U.S. patent application number 10/849116 was filed with the patent office on 2004-11-25 for prism optical element, image observation apparatus and image display apparatus.
This patent application is currently assigned to Olympus Corporation. Invention is credited to Takahashi, Junko, Takahashi, Koichi.
Application Number | 20040233551 10/849116 |
Document ID | / |
Family ID | 27470370 |
Filed Date | 2004-11-25 |
United States Patent
Application |
20040233551 |
Kind Code |
A1 |
Takahashi, Junko ; et
al. |
November 25, 2004 |
Prism optical element, image observation apparatus and image
display apparatus
Abstract
An extremely compact prism optical element, image observation
apparatus and image display apparatus which are capable of
providing an observation image that is clear and has minimal
aberration and minimal distortion even at a wide field angle. Light
rays emitted from an image display device (7) enter an ocular
optical system (12) through a fourth surface (6) and are totally
reflected toward an observer's pupil (1) by a third surface (5).
The reflected light rays are reflected by a first surface (3)
disposed immediately in front of the observer's pupil (1) and then
reflected toward the observer's pupil (1) by a second surface (4).
The reflected light rays pass through the first surface (3) and are
projected into an observer's eyeball (15) with the observer's iris
position as an exit pupil (1). When an external-scene image is
observed, light rays from an object point in,the external scene
enter the ocular optical system (12) through the third surface (5),
pass through the first surface (3) and are projected into the
observer's eyeball (15). Assuming that the angle of internal
reflection of an arbitrary light ray at the third surface (5) is
.theta..sub.r3, the ocular optical system (12) satisfies the
condition of
sin.sup.-1(1/n.sub.d).ltoreq..theta..sub.r3.ltoreq.60.de- gree.,
where n.sub.d is the refractive index for the spectral d-line of
the medium of the ocular optical system (12).
Inventors: |
Takahashi, Junko;
(Atsugi-shi, JP) ; Takahashi, Koichi; (Tokyo,
JP) |
Correspondence
Address: |
PILLSBURY WINTHROP, LLP
P.O. BOX 10500
MCLEAN
VA
22102
US
|
Assignee: |
Olympus Corporation
Tokyo
JP
|
Family ID: |
27470370 |
Appl. No.: |
10/849116 |
Filed: |
May 20, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10849116 |
May 20, 2004 |
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10038584 |
Jan 8, 2002 |
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6760169 |
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10038584 |
Jan 8, 2002 |
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09570652 |
May 12, 2000 |
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09570652 |
May 12, 2000 |
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08867779 |
Jun 3, 1997 |
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Current U.S.
Class: |
359/837 ;
359/834 |
Current CPC
Class: |
G02B 2027/0178 20130101;
G02B 27/0172 20130101; G02B 2027/011 20130101; G02B 17/08 20130101;
G02B 5/04 20130101; G02B 27/0176 20130101; G02B 17/086 20130101;
G02B 2027/012 20130101; G02B 17/0832 20130101; G02B 27/18 20130101;
G02B 17/0816 20130101; G02B 2027/0174 20130101 |
Class at
Publication: |
359/837 ;
359/834 |
International
Class: |
G02B 027/10 |
Foreign Application Data
Date |
Code |
Application Number |
May 7, 1997 |
JP |
9-116724 |
May 7, 1997 |
JP |
9-116725 |
Claims
1. A prism optical element comprising a plurality of surfaces
facing each other across a medium having a refractive index (n)
larger than 1 (n>1), wherein said plurality of surfaces include
a first surface having both a transmitting action through which
light rays enter said prism optical element or exit therefrom and a
reflecting action by which light rays are internally reflected in
said prism optical element; a second surface disposed to face said
first surface across said medium and having a reflecting action by
which light rays are internally reflected in said prism optical
element; a third surface disposed substantially close to said
second surface to face said first surface across said medium and
having a reflecting action by which light rays are internally
reflected in said prism optical element; and a fourth surface
having such a transmitting action that when said first surface has
an action through which light rays enter said prism optical
element, said fourth surface has an action through which light rays
exit from said prism optical element, whereas, when said first
surface has an action through which light rays exit from said prism
optical element, said fourth surface has an action through which
light rays enter said prism optical element, and wherein the
following condition is satisfied: sin.sup.-1(1/n.sub.d).ltore-
q..theta..sub.r3.ltoreq.60.degree. (1) where n.sub.d is a
refractive index for the spectral d-line of said medium, and
.theta..sub.r3 is an angle of internal reflection of an arbitrary
light ray at said third surface.
2. A prism optical element according to claim 1, which satisfies
the following condition:
sin.sup.-1(1/n.sub.d).ltoreq..theta..sub.r3.ltoreq.5- 0.degree.
(2)
3. A prism optical element according to claim 1, wherein reflection
at said first surface is total reflection.
4. A prism optical element according to claim 1, wherein the
refractive index (n) of said 0 medium is larger than 1.3
(n>1.3).
5. A prism optical element according to claim 1, wherein at least
one of surfaces constituting said prism optical element is a plane
surface.
6. An observation optical system comprising the prism optical
element according to claim 1, said prism optical element being
disposed in an observation optical system unit.
7. An observation optical system according to claim 6, wherein said
prism optical element is disposed in an objective lens.
8. A camera finder optical system comprising the observation
optical system of claim 6, wherein said prism optical element is
disposed in image-erecting means disposed behind an objective lens
to erect an object image formed by said objective lens.
9. A camera finder optical system according to claim 8, wherein
said prism optical element has an ocular lens action in addition to
an image erecting action.
10. A head-mounted image display apparatus comprising: the prism
optical element according to claim 1; image forming means disposed
to face said fourth surface of said prism optical element; and a
retaining member that retains both said prism optical element and
said image forming means on an observer's face wherein a bundle of
light rays emitted from said image forming means enters said prism
optical element through said fourth surface and passes sequentially
along an optical path in said prism optical element such that the
light rays are reflected successively by said third surface, said
first surface and said second surface and exit from said prism
optical element through said first surface.
11. An image observation apparatus comprising image forming means
and an ocular optical system having an action by which an image
formed by said image forming means is led to an eyeball of an
observer, wherein said ocular optical system includes a prism
member having at least three surfaces, wherein a space between said
at least three surfaces is filled with a single medium having a
refractive index (n) larger than 1 (n>1), said prism member
having an action by which light rays emitted from said image
forming means are internally reflected at least three times,
wherein at least two of the at least three internal reflections are
total reflections, and wherein at least one of the at least two
total reflections is performed by a surface disposed on a side of
said single medium that is closer to said observer, said surface
being curved so as to correct aberrations produced by the internal
reflections in said prism member, and wherein at least two of the
at least three surfaces of said prism member are disposed to face
each other such that an external scene can be observed through said
at least two surfaces, and that a distortion produced when the
external scene is observed through said single medium is
minimized.
12-32. (canceled)
33. An image observation apparatus according to claim 10, further
comprising positioning means for positioning said image forming
means and said ocular optical system with respect to an observer's
head.
34. An image observation apparatus according to claim 10, further
comprising support means for supporting at least a pair of said
image observation apparatuses at a predetermined spacing.
35. A prism optical element or prism member according to claim 1,
wherein said second surface and said third surface act as different
surfaces in terms of optical action but are formed structurally
from a single surface.
36. A prism optical element or prism member according to claim 35,
wherein said single surface constituting said second and third
surfaces is arranged such that a region of said surface closer to
said fourth surface acts as said third surface, and a region of
said surface remote from said fourth surface acts as said second
surface.
37. A prism optical element or prism member according to claim 36,
wherein said single surface constituting said second and third
surfaces is arranged such that a central region of said surface
acts as both said second and third surfaces.
38. An image display apparatus comprising an image display device
and an ocular optical system for leading an image formed by said
image display device to an eyeball of an observer such that said
image can be observed as a virtual image, wherein said ocular
optical system includes: a decentered prism in which a space formed
by at least two surfaces is filled with a medium having a
refractive index larger than 1, said at least two surfaces
including a first surface positioned immediately in front of the
observer's eyeball, and a second surface which is a reflecting
surface facing said first surface, at least one of said at least
two surfaces being a curved surface decentered or tilted with
respect to an observer's visual axis, and aberration correcting
means disposed outside said second surface to correct aberrations
due to decentration produced by said first and second surfaces with
respect to light from an external scene.
39. An image display apparatus according to claim 38, wherein said
aberration correcting means comprises a Fresnel lens.
40. An image display apparatus according to claim 39, wherein a
center of an annular zone of said Fresnel lens lies in a plane
containing an optical path of an axial principal ray from said
image display device, and said Fresnel lens is decentered
perpendicularly to the observer's visual axis in the plane
containing the optical path of the axial principal ray.
41. An image display apparatus according to claim 39, wherein a
center of an annular zone of said Fresnel lens lies in a plane
containing an optical path of an axial principal ray from said
image display device, and said Fresnel lens is tilted with respect
to the observer's visual axis so as to extend along a surface
configuration of said second surface.
42. An image display apparatus according to claim 38, wherein said
aberration correcting means comprises a diffractive optical
element.
43. An image display apparatus according to claim 38, wherein said
aberration correcting means comprises a holographic optical
element.
44. An image display apparatus comprising an image display device
and an ocular optical system for leading an image formed by said
image display device to an eyeball of an observer such that said
image can be observed as a virtual image, wherein said ocular
optical system includes a decentered prism in which a space formed
by at least three surfaces is filled with a medium having a
refractive index larger than 1; said at least three surfaces
including: a refracting and internally reflecting surface
positioned immediately in front of said observer's eyeball; an
outside world-side internally reflecting surface disposed on an
outside world side of said ocular optical system to face said
refracting and internally reflecting surface; and a refracting
surface through which a bundle of light rays emitted from said
image display device enters said decentered prism, wherein at least
one of said at least three surfaces is decentered or tilted with
respect to an observer's visual axis, and said at least three
surfaces are arranged to perform at least three internal
reflections, said ocular optical system further includes a second
optical element that cancels a power produced by said refracting
and internally reflecting surface, which is positioned immediately
in front of said observer's eyeball, and said outside world-side
internally reflecting surface with respect to external light when
an external scene is observed through said two surfaces, said
second optical element being disposed on an outside world side of
said outside world-side internally reflecting surface.
45. An image display apparatus according to claim 44, wherein said
ocular optical system comprises a decentered prism in which a space
formed by four surfaces is filled with a medium having a refractive
index larger than 1, said four surfaces including a first surface
positioned on an observer's eyeball side of said ocular optical
system and serving as both refracting and reflecting surfaces, a
second surface which is a reflecting surface disposed to face said
first surface; a third surface which is a reflecting surface
disposed to face said first surface at a position adjacent to said
second surface; and a fourth surface which is a refracting surface
closest to said image display device, wherein at least one of said
four surfaces is decentered or tilted with respect to the
observer's visual axis.
46. An image display apparatus according to claim 45, wherein at
least one second optical element is disposed on an outside world
side of said second or third surface so that an external scene can
be observed through said first surface, said second surface and
said second optical element or through said first surface, said
third surface and said second optical element.
47. An image display apparatus according to claim 46, wherein said
second optical element simultaneously cancels a composite power of
said first and second surfaces and a composite power of said first
and third surfaces with respect to light from the external
scene.
48. An image display apparatus according to claims 38 or 44,
further comprising positioning means for positioning said image
display device and said ocular optical system with respect to an
observer's head.
49. An image display apparatus according to claims 38 or 44,
further comprising support means for supporting said image display
device and said ocular optical system with respect to an observer's
head such that said apparatus can be mounted on the observer's
head.
50. An image display apparatus according to claims 38 or 44,
further comprising support means for supporting at least a pair of
said image display apparatuses at a predetermined spacing.
51. An image display apparatus according to claims 38 or 44,
wherein said ocular optical system is used as an image-forming
optical system.
52. An optical system comprising: a decentered prism having at
least two surfaces, wherein a space formed by said at least two
surfaces is filled with a medium having a refractive index larger
than 1; and aberration correcting means provided at a position
separate from said decentered prism; wherein at least one of said
at least two surfaces is a curved surface decentered or tilted with
respect to a predetermined axis, and wherein said aberration
correcting means is provided so that light that has passed through
said aberration correcting means passes through said decentered
prism.
53. An optical system comprising: a decentered prism having at
least three surfaces, wherein a space formed by said at least three
surfaces is filled with a medium having a refractive index larger
than 1; and a second optical element provided at a position
separate from said decentered prism; wherein at least one of said
at least three surfaces is a curved surface decentered or tilted
with respect to a predetermined axis; said at least three surfaces
including a first surface and a second surface; said second surface
being positioned closest to said second optical element; said first
surface being positioned to face said second optical element across
said second surface; and wherein said second optical element is
provided so that light that has passed through said second optical
element passes through said decentered prism, and said second
optical element cancels a power produced by said second surface.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a prism optical element, an
image observation apparatus and an image display apparatus. More
particularly, the present invention relates to a head- or
face-mounted image display apparatus that can be retained on the
observer's head or face.
[0002] 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. In this 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.
[0003] U.S. Pat. No. 4,669,810 discloses another type of convention
image display apparatus. In this apparatus, 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.
[0004] U.S. Pat. No. 4,026,641 discloses another type of
conventional image display apparatus. In the conventional image
display apparatus, 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 reflecting surface.
[0005] U.S. Reissued Pat. No. 27,356 discloses another type of
conventional image display apparatus. This apparatus is an ocular
optical system designed to project an object surface onto an exit
pupil by a semi-transparent concave mirror and a semitransparent
plane mirror.
[0006] Other known image display apparatuses include those which
are disclosed in U.S. Pat. Nos. 4,322,135 and 4,969,724, European
Patent No. 0,583,116A2, and Japanese Patent Application Unexamined
Publication (KOKAI) No. 7-333551 (1995).
[0007] However, an image display apparatus of the type in which an
image of an image display device is relayed, as in Japanese Patent
Application Unexamined Publication (KOKAI) No. 3-101709 (1991) and
U.S. Pat. No. 4,669,810, 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.
[0008] Because 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 arrangement
of the optical system.
[0009] 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 for observation 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.
[0010] In an image display apparatus of the type in which an image
of an image display device is projected into an observer's eyeball
by using a toric reflecting surface as in U.S. Pat. No. 4,026,641,
field curvature that is produced by the decentered toric reflecting
surface is corrected by curving the object surface itself.
Therefore, it is difficult to use a flat display, e.g. an LCD
(Liquid Crystal Display), as an image display device.
[0011] 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 in U.S. Reissued Pat. No. 27,356, because 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, because 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
[0012] In view of the above-described problems of the conventional
techniques, an object of the present invention is to provide an
extremely compact image observation apparatus and image display
apparatus which are capable of providing an observation image that
is clear and has minimal aberration and minimal distortion even at
a wide field angle, and a prism optical element for use in these
apparatuses.
[0013] To attain the above-described object, the present invention
provides a prism optical element formed from a plurality of
surfaces facing each other across a medium having a refractive
index (n) larger than 1 (n>1). The prism optical element has a
first surface, a second surface, a third surface, and a fourth
surface. The first surface has both a transmitting action through
which light rays enter the prism optical element or exit therefrom
and a reflecting action by which light rays are internally
reflected in the prism optical element. The second surface is
disposed to face the first surface across the medium and has a
reflecting action by which light rays are internally reflected in
the prism optical element. The third surface is disposed
substantially close to the second surface to face the first surface
across the medium and has a reflecting action by which light rays
are internally reflected in the prism optical element. The fourth
surface has such a transmitting action that when the first surface
has an action through which light rays enter the prism optical
element, the fourth surface has an action through which light rays
exit from the prism optical element, whereas, when the first
surface has an action through which light rays exit from the prism
optical element, the fourth surface has an action through which
light rays enter the prism optical element. The prism optical
element satisfies the following condition:
sin.sup.-1(1/n.sub.d).ltoreq..theta..sub.r3.ltoreq.60.degree.
(1)
[0014] where n.sub.d is the refractive index for the spectral
d-line of the medium, and .theta..sub.r3 is the angle of internal
reflection of an arbitrary light ray at the third surface.
[0015] In the present invention, the arrangement of the second and
third surfaces is not necessarily limited to the one in which
surfaces designed separately from each other are disposed adjacent
to each other, but includes an arrangement in which the second and
third surfaces are formed by using one identical surface such that
one region of the surface acts as the second surface, and another
region of the surface acts as the third surface. In this case, an
overlap region that acts as both the second and third surfaces may
be present because a bundle of light rays has a width.
