Optical: systems and elements – Prism
Reexamination Certificate
2001-05-22
2002-05-14
Sikder, Mohammad (Department: 2872)
Optical: systems and elements
Prism
C359S832000, C359S630000, C359S631000, C359S632000
Reexamination Certificate
active
06388827
ABSTRACT:
This application claims benefit of Japanese Application No. 2000-149673 filed in Japan on May 22, 2000, the contents of which are incorporated by this reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to image display apparatus having a three-dimensionally decentered optical path. More particularly, the present invention relates to a head- or face-mounted image display apparatus that can be retained on an observer's head or face.
2. Discussion of Related Art
An image display apparatus using a single decentered prism has heretofore been known, for example, in Japanese Patent Application Unexamined Publication (KOKAI) No. Hei 7-333551. The decentered prism has reflecting surfaces arranged to effect two internal reflections. One of the reflecting surfaces is a totally reflecting surface serving as both a reflecting surface and a transmitting surface.
The conventional image display apparatus using the decentered prism suffers, however, from some problems. That is, when the image display device used therein decreases in size, it is necessary to shorten the focal length of the optical system while ensuring the required eye relief. Therefore, it is difficult to construct a viewing optical system of wide field angle.
To solve the above-described problem, the present applicant proposed an image display apparatus in Japanese Patent Application Unexamined Publication (KOKAI) No. 2000-66106, in which a decentered prism similar to the above is disposed on the pupil side, and another decentered prism is disposed on the image display device side.
The above-described arrangement using a combination of two decentered prisms forms a two-dimensionally decentered optical system, and the two decentered prisms have the same decentration plane. Consequently, the image display apparatus is likely to increase in size in the direction of decentration. Therefore, it is difficult to achieve a compact image display apparatus.
Further, an image display apparatus requires various constituent members such as an image display device, a circuit for driving it and an illuminating system in addition to a viewing optical system. With the above-described arrangement, these members cannot effectively be placed in a dead space.
In addition, design is very important for image display apparatus. With the above-described arrangement, the design freedom is limited to a very low degree.
SUMMARY OF THE INVENTION
The present invention was made in view of the above-described problems with the prior art.
An object of the present invention is to provide an image display apparatus attaining a reduction in overall size of the apparatus by using an optical system in which all the segments of an axial principal ray extending from a pupil to an image display device are not within the same plane. The image display apparatus further allows various constituent members to be effectively placed in a dead space, thereby permitting the image display apparatus to be designed in a variety of ways.
Another object of the present invention is to provide an image display apparatus favorably corrected for decentration aberrations despite the use of an optical system decentered in a three-dimensional space.
To attain the above-described objects, the present invention provides an image display apparatus having a three-dimensionally decentered optical path. The image display apparatus includes an image display device and a viewing optical system for leading an image formed by the image display device to a pupil corresponding to a position where an observer's eyeball is to be placed.
The viewing optical system has at least a first reflecting surface and a second reflecting surface positioned closer to the pupil than the first reflecting surface along the optical path. A first plane defined by the optical axis incident on the first reflecting surface and the optical axis reflected therefrom and a second plane defined by the optical axis incident on the second reflecting surface and the optical axis reflected therefrom intersect each other at an arbitrary angle, thereby forming a three-dimensionally decentered optical path. At least either one of the first and second reflecting surfaces has a curved surface configuration.
The reasons for adopting the above-described arrangement in the present invention, together with the function thereof, will be described below.
The image display apparatus according to the present invention includes an image display device and a viewing optical system for leading an image formed by the image display device to a pupil corresponding to a position where an observer's eyeball is to be placed. The viewing optical system has at least a first reflecting surface and a second reflecting surface disposed closer to the pupil along the optical path. The first reflecting surface corresponds to the surface
24
in Examples (described later). The second reflecting surface corresponds to the surface
22
. The optical system is arranged so that a first plane defined by the optical axis incident on the first reflecting surface and the optical axis reflected therefrom and a second plane defined by the optical axis incident on the second reflecting surface and the optical axis reflected therefrom do not extend in the same plane or parallel to each other but intersect each other at an arbitrary angle, whereby the viewing optical system can be decentered three dimensionally. Accordingly, it is possible to fold the optical system in any desired direction and hence possible to reduce the overall size of the image display apparatus. Thus, it is possible to provide an image display apparatus having a minimized dead space in consideration of other associated members. In addition, the degree of design freedom increases favorably.
In a case where a decentered optical system is used as a viewing optical system of a head-mounted image display apparatus, it is desirable with a view to eliminating a dead space and further reducing the overall size of the apparatus to arrange the optical system so that a first plane defined by the optical axis incident on the first reflecting surface and the optical axis reflected therefrom and a second plane defined by the optical axis incident on the second reflecting surface and the optical axis reflected therefrom intersect each other at an arbitrary angle, as stated above. In such a case, the optical system must inevitably be decentered three dimensionally, and this causes rotationally asymmetric aberrations to occur. It is impossible to correct the rotationally asymmetric aberrations by only a rotationally symmetric optical system. The best surface configuration for correcting the rotationally asymmetric aberrations due to three-dimensional decentration is a rotationally asymmetric surface. Therefore, in the image display apparatus according to the present invention, it is desirable that at least either one of the first and second reflecting surfaces should have a rotationally asymmetric curved surface configuration that corrects decentration aberrations.
It is preferable that the viewing optical system should have at least one reflecting surface in addition to the first and second reflecting surfaces, i.e. reflecting surfaces corresponding to the surfaces
12
,
13
,
22
,
23
and
24
in Examples (described later), and at least two of the plurality of reflecting surfaces should have a rotationally asymmetric curved surface configuration that corrects decentration aberrations.
In the present invention, a free-form surface is used as a typical example of a surface having a rotationally asymmetric curved surface configuration. A free-form surface is defined by the following equation. The Z-axis of the defining equation is the axis of a free-form surface.
Z
=
cr
2
/
[
1
+
{
1
-
(
1
+
k
)
c
2
r
2
}
]
+
∑
j
=
2
66
C
j
X
m
Y
n
(
a
)
In the equation (a), the first term is a spherical surface term, and the second term is a free-form surface term.
In the spherical surface term:
c: the curvature at the vertex
k: a co
Nagata Tetsuo
Togino Takayoshi
Olympus Optical Co,. Ltd.
Pillsbury & Winthrop LLP
Sikder Mohammad
LandOfFree
Image display apparatus having three-dimensionally... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Image display apparatus having three-dimensionally..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Image display apparatus having three-dimensionally... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2833574