Optical: systems and elements – Lens – With reflecting element
Reexamination Certificate
1999-07-28
2001-03-20
Nguyen, Thong (Department: 2872)
Optical: systems and elements
Lens
With reflecting element
C359S366000, C359S631000
Reexamination Certificate
active
06204978
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an optical system, and particularly to an optical system including a curved surface (off-axial curved surface) on which with the route of a certain reference axis ray leading from an object surface to an image surface as a reference axis, a surface normal at a point on which the reference axis is incident does not coincide with the reference axis.
2. Related Background Art
As an optical system for forming the image of an object on an object surface onto an image surface, use has heretofore been made of a coaxial optical system in which on an optical axis, there is disposed a refracting surface or a reflecting surface rotation-symmetrical with respect to the optical axis.
Recently, however, in an image display apparatus such as a head mounting type display apparatus (HMD), an off-axial optical system using an asymmetrical aspherical surface not belonging to the category of the conventional coaxial optical system chiefly as a reflecting surface has come to be often seen. This is because the designing of such an optical system has become easy due to the improvements in the calculating capability of the computer and automatic designing technique.
In the above-described off-axial optical system, an off-axial reflecting surface or the like is used and therefore, the occurrence of eccentric aberration is unavoidable. Particularly, even in a light beam (on-axis light beam) relating to the center of the image field, astigmatism (on-axis astigmatism) occurs from the rotation asymmetry of the refractive power (power) of each surface.
In such an off-axial optical system, there is the condition that primary spherical aberration (on-axis astigmatism) can be corrected if all surfaces constituting the optical system are designed so as not to have azimuth dependency with respect to power.
However, if on an off-axial curved surface, the power thereof is designed so as not to have azimuth dependency, there arises the problem that the ratio of curvature in two cross-sections orthogonal to each other is determined and the degree of freedom of designing is taken away.
SUMMARY OF THE INVENTION
The present invention has as its object the provision of an optical system including an off-axial curved surface in which some of a plurality of groups (or surfaces) constituting it are designed such that the power thereof has azimuth dependency, and as a whole, the azimuth dependency of the power is null in such a manner that the some groups (or surfaces) negate the azimuth dependency with one another, and primary spherical aberration (on-axis astigmatism) is corrected.
The optical system of the present invention is
(1-1) an optical system having three partial systems through which rays of light from an object pass, i.e., a first partial system having at least one off-axial curved surface, a second partial system and a third partial system having at least one off-axial curved surface, characterized in that when the route of a ray of light passing from the object through the center of a stop to the center of the last image surface is defined as a reference axis and the converted principal point interval between the first partial system and the second partial system is defined as e1 and the converted principal point interval between the second partial system and the third partial system is defined as e2 and the power of the second partial system at a certain azimuth angle is defined as &phgr;2 (&xgr;), the condition that
0.8
≤
|
φ2
(
ξ
)
/
φ2
m
|
≤
1.25
where
φ2
m
=
1
/
2
π
∫
0
2
π
φ2
(
ξ
)
ⅆ
ξ
is satisfied, and when the powers of the first partial system and the third partial system at a certain azimuth angle are defined as &phgr;1 (&xgr;) and &phgr;3 (&xgr;), respectively, the conditions that
0.80
≤
(
e1
+
e2
)
/
(
e1
·
e2
)
÷
φ2
(
ξ
)
≤
1.25
0.80
≤
-
[
(
e1
/
e2
)
2
(
φ1
(
ξ
)
-
φ1
m
)
]
÷
(
φ3
(
ξ
)
-
φ3
m
)
≤
1.25
where
φ1
m
=
1
/
2
π
∫
0
2
π
φ1
(
ξ
)
ⅆ
ξ
φ3
m
=
1
/
2
π
∫
0
2
π
φ3
(
ξ
)
ⅆ
ξ
are satisfied.
The optical system of the present invention is
(1-2) an optical system having a transparent body provided with three reflecting surfaces by which rays of light from an object are internally reflected and pass, i.e., a first reflecting surface, a second reflecting surface and a third reflecting surface, characterized in that when the route of a ray of light passing from the object through the center of a stop to the center of the last image surface is defined as a reference axis and the converted interval between the first reflecting surface and the second reflecting surface is defined as e1 and the converted interval between the second reflecting surface and the third reflecting surface is defined as e2 and the power of the second reflecting surface at a certain azimuth angle is defined as &phgr;2 (&xgr;), the condition that
0.8≦|&phgr;2(&xgr;)/&phgr;2
m
|≦1.25
where
φ
2
m
=
1
/
2
π
∫
0
2
π
φ2
(
ξ
)
ⅆ
ξ
is satisfied, and when the powers of the first reflecting surface and the third reflecting surface at a certain azimuth angle are defined as &phgr;1 (&xgr;) and &phgr;3 (&xgr;), respectively, the conditions that
0.80
≤
(
e1
+
e2
)
/
(
e1
·
e2
)
÷
φ2
(
ξ
)
≤
1.25
0.80
≤
-
[
(
e1
/
e2
)
2
(
φ1
(
ξ
)
-
φ1
m
)
]
÷
(
φ3
(
ξ
)
-
φ3
m
)
≤
1.25
where
φ1
m
=
1
/
2
π
∫
0
2
π
φ1
(
ξ
)
ⅆ
ξ
φ3
m
=
1
/
2
π
∫
0
2
π
φ3
(
ξ
)
ⅆ
ξ
are satisfied.
The optical system of the present invention is
(1-3) an optical system having three reflecting surfaces through which rays of light from an object pass, i.e., a first reflecting surface, a second reflecting surface and a third reflecting surface, characterized in that when the route of a ray of light passing from the object through the center of a stop to the center of the last image surface is defined as a reference axis and the converted interval between the first reflecting surface and the second reflecting surface is defined as e1 and the converted interval between the second reflecting surface and the third reflecting surface is defined as e2 and the power of the second reflecting surface at a certain azimuth angle is defined as &phgr;2 (&xgr;), the condition that
0.8
≤
|
φ2
(
ξ
)
/
φ2
m
|
≤
1.25
where
φ2
m
=
1
/
2
π
∫
0
2
π
φ2
(
ξ
)
ⅆ
ξ
is satisfied, and when the powers of the first reflecting surface and the third reflecting surface at a certain azimuth angle are defined as &phgr;1 (&xgr;) and &phgr;3 (&xgr;), respectively, the conditions that
0.80
≤
(
e1
+
e2
)
/
(
e1
·
e2
)
÷
φ2
(
ξ
)
≤
1.25
0.80
≤
-
[
(
e1
/
e2
)
2
(
φ1
(
ξ
)
-
φ1
m
)
]
÷
(
φ3
(
ξ
)
-
φ3
m
)
≤
1.25
where
φ1
m
=
1
/
2
π
∫
0
2
π
φ1
(
ξ
)
ⅆ
ξ
φ3
m
=
1
/
2
π
∫
0
2
π
φ3
(
ξ
)
ⅆ
ξ
are satisfied.
REFERENCES:
patent: 4750022 (1988-06-01), Araki
patent: 5909317 (1999-06-01), Nakaoka et al.
patent: 5917656 (1999-06-01), Hayakawa et al.
p
Akiyama Takeshi
Araki Keisuke
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Nguyen Thong
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