[0016] One image observation apparatus according to the present
invention has an image forming device and an ocular optical system
having an action by which an image formed by the image forming
device is led to an eyeball of an observer. The ocular optical
system includes a prism member having at least three surfaces. The
space between the at least three surfaces is filled with a single
medium having a refractive index (n) larger than 1 (n>1). The
prism member has an action by which light rays emitted from the
image forming device are internally reflected at least three times.
At least two of the at least three internal reflections are total
reflections. At least one of the at least two total reflections is
performed by a surface disposed on a side of the single medium that
is closer to the observer. The surface is curved so as to correct
aberrations produced by the internal reflections in the prism
member. At least two of the at least three surfaces of the prism
member are disposed to face each other such that an external scene
can be observed through the at least two surfaces, and that a
distortion produced when the external scene is observed through the
single medium is minimized.
[0017] Another image observation apparatus according to the
present-invention has an image forming device and an ocular optical
system having an action by which an image formed by the image
forming device is led to an eyeball of an observer. The ocular
optical system includes at least a prism member. The prism member
has at least four optical surfaces having a transmitting or
reflecting optical action. The space surrounded by the at least
four optical surfaces is filled with a single medium having a
refractive index (n) larger than 1 (n>1). The at least four
optical surfaces include a first surface, a second surface, a third
surface, and a fourth surface. The first surface has both a
transmitting action and a reflecting action and is disposed on a
side of the prism member that is closer to the observer's eyeball.
The second surface has a reflecting action and is disposed to face
the first surface across the medium. The second surface is at least
decentered or tilted with respect to the observer's visual axis.
The third surface has a reflecting action and is disposed to face
the first surface across the medium at a position substantially
adjacent to the second surface. The fourth surface is disposed such
that one end thereof is substantially adjacent to the first
surface, and the other end thereof is substantially close to the
third surface. At least the third surface has a totally reflecting
action. The first surface, the single medium and the third surface
are arranged to have an external scene observation action by which
an external scene can be observed through the first surface, the
single medium and the third surface.
[0018] Still another image observation apparatus according to the
present invention has an image forming device and an ocular optical
system having an action by which an image formed by the image
forming device is led to an eyeball of an observer. The ocular
optical system includes at least a prism member. The prism member
has at least four optical surfaces having a transmitting or
reflecting optical action. The space surrounded by the at least
four surfaces is filled with a single medium having a refractive
index (n) larger than 1 (n>1). The at least four optical
surfaces include a first surface, a second surface, a third
surface, and a fourth surface. The first surface has both a
transmitting action and a reflecting action and is disposed on a
side of the prism member that is closer to the observer's eyeball.
The second surface has a reflecting action and is disposed to face
the first surface across the medium. The second surface is at least
decentered or tilted with respect to the observer's visual axis.
The third surface has a reflecting action and is disposed to face
the first surface across the medium at a position substantially
adjacent to the second surface. The fourth surface is disposed such
that one end thereof is substantially adjacent to the first
surface, and the other end thereof is substantially close to the
third surface. At least the second or third surface has a totally
reflecting action. In addition, a line-of-sight detecting device
for detecting an observer's line of sight is disposed near a
totally reflecting region of the second or third surface that has a
totally reflecting action.
[0019] An image display apparatus according to the present
invention has an image display device and an ocular optical system
for leading an image formed by the image display device to an
eyeball of an observer such that the image can be observed as a
virtual image. The ocular optical system includes a decentered
prism in which a space formed by at least two surfaces is filled
with a medium having a refractive index larger than 1. The at least
two surfaces include a first surface positioned immediately in
front of the observer's eyeball, and a second surface which is a
reflecting surface facing the first surface. At least one of the at
least two surfaces is a curved surface decentered or tilted with
respect to the observer's visual axis. The ocular optical system
further includes an aberration correcting device disposed outside
the second surface to correct aberrations due to decentration
produced by the first and second surfaces with respect to light
from an external scene.
[0020] Another image display apparatus according to the present
invention has an image display device and an ocular optical system
for leading an image formed by the image display device to an
eyeball of an observer such that the image can be observed as a
virtual image. The ocular optical system includes a decentered
prism in which a space formed by at least three surfaces is filled
with a medium having a refractive index larger than 1. The at least
three surfaces include a refracting and internally reflecting
surface positioned immediately in front of the observer's eyeball;
an outside world-side internally reflecting surface disposed on the
outside world side of the ocular optical system to face the
refracting and internally reflecting surface; and a refracting
surface through which a bundle of light rays emitted from the image
display device enters the decentered prism. At least one of the at
least three surfaces is decentered or tilted with respect to the
observer's visual axis. The at least three surfaces are arranged to
perform at least three internal reflections. The ocular optical
system further includes a second optical element that cancels a
power produced by the refracting and internally reflecting surface,
which is positioned immediately in front of the observer's eyeball,
and the outside world-side internally reflecting surface with
respect to external light when an external scene is observed
through the two surfaces. The second optical element is disposed on
the outside world side of the outside world-side internally
reflecting surface.
[0021] In the present invention, the arrangement of the second and
third surfaces is not necessarily limited to-the one in which
surfaces designed separately from each other are disposed adjacent
to each other, but includes an arrangement in which the second and
third surfaces are formed by using one identical surface such that
one region of the surface acts as the second surface, and another
region of the surface acts as the third surface. In this case, an
overlap region that acts as both the second and third surfaces may
be present because a bundle of light rays has a width.
[0022] The arrangements and operations of the prism optical
element, image observation apparatus and image display apparatus
according to the present invention will be described. In the
description of the image observation apparatus and image display
apparatus in particular, the explanation will be made on the basis
of backward ray tracing in which light rays are traced from the
observer's pupil position toward the image display device for the
convenience of designing the optical system, unless otherwise
specified.
[0023] In the image observation apparatus according to the present
invention, light rays from the image display device (image forming
device) are internally reflected three times in the ocular optical
system, thereby enabling the optical path to be folded very
effectively, and thus realizing an extremely thin ocular optical
system. Two of the three internal reflections are specified as
total reflections. Consequently, the area that requires reflection
coating is markedly reduced, thereby succeeding in realizing a
compact, lightweight and low-cost ocular optical system. By
specifying two of the three reflections as total reflections, it is
possible to minimize the incidence of a ghost image due to the
occurrence of unwanted light or the reduction in contrast-caused by
flare. Usually, in an optical system having internal reflection and
filled with an optical medium having a refractive index larger than
1, the influence of unwanted light emerging from an image display
device at a large exit angle and unwanted light due to reflection
in a path other than the proper ray path gives rise to a problem.
In the present invention, the number of reflection coating surfaces
is reduced by using two totally reflecting surfaces. Consequently,
unwanted light other than the desired bundle of light rays
emanating from the image display device and reaching the observerts
pupil is transmitted by the two internally reflecting surfaces.
Thus, unwanted light reaching the observer's pupil is markedly
reduced.
[0024] The above-described action will be described in detail with
reference to FIGS. 20(a) and 20(b). FIGS. 20(a) and 20(b) are
fragmentary enlarged views showing a part of a decentered prism 12
through which light from an image display device 7 enters. The
decentered prism 12 has three surfaces 101, 102 and 103 decentered
with respect to the optical axis, and the space formed by the
surfaces 101, 102 and 103 is filled with a medium having a
refractive index larger than 1. Reference numeral 15 denotes an
observer's eyeball. Reference numeral 101 denotes an entrance
surface. Reference numeral 102 denotes an outside world-side
reflecting or totally reflecting surface. Reference numeral 103
denotes an observer-side refracting or reflecting surface. FIG.
20(a) shows an arrangement in which the reflecting surface 102 is
provided with reflection coating. FIG. 20(b) shows an arrangement
in which the reflecting surface 102 is a totally reflecting
surface, which is provided-with no reflection coating. In the case
of FIG. 20(a), light emitted from the left-hand end of the image
display device 7 at a large exit angle enters the decentered prism
12 while being refracted by the entrance surface 101. The incident
light is reflected by the reflecting surface 102, which is provided
with reflection coating. The reflected light passes through the
refracting surface 103 and enters the observer's eyeball 15.
Accordingly, the observer sees an unwanted electronic image in the
upper part of the observer's visual field in addition to the proper
image (hereinafter referred to as "electronic image") of the image
display device 7. Alternatively, flare appears in the upper part of
the observer's visual field.
[0025] In the case of FIG. 20(b), light emitted from the left-hand
end of the image display device 7 at a large exit angle enters the
decentered prism 12 while-being refracted by the entrance surface
101, and is incident on the reflecting surface 102, which is
provided with no reflection coating. Because the incident angle is
smaller than the critical angle, the unwanted light passes through
the reflecting surface 102. Accordingly, the unwanted light is
transmitted to a side of the decentered prism 12 that is remote
from the observer and therefore does not enter the observer's
eyeball 15. In other words, neither a ghost image nor flare
occurs.
[0026] The above-described action can be similarly caused to take
place at any totally reflecting surface in addition to the
reflecting surface in this example. That is, the above-described
action can be attained by setting the optical system such that a
bundle of light rays in the ray path for observation of the proper
electronic image has an incident angle not smaller than the
critical angle, and that any other ray bundle having an exit angle
which may cause ghost or flare has an incident angle smaller than
the critical angle at a totally reflecting surface. It becomes easy
to obtain the above-described effect by setting two totally
reflecting surfaces as described above. Thus, it becomes possible
to provide the observer with a clear observation image which is
free from a ghost image and which has a minimal reduction in
contrast due to flare.
[0027] First, assuming that the prism optical element according to
the present invention is used as an ocular optical system
(observation optical system) of an image observation apparatus or
an image display apparatus, the prism optical element is formed
from a prism member in which at least three internal reflections
take place, and the prism member is filled with a medium having a
refractive index larger than 1. Therefore, the ocular optical
system can be made extremely thin by the above-described optical
path folding effect. In addition, aberration correction can be made
even more effectively by the arrangement in which at least three
internal reflections take place. Thus, it is possible to present an
observation image which is clear as far as the edges of the image
field. In this regard, the prism optical element according to the
present invention will be described below more specifically.
[0028] The principal power of the prism optical element is given by
the second surface, which is a reflecting surface. In this case,
the second surface can be formed with a large radius -of curvature
in comparison to a refracting system of the same power as that of
the reflecting surface. Therefore, aberrations produced by the
second surface can be minimized. Further, the outside world-side
reflecting surface is divided into two different surfaces (i.e. the
second and third surfaces). Therefore, it becomes possible to set
the direction of reflected light as desired independently of the
curvature of each surface. Accordingly, the optical system can be
so shaped as to conform to the curve of the observer's face, and
the image display device can be disposed such that the back of the
device faces the observer. In particular, when the image display
device is an LCD or the like that requires a back light, the back
light and the associated electric system are provided on the
observer side. Therefore, no part of the image display device
projects forwardly, and the amount to which the whole image display
apparatus projects from the observer's face can be minimized.
[0029] In general, when a concave mirror is decentered or tilted
with respect to the optical axis, aberrations due to decentration
are produced, which do not occur in a coaxial system. In the case
of the prism optical element according to the present invention
also, when it is used in an image observation apparatus or an image
display apparatus, aberrations due to decentration are produced
because the second surface is decentered or tilted with respect to
the observer's visual axis. In particular, astigmatism and coma
occur even on the optical axis because there is a difference in
power between a direction along a plane containing the optical path
of the axial principal ray (i.e. tangential direction) and a
direction perpendicular to a plane containing the visual axis and
the optical path of the axial principal ray (i.e. sagittal
direction). The aberrations due to decentration produced by the
second surface can be corrected by forming at least one of the at
least four surfaces constituting the prism optical element from a
surface having different powers in the tangential and sagittal
directions, i.e. a rotationally asymmetric surface.
[0030] An even more effective way of correcting the aberrations due
to decentration is to use a surface-having only one plane of
symmetry to form at least one of the surfaces constituting the
prism optical element. When the image display device is disposed on
the observer's visual axis (i.e. axial principal ray), a
bilaterally symmetric observation image can be projected into the
observer's eyeball by using a surface having a plane of symmetry in
the sagittal direction as at least one of the surfaces constituting
the ocular optical system. On the other hand, if the surface is
arranged to have no plane of symmetry in the tangential direction,
the degree of freedom in the tangential direction increases, and it
is possible to even more favorably correct decentration aberrations
occurring in a plane containing the optical path of the axial
principal ray.
[0031] When the above-described ocular optical system comprises at
least four surfaces, reflection taking place at the first surface
may be total reflection. If the first surface, which is a surface
disposed immediately in front of the observerts pupil, is a totally
reflecting surface, a region through which light rays exit from the
ocular optical system and an internally reflecting region can be
arranged to overlap each other. In other words, a single surface
can be arranged to perform both transmitting and reflecting
actions. Accordingly, it is possible to construct a compact ocular
optical system.
[0032] In addition, it is possible to provide a clearer observation
image because the above-described ghost and flare reducing effect
by the totally reflecting surface can also be obtained at the first
surface. Further, because only the second surface requires
reflection coating, the productivity improves, and a lower-cost
image display apparatus can be realized.
[0033] In the above-described prism optical element, it is
desirable to satisfy the following condition:
sin.sup.-1(1/n.sub.d).ltoreq..theta..sub.r3.ltoreq.60.degree.
(1)
[0034] where n.sub.d is the refractive index for the spectral
d-line of the medium, and .theta..sub.r3 is the angle of internal
reflection of an arbitrary light ray at the third surface.
[0035] It is important to satisfy the condition (1). By setting
.theta..sub.r3 equal to or greater than sin.sup.-1 (1/n.sub.d), the
angle of internal reflection at the third surface becomes equal to
or greater than the critical angle. Consequently, it is possible
for an arbitrary light ray emitted from the image display device to
be totally reflected at the third surface.
[0036] If the angle of reflection at the third surface is
excessively large, the prism optical element becomes undesirably
long in the direction (tangential direction) perpendicular to the
visual axis. In the case of a wide-field image display apparatus in
particular, extra-axial rays diverge to such an extent that the
rays cannot reach the first surface, which is the subsequent
reflecting surface. Consequently, it becomes impossible to realize
the desired image display apparatus. Accordingly, it is desirable
that at the third surface the angle of internal reflection of an
arbitrary light ray emitted from the image display device should be
set not larger than the upper limit of the condition (1), i.e.
60.degree..
[0037] It is more desirable to satisfy the following condition:
sin.sup.-1(1/n.sub.d).ltoreq..theta..sub.r3.ltoreq.50.degree.
(2)
[0038] Because the third surface is a curved surface tilted or
decentered with respect to the optical axis (axial principal ray),
the angle of reflection at this surface should be as small as
possible. The smaller the reflection angle, the smaller the amount
of aberration caused by decentration, particularly comatic
aberration due to decentration. Accordingly, it is desirable that
at the third surface the angle of internal reflection of an
arbitrary light ray emitted from the image display device should be
set not greater than the upper limit of the condition (2), i.e.
50.degree..
[0039] It is important from the viewpoint of realizing a low-cost
image display apparatus to use a plane surface as at least one of
the surfaces constituting the prism optical element. By doing so,
another surface can be defined on the basis of the at least one
plane surface. Therefore, it is possible to facilitate the
mechanical design and production of an optical system.
Consequently, it is possible to shorten the machining or processing
time and to facilitate the layout of the whole apparatus. Thus, it
is possible to realize substantial reductions in manufacturing
costs.
[0040] Similar advantageous effects can be obtained by using a
spherical surface as at least one of the surfaces constituting the
prism optical element. In this case, another surface can be readily
defined on the basis of the at least one spherical surface.
Therefore, the layout of the whole apparatus is also facilitated.
Thus, it is possible to realize substantial reductions in
manufacturing costs.
[0041] It is desirable that the refractive index n of the medium
constituting the prism optical element should be larger than
1.3.
[0042] It will be clear from the foregoing description that an
observation optical apparatus can be constructed by disposing the
above-described prism optical element in an observation optical
system.
[0043] In this case, the prism optical element may be disposed in
an objective lens. Alternatively, the prism-optical element may be
disposed in an image erecting device which is disposed behind an
objective lens to erect an object image formed by the objective
lens. In the latter arrangement, the prism optical element can be
arranged to have both an image erecting action and an ocular lens
action.
[0044] The prism optical element according to the present invention
can be used to construct a head-mounted image display apparatus
having an image forming device consisting essentially of an LCD
(Liquid Crystal Display) or a CRT disposed to face the fourth
surface of the prism optical element, or an image-forming device
consisting essentially of an LCD, a CRT or the like which is
relayed by a relay optical system. The head-mounted image display
apparatus further has a retaining member adapted to retain both the
prism optical element and the image forming device on the
observer's face. A bundle of light rays emitted from the image
forming device enters the prism optical element through the fourth
surface and passes sequentially along the optical path in the prism
optical element. More specifically, the incident ray bundle is
reflected successively by the third surface, the first surface and
the second surface and exits from the prism optical element through
the first surface.
