Optical: systems and elements – Single channel simultaneously to or from plural channels – By partial reflection at beam splitting or combining surface
Reexamination Certificate
2000-04-26
2001-02-27
Epps, Georgia (Department: 2873)
Optical: systems and elements
Single channel simultaneously to or from plural channels
By partial reflection at beam splitting or combining surface
C359S631000, C359S633000
Reexamination Certificate
active
06195207
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an optical apparatus and, more particularly, to a head- or face-mounted image display apparatus that can be retained on the observer's head or face.
As an example of conventional head- or face-mounted image display apparatus, an image display apparatus disclosed in Japanese Patent Application Unexamined Publication (KOKAI) No. 3-101709 (1991) is known. FIG.
19
(
a
) shows the entire optical system of the conventional image display apparatus, and FIG.
19
(
b
) shows a part of an ocular optical system used in the image display apparatus. As illustrated in these figures, in the conventional image display apparatus, an image that is displayed by an image display device is transmitted as an aerial image by a relay optical system including a positive lens, and the aerial image is projected into an observer's eyeball as an enlarged image by an ocular optical system formed from a concave reflecting mirror.
U.S. Pat. No. 4,669,810 discloses another type of convention image display apparatus. In this apparatus, as shown in
FIG. 20
, an image of a CRT is transmitted through a relay optical system to form an intermediate image, and the image is projected into an observer's eye by a combination of a reflection holographic element and a combiner having a hologram surface.
Japanese Patent Application Unexamined Publication (KOKAI) No. 62-214782 (1987) discloses another type of conventional image display apparatus. As shown in FIGS.
21
(
a
) and
21
(
b
), the conventional image display apparatus is designed to enable an image of an image display device to be directly observed as an enlarged image through an ocular lens.
U.S. Pat. No. 4,026,641 discloses another type of conventional image display apparatus. In the conventional image display apparatus, as shown in
FIG. 22
, an image of an image display device is transferred to a curved object surface by an image transfer device, and the image transferred to the object surface is projected in the air by a toric reflector.
U.S. Reissued Pat. No. 27,356 discloses another type of conventional image display apparatus. As shown in
FIG. 23
, the apparatus is an ocular optical system designed to project an object surface on an exit pupil by a semitransparent concave mirror and a semitransparent plane mirror.
However, an image display apparatus of the type in which an image of an image display device is relayed, as in the image display apparatuses shown in FIGS.
19
(
a
),
19
(
b
) and
20
, must use several lenses as a relay optical system in addition to an ocular optical system, regardless of the type of ocular optical system. Consequently, the optical path length increases, and the optical system increases in both size and weight.
In a case where only the ocular optical system shown in FIG.
19
(
a
) is used, since only a reflecting surface having a concave surface directed toward the observer has positive power, as shown in FIG.
19
(
b
), large negative field curvature is produced as shown by reference symbol P
1
in the figure.
In a layout such as that shown in FIGS.
21
(
a
) and
21
(
b
), the amount to which the apparatus projects from the observer's face undesirably increases. Further, since an image display device and an illumination optical system are attached to the projecting portion of the apparatus, the apparatus becomes increasingly large in size and heavy in weight.
Since a head-mounted image display apparatus is fitted to the human body, particularly the head, if the amount to which the apparatus projects from the user's face is large, the distance from the supporting point on the head to the center of gravity of the apparatus is long. Consequently, the weight of the apparatus is imbalanced when the apparatus is fitted to the observer's head. Further, when the observer moves or turns with the apparatus fitted to his/her head, the apparatus may collide with something.
That is, it is important for a head-mounted image display apparatus to be small in size and light in weight. An essential factor in determining the size and weight of the apparatus is the layout of the optical system.
However, if an ordinary magnifier alone is used as an ocular optical system, exceedingly large aberrations are produced, and there is no device for correcting them. Even if spherical aberration can be corrected to a certain extent by forming the configuration of the concave surface of the magnifier into an aspherical surface, other aberrations such as coma and field curvature remain. Therefore, if the field angle is increased, the image display apparatus becomes impractical. Alternatively, if a concave mirror alone is used as an ocular optical system, it is necessary to use not only ordinary optical elements (lens and mirror) but also a device for correcting field curvature by an image transfer device (fiber plate) having a surface which is curved in conformity to the field curvature produced, as shown in FIG.
22
.
In a coaxial ocular optical system in which an object surface is projected on an observer's pupil by using a semitransparent concave mirror and a semitransparent plane mirror, as shown in
FIG. 23
, since two semitransparent surfaces are used, the brightness of the image is reduced to as low a level as {fraction (1/16)}, even in the case of a theoretical value. Further, since field curvature that is produced by the semitransparent concave mirror is corrected by curving the object surface itself, it is difficult to use a flat display, e.g. an LCD (Liquid Crystal Display), as an image display device.
SUMMARY OF THE INVENTION
In view of the above-described problems of the conventional techniques, an object of the present invention is to provide an optical apparatus, e.g. an image display apparatus, which enables observation of a clear image at a wide field angle with substantially no reduction in the brightness of the observation image, and which is extremely small in size and light in weight and hence unlikely to cause the observer to be fatigued.
To attain the above-described object, the present invention provides an optical apparatus which has a device for forming an image to be observed, and an ocular optical system for leading the image to an observer's eyeball. The ocular optical system includes, in order from the image side, a third surface which forms an entrance surfacer a first surface which forms both a reflecting surface and an exit surface, and a second surface which forms a reflecting surface. The first to third surfaces are integrally formed with a medium put therebetween which has a refractive index larger than 1.
In this case, the optical apparatus may be used as a finder optical system in which the image forming device is an objective lens system having positive refractive power as a whole and designed to form an object image, and in which the object image is formed in a space between the objective lens system and the ocular optical system. Alternatively, the image forming device may be an image display device for forming an image for observation. In this case, the optical apparatus may have a device for fitting both the image display device and the ocular optical system to the observer's head.
In addition, the present invention provides an optical apparatus which has a device for displaying an image, and an ocular optical system for projecting an image formed by the image display device and for leading the image to an observer's eyeball. The ocular optical system has at least three surfaces, and a space that is formed by these surfaces is filled with a medium having a refractive index larger than 1. The at least three surfaces include, in order from the observer's eyeball side toward the image display device, a first surface serving as both a refracting surface and an internally reflecting surface, a second surface serving as a reflecting surface of positive power which faces the first surface and is decentered or tilted with respect to an observer's visual axis, and a third surface serving as a refract
Epps Georgia
Olympus Optical Co,. Ltd.
Pillsbury Madison & Sutro LLP
Thompson Tim
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