicular to an optical axis from the second mirror to the combining optical system, and
in the color separating optical system, the dichroic mirror and the first mirror are arranged substantially in parallel to each other.
6. The projector according to claim 1 , wherein,
in the illumination optical system, an optical axis up to the second mirror is not perpendicular to an optical axis from the second mirror to the combining optical system, and
in the color separating optical system, the dichroic mirror and the second mirror are arranged substantially in parallel to each other.
7. The projector according to claim 1 , wherein
the first color light component is a red light component, and
the length the first optical path is larger than the length of the second optical path.
8. The projector according to claim 1 , wherein
the first color light component is a blue light component, and the length of the first optical path is shorter than the length of the second optical path.