[0045] In the present invention, the second and third surfaces may
be formed from a single identical surface. In this case, the number
of physical surfaces can be reduced by one, and-it is therefore
possible to simplify the process in terms of the optical design and
the production of prism and hence possible to contribute to the
achievement of an increase in mass-productivity and reductions in
costs. It is desirable that a physically single surface should be
arranged to have both the functions of the second and third
surfaces, and that internally reflecting regions should overlap
each other. By doing so, it is possible to realize a reduction in
the size of the prism member.
[0046] One image observation apparatus according to the present
invention has an image forming device and an ocular optical system
having an action by which an image formed by the image forming
device is led to an eyeball of an observer. The ocular optical
system includes a prism member having at least three surfaces. The
space between the at least three surfaces is filled with a single
medium having a refractive index (n) larger than 1 (n>1). The
prism member has an action by which light rays emitted from the
image forming device are internally reflected at least three times.
At least two of the at least three internal reflections are total
reflections. At least one of the at least two total reflections is
performed by a surface disposed on a side of the single medium that
is closer to the observer. The surface is curved so as to correct
aberrations produced by the internal reflections in the prism
member. At least two of the at least three surfaces of the prism
member are disposed to face each other such that an external scene
can be observed through the at least two surfaces, and that a
distortion produced when the external scene is observed through the
single medium is minimized.
[0047] In the image observation apparatus according to the present
invention, the third surface 5 is a totally reflecting surface,
which is provided with no reflection coating. Therefore, external
light passing through the third surface 5 and the first surface 3
reaches the observer's eyeball 15. Accordingly, it is possible to
observe an external scene in a range .alpha. different from an
electronic image observation range .beta.. The fact that the
observer can observe an external scene image and an electronic
image in different partial regions of the visual field means that
the observer can simultaneously observe the external scene in the
upper region of the observer's visual field and the electronic
image in the lower region of the visual field, by way of example.
It should, however, be noted that the partial regions of the visual
field for observation of different images may be divided in any
direction and in any form, e.g. upper and lower regions, or left
and right regions, as long as the observer can observe the
different images in the respective partial regions. This function
enables the observer to recognize the outside world with the image
observation apparatus mounted on his or her head or face. Thus, it
is possible to provide a safe image observation apparatus that
enables the observer to avoid a dangerous situation and to cope
with an emergency situation. Consequently, the range of
applications of the image observation apparatus widens.
[0048] In this image observation apparatus, it is desirable that
the image forming device should be an image display device, e.g. an
LCD or a CRT disposed such that the image forming surface thereof
faces the fourth surface (it should be noted that an image display
device which is relayed by a relay optical system is not expected
as the image forming device in the image observation apparatus),
and that the second surface should be formed from a curved
surface.
[0049] The above-described image observation apparatus can be
constructed as a head-mounted image display apparatus by providing
a retaining member that retains both the image display device and
the ocular optical system in front of an observer's eyeball, and
arranging the prism member such that a bundle of light rays emitted
from the image display device enters the prism member through the
fourth surface, and the incident ray bundle is reflected
successively by the third surface, the first surface and the second
surface so as to exit from the first surface.
[0050] In the above-described image observation apparatus, the
prism member may be fixed at the same position regardless of
whether the observer views the image formed by the image forming
device or an image of an external scene. In this case, it is
desirable that the image from the image forming device and the
external-scene image should be capable of being observed in the
respective partial regions through the first and third surfaces, as
described later with reference to FIG. 7.
[0051] The prism member may be provided with a switching device
that moves the prism member so as to enable observation modes to
change between the observation of the image formed by the image
forming device and the observation of the external-scene image.
[0052] More specifically, if the prism member is moved such that
the first surface of the ocular optical system, which is disposed
immediately in front of the observer's eyeball, and the third
surface, which is disposed on the outside world side of the ocular
optical system to totally reflect a part of the principal rays, lie
in the vicinity of the observer's visual axis, the observer can
view an external-scene image around-the observer's visual axis
lying when he or she looks straight ahead, i.e. in the vicinity of
the center of the visual field. Therefore, the observer can confirm
the external scene in front of his/her eye with the image display
apparatus mounted on his/her head or face. Accordingly, it is
possible to realize an image display apparatus ensured safety.
[0053] If the electronic image is kept displayed, the external
scene can be confirmed by moving and returning the ocular optical
system to thereby switch the external-scene image and the
electronic image from each other. Accordingly, the range of
applications widens.
[0054] In this case, it is desirable for the switching device to
move the prism member such that an optical path extending from the
prism member to the observer's eyeball to observe the image formed
by the image forming device is approximately coincident with an
optical path extending from the prism member to the observer's
eyeball to observe the external-scene image.
[0055] If the prism member is adapted to move along a plane
containing the optical path of the axial principal ray, the
movement of the prism member is rectilinear. Therefore, the
arrangement of the moving mechanism is simplified, and the layout
of the whole apparatus is facilitated. Consequently, a low-cost
image display apparatus can be realized.
[0056] If the prism member is movable in a direction perpendicular
to the visual axis, the layout of the whole apparatus is
facilitated, and the arrangement of the moving mechanism is
simplified. Moreover, because there is no change in the amount to
which the ocular optical system projects forward from the
observer's face even after the movement of the ocular optical
system, a small-sized and compact image display apparatus can be
provided.
[0057] If the prism member is rotatable, it is possible to observe
the external scene by moving the prism member through a simple
rotating mechanism. Therefore, the mechanism itself becomes less
costly. Moreover, if the prism members for the left and right eyes
are simultaneously rotated, the external scene can be confirmed
with both eyes. Accordingly, the safety is enhanced, and the layout
of the apparatus can be simplified.
[0058] Another image observation apparatus according to the present
invention has an image forming device and an ocular optical system
having an action by which an image formed by the image forming
device is led to an eyeball of an observer. The ocular optical
system includes at least a prism member. The prism member has at
least four optical surfaces having a transmitting or reflecting
optical action. The space surrounded by the at least four optical
surfaces is filled with a single medium having a refractive index
(n) larger than 1 (n>1). The at least four optical surfaces
include a first surface, a second surface, a third surface, and a
fourth surface. The first surface has both a transmitting action
and a reflecting action and is disposed on a side of the prism
member that is closer to the observer's eyeball. The second surface
has a reflecting action and is disposed to face the first surface
across the medium. The second surface is at least decentered or
tilted with respect to the observer's visual axis. The third
surface has a reflecting action and is disposed to face the first
surface across the medium at a position substantially adjacent to
the second surface. The fourth surface is disposed such that one
end thereof is substantially adjacent to the first surface, and the
other end thereof is substantially close to the third surface. At
least the third surface has a totally reflecting action. The first
surface, the single medium and the third surface are arranged to
have an external scene observation action by which an external
scene can be observed through the first surface, the single medium
and the third surface. It should be noted that the term a surface
other than the four optical surfaces" as used in this description
means a prism side surface or a cut surface which has no optical
action.
[0059] These image observation apparatuses are arranged such that
an external scene can be observed through the surface disposed
immediately in front of the observer's eyeball and the surface
disposed on the outside world side of the ocular optical system.
The action and effect of this arrangement will be described below
with reference to FIG. 7. FIG. 7 is a sectional view of a
decentered prism 12 in which a space formed by four surfaces 3, 4,
5 and 6 which are decentered with respect to an optical axis is
filled with a medium having a refractive index larger than 1. In
the figure, reference numeral 1 denotes an observer's pupil; 2
denotes an observer's visual axis; 3 denotes a first surface of the
decentered prism 12; 4 denotes a second surface of the decentered
prism 12; 5 denotes a third surface of the decentered prism 12; 6
denotes a fourth surface of the decentered prism 12; 7 denotes an
image display device; 15 denotes an observer's eyeball; and 16
denotes an optical filter. In the actual path of light rays from
the image display device 7, light rays emitted from the image
display device 7 enter the decentered prism 12 through the fourth
surface 6 and are totally reflected by the third surface 5. The
reflected light rays are totally reflected by the first surface 3
and then reflected by the second surface 4. Then, the reflected
light rays pass through the first surface 3 to project the image of
the image display device 7 into the observer's eyeball 15 with the
observer's pupil 1 as an exit pupil.
[0060] In the image observation apparatuses according to the
present invention, the third surface 5 is a totally reflecting
surface, which is provided with no reflection coating. Therefore,
external light passing through the third surface 5 and the first
surface 3 reaches the observer's eyeball 15. Accordingly, an
external scene can be observed in a range .alpha. different from an
electronic image observation range .beta.. The fact that the
observer can observe an external scene image and an electronic
image in different partial regions of the visual field means that
the observer can simultaneously observe the external scene in the
upper region of the observer's visual field and the electronic
image in the lower region of the visual field, by way of example.
It should, however, be noted that the partial regions of the visual
field for observation of different images may be divided in any
direction and in any form, e.g. upper and lower-regions, or left
and right regions, as long as the observer can observe the
different images in the respective partial regions. This function
enables the observer to recognize the external scene with the image
observation apparatus mounted on his or her head or face. Thus, it
is possible to provide a safe image observation apparatus that
enables the observer to avoid a dangerous situation and to cope
with an emergency situation. Consequently, the range of
applications of the image observation apparatus widens.
[0061] In this image observation apparatus, it is desirable that
the image forming device should be an image display device, e.g. an
LCD or a CRT disposed such-that the image forming surface thereof
faces the fourth surface (it should be noted that an image display
device which is relayed by a relay optical system is not expected
as the image forming device in the image observation apparatus)-,
and that the second surface should be formed from a curved
surface.
[0062] The above-described image observation apparatus can be
constructed as a head-mounted image display apparatus by providing
a retaining member that retains both the image display device and
the ocular optical system in front of an observer's eyeball, and
arranging the prism member such that a bundle of light rays emitted
from the image display device enters the prism member through the
fourth surface, and the incident ray bundle is reflected
successively by the third surface, the first surface and the second
surface so as to exit from the first surface.
[0063] In the above-described image observation apparatus, it is
desirable to arrange the surface disposed immediately in front of
the observer's eyeball and the surface disposed on the outside
world side of the ocular optical system such that the composite
power of the two surfaces for external light at respective
arbitrary positions thereof is approximately zero. If the composite
power for external light is approximately zero, conditions under
which an image of an external scene is observed become
approximately equal to those for observation with the naked eye,
and the external scene can be observed even more naturally.
Accordingly, when a dangerous or emergency situation occurs, the
external scene can be accurately recognized. Consequently, a
remarkably safe image display apparatus can be provided.
[0064] In this case, the first and third surfaces may be formed
from curved, spherical or plane surfaces. When the observer views
the external scene, light rays from the external scene pass through
the totally reflecting region of the internally reflecting surface
disposed on the outside world side of the ocular optical system and
further through the refracting surface disposed immediately in
front of the observer's eyeball and are projected into the
observer's pupil. If the two surfaces are not aspherical surfaces
but spherical surfaces, an even more natural external-scene image
can be readily observed at an off-axis position because there is no
change in the curvature of each surface. If the first surface,
which is disposed immediately in front of the observer's eyeball,
and the third surface, which is disposed on the outside world side
of the ocular optical system, are plane surfaces, a natural
external-scene image can be observed because each surface has no
power. In a case where the two surfaces are perpendicular to the
observer's visual axis and parallel to each other, the external
scene is observed through merely transparent plates. Accordingly,
it is possible to observe an extremely natural external-scene
image.
[0065] Assuming that .phi..sub.t1 denotes the composite power for
external light at respective arbitrary regions of the surface
disposed immediately in front of the observer's eyeball and the
surface disposed on the outside world side of the ocular optical
system, it is desirable to satisfy the following condition:
-0.5.ltoreq..phi..sub.t1.ltoreq.0.5 (1/millimeter) (3)
[0066] where .phi..sub.t1 corresponds to each of the power
.phi..sub.t1 (yz) in a plane containing the axial principal ray and
the power .phi..sub.t1 (xz) in a plane perpendicular to the plane
containing the axial principal ray.
[0067] By satisfying the condition (3), the magnification for
external light passing through the decentered prism can be set in
the neighborhood of 1. Therefore, it is possible to observe an even
more natural external-scene image.
[0068] In the above-described image observation apparatus, the
prism member may be fixed at the same position regardless of
whether the observer views an image formed by the image forming
device or an external-scene image. In this case, it is desirable
that the image from the image forming device and the external-scene
image should be capable of being observed in the respective partial
regions through the first and third surfaces, as stated above with
reference to FIG. 7.
[0069] The prism member may be provided with a switching device
that moves the prism member so as to enable observation modes to
change between the observation of the image formed by the image
forming device and the observation of the external-scene image.
[0070] More specifically, if the prism member is moved such that
the first surface of the ocular optical system, which is disposed
immediately in front of the observer's eyeball, and the third
surface, which is disposed on the outside world side of the ocular
optical system to totally reflect a part of the principal rays, lie
in the vicinity of the observer's visual axis, the observer can
view an external-scene image around the observer's visual axis
lying when he or she looks straight ahead, i.e. in the vicinity of
the center of the visual field. Therefore, the observer can confirm
the external scene in front of his/her eye with the image display
apparatus mounted on his/her head or face. Accordingly, it is
possible to realize an image display apparatus ensured safety.
[0071] If the electronic image is kept displayed, the external
scene can be confirmed by moving and returning the ocular optical
system to thereby switch the external-scene image and the
electronic image from each other. Accordingly, the range of
applications widens.
[0072] In this case, it is desirable to arrange the surface
disposed immediately in front of the observer's eyeball and the
surface disposed on the outside world side of the ocular optical
system such that the composite power of the two surfaces for
external light at respective arbitrary positions thereof is
approximately zero. If the composite power for external light is
approximately zero, the external scene can be observed even more
naturally. Accordingly, it is possible to avoid a dangerous
situation and to cope appropriately with an emergency situation.
Consequently, a remarkably safe image display apparatus can be
provided.
[0073] Assuming that .phi..sub.t2 denotes the composite power for
external light at respective arbitrary positions of the surface
disposed immediately in front of the observer's eyeball and the
surface disposed on the outside world side of the ocular optical
system, it is desirable to satisfy the following condition:
-0.5.ltoreq..phi..sub.t2.ltoreq.0.5 (1/millimeter) (4)
[0074] where .phi..sub.t2 corresponds to each of the power
.phi..sub.t2 (yz) in a plane containing the axial principal ray and
the power .phi..sub.t2 (xz) in a plane perpendicular to the plane
containing the axial principal ray.
[0075] By satisfying the condition (4), the magnification for
external light passing through the decentered prism can be set in
the neighborhood of 1. Therefore, it is possible to observe an even
more natural external-scene image.
[0076] In this case, it is desirable for the switching device to
move the prism member such that an optical path formed from the
prism member to the observer's eyeball to observe an image formed
by the image forming device is approximately coincident with an
optical path formed from the prism member to the observer's eyeball
to observe an external-scene image.
[0077] If the prism member is adapted to move along a plane
containing the optical path of the axial principal ray, the
movement of the prism member is rectilinear. Therefore, the
arrangement of the moving mechanism is simplified, and the layout
of the whole apparatus is facilitated. Consequently, a low-cost
image display apparatus can be realized.
[0078] If the prism member is movable in a direction perpendicular
to the visual axis, the layout of the whole apparatus is
facilitated, and the arrangement of the moving mechanism is
simplified. Moreover, because there is no change in the amount to
which the ocular optical system projects forward from the
observer's face even after the movement of the ocular optical
system, a small-sized and compact image display apparatus can be
provided.
[0079] If the prism member is rotatable, it is possible to observe
the external scene by moving the prism member through a simple
rotating mechanism. Therefore, the mechanism itself becomes less
costly. Moreover, if the prism members for the left and right eyes
are simultaneously rotated, the external scene can be confirmed
with both eyes. Accordingly, the safety is enhanced, and the layout
of the apparatus can be simplified.
[0080] Still another image observation apparatus according to the
present invention has an image forming device and an ocular optical
system having an action by which an image formed by the image
forming device is led to an eyeball of an observer. The ocular
optical system includes at least a prism member. The prism member
has at least four optical surfaces having a transmitting or
reflecting optical action. The space surrounded by the at least
four surfaces is filled with a single medium having a refractive
index (n) larger than 1 (n>1). The at least four optical
surfaces include a first surface, a second surface, a third
surface, and a fourth surface. The first surface has both a
transmitting action and a reflecting action and is disposed on a
side of the prism member that is closer to the observer's eyeball.
