Illumination optical system, and spectrophotometric apparatus and image forming apparatus including the same
Provided is an illumination optical system includes: a light source; and a light guiding member configured to guide a light flux emitted from the light source to an illuminated surface, the light guiding member having: an incident surface into which the light flux from the light source enters; an ellipsoidal reflection surface configured to reflect the light flux from the incident surface; and an exit surface from which the light flux reflected by the ellipsoidal reflection surface exits, in which the light source is arranged so as to be separated from a first focal point of the ellipsoidal reflection surface at a position farther from the illuminated surface, in a direction perpendicular to a light emitting surface of the light source.
1. An illumination optical system, comprising:
a light source; and
a light guiding member configured to guide a light flux emitted from the light source to an illuminated surface,
the light guiding member having:
an incident surface into which the light flux from the light source enters;
an ellipsoidal reflection surface configured to reflect the light flux from the incident surface; and
an exit surface from which the light flux reflected by the ellipsoidal reflection surface exits,
wherein the light source is arranged so as to be separated from a first focal point of the ellipsoidal reflection surface at a position farther from the illuminated surface, in a direction perpendicular to a light emitting surface of the light source.
2. An illumination optical system according to claim 1 , wherein the light emitting surface of the light source is arranged close to the incident surface of the light guiding member.
3. An illumination optical system according to claim 1 , wherein, when a direction including two focal points of a spheroid defining the ellipsoidal reflection surface is defined as a z-axis, an intersection of the spheroid with the z-axis is defined as an origin, two directions that are orthogonal to the z-axis and perpendicular to each other are defined as an x-axis and a y-axis, and a surface shape of the spheroid is defined as:
Z
=
(
x
2
+
y
2
)
R
1
+
1
-
(
1
+
k
)
x
2
+
y
2
R
2
and when Δ max is set as follows:
Δ
ma
x
=
R
1
+
1
-
(
k
+
1
)
cos
θ
where R represents a curvature radius of the spheroid at the origin, k represents a conic constant, and θ represents an angle formed between the z-axis and a direction perpendicular to the light emitting surface of the light source,
the light source is arranged so as to be separated by a distance Δ satisfying:
0.1Δ max ≤Δ≤0.5Δ max
from the first focal point of the ellipsoidal reflection surface in the direction perpendicular to the light emitting surface of the light source.
4. An illumination optical system according to claim 1 , wherein, when a direction including two focal points of a spheroid defining the ellipsoidal reflection surface is defined as a z-axis, an intersection of the spheroid with the z-axis is defined as an origin, two directions that are orthogonal to the z-axis and perpendicular to each other are defined as an x-axis and a y-axis, and a surface shape of the spheroid is defined as:
Z
=
(
x
2
+
y
2
)
R
1
+
1
-
(
1
+
k
)
x
2
+
y
2
R
2
and when Δ max is set as follows:
Δ
ma
x
=
R
1
+
1
-
(
k
+
1
)
cos
θ
where R represents a curvature radius of the spheroid at the origin, k represents a conic constant, and θ represents an angle formed between the z-axis and a direction perpendicular to the light emitting surface of the light source,
the following expression is satisfied:
2
R
(
k
+
1
)
Δ
ma
x
-
1
>
1.
5. An illumination optical system according to claim 1 , wherein, when a direction including two focal points of a spheroid defining the ellipsoidal reflection surface is defined as a z-axis, an intersection of the spheroid with the z-axis is defined as an origin, two directions that are orthogonal to the z-axis and perpendicular to each other are defined as an x-axis and a y-axis, and a surface shape of the spheroid is defined as:
Z
=
(
x
2
+
y
2
)
R
1
+
1
-
(
1
+
k
)
x
2
+
y
2
R
2
and when Δ max is set as follows:
Δ
ma
x
=
R
1
+
1
-
(
k
+
1
)
cos
θ
where R represents a curvature radius of the spheroid at the origin, k represents a conic constant, and θ represents an angle formed between the z-axis and a direction perpendicular to the light emitting surface of the light source,
the following expression is satisfied:
1
2
arccos
(
2
R
2
Δ
ma
x
[
2
R
-
(
k
+
1
)
Δ
ma
x
]
-
1
}
≥
arcsin
(
1
n
)
,
where n represents a refractive index of the light guiding member.
6. An illumination optical system according to claim 1 , wherein the incident surface is a plane.
7. An illumination optical system according to claim 1 , wherein the exit surface is a plane.
8. An illumination optical system according to claim 1 , wherein the first focal point of the ellipsoidal reflection surface is located outside of the light guiding member.
9. An illumination optical system according to claim 1 , wherein a second focal point of the ellipsoidal reflection surface is located on the illuminated surface.
10. An illumination optical system according to claim 1 , wherein the incident surface is parallel to a major axis of the ellipsoidal reflection surface.
11. An illumination optical system according to claim 1 , wherein the incident surface is non-parallel to a major axis of the ellipsoidal reflection surface.
12. An illumination optical system according to claim 1 , wherein the exit surface is perpendicular to a major axis of the ellipsoidal reflection surface.
13. An illumination optical system according to claim 1 , wherein the exit surface is prevented from being perpendicular to a major axis of the ellipsoidal reflection surface.
14. An illumination optical system according to claim 1 , wherein the light guiding member comprises a solid light guiding member made of resin.
15. An illumination optical system according to claim 1 , wherein the light source comprises one of an LED and an OLED.
16. An illumination optical system according to claim 1 , wherein the light guiding member has only one reflection surface.
17. An illumination optical system according to claim 1 , wherein the ellipsoidal reflection surface is subjected to reflection film.
18. A spectrophotometric apparatus, comprising:
an illumination optical system configured to illuminate an illuminated surface; and
a spectral optical system configured to disperse scattered light from an object arranged on the illuminated surface to form an image of the object on a light receiving element,
the illumination optical system comprising:
a light source; and
a light guiding member configured to guide a light flux emitted from the light source to the illuminated surface,
the light guiding member having:
an incident surface into which the light flux from the light source enters;
an ellipsoidal reflection surface configured to reflect the light flux from the incident surface; and
an exit surface from which the light flux reflected by the ellipsoidal reflection surface exits,
wherein the light source is arranged so as to be separated from a first focal point of the ellipsoidal reflection surface at a position farther from the illuminated surface, in a direction perpendicular to a light emitting surface of the light source.
19. An image forming apparatus, comprising:
a spectrophotometric apparatus;
developing units configured to develop, as toner images, electrostatic latent images formed on photosensitive surfaces of a plurality of photosensitive bodies, respectively;
transfer units configured to transfer the developed toner images onto a transfer material; and
a fixing unit configured to fix the transferred toner images to the transfer material,
the spectrophotometric apparatus comprising:
an illumination optical system configured to illuminate an illuminated surface; and
a spectral optical system configured to disperse scattered light from an object arranged on the illuminated surface to form an image of the object on a light receiving element,
the illumination optical system comprising:
a light source; and
a light guiding member configured to guide a light flux emitted from the light source to the illuminated surface,
the light guiding member having:
an incident surface into which the light flux from the light source enters;
an ellipsoidal reflection surface configured to reflect the light flux from the incident surface; and
an exit surface from which the light flux reflected by the ellipsoidal reflection surface exits,
wherein the light source is arranged so as to be separated from a first focal point of the ellipsoidal reflection surface at a position farther from the illuminated surface, in a direction perpendicular to a light emitting surface of the light source.