The second surface has a reflecting action and is disposed to face
the first surface across the medium. The second surface is at least
decentered or tilted with respect to the observer's visual axis.
The third surface has a reflecting action-and is disposed to face
the first surface across the medium at a position substantially
adjacent to the second surface. The fourth surface is disposed such
that one end thereof is substantially adjacent to the first
surface, and the other end thereof is substantially close to the
third surface. At least second or third surface has a totally
reflecting action. In addition, a line-of-sight detecting device
for detecting an observer's line of sight is disposed near a
totally reflecting region of the second or third surface that has a
totally reflecting action. In this case also, the term "a surface
other than the four optical surfaces" means a prism side surface or
a cut surface which has no optical action.
[0081] The action and effect of the image observation apparatus
when constructed as an image display apparatus will be described
below. Disposing the line-of-sight detecting device near the
optical system makes it possible to detect the observer's line of
sight. Detection of the observer's line of sight will be described
below with reference to FIGS. 5(a), 5(b) and 6. FIG. 5(a) is a
sectional view of an image display apparatus comprising an image
display device 7 and a decentered prism 12 in which a space formed
by three surfaces 3, 4 and 6 decentered with respect to an optical
axis is filled with a medium having a refractive index larger than
1. FIG. 5(b) is a sectional view of an image display apparatus
comprising an image display device 7 and a decentered prism 12 in
which a space formed by four surfaces 3, 4, 5 and 6 decentered with
respect to an optical axis is filled with a medium having a
refractive index larger than 1. FIG. 6 is a sectional view of
another image display apparatus comprising an image display device
7 and a decentered prism 12 in which a space formed by four
surfaces 3, 4, 5 and 6 decentered with respect to an optical axis
is filled with a medium having a refractive index larger than 1. In
these figures, reference numeral 1 denotes an observer's pupil; 2
denotes an observer's visual axis; 3 denotes a first surface of an
ocular optical system 12; 4 denotes a second surface of the ocular
optical system 12; 5 denotes a third surface of the ocular optical
system 12; 6 denotes a fourth surface of the ocular optical system
12; 7 denotes an image display device; 9 denotes a line-of-sight
detecting optical system; 10 denotes a line-of-sight detector; 11
denotes an illuminating device; 12 denotes an ocular optical
system; and 15 denotes an observer's eyeball.
[0082] In the arrangement shown in FIG. 5(a), a line-of-sight
detecting device comprising the line-of-sight detecting optical
system 9 and the line-of-sight detector 10 is disposed on the
outside world side of a decentered prism constituting the ocular
optical system 12 so as to face the observer's eyeball 15 across
the decentered prism. In this case, the image of the observer's
pupil 1 needs to pass through the first surface 3, which is
disposed immediately in front of the observer's pupil 1, and the
second surface 4, which is a reflecting surface disposed on the
outside world side of the ocular optical system 12, to enter the
line-of-sight detecting device (9 and 10). However, the second
surface 4, which is disposed on the outside world side of the
ocular optical system 12, is a reflecting surface and hence
provided with reflection coating. Accordingly, it is necessary in
order to lead the image of the observer's pupil 1 to the
line-of-sight detecting device (9 and 10) to provide the reflecting
surface with a non-coated portion NC (i.e. a hole in the reflection
coating). Such a non-coated portion NC would have an adverse effect
on the image to be observed.
[0083] FIGS. 5(b) and 6 show image display apparatuses according to
the present invention. The third surface 5, which is a reflecting
surface disposed on the outside world side of the ocular optical
system 12, is provided such that a part of the third surface 5
totally reflects light incident thereon. The totally reflecting
portion of the third surface 5 can reflect light from the image
display device 7 without the need of reflection coating.
Accordingly, it is unnecessary to provide reflection coating. Thus,
the image of the observer's pupil 1 passes through the first
surface 3, which is disposed immediately in front of the observer's
pupil 1, and further through the totally reflecting portion of the
third surface 5, which is disposed on the outside world side of the
ocular optical system, and it can be detected by the line-of-sight
detecting device (9 and 10). Therefore, the observer's line of
sight can be detected without the need for providing the reflecting
surface of the ocular optical system 12 with a coating hole, which
has an adverse effect on the observation of the electronic
image.
[0084] In this case, it is desirable for the first surface of the
decentered prism to have a totally reflecting action. In such a
case, it is desirable that the line-of-sight detecting device
should be disposed at a position where it detects the observer's
line of sight through the totally reflecting region of the second
or third surface.
[0085] It is desirable for the image display apparatus to have an
illuminating device that illuminates the observer's eyeball. By
illuminating the observer's eyeball, the image display apparatus
can detect a bright image, and it is therefore possible to
accurately detect the observer's line of sight. It is desirable
that the illuminating device should be provided on the outside
world side of the ocular optical system. If an illuminating device
11 is disposed between the observer's face and the ocular optical
system 12 as shown in FIG. 5(a), the illuminating device 11 is
likely to interfere with the observer's glasses or other thing.
However, if the illuminating device 11 is disposed on the outside
world side of the ocular optical system 12, it is possible to avoid
an interference between the illuminating device 11 and the
observer's face. If the illuminating device 11 is provided such
that illuminating light from the illuminating device 11 passes
through the totally reflecting portion of the reflecting surface of
the ocular optical system 12, the observer's pupil can be
illuminated without providing a coating hole.
[0086] It is desirable to use an illuminating device employing
infrared light. Observation of the electronic image means that the
observer's pupil is illuminated by light from the image display
device. In the case of a line-of-sight detecting device that needs
an image analysis by capturing a feeble virtual image, e.g. cornea
reflection method, it is necessary to eliminate a reflection image
formed by a bundle of light rays from the image display device, the
illumination light quantity of which varies every moment. Usually,
the image display device is an LCD or the like, which emits light
in the visible wavelength region. Accordingly, the use of infrared
light as light emitted from the illuminating device makes it
possible to reduce the influence of light from the image display
device.
[0087] In this case also, the image observation apparatus can be
constructed as a head-mounted image display apparatus by providing
a retaining member that retains the ocular optical system, the
image forming device and the line-of-sight detecting device in
front of an observer's face.
[0088] The above-described image observation apparatus may have a
device for positioning the image forming device and the ocular
optical system with respect to the observer's head.
[0089] Further, it is possible to observe a stereoscopic image with
both eyes by providing a device for supporting at least a pair of
such image observation apparatuses at a predetermined spacing.
[0090] Next, an image display apparatus according to the present
invention has an image display device and an ocular optical system
for leading an image formed by the image display device to an
eyeball of an observer such that the image can be observed as a
virtual image. The ocular optical system includes a decentered
prism in which a space formed by at least two surfaces is filled
with a medium having a refractive index larger than 1. The at least
two surfaces include a first surface positioned immediately in
front of the observer's eyeball, and a second surface which is a
reflecting surface facing the first surface. At least one of the at
least two surfaces is a curved surface decentered or tilted with
respect to the observer's visual axis. The ocular optical system
further includes an aberration correcting device disposed outside
the second surface to correct aberrations due to decentration
produced by the first and second surfaces with respect to light
from an external scene.
[0091] In this image display apparatus, when an image of an
external scene is observed through the first surface, which is
positioned immediately in front of the observer's eyeball, and the
second surface, which is a reflecting surface disposed to face the
first surface, the external-scene image is observed in the same way
as in the case of observing it through a lens having power
asymmetric with respect to the optical axis because at least one of
the first and second surfaces is decentered or tilted with respect
to the observer's visual axis. Therefore, if an aberration
correcting device, e.g. a Fresnel lens, which is arranged to cancel
the eccentric power, is disposed on the outside world side of the
second surface, it becomes possible for the observer to view an
even more natural external-scene image. Further, because a Fresnel
lens is an extremely thin optical element, it is possible to
provide a compact image display apparatus without causing an
increase in the size of the apparatus.
[0092] According to the present invention, the Fresnel lens may be
replaced by another optical element, e.g. a diffractive optical
element or a holographic optical element, provided that the
above-described effect can be obtained.
[0093] When a Fresnel lens is used, it is desirable that the center
of the annular zone of the Fresnel lens should lie in a plane
containing the optical path of the axial principal ray from the
image display device, and that the Fresnel lens should be
decentered perpendicularly to the visual axis in the plane
containing the optical path of the axial principal ray. If the
Fresnel lens has an axially symmetric configuration, the apparatus
becomes excellent in productivity, and the production cost can be
reduced. If a Fresnel lens having an axially symmetric power is
disposed in the plane containing the optical path of the axial
principal ray in such a manner as to be decentered with respect to
the visual axis, aberrations due to decentration which are produced
by the first and second surfaces with respect to external light can
be corrected even more favorably.
[0094] The Fresnel lens may be disposed such that the center of the
annular zone of the Fresnel lens should lie in the plane containing
the optical path of the axial principal ray, and that the Fresnel
lens should be tilted with respect to the visual axial so as to
extend along the surface configuration of the second surface. When
disposed to extend along the surface configuration of the second
surface, the Fresnel lens is tilted with respect to the observer's
visual axis. Accordingly, it-is possible to set a power asymmetric
with respect to the optical axis and hence possible to correct even
more favorably aberrations due to decentration which are produced
by the first and second surfaces with respect to external light.
Moreover, the amount to which the apparatus projects from the
observer's face reduces, and the space between the ocular optical
system and the Fresnel lens also reduces. Accordingly, it is
possible to provide a remarkably compact image display apparatus
having no useless space.
[0095] Another image display apparatus according to the present
invention has an image display device and an ocular optical system
for leading an image formed by the image display device to an
eyeball of an observer such that the image can be observed as a
virtual image. The ocular optical system includes a decentered
prism in which a space formed by at least three surfaces is filled
with a medium having a refractive index larger than 1. The at least
three surfaces include a refracting and internally reflecting
surface positioned immediately in front of the observer's eyeball;
an outside world-side internally reflecting surface disposed on the
outside world side of the ocular optical system to face the
refracting and internally reflecting surface; and a refracting
surface through which a bundle of light rays emitted from the image
display device enters the decentered prism. The at least three
surfaces are arranged to perform at least three internal
reflections. The ocular optical system further includes a second
optical element that cancels the power produced by the refracting
and internally-reflecting surface, which is positioned immediately
in front of the observer's eyeball, and the outside world-side
internally reflecting surface with respect to-external light when
an external scene is observed through the two surfaces. The second
optical element is disposed on the outside world side of the
outside world-side internally reflecting surface.
[0096] When an image of an external scene is observed through the
first surface, which is positioned immediately in front of the
observer's eyeball, and the second surface, which is a reflecting
surface disposed to face the first surface, the external-scene
image is observed in the same way as in the case of observing it
through a lens having an eccentric power different for each image
height because at least one of the first and second surfaces is
decentered or tilted with respect to the observer's visual axis.
Therefore, if the second optical element, which is adapted to
cancel the eccentric power produced by the two surfaces with
respect to external light, is disposed on the outside world side of
the ocular optical system, it becomes possible for the observer to
view an even more natural external-scene image in a wide range.
Accordingly, it is possible to provide a safe image display
apparatus which enables the observer to avoid a dangerous situation
and to cope with an emergency situation.
[0097] In this case, the ocular optical system may be formed from a
decentered prism in which a space formed by four surfaces is filled
with a medium having a refractive index larger than 1. The four
surfaces include a first surface positioned on the observer's
eyeball side and serving as both refracting and reflecting
surfaces; a second surface which is a reflecting surface disposed
to face the first surface; a third surface which is a reflecting
surface disposed to face the first surface at a position adjacent
to the second surface; and a fourth surface which is a refracting
surface closest to the image display device. At least one of the
four surfaces is decentered or tilted with respect to the
observer's visual axis. In a case where the ocular optical system
comprises four surfaces as described above, the external scene is
recognized by-external light passing through the first and second
surfaces. In this case, it is possible to realize an added function
without increasing the overall size of the ocular optical system by
disposing the second optical element adapted to cancel the
eccentric power only at a region covering the second surface.
[0098] It is desirable to dispose at least one second optical
element on the outside world side of the second or third surface so
that the external scene can be observed through the first surface,
the second surface and the second optical element or through the
first surface, the third surface and the second optical element. If
the second optical element having the action of canceling the
eccentric power is provided on the outside world side of the second
surface, a natural external-scene image can be observed in
approximately the same region as the region for observation of the
electronic image. If the second optical having the action of
canceling the eccentric power is provided on the outside world side
of the third surface, a natural external-scene image can be
observed in a region different from the region for observation of
the-electronic image. If two second optical elements are disposed
on the outside world sides of the second and third surfaces,
respectively, the observer can view all the external-scene image
passing through the first and second surfaces and through the first
and third surfaces. Accordingly, the field angle for observation of
the external-scene image becomes wider than the field angle for
observation of the electronic image. Thus, a natural and wide
external-scene image can be observed. Consequently, it is possible
to provide a remarkably safe image display apparatus which enables
the observer to avoid a dangerous situation and to cope
appropriately with an emergency situation.
[0099] It is desirable for the second optical element to be capable
of simultaneously canceling the composite power of the first and
second surfaces and the composite power of the first and third
surfaces with respect to external light. If the second optical
element capable of simultaneously canceling the composite powers is
formed from a single optical element and it is disposed on the
outside world side of the ocular optical system, it is possible to
observe the external scene over a wide range. Because the second
optical element simultaneously cancels the composite powers, there
is no break in the external-scene image. Thus, it is possible to
observe an even more natural external-scene is image. Accordingly,
the external scene can be recognized over a wide range with a
single optical element, and it is possible to provide an image
display apparatus of reduced cost and enhanced safety which enables
the observer to avoid a dangerous situation and to cope with an
emergency situation.
[0100] The above-described image observation apparatus may have a
device for positioning the image display device and the ocular
optical system with respect to the observer's head. It becomes
possible for the observer to see a stable electronic image by
providing a device for positioning both the image display device
and the ocular optical system with respect to the observer's
head.
[0101] The image display apparatus may have a device for supporting
both the image display device and the ocular optical system with
respect to the observer's head such that the apparatus can be
mounted on the observer's head. By allowing both the image display
device and the ocular optical system to be mounted on the
observer's head with a supporting device, it becomes possible for
the observer to see the observation image in a desired posture and
from a desired direction.
[0102] Further, it is possible to provide a device for supporting
at least a pair of image display apparatuses at a predetermined
spacing. It becomes possible for the observer to see the electronic
image with both eyes without fatigue by providing a device for
supporting at least two image display apparatuses at a
predetermined spacing. Further, if images with a disparity
therebetween are displayed on the right and left image display
devices, and these images are observed with both eyes, it is
possible to enjoy viewing a stereoscopic image.
[0103] The ocular optical system in the above-described image
display apparatus can be used as an image-forming optical system.
If the ocular optical system is arranged to form an image of an
object at infinity with the image display surface in the ocular
optical system-defined as an image plane, the ocular optical system
can be used as an image-forming optical system, e.g. a finder
optical system for a camera such as that shown in FIG. 24.
[0104] It should be noted that in the present invention, the second
and third surfaces may be formed from a single identical surface.
In this case, the number of physical surfaces can be reduced by
one, and it is therefore possible to simplify the process in terms
of the optical design and the production of prism and hence
possible to contribute to the achievement of an increase in
mass-productivity and reductions-in costs. It is desirable that a
physically single surface should be arranged to have both the
functions of the second and third surfaces, and that internally
reflecting regions should overlap each other. By doing so, it is
possible to realize a reduction in the size of the prism
member.
[0105] Still other objects and advantages of the invention will in
part be obvious and will in part be apparent from the
specification.
[0106] The invention accordingly comprises the features of
construction, combinations of elements, and arrangement of parts
which will be exemplified in the construction hereinafter set
forth, and the scope of the invention will be indicated in the
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0107] FIG. 1 is a sectional view of an optical system for a single
eye of a head-mounted image display apparatus which uses an ocular
optical system according to Example 1 of the present invention.
[0108] FIG. 2 is a sectional view of an optical system for a single
eye of a head-mounted image display apparatus which uses an ocular
optical system according to Example 2 of the resent invention.
[0109] FIG. 3 is a sectional view of an optical system for a single
eye of a head-mounted-image display apparatus which uses an ocular
optical system according to Example 3 of the present invention.
[0110] FIG. 4 is a sectional view of an optical system for a single
eye of a head-mounted image display apparatus which uses an ocular
optical system according to Example 4 of the present invention.
[0111] FIGS. 5(a) and 5(b) are sectional views for describing an
optical system for a single eye of a head-mounted image display
apparatus which uses an ocular optical system according to Example
5 of the present invention in comparison to a modification, in
which FIG. 5(a) shows the modification, and FIG. 5(b) shows Example
5.
[0112] FIG. 6 is a sectional view of an optical system for a single
eye of a head-mounted image display apparatus which uses an ocular
optical system according to Example 6 of the present invention.
[0113] FIG. 7 is a sectional view of an optical system for a single
eye of a head-mounted image display apparatus which uses an ocular
optical system according to Example 7 of the present invention.
[0114] FIGS. 8(a), 8(b) and 8(c) are sectional views of an optical
system for a single eye of a head-mounted image display apparatus
which uses an ocular optical system according to Example 8 of the
present invention.
[0115] FIGS. 9(a), 9(b) and 9(c) are sectional views of an optical
system for a single eye of a head-mounted image display apparatus
which uses an ocular optical system according to Example 9 of the
present invention.
[0116] FIG. 10 is a sectional view of an optical system for a
single eye of a head-mounted image display apparatus which uses an
ocular optical system according to Example 10 of the present
invention.
[0117] FIG. 11 is a sectional view of an optical system for a
single eye of a head-mounted image display apparatus which uses an
ocular optical system according to Example 11 of the present
invention.
[0118] FIG. 12 is a sectional view of an optical system for a
single eye of a head-mounted image display apparatus which uses an
ocular optical system according to Example 12 of the present
invention.
[0119] FIG. 13 is a sectional view of an optical system for a
single eye of a head-mounted image display apparatus which uses an
ocular optical system according to Example 13 of the present
invention.
[0120] FIG. 14 is a sectional view of an optical system for a
single eye of a head-mounted image display apparatus which uses an
ocular optical system according to Example 14 of the present
invention.
[0121] FIG. 15 is a sectional view of an optical system for a
single eye of a head-mounted image display apparatus which uses an
ocular optical system according to Example 15 of the present
invention.
[0122] FIG. 16 is a sectional view of an optical system for a
single eye of a head-mounted image display apparatus which uses an
ocular optical system according to Example 16 of the present
invention.
[0123] FIG. 17 is a sectional view of an optical system for a
single eye of a head-mounted image display apparatus which uses an
ocular optical system according to Example 17 of the present
invention.
[0124] FIG. 18 is a sectional view of an ocular optical system
arranged as in Example 17, which is provided with a line-of-sight
detecting device.
[0125] FIGS. 19(a), 19(b) and 19(c) show a mechanism for moving an
ocular optical system arranged as in Example 17 to change
observation positions from an electronic image observation position
to an external-scene image observation position, and also show a
direction of movement for changing the observation positions.
[0126] FIGS. 20(a) and 20(b) are fragmentary sectional views for
describing an action in which unwanted light is eliminated by a
totally reflecting surface in the present invention.
[0127] FIG. 21 shows an image display apparatus according to the
present invention which is arranged in the form of an image display
apparatus for a single eye.
[0128] FIG. 22 shows an image display apparatus according to the
present invention which is arranged in the form of an image display
apparatus for both eyes.
[0129] FIG. 23 shows an arrangement of an optical system according
to the present invention which is used as an image-forming optical
system.
[0130] FIG. 24 shows an arrangement of an optical system according
to the present invention which is used as an image-forming optical
system.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0131] Examples 1 to 17 of the image display apparatus according to
the present invention will be described below.
[0132] In constituent parameters of each example (described later),
as shown typically in FIG. 1, an exit pupil 1 of an ocular optical
system 12 is defined as the origin of the optical system, and an
optical axis 2 is defined by a light ray passing through both the
center of the display area of an image display device 7 and the
center (the origin) of the exit pupil 1. A Z-axis is taken in a
direction in which light rays travel from the exit pupil 1 along
the optical axis 2. A Y-axis is taken in a direction extending
through the center of the exit pupil 1 at right angles to the
Z-axis in a plane in which light rays are bent by the ocular
optical system 12. An X-axis is taken in a direction extending
through the center of the exit pupil 1 at right angles to both the
Z- and Y-axes. A direction in which the Z-axis extends from the
exit pupil 1 toward the ocular optical system 12 is defined as a
positive direction of the Z-axis. A direction in which the Y-axis
extends from the optical axis 2 toward the image display device 7
is defined as a positive direction of the Y-axis. A direction in
which the X-axis constitutes a right-handed system in combination
with the Z- and Y-axes is defined as a positive direction of the
X-axis. It should be noted that ray tracing is carried out by
backward tracing from the exit pupil 1 of the ocular optical system
12, which is defined as the object side, toward the image display
device 7, which is defined as the image plane side.
[0133] Regarding each surface for which displacements Y and Z and
tilt angle .theta. are shown, the displacement Y is a distance by
which the surface is displaced in the Y-axis direction from the
exit pupil 1, which is the origin of the optical system, while the
displacement Z is a distance by which the surface is displaced in
the Z-axis direction from the exit pupil 1, and the tilt angle
.theta. is an angle of inclination of the center axis of the
surface with respect to the Z-axis unless otherwise specified in
the constituent data (specified in Examples 6 and 9). It should be
noted that, for the tilt angle, the counterclockwise direction is
defined as a positive direction. In a case where a reference
surface is particularly specified, displacements and tilt angle are
similarly given with respect to the vertex of the reference
surface.
[0134] In the constituent parameters (shown later), the surface
separation in the coaxial portion is shown as the distance from the
surface concerned to the next surface. In addition, the radius of
curvature of each spherical surface, refractive index of each
medium, and Abbe's number are given according to the conventional
method.
[0135] FIGS. 1 to 4 and 5(b) to 17 are sectional views of image
display apparatuses according to Examples 1 to 4 and 5 to 17 of the
present invention, taken along a plane containing the optical axis
in the examples shown in FIGS. 1 to 4, 5(b) to 11, 15 and 16, the
image display apparatuses each comprise a decentered prism 12 in
which a space formed by four surfaces 3, 4, 5 and 6 which are
decentered with respect to the optical axis is filled with a medium
having a refractive index larger than 1. In the example shown in
FIG. 17, the image display apparatus comprises a decentered prism
12 in which a space formed by three surfaces 3, 4 and 6 which are
decentered with respect to the optical axis is filled with a medium
having a refractive index larger than 1. In each figure, reference
numeral 1 denotes an observer's pupil; 2 denotes an observer's
visual axis; 3 denotes a first surface of an ocular optical system
12; 4 denotes a second surface of the ocular optical system 12; 5
denotes a third surface of the ocular optical system 12; 6 denotes
a fourth surface of the ocular optical system 12; 7 denotes an
image display device; 8 denotes a Fresnel; 9 denotes a
line-of-sight detecting optical system.; 10 denotes a line-of-sight
detector; 11 denotes an illuminating device; 12 denotes an ocular
optical system (decentered prism); 13 and 14 denote second optical
elements; 15 denotes an observer's eyeball; 16 denotes an optical
filter; 17 denotes a linear motor; 18 denotes projections provided
on an optical element; and 19 denotes a guide (rail) provided on a
casing. In the examples shown in FIGS. 1 to 4, 5(b) to 11, 15 and
16, the actual path of light rays during the observation of the
electronic image is as follows: Light rays emitted from the
electronic image of the image display device 7 enter the ocular
optical system 12 through the fourth surface 6, which is a
refracting surface disposed to face the image display device 7. The
incident light rays are reflected toward the observer's pupil 1 by
the third surface 5, which is adjacent to the fourth surface 6 in
the group of two surfaces 4 and 5 located on the side of the ocular
optical system 12 that is remote from the observer's face. The
reflected-light rays are reflected so as to travel away from the
observer's pupil 1 by the first surface 3, which is disposed
immediately in front of the observer's pupil 1. Then, the reflected
light rays are reflected toward the observer's pupil 1 by the
second surface 4, which is disposed immediately in front of the
observer's pupil 1 in the group of two surfaces 4 and 5 located on
the side of the ocular optical system 12 that is remote from the
observer's face. The reflected light rays pass through the first
surface 3 and are projected into the observer's eyeball 15 with the
observer's iris position or eyeball rolling center as an exit pupil
1. In Example 17 shown in FIG. 17, light rays emitted from the
electronic image of the image display device 7 enter the ocular
optical system 12 through the fourth surface 6, which is a
refracting surface disposed to face the image display device 7. The
incident light rays are reflected toward the observer's pupil 1 by
that region (third surface 5) of the second surface 4 which is
adjacent to the fourth surface 6. The second surface 4 also serves
as the third surface 5, which is located on the side of the ocular
optical system 12 that is remote from the observer's face. The
reflected light rays are reflected so as to travel away from the
observer's pupil 1 by the first surface 3, which is disposed
immediately in front of the observer's pupil 1. Then, the reflected
light rays are reflected toward the observer's pupil 1 by that
region of the second surface 4 which is remote from the fourth
surface 6 and located on the side of the ocular optical system 12
that is remote from the observer's face. The reflected light rays
pass through the first surface 3 and are projected into the
observer's eyeball 15 with the observer's iris position or eyeball
rolling center as an exit pupil 1.
[0136] FIGS. 5(b) and 6 show examples of an image display apparatus
according to the present invention that has a line-of-sight
detecting device. The third surface 5, which is a reflecting
surface disposed on the outside world side of the ocular optical
system 12, is set so that a part of the third surface 5 totally
reflects light rays. The totally reflecting portion of the third
surface 5 can reflect light from the image display device 7 without
reflection coating. Therefore, no reflection coating is needed. The
actual path of light rays during the detection of the observer's
line of sight is as follows: Illuminating light from the light
source 11 passes through the third and first surfaces 5 and 3 of
the ocular optical system 12 to illuminate the observer's eyeball
15. Light rays reflected from the observer's eyeball 15 enter the
ocular optical system 12 through the first surface 3, which is
disposed immediately in front of the observer's pupil 1. The light
rays pass through a totally reflecting region provided in at least
a part of the third surface 5, which is located on the side of the
ocular optical system 12 that is remote from the observer's face.
The light rays passing through the totally reflecting region of the
third surface 5 are led to the line-of-sight detector 10 through
the line-of-sight detecting optical system 9 to form an image of
the observer's pupil 1. To reduce the effect of light from the
electronic image or the like, it is possible to use an infrared
light illuminating device as the light source 11 and an infrared
light detector as the line-of-sight detector 10. The position of
the illuminating device 11 is not necessarily limited to the
illustrated position. The illuminating device 11 may be disposed at
any position, provided that the observer's eyeball 15 can be
illuminated.
[0137] FIG. 18 is a sectional view of an arrangement in which a
line-of-sight detecting device similar to the above, which
comprises a line-of-sight detecting optical system 9, a
line-of-sight detector 10, and a light source 11, is provided in an
ocular optical system 12 comprising three surfaces 3, 4 and 6
decentered with respect to the optical axis as in Example 17. The
actual path of light rays during the detection of the observer's
line of sight is similar to that in the case of FIGS. 5(b) and 6;
therefore, a description thereof is omitted.
[0138] FIG. 7 shows an example of an image display apparatus
according to the present invention that enables the electronic
image and the external-scene image to be simultaneously observed
through the-ocular optical system 12. The actual path of light rays
during the observation of the external-scene image is as follows:
Light rays from an object point in the external scene enter the
ocular optical system 12 through the third surface 5, pass through
the first surface 3 and are projected into the observer's eyeball
15 with the observer's iris position or eyeball rolling center as
an exit pupil 1. It may be made easy for the observer to view
either or both of the-electronic image and the external-scene image
by disposing a light-reducing filter or optical element 16 that
controls the quantity of external light at the outside world side
of the third surface 5. By moving the light-reducing filter or
optical element 16 between the observation ranges .alpha. and
.beta., it is possible to control the quantity of light from either
of the electronic image and the external-scene image.
[0139] FIGS. 8(a), 8(b) and 8(c) and FIGS. 9(a), 9(b) and 9(c) show
examples of another image display apparatus according to the
present invention that enables the external-scene image to be
observed by moving the ocular optical system 12. In the example
shown in FIGS. 8(a), 8(b) and 8(c), the ocular optical system 12 is
moved from the electronic image observation position shown in FIG.
8(a) in the negative direction of the Y-axis relative to the
observer's pupil 1 to reach the external-scene image observation
position shown in FIG. 8(b). In the example shown in FIGS. 9(a),
9(b) and 9(c),, the ocular optical system 12 is rotated clockwise
relative to-the observer's pupil 1 from the electronic image
observation position shown in FIG. 9(a) to reach the external-scene
image observation position shown in FIG. 9(b). Therefore, in either
case, the external scene can be observed in the direction of the
observer's visual axis. Light rays from an object point in the
external scene enter the ocular optical system 12 through the third
surface 5, pass through the first surface 3 and are projected into
the observer's eyeball with the observer's iris position or eyeball
rolling center as an exit pupil 1. In the position shown in FIG.
8(b), the observer can view the electronic image in a region below
the observer's visual axis 2. The direction of observation of the
electronic image differs depending on the way in which the ocular
optical system 12 is disposed and the direction in which the ocular
optical system 12 is moved. Therefore, the observation of the
electronic image may be performed in any direction.
[0140] FIGS. 8(c) and 9(c) show examples of a mechanism for moving
the ocular optical system 12. In either case, the ocular optical
system 12 is moved along a guide (rail) 19 provided on the casing
by a linear motor 17 through projections 18 provided on the optical
element. In the case of FIG. 8(c), the guide (rail) 19 is
rectilinear.
[0141] Therefore, the ocular optical system 12 is moved
rectilinearly. In the case of FIG. 9(c), the guide (rail) 19 is
arcuate. Therefore, the ocular optical system 12 is rotated.
[0142] FIGS. 19(a), 19(b) and 19(c) show an example in which an
ocular optical system 12 comprising three surfaces 3, 4 and 5
decentered with respect to the optical axis as in Example 17 is
moved from the electronic image observation position in the
negative direction of the Y-axis relative to the observer's pupil 1
to reach the external-scene image observation position as in the
case of the example shown in FIGS. 8(a), 8(b) and 8(c). The
operation of this example is similar to that of the example shown
in FIGS. 8(a), 8(b) and 8(c). Therefore, a description thereof is
omitted.
[0143] FIGS. 10 to 14 show examples of an image display apparatus
according to the present invention in which a Fresnel lens 8
serving as an aberration correcting device is disposed in an
optical path for observation of the external-scene image. The
actual path of light rays during the observation of the
external-scene image is as follows: Light rays from an object point
in the external scene pass through the Fresnel lens 8 and enter the
decentered prism 12 through the second surface 4. Then, the light
rays pass through the first surface 3 and are projected into the
observer's eyeball with the observer's iris position or eyeball
rolling center as an exit pupil 1. In this arrangement, the Fresnel
lens 8 is only necessary to dispose at a predetermined position
when the external scene is observed. When the observer does
not-want to view the external scene, the Fresnel lens 8 is moved to
another position by a moving mechanism, e.g. a mechanism for moving
the Fresnel lens 8 vertically, or a mechanism for rotating the
Fresnel lens 8. Alternatively, the Fresnel lens 8 may be arranged
to be detachable.
[0144] In the examples shown in FIGS. 10 to 14, those which are
shown in FIGS. 10 and 11 are arranged as in the case of FIG. 1.
That is, the ocular optical system (decentered prism) 12 comprises
four surfaces 3, 4, 5 and 6 decentered with respect to the optical
axis, and when the electronic image is observed, light rays travel
along the same path as in the case of FIG. 1. However, the ocular
optical system shown in FIG. 12 comprises a decentered prism 12 in
which a space formed by three surfaces 3, 4 and 6 decentered with
respect to the optical axis is filled with a medium having a
refractive index larger than 1. The actual path of light rays
during the observation of the electronic image is as follows: Light
rays emitted from the electronic image of the image display device
7 enter the ocular optical system 12 through the fourth surface
(the third surface as counted in the sequence of surfaces) 6, which
is a refracting surface disposed to face the image display device
7. The incident light rays are reflected so as to travel away from
the observer's pupil 1 by the first surface 3, which is disposed
immediately in front of the observer's pupil 1. The reflected light
rays are reflected toward the observer's pupil 1 by the second
surface 4, which is disposed on the side of the ocular optical
prism 12 that is remote from the observer's face. Then, the
reflected light rays pass through the first surface 3 and are
projected into the observer's eyeball 15 with the observer's iris
position or eyeball rolling center as an exit pupil 1.
[0145] The ocular optical system shown in FIG. 13 comprises a
decentered prism 12 in which a space formed by three surfaces 3, 4
and 6 decentered with respect to the optical axis is filled with a
medium having a refractive index larger than 1. The actual path of
light rays during the observation of the electronic image is as
follows: Light rays emitted from the electronic image of the image
display device 7 enter the ocular optical system 12 through the
fourth surface (the third surface as counted in the sequence of
surfaces) 6, which is a refracting surface disposed to face the
image display device 7. The incident light rays are reflected
toward the observer's pupil 1 by the second surface 4, which is
disposed on the side of the ocular optical system 12 that is remote
from the observer's face. The reflected light rays pass through the
first surface 3 and are projected into the observer's eyeball 15
with the observer's iris position or eyeball rolling center as an
exit pupil 1.
[0146] The ocular optical system 12 shown in FIG. 14 comprises a
decentered prism 12 in which a space formed by two surfaces 3 and 4
decentered with respect to the optical axis is filled with a medium
having a refractive index larger than 1. The actual path of-light
rays during the observation of the electronic image is as follows:
Light rays emitted from the electronic image of the image display
device 7 enter the ocular optical system 12 through the first
surface 3, which is a refracting surface disposed to face the image
display device 7. The incident light rays are reflected toward the
observer's pupil 1 by the second surface 4, which is-located on the
side of-the ocular optical system 12 that is remote from the
observer's face. The reflected light rays pass through the first
surface 3 and are projected into the observer's eyeball 15 with the
observer's iris position or eyeball rolling center as an exit pupil
1.
[0147] FIGS. 15 and 16 show examples of an image display apparatus
according to the present invention which is adapted to observe the
external scene through the first surface 3 of the ocular optical
system 12, which is located immediately in front of the observer's
eyeball, and further through either of the second and third
surfaces 4 and 5 of the ocular optical system 12, which are outside
world-side internally reflecting surfaces. When the external scene
is to be observed, second optical elements 13 and 14, which are
adapted to cancel powers produced by the two surfaces 3 and 4 or 3
and 5 with respect to external light, are disposed in the optical
paths for observation of the external-scene image. The actual path
of light rays during the observation of the external-scene image is
as follows: Light rays from an object point in the external scene
pass through a second optical element 13 or another second optical
element 14 and enter the decentered prism 12 through the second
surface"4 or the third surface 5. Then, the light rays pass through
the first surface 3 and are projected into the observer's eyeball
15 with the observer's iris position or eyeball rolling center as
an exit pupil 1.
[0148] It should be noted that the present invention is not
necessarily limited to the optical systems shown in FIGS. 1 to 4
and 5(b) to 19 but may also be applied to other known optical
systems.
[0149] In the constituent parameters of each of the following
examples, the rotationally symmetric aspherical configuration of
each surface may be given by the following equation on the
assumption that the paraxial curvature radius is denoted by R. The
Z-axis is the axis of the rotationally symmetric aspherical
surface. 1 Z = ( h 2 / R ) / [ 1 + { 1 - ( 1 + K ) ( h 2 / R 2 ) }
1 / 2 ] + A h 4 + B h 6 + Ch 8 + Dh 10 ( h 2 = x 2 + y 2 ) ( a
)
[0150] where Z is the amount of deviation from a plane tangent to
the origin of the surface configuration; K is the conical
coefficient; and A, B, C and D are 4th-, 6th-, 8th- and 10th-order
aspherical coefficients, respectively.
[0151] The configuration of an anamorphic surface is defined by the
following equation. A straight line which passes through the origin
of the surface configuration and which is perpendicular to the
optical surface is defined as the axis of the anamorphic surface. 2
Z = ( CX x 2 + CY y 2 ) / [ 1 + { 1 - ( 1 + K x ) CX 2 x 2 - ( 1 +
K y ) CY 2 y 2 } 1 / 2 ] + m = 1 R m { ( 1 - P m ) x 2 + ( 1 + P m
) y 2 } m + 1
[0152] Assuming that m=4 (polynomial of degree 4), for example, the
equation, when expanded, may be given by: 3 Z = ( CX x 2 + CY y 2 )
/ [ 1 + { 1 - ( 1 + K x ) CX 2 x 2 - ( 1 + K y ) CY 2 y 2 } 1 / 2 +
R 1 { ( 1 - P 1 ) x 2 + ( 1 + P 1 ) y 2 } 2 + R 2 { ( 1 - P 2 ) x 2
+ ( 1 + P 2 ) y 2 } 3 + R 3 { ( 1 - P 3 ) x 2 + ( 1 + P 3 ) y 2 } 4
+ R 4 { ( 1 - P 4 ) x 2 + ( 1 + P 4 ) y 2 } 5 ( b )
[0153] where Z is the amount of deviation from a plane tangent to
the origin of the surface configuration; CX is the curvature in the
X-axis direction; CY is the curvature in the Y-axis direction;
K.sub.x is the conical coefficient in the X-axis direction; K.sub.y
is the conical coefficient in the Y-axis direction; R.sub.m is the
rotationally symmetric component of the aspherical surface term;
and P.sub.m is the rotationally asymmetric component of the
aspherical surface term. It should be noted that in the constituent
parameters of the examples (described later), the following
parameters are employed:
[0154] R.sub.x: the radius of curvature in the X-axis direction
[0155] R.sub.y: the radius of curvature in the Y-axis direction
[0156] The curvature radii are related to the curvatures CX and CY
as follows:
R.sub.x=1/CX, R.sub.y=1/CY
[0157] The configuration of a three-dimensional surface is defined
by the following equation. The Z-axis of the defining equation is
the axis of the three-dimensional surface. 4 Z = n = 0 k m = k n C
n m X n Y n - m
[0158] Assuming that k=7 (polynomial of degree 7), for example, a
three-dimensional surface is expressed by an expanded form of the
above equation as follows: 5 Z = C 2 + C 3 Y + C 4 X + C 5 Y 2 + C
6 YX + C 7 X 2 + C 8 Y 3 + C 9 Y 2 X + C 10 YX 2 + C 11 X 3 + C 12
Y 4 + C 13 Y 3 X + C 14 Y 2 X 2 + C 15 YX 3 + C 16 X 4 + C 17 Y 5 +
C 18 Y 4 X + C 19 Y 3 X 2 + C 20 Y 2 X 3 + C 21 YX 4 + C 22 X 5 + C
23 Y 6 + C 24 Y 5 X + C 25 Y 4 X 2 + C 26 Y 3 X 3 + C 27 Y 2 X 4 +
C 28 YX 5 + C 29 X 6 + C 30 Y 7 + C 31 Y 6 X + C 32 Y 5 X 2 + C 33
Y 4 X 3 + C 34 Y 3 X 4 + C 35 Y 2 X 5 + C 36 YX 6 + C 37 X 7 ( c
)
[0159] In the examples of the present invention, each ocular
optical system is designed as an optical system symmetric with
respect to the X-axis direction. Therefore, the coefficients of the
terms with odd-numbered powers of X are set equal to zero [in the
above equation (c), C.sub.4, C.sub.6, C.sub.9, . . . =0].
[0160] In the constituent parameters (shown later), those terms
concerning aspherical surfaces for which no data is shown are zero.
The refractive index is expressed by the refractive index for the
spectral d-line (wavelength: 58.7.56 nanometers). Lengths are given
in millimeters.
[0161] FIGS. 1 to 4 and 5(b) to 17 are sectional views of Examples
1 to 4 and 5 to 17 taken along the YZ-plane containing the optical
axis 2. In Examples 1 to 11, 13 and 14, the observation field
angles are as follows: The horizontal field angle is 30.0.degree.,
and the vertical field angle is 22.72.degree.. In Example 12, the
observation field angles are as follows: The horizontal field angle
is 40.0.degree., and the vertical field angle is 30.53.degree.. In
Examples 15 and 16, the observation field angles are-as follows:
The horizontal field angle is 35.0.degree., and the vertical field
angle is 26.60.degree.. In Examples 1 to 16, the pupil diameter is
4 millimeters.
[0162] The constituent parameters and the values of the conditions
in the above-described Examples 1 to 6, 9 to 14 and 17 are shown
below. The constituent parameters of Examples 7 and 8 are the same
as those of Example 3; therefore a description thereof is omitted.
The constituent parameters of Examples 10 and 11 during the
observation of the image display device are the same as those of
Example 5. Therefore, the constituent parameters during the
observation of the external scene are shown for Examples 10 and 11.
The constituent parameters of Example 12 during the observation of
the image display device are shown under "Example 12(1)". The
constituent parameters of Example 12 during the observation of the
external scene are shown under "Example 12(2)". It should be noted
that in the table below, "ASPH" denotes an aspherical surface;
"ANAM" denotes an anamorphic surface; "SF" denotes a surface; and
"REFL" denotes a reflecting surface.
EXAMPLE 1
[0163]
1 Refractive Surface Radius of Surface index Abbe's No. No.
curvature separation (Displacement) (Tilt angle) 1 .infin.(Pupil) 2
ASPH .infin. 1.5254 56.25 (1ST SF) K 0.0000 Y 18.114 .theta.
4.44.degree. A 0.0000 Z 37.091 B 0.0000 C 1.1599 .times. 10.sup.-13
D 4.4930 .times. 10.sup.-16 3 ANAM R.sub.y -142.541 1.5254 56.25
(2ND SF) R.sub.x -122.057 Y 3.041 .theta. -17.79.degree. (REFL)
K.sub.y -5.4587 Z 52.132 K.sub.x -0.2658 R.sub.1 -5.0900 .times.
10.sup.-10 R.sub.2 3.0528 .times. 10.sup.-10 R.sub.3 6.2600 .times.
10.sup.-13 R.sub.4 4.9434 .times. 10.sup.-15 P.sub.1 -1.1948
.times. 10.sup.+1 P.sub.2 2.3791 .times. 10.sup.-1 P.sub.3 4.8713
.times. 10.sup.-1 P.sub.4 3.3074 .times. 10.sup.-1 4 ASPH .infin.
1.5254 56.25 (1ST SF) K 0.0000 Y 18.114 .theta. 4.44.degree. (REFL)
A 0.0000 Z 37.091 B 0.0000 C 1.1599 .times. 10.sup.-13 D 4.4930
.times. 10.sup.-16 5 .infin. 1.5254 56.25 (3RD SF) Y 18.114 .theta.
4.44.degree. (REFL) Z 53.502 6 ANAM R.sub.y 47.391 Y 41.220 .theta.
-55.16.degree. (4TH SF) R.sub.x 86.005 Z 47.787 K.sub.y 1.9910
K.sub.x -0.1607 R.sub.1 1.1694 .times. 10.sup.-7 R.sub.2 -2.2052
.times. 10.sup.-10 R.sub.3 -1.8410 .times. 10.sup.-11 R.sub.4
-4.2076 .times. 10.sup.-14 P.sub.1 -6.2804 P.sub.2 -4.0710 P.sub.3
4.2066 .times. 10.sup.-1 P.sub.4 5.1697 .times. 10.sup.-1 7 .infin.
Y 40.079 .theta. -25.63.degree. (Image display plane) Z 38.041 (1)
.theta..sub.r3 = 43.85.degree. (3) .PHI..sub.t1 (yz) = 0 (1/mm)
.PHI..sub.t1 (xz) = 0 (1/mm)
EXAMPLE 2
[0164]
2 Refractive Surface Radius of Surface index Abbe's No. No.
curvature separation (Displacement) (Tilt angle) 1 .infin.(Pupil) 2
Three-dimensional surface(1) 1.5000 55.55 (1ST SF) Y 8.738 .theta.
-0.43.degree. Z 38.294 3 Three-dimensional surface(2) 1.5000 55.55
(2ND SF) Y 0.000 .theta. -26.39.degree. (REFL) Z 47.232 4
Three-dimensional surface(1) 1.5000 55.55 (1ST SF) Y 8.738 .theta.
-0.43.degree. (REFL) Z 38.294 5 Three-dimensional surface(3) 1.5000
55.55 (3RD SF) Y 28.900 .theta. 4.00.degree. (REFL) Z 51.503 6
Three-dimensional surface(4) 1.5000 55.55 (4TH SF) Y 37.094 .theta.
-42.91.degree. Z 43.146 7 .infin. Y 39.222 .theta. -39.45.degree.
(Image display plane) Z 41.032 Three-dimensional surface(1) C.sub.5
-4.3507 .times. 10.sup.-4 C.sub.7 -8.3810 .times. 10.sup.-3 C.sub.8
-7.2046 .times. 10.sup.-5 C.sub.10 -1.6070 .times. 10.sup.-4
C.sub.12 -5.7849 .times. 10.sup.-7 C.sub.14 -7.6285 .times.
10.sup.-7 C.sub.16 2.6344 .times. 10.sup.-6 C.sub.17 -7.4711
.times. 10.sup.-9 C.sub.19 -1.9337 .times. 10.sup.-8 C.sub.21
9.3990 .times. 10.sup.-8 Three-dimensional surface(2) C.sub.5
-4.4979 .times. 10.sup.-3 C.sub.7 -8.5757 .times. 10.sup.-3 C.sub.8
-6.4211 .times. 10.sup.-5 C.sub.10 -3.1176 .times. 10.sup.-5
C.sub.12 1.3495 .times. 10.sup.-6 C.sub.14 4.8979 .times. 10.sup.-8
C.sub.16 -2.4100 .times. 10.sup.-8 C.sub.17 -4.2204 .times.
10.sup.-8 C.sub.19 -3.8212 .times. 10.sup.-8 C.sub.21 -9.1979
.times. 10.sup.-9 Three-dimensional surface(3) C.sub.5 -4.6997
.times. 10.sup.-4 C.sub.7 -3.2125 .times. 10.sup.-3 C.sub.8 -8.6078
.times. 10.sup.-5 C.sub.10 -1.0181 .times. 10.sup.-4 C.sub.12
-2.7246 .times. 10.sup.-6 C.sub.14 2.7277 .times. 10.sup.-6
C.sub.16 3.7002 .times. 10.sup.-6 C.sub.17 -3.1103 .times.
10.sup.-8 C.sub.19 1.0092 .times. 10.sup.-8 C.sub.21 2.0208 .times.
10.sup.-7 Three-dimensional surface(4) C.sub.5 3.6987 .times.
10.sup.-3 C.sub.7 8.3763 .times. 10.sup.-3 C.sub.8 -8.9771 .times.
10.sup.-4 C.sub.10 5.0916 .times. 10.sup.-6 C.sub.12 -5.7678
.times. 10.sup.-5 C.sub.14 4.5123 .times. 10.sup.-7 C.sub.16
-2.3865 .times. 10.sup.-6 (1) .theta..sub.r3 = 48.44.degree. (3)
.PHI..sub.t1 (yz) = -0.0037 (1/mm) .PHI..sub.t1 (xz) = -0.0072
(1/mm)
EXAMPLE 3
[0165]
3 Refractive Surface Radius of Surface index Abbe's No. No.
curvature separation (Displacement) (Tilt angle) 1 .infin.(Pupil) 2
.infin. 1.5254 56.25 (1ST SF) Y -27.000 .theta. 0.00.degree. Z
37.395 3 ANAM R.sub.y -143.929 1.5254 56.25 (2ND SF) R.sub.x
-123.293 Y -14.868 .theta. -28.80.degree. (REFL) K.sub.y 0.3713 Z
42.871 K.sub.x -1.9942 R.sub.1 2.1403 .times. 10.sup.-8 R.sub.2
9.6413 .times. 10.sup.-13 R.sub.3 6.3684 .times. 10.sup.-14 R.sub.4
-1.2452 .times. 10.sup.-17 P.sub.1 -3.9989 .times. 10.sup.-3
P.sub.2 -3.0463 P.sub.3 2.5677 .times. 10 - 1 P.sub.4 4.2810
.times. 10 - 1 4 .infin. 1.5254 56.25 (1ST SF) Y -27.000 .theta.
0.00.degree. (REFL) Z 37.395 5 .infin. 1.5254 56.25 (3RD SF) Y
0.079 .theta. 0.00.degree. (REFL) Z 53.539 6 ANAM R.sub.y 39.861 Y
44.498 .theta. -66.77.degree. (4TH SF) R.sub.x 62.319 Z 51.066
K.sub.y 1.5656 K.sub.x 4.2425 R.sub.1 3.9064 .times. 10.sup.-6
R.sub.2 5.0520 .times. 10.sup.-10 R.sub.3 4.9921 .times. 10.sup.-13
R.sub.4 -6.6158 .times. 10.sup.-15 P.sub.1 -1.5408 .times.
10.sup.-1 P.sub.2 4.0979 P.sub.3 1.6631 P.sub.4 1.0506 7 .infin. Y
42.800 .theta. -21.40.degree. (Image display plane) Z 38.475 (1)
.theta..sub.r3 = 44.53.degree. (3) .PHI..sub.t1 (yz) = 0 (1/mm)
.PHI..sub.t1 (xz) = 0 (1/mm)
EXAMPLE 4
[0166]
4 Refractive Surface Radius of Surface index Abbe's No. No.
curvature separation (Displacement) (Tilt angle) 1 .infin.(Pupil) 2
ANAM R.sub.y -242.348 1.5254 56.25 (1ST SF) R.sub.x -159.768 Y
5.082 .theta. -3.86.degree. K.sub.y 12.1104 Z 32.396 K.sub.x 4.7358
R.sub.1 -2.5719 .times. 10.sup.-10 R.sub.2 -4.9792 .times.
10.sup.-12 R.sub.3 8.8695 .times. 10.sup.-13 R.sub.4 6.7191 .times.
10.sup.-20 P.sub.1 -1.8150 .times. 10.sup.+1 P.sub.2 -4.7838
P.sub.3 -1.2978 P.sub.4 -7.1284 3 ANAM R.sub.y -119.562 1.5254
56.25 (2ND SF) R.sub.x -98.451 Y 27.149 .theta. -11.26.degree.
(REFL) K.sub.y -0.1186 Z 52.500 K.sub.x 0.7866 R.sub.1 -1.6969
.times. 10.sup.-9 R.sub.2 -6.2266 .times. 10.sup.-11 R.sub.3 8.5459
.times. 10.sup.-16 R.sub.4 8.0998 .times. 10.sup.-16 P.sub.1
-1.8331 P.sub.2 -4.9789 .times. 10.sup.-1 P.sub.3 -2.3604 P.sub.4
-9.6450 .times. 10.sup.-1 4 ANAM R.sub.y -242.348 1.5254 56.25 (1ST
SF) R.sub.x -159.768 Y 5.082 .theta. -3.86.degree. (REFL) K.sub.y
12.1104 Z 32.396 K.sub.x 4.7358 R.sub.1 -2.5719 .times. 10.sup.-10
R.sub.2 -4.9792 .times. 10.sup.-12 R.sub.3 8.8695 .times.
10.sup.-13 R.sub.4 6.7191 .times. 10.sup.-20 P.sub.1 -1.8150
.times. 10.sup.+1 P.sub.2 -4.7838 P.sub.3 -1.2978 P.sub.4 -7.1284 5
ANAM R.sub.y -179.007 1.5254 56.25 (3RD SF) R.sub.x -231.111 Y
27.820 .theta. 1.74.degree. (REFL) K.sub.y 2.2288 Z 47.835 K.sub.x
-72.7188 R.sub.1 6.1912 .times. 10.sup.-8 R.sub.2 -9.4470 .times.
10.sup.-13 R.sub.3 2.8064 .times. 10.sup.-15 R.sub.4 2.0069 .times.
10.sup.-18 P.sub.1 2.0705 .times. 10.sup.-2 P.sub.2 6.7667 P.sub.3
-5.5003 P.sub.4 -4.0534 6 ANAM R.sub.y 72.293 Y 42.329 .theta.
-42.24.degree. (4TH SF) R.sub.x 39.167 Z 43.924 K.sub.y -1.0213
K.sub.x -7.8305 R.sub.1 -7.5404 .times. 10.sup.-7 R.sub.2 -5.8510
.times. 10.sup.-10 R.sub.3 5.8345 .times. 10.sup.-13 R.sub.4 1.5291
.times. 10.sup.-15 P.sub.1 -1.2077 .times. 10.sup.-1 P.sub.2 2.1174
.times. 10.sup.-2 P.sub.3 2.9220 .times. 10.sup.-1 P.sub.4 -1.4519
7 .infin. Y 42.878 .theta. -19.36.degree. (Image display plane) Z
30.211 (1) .theta..sub.r3 = 42.75.degree. (3) .PHI..sub.t1 (yz) =
0.0008 (1/mm) .PHI..sub.t1 (xz) = -0.001 (1/mm)
EXAMPLE 5
[0167]
5 Refractive Surface Radius of Surface index Abbe's No. No.
curvature separation (Displacement) (Tilt angle) 1 .infin.(Pupil) 2
-104.851 1.5254 56.25 (1ST SF) Y 2.540 .theta. -7.02.degree. Z
33.527 3 ANAM R.sub.y -54.751 1.5254 56.25 (2ND SF) R.sub.x -62.006
Y -19.747 .theta. -48.21.degree. (REFL) K.sub.y -1.3614 Z 30.166
K.sub.x 0.1944 R.sub.1 2.4430 .times. 10.sup.-10 R.sub.2 -1.1189
.times. 10.sup.-10 R.sub.3 -2.4892 .times. 10.sup.-16 R.sub.4
1.9084 .times. 10.sup.-22 P.sub.1 -2.7674 .times. 10.sup.+1 P.sub.2
5.3845 .times. 10.sup.-1 P.sub.3 -4.1468 P.sub.4 1.0048 .times.
10.sup.+1 4 -104.851 1.5254 56.25 (1ST SF) Y 2.540 .theta.
-7.02.degree. (REFL) Z 33.527 5 ANAM R.sub.y -8201.935 1.5254 56.25
(3RD SF) R.sub.x 1243.857 Y -37.497 .theta. 4.95.degree. (REFL)
K.sub.y 0.0000 Z 53.061 K.sub.x 0.0000 R.sub.1 9.7227 .times.
10.sup.-8 R.sub.2 1.2246 .times. 10.sup.-12 R.sub.3 -1.5956 .times.
10.sup.-16 R.sub.4 6.7677 .times. 10.sup.-21 P.sub.1 8.5858 .times.
10.sup.-1 P.sub.2 -4.4664 P.sub.3 1.9991 P.sub.4 2.2019 6 46.674 Y
28.160 .theta. -29.19.degree. (4TH SF) Z 36.643 7 .infin. Y 31.793
.theta. -26.09.degree. (Image display plane) Z 35.135 (1)
.theta..sub.r3 = 36.51.degree.
EXAMPLE 6
[0168]
6 Refractive Surface Radius of Surface index Abbe's No. No
curvature separation (Displacement) (Tilt angle) 1 .infin.(Pupil) 2
.infin. Y 0.000 .theta. 20.00.degree. (Hypothetic plane) Z 0.000 3
.infin. 1.5254 56.25 (1ST SF) (from hypothetic plane) Y 0.000
.theta. 0.00.degree. Z 40.495 4 ANAM R.sub.y -146.661 1.5254 56.25
(2ND SF) R.sub.x -131.067 (from hypothetic plane) (REFL) K.sub.y
-0.1158 Y -23.006 .theta. -32.35.degree. K.sub.x -0.6570 Z 49.040
R.sub.1 1.4710 .times. 10.sup.-8 R.sub.2 2.4181 .times. 10.sup.-10
R.sub.3 8.0445 .times. 10.sup.-14 R.sub.4 -1.0655 .times.
10.sup.-16 P.sub.1 -6.7968 .times. 10.sup.-1 P.sub.2 1.1524 .times.
10.sup.-2 P.sub.3 9.6151 .times. 10.sup.-1 P.sub.4 5.6260 .times.
10.sup.-1 5 .infin. 1.5254 56.25 (1ST SF) (from hypothetic plane)
(REFL) Y 0.000 .theta. 0.00.degree. Z 40.495 6 .infin. 1.5254 56.25
(3RD SF) (from hypothetic plane) (REFL) Y 0.000 .theta.
0.00.degree. Z 56.475 7 ANAM R.sub.y 70.881 (from hypothetic plane)
(4TH SF) R.sub.x 99.816 Y 30.811 .theta. -80.98.degree. K.sub.y
6.0488 Z 62.245 K.sub.x 7.1389 R.sub.1 1.8385 .times. 10.sup.-5
R.sub.2 1.8499 .times. 10.sup.-10 R.sub.3 -3.4116 .times.
10.sup.-12 R.sub.4 -7.2747 .times. 10.sup.-15 P.sub.1 3.2623
.times. 10.sup.-1 P.sub.2 3.8697 P.sub.3 9.0201 .times. 10.sup.-1
P.sub.4 1.1638 .times. 10.sup.-1 8 .infin. Y 40.634 .theta.
-2.65.degree. (Image display plane) Z 30.403 (1) .theta..sub.r3 =
46.70.degree. (3) .PHI..sub.t1 (yz) = 0 (1/mm) .PHI..sub.t1 (xz) =
0 (1/mm)
EXAMPLE 9
[0169]
7 Refractive Surface Radius of Surface index Abbe' s No. No.
curvature separation (Displacement) (Tilt angle) 1 .infin.(Pupil) 2
.infin. Y 0.000 .theta. 15.00.degree. (Hypothetic plane) Z 0.000 3
-221.433 1.5254 56.25 (1ST SF) (from hypothetic plane) Y 0.000
.theta. 0.00.degree. Z 38.879 4 -106.803 1.5254 56.25 (2ND SF)
(from hypothetic plane) (REFL) Y -16.310 .theta. -30.86.degree. Z
48.157 5 -221.433 1.5254 56.25 (1ST SF) (from hypothetic plane)
(REFL) Y 0.000 .theta. 0.00.degree. Z 38.879 6 -208.964 1.5254
56.25 (3RD SF) (from hypothetic plane) (REFL) Y 0.000 .theta.
0.00.degree. Z 55.417 7 154.685 (from hypothetic plane) (4TH SF) Y
22.393 .theta. -20.71.degree. Z 41.581 8 .infin. Y 39.534 .theta.
-5.00.degree. (Image display plane) Z 27.732 (1) .theta..sub.r3 =
41.68.degree. (3) .PHI..sub.t1 (yz) = 0.00024 (1/mm) .PHI..sub.t1
(xz) = 0.00024 (1/mm)
EXAMPLE 10
[0170]
8 Refractive Surface Radius of Surface index Abbe's No. No.
curvature separation (Displacement) (Tilt angle) 1 .infin.(Pupil) 2
-104.851 1.5254 56.25 (1ST SF) Y 2.540 .theta. -7.02.degree. Z
33.527 3 ANAM R.sub.y -54.751 Y -19.747 .theta. -48.21.degree. (2ND
SF) R.sub.x -62.006 Z 30.167 (REFL) K.sub.y -1.3614 K.sub.x 0.1944
R.sub.1 2.4430 .times. 10.sup.-10 R.sub.2 -1.1189 .times.
10.sup.-10 R.sub.3 -2.4892 .times. 10.sup.-16 R.sub.4 1.9084
.times. 10.sup.-22 P.sub.1 -2.7674 .times. 10.sup.+1 P.sub.2 5.3845
.times. 10.sup.-1 P.sub.3 -4.1468 P.sub.4 1.0048 .times. 10.sup.+1
4 .infin. 2.000 1.4922 57.50 (Fresnel-lens's first surface) Y
45.000 .theta. 0.00.degree. Z 51.527 5 .infin. (Fresnel-lens's
second surface) K 0.0000 A 2.0658 .times. 10.sup.-6 B -4.2780
.times. 10.sup.-10 C 3.2196 .times. 10.sup.-14 D 2.1256 .times.
10.sup.-18
EXAMPLE 11
[0171]
9 Refractive Surface Radius of Surface index Abbe's No. No.
curvature separation (Displacement) (Tilt angle) 1 .infin.(Pupil) 2
-104.851 1.5254 56.25 (1ST SF) Y 2.540 .theta. -7.02.degree. Z
33.527 3 ANAM R.sub.y -54.751 Y -19.747 .theta. -48.21.degree. (2ND
SF) R.sub.x -62.006 Z 30.166 (REFL) K.sub.y -1.3614 K.sub.x 0.1944
R.sub.1 2.4430 .times. 10.sup.-10 R.sub.2 -1.1189 .times.
10.sup.-10 R.sub.3 -2.4892 .times. 10.sup.-16 R.sub.4 1.9084
.times. 10.sup.-22 P.sub.1 -2.7674 .times. 10.sup.+1 P.sub.2 5.3845
.times. 10.sup.-1 P.sub.3 -4.1468 P.sub.4 1.0048 .times. 10.sup.+1
4 .infin. 2.000 1.4922 57.50 (Fresnel-lens's first surface) Y
20.000 .theta. -22.00.degree. Z 53.527 5 .infin. (Fresnel-lens's
second surface) K 0.0000 A 4.4111 .times. 10.sup.-5 B -1.0534
.times. 10.sup.-7 C 1.1649 .times. 10.sup.-10 D -4.9416 .times.
10.sup.-14 .degree.
EXAMPLE 12 (1)
[0172]
10 Refractive Surface Radius of Surface index Abbe's No. No.
curvature separation (Displacement) (Tilt angle) 1 .infin.(Pupil) 2
Three-dimensional surface(1) 1.5254 56.25 (1ST SF) Y 13.983 .theta.
9.46.degree. Z 33.974 3 Three-dimensional surface(2) 1.5254 56.25
(2ND SF) Y 4.596 .theta. -15.22.degree. (REFL) Z 49.231 4
Three-dimensional surface(1) 1.5254 56.25 (1ST SF) Y 13.983 .theta.
9.46.degree. (REFL) Z 33.974 5 Three-dimensional surface(3) Y
27.094 .theta. 79.39.degree. (3RD SF) Z 35.215 6 .infin. Y 29.266
.theta. 46.34.degree. (Image display plane) Z 46.318
Three-dimensional surface(1) C.sub.5 -2.6152 .times. 10.sup.-3
C.sub.7 -3.9706 .times. 10.sup.-3 C.sub.8 -7.5434 .times. 10.sup.-5
C.sub.10 -1.5120 .times. 10.sup.-6 C.sub.12 2.6572 .times.
10.sup.-7 C.sub.14 1.3359 .times. 10.sup.-6 C.sub.16 1.7946 .times.
10.sup.-7 C.sub.17 -2.9881 .times. 10.sup.-9 C.sub.19 -3.0362
.times. 10.sup.-9 C.sub.21 -2.0258 .times. 10.sup.-7 C.sub.23
-3.8978 .times. 10.sup.-10 C.sub.25 1.4986 .times. 10.sup.-9
C.sub.27 -3.8974 .times. 10.sup.-9 C.sub.29 -2.5335 .times.
10.sup.-9 C.sub.30 4.3101 .times. 10.sup.-12 C.sub.32 -1.4923
.times. 10.sup.-11 C.sub.34 7.6026 .times. 10.sup.-11 C.sub.36
-4.2410 .times. 10.sup.-11 Three-dimensional surface(2) C.sub.5
-6.2524 .times. 10.sup.-3 C.sub.7 -7.5944 .times. 10.sup.-3 C.sub.8
-1.0605 .times. 10.sup.-5 C.sub.10 9.3276 .times. 10.sup.-6
C.sub.12 8.3882 .times. 10.sup.-7 C.sub.14 -5.6861 .times.
10.sup.-7 C.sub.16 -4.9904 .times. 10.sup.-7 C.sub.17 -2.0403
.times. 10.sup.-10 C.sub.19 -8.0184 .times. 10.sup.-9 C.sub.21
-4.4196 .times. 10.sup.-8 C.sub.23 4.4149 .times. 10.sup.-10
C.sub.25 3.8170 .times. 10.sup.-10 C.sub.27 8.4970 .times.
10.sup.-11 C.sub.29 -2.8006 .times. 10.sup.-10 C.sub.30 1.3964
.times. 10.sup.-12 C.sub.32 -1.7677 .times. 10.sup.-10 C.sub.34
3.3220 .times. 10.sup.-12 C.sub.36 6.9401 .times. 10.sup.-l2
Three-dimensional surface(3) C.sub.5 -1.2118 .times. 10.sup.-2
C.sub.7 -3.7062 .times. 10.sup.-3 C.sub.8 -1.2290 .times. 10.sup.-4
C.sub.10 9.9763 .times. 10.sup.-4 C.sub.12 -8.0746 .times.
10.sup.-5 C.sub.14 -3.8939 .times. 10.sup.-5 C.sub.16 2.6861
.times. 10.sup.-5 C.sub.17 -1.7720 .times. 10.sup.-6 C.sub.19
-3.4243 .times. 10.sup.-6 C.sub.21 -3.5310 .times. 10.sup.-7
C.sub.23 1.2185 .times. 10.sup.-7 C.sub.25 1.0019 .times. 10.sup.-7
C.sub.27 1.4838 .times. 10.sup.-7 C.sub.29 -5.3531 .times.
10.sup.-8
EXAMPLE 12 (2)
[0173]
11 Refractive Surface Radius of Surface index Abbe's No. No.
curvature separation (Displacement) (Tilt angle) 1 .infin.(Pupil) 2
Three-dimensional 1.5254 56.25 surface(1) (1ST SF) Y 13.983 .theta.
9.46.degree. Z 33.974 3 Three-dimensional Y 4.596 .theta.
-15.22.degree. surface(2) (2ND SF) Z 49.231 4 .infin. 2.000 1.4922
57.50 (Fresnel-lens's first surface) Y 45.982 .theta.
-18.17.degree. Z 65.000 5 .infin. (Fresnel-lens's second surface) K
0.0000 A 3.9372 .times. 10.sup.-6 B -1.6979 .times. 10.sup.-9 C
4.2377 .times. 10.sup.-13 D -4.1829 .times. 10.sup.-17
Three-dimensional surface(1) C.sub.5 -2.6152 .times. 10.sup.-3
C.sub.7 -3.9706 .times. 10.sup.-3 C.sub.8 -7.5434 .times. 10.sup.-5
C.sub.10 -1.5120 .times. 10.sup.-6 C.sub.12 2.6572 .times.
10.sup.-7 C.sub.14 1.3359 .times. 10.sup.-6 C.sub.16 1.7946 .times.
10.sup.-7 C.sub.17 -2.9881 .times. 10.sup.-9 C.sub.17 -3.0362
.times. 10.sup.-9 C.sub.21 -2.0258 .times. 10.sup.-7 C.sub.23
-3.8978 .times. 10.sup.-10 C.sub.25 1.4986 .times. 10.sup.-9
C.sub.27 -3.8974 .times. 10.sup.-9 C.sub.29 -2.5335 .times.
10.sup.-9 C.sub.30 4.3101 .times. 10.sup.-12 C.sub.32 -1.4923
.times. 10.sup.-11 C.sub.34 7.6026 .times. 10.sup.-11 C.sub.36
-4.2410 .times. 10.sup.-11 Three-dimensional surface(2) C.sub.5
-6.2524 .times. 10.sup.-3 C.sub.7 -7.5944 .times. 10.sup.-3 C.sub.8
1.0605 .times. 10.sup.-5 C.sub.10 9.3276 .times. 10.sup.-6 C.sub.2
8.3882 .times. 10.sup.-7 C.sub.14 -5.6861 .times. .sup.10.sup.-7
C.sub.16 -4.9904 .times. 10.sup.-7 C.sub.17 -2.0403 .times.
10.sup.-10 C.sub.19 -8.0184 .times. 10.sup.-9 C.sub.21 4.4196
.times. 10.sup.-8 C.sub.23 4.4149 .times. 10.sup.-10 C.sub.25
3.8170 .times. 10.sup.-10 C.sub.27 8.4970 .times. 10.sup.-11
C.sub.29 -2.8006 .times. 10.sup.-10 C.sub.30 1.3964 .times.
10.sup.-12 C.sub.32 -1.7677 .times. 10.sup.-10 C.sub.34 3.3220
.times. 10.sup.-12 C.sub.36 6.9401 .times. 10.sup.-12
EXAMPLE 13
[0174]
12 Refractive Surface Radius of Surface index Abbe's No. No.
curvature separation (Displacement) (Tilt angle) 1 .infin.(Pupil) 2
Three-dimensional 1.5163 64.15 surface(1) (1ST SF) Y 0.000 .theta.
24.79.degree. Z 35.567 3 Three-dimensional 1.5163 64.15 surface(2)
(2ND SF) Y 5.402 .theta. -9.11.degree. (REFL) Z 70.723 4
Three-dimensional Y 21.138 .theta. -25.12.degree. surface(3) (3RD
SF) Z 39.783 5 .infin. Y 23.963 .theta. -11.11.degree. (Image
display plane) Z 34.441 Three-dimensional surface(1) C.sub.5 6.8620
.times. 10.sup.-3 C.sub.7 7.4153 .times. 10.sup.-3 C.sub.8 5.9417
.times. 10.sup.-5 C.sub.10 2.9033 .times. 10.sup.-5 C.sub.12
-4.6823 .times. 10.sup.-7 C.sub.14 3.8805 .times. 10.sup.-6
C.sub.16 5.0284 .times. 10.sup.-7 C.sub.17 2.3906 .times. 10.sup.-8
C.sub.19 7.1030 .times. 10-8 C.sub.21 2.8323 .times. 10.sup.-8
Three-dimensional surface(2) C.sub.5 -3.7101 .times. 10.sup.-3
C.sub.7 -4.1036 .times. 10-3 C.sub.8 4.2896 .times. 10-6 C.sub.10
-8.4314 .times. 10.sup.-6 C.sub.12 -8.1477 .times. 10.sup.-8
C.sub.14 1.1846 .times. 10.sup.-6 C.sub.16 2.8608 .times. 10.sup.-7
C.sub.17 8.8332 .times. 10.sup.-9 C.sub.19 3.2284 .times. 10.sup.-8
C.sub.21 1.2745 .times. 10.sup.-8 Three-dimensional surface(3)
C.sub.5 1.5613 .times. 10.sup.-2 C.sub.7 1.5901 .times. 10.sup.-2
C.sub.8 3.8223 .times. 10.sup.-4 C.sub.10 -5.9546 .times. 10.sup.-5
C.sub.12 -5.8106 .times. 10.sup.-5 C.sub.14 -4.2859 .times.
10.sup.-5 C.sub.16 -2.2163 .times. 10.sup.-5 C.sub.17 1.1940
.times. 10.sup.-6 C.sub.19 2.0760 .times. 10.sup.-6 C.sub.21 1.0626
.times. 10.sup.-6
EXAMPLE 14
[0175]
13 Refractive Surface Radius of Surface index Abbe's No. No.
curvature separation (Displacement) (Tilt angle) 1 .infin.(Pupil) 2
Three-dimensional 1.5163 64.15 surface(1) (1ST SF) Y -10.123
.theta. 20.33.degree. Z 43.489 3 Three-dimensional 1.5163 64.15
surface(2) (2ND SF) Y 1.103 .theta. -10.31.degree. (REFL) Z 65.000
4 Three-dimensional Y -10.123 .theta. 20.33.degree. surface(1) (1ST
SF) Z 43.489 5 .infin. Y 17.608 .theta. -13.99.degree. (Image
display plane) Z 30.846 Three-dimensional surface(1) C.sub.5 1.0401
.times. 10.sup.-2 C.sub.7 8.6572 .times. 10.sup.-3 C.sub.8 9.8267
.times. 10.sup.-5 C.sub.10 2.0456 .times. 10.sup.-4 C.sub.12
-9.4226 .times. 10.sup.-6 C.sub.14 1.6262 .times. 10.sup.-6
C.sub.16 4.0506 .times. 10.sup.-6 C.sub.17 3.2669 .times. 10.sup.-7
C.sub.19 2.1072 .times. .sup.10.sup.-7 C.sub.21 1.5355 .times.
10.sup.-7 Three-dimensional surface(2) C.sub.5 -2.5798 .times.
10.sup.-3 C.sub.7 -3.0708 .times. 10.sup.-3 C.sub.8 -3.2024 .times.
10.sup.-6 C.sub.10 -3.3909 .times. 10.sup.-6 C.sub.12 2.9430
.times. 10.sup.-6 C.sub.14 4.3427 .times. .sup.-8 C.sub.16 3.4981
.times. 10.sup.-6 C.sub.17 -2.8763 .times. .sup.-8 C.sub.19 4.0895
.times. .sup.-8 C.sub.21 5.4666 .times. 10.sup.-8
EXAMPLE 17
[0176]
14 Refractive Surface Radius of Surface index Abbe's No. No.
curvature separation (Displacement) (Tilt angle) 1 .infin.(Pupil) 2
Three-dimensional 1.5000 55.55 surface(1) (1ST SF) Y 18.958 .theta.
7.69.degree. Z 30.730 3 Three-dimensional 1.5000 55.55 surface(2)
(2ND SF) Y 9.165 .theta. -13.84.degree. (REFL) Z 48.107 4
Three-dimensional 1.5000 55.55 surface(1) (1ST SF) Y 18.958 .theta.
7.69.degree. (REFL) Z 30.730 5 Three-dimensional 1.5000 55.55
surface(2) (2ND SF) Y 9.165 .theta. -13.84.degree. (REFL) Z 48.107
6 Three-dimensional 1.5000 55.55 surface(3) (4TH SF) Y 34.128
.theta. -31.50.degree. Z 30.758 7 .infin. Y 47.350 .theta.
-34.92.degree. (Image display plane) Z 35.893 Three-dimensional
surface(1) C.sub.5 -4.9463 .times. 10.sup.-3 C.sub.7 -3.4912
.times. 10.sup.-3 C.sub.8 6.9477 .times. 10.sup.-5 C.sub.10 1.7114
.times. 10.sup.-4 C.sub.12 1.0830 .times. 10.sup.-6 C.sub.14
-2.2541 .times. 10.sup.-7 C.sub.16 4.5743 .times. 10.sup.-6
C.sub.17 6.1581 .times. 10.sup.-8 C.sub.19 4.7667 .times. 10.sup.-8
C.sub.21 -1.9359 .times. 10.sup.-7 C.sub.23 -1.3103 .times.
10.sup.-10 C.sub.25 -7.7572 .times. 10.sup.-10 C.sub.27 7.0783
.times. 10.sup.-10 C.sub.29 5.3774 .times. 10.sup.-9 C.sub.30
4.7726 .times. 10.sup.-12 C.sub.32 1.3699 .times. 10.sup.-11
C.sub.34 7.4217 .times. 10.sup.-11 C.sub.36 -1.3460 .times.
10.sup.-10 Three-dimensional surface(2) C.sub.5 -5.9243 .times.
10.sup.-3 C.sub.7 -5.4509 .times. 10.sup.-3 C.sub.8 3.4016 .times.
10.sup.-5 C.sub.10 7.9633 .times. 10.sup.-5 C.sub.12 -4.1470
.times. 10.sup.-7 C.sub.14 1.0233 .times. 10.sup.-6 C.sub.16 2.6471
.times. 10.sup.-6 C.sub.17 2.3016 .times. 10.sup.-9 C.sub.19 3.3134
.times. 10.sup.-8 C.sub.21 -1.6456 .times. 10.sup.-8 C.sub.23
-1.3255 .times. 10.sup.-10 C.sub.25 -4.9215 .times. 10.sup.-10
C.sub.27 -3.3070 .times. 10.sup.-10 C.sub.29 4.1802 .times.
10.sup.-9 Three-dimensional surface(3) C.sub.5 7.9798 .times.
10.sup.-3 C.sub.7 1.7546 .times. 10.sup.-2 C.sub.8 -1.1020 .times.
10.sup.-4 C.sub.10 9.4392 .times. 10.sup.-4 C.sub.12 -3.9282
.times. 10.sup.-6 C.sub.14 -7.3326 .times. 10.sup.-6 C.sub.16
-1.4273 .times. 10.sup.-5 (1) .theta..sub.r3 = 46.48.degree.
[0177] Although in the above-described examples the optical systems
are constructed by using aspherical surfaces, anamorphic surfaces
and three-dimensional surfaces defined by the above equations (a),
(b) and (c), it is also possible to use surface configurations
expressed by Zernike polynomials as defined by the following
equation (d) and three-dimensional surfaces symmetric with respect
to the X-axis direction as defined by the following equation (e).
That is, curved surfaces expressed by any defining equations can be
used.
[0178] Plane-symmetry three-dimensional surfaces may also be
defined by Zernike polynomials. That is, the configuration of a
plane-symmetry three-dimensional surface may be defined by the
following equation (d). The Z-axis of the defining equation (d) is
the axis of Zernike polynomial. 6 X = R .times. cos ( A ) Y = R
.times. sin ( A ) Z = D 2 + D 3 R cos ( A ) + D 4 R sin ( A ) + D 5
R 2 cos ( 2 A ) + D 6 ( R 2 - 1 ) + D 7 R 2 sin ( 2 A ) + D 8 R 3
cos ( 3 A ) + D 9 ( 3 R 3 - 2 R ) cos ( A ) + D 10 ( 3 R 3 - 2 R )
sin ( A ) + D 11 R 3 sin ( 3 A ) + D 12 R 4 cos ( 4 A ) + D 13 ( 4
R 4 - 3 R 2 ) cos ( 2 A ) + D 14 ( 6 R 4 - 6 R 2 + 1 ) + D 15 ( 4 R
4 - 3 R 2 ) sin ( 2 A ) + D 16 R 4 sin ( 4 A ) + D 17 R 5 cos ( 5 A
) + D 18 ( 5 R 5 - 4 R 3 ) cos ( 3 A ) + D 19 ( 10 R 5 - 12 R 3 + 3
R ) cos ( A ) + D 20 ( 10 R 5 - 12 R 3 + 3 R ) sin ( A ) + D 21 ( 5
R 5 - 4 R 3 ) sin ( 3 A ) + D 22 R 5 sin ( 5 A ) + D 23 R 6 cos ( 6
A ) + D 24 ( 6 R 6 - 5 R 4 ) cos ( 4 A ) + D 25 ( 15 R 6 - 20 R 4 +
6 R 2 ) cos ( 2 A ) + D 26 ( 20 R 6 - 30 R 4 + 12 R 2 - 1 ) + D 27
( 15 R 6 - 20 R 4 + 6 R 2 ) sin ( 2 A ) + D 28 ( 6 R 6 - 5 R 4 )
sin ( 4 A ) + D 29 R 6 sin ( 6 A ) ( d )
[0179] It should be noted that the plane-symmetry three-dimensional
surface in the above equation is expressed as a surface which is
symmetric with respect to the X-axis direction. In the above
equation, D.sub.m (m is an integer of 2 or higher) are
coefficients.
[0180] A three-dimensional surface symmetric with respect to the
X-axis direction may be defined in correspondence to the above
equation (c) as follows: 7 Z = C 2 + C 3 Y + C 4 X + C 5 Y 2 + C 6
Y X + C 7 X 2 + C 8 Y 3 + C 9 Y 2 X + C 10 YX 2 + C 11 X 3 + C 12 Y
4 + C 13 Y 3 X + C 14 Y 2 X 2 + C 15 Y X 3 + C 16 X 4 + C 17 Y 5 +
C 18 Y 4 X + C 19 Y 3 X 2 + C 20 Y 2 X 3 + C 21 YX 4 + C 22 X 5 + C
23 Y 6 + C 24 Y 5 X + C 25 Y 4 X 2 + C 26 Y 3 X 3 + C 27 Y 2 X 4 +
C 28 Y X 5 + C 29 X 6 + C 30 Y 7 + C 31 Y 6 X + C 32 Y 5 X 2 + C 33
Y 4 X 3 + C 34 Y 3 X 4 + C 35 Y 2 X 5 + C 36 YX 6 + C 37 X 7 ( e
)
[0181] Incidentally, it is possible to construct an image display
apparatus for a single eye by preparing a combination of an ocular
optical system arranged as described above and an image display
device. Alternatively, it is possible to construct an image display
apparatus for both eyes by preparing a pair of combinations of an
ocular optical system arranged as described above and an image
display device for the left and right eyes, and supporting them
apart from each other by the interpupillary distance, i.e. the
distance between the two eyes. In this way, it is possible to form
a stationary or portable image display apparatus which enables the
observer to see with a single eye or both eyes.
[0182] FIG. 21 shows an image display apparatus designed for a
single eye (in this case, the apparatus is designed for the left
eye), and FIG. 22 shows an image display apparatus designed for
both eyes. In FIGS. 21 and 22, reference numeral 31 denotes a
display apparatus body unit. In the case of FIG. 21, the display
apparatus body unit 31 is supported by a support member through the
observer's head such that the display apparatus body unit 31 is
held in front of the observer's left eye. In the case of FIG. 22,
the display apparatus body unit 31 is supported by a support member
through the observer's head such that the display apparatus body
unit 31 is held in front of both the observer's eyes. The support
member has a pair of left and right front frames 32 each joined at
one end thereof to the display apparatus body unit 31. The left and
right front frames 32 extend from the observer's temples to the
upper portions of his/her ears, respectively. A pair of left and
right rear frames 33 are joined to the other ends of the left and
right front frames 32, respectively, and extend over the left and
right side portions of the observer's head. In the case of FIG. 22,
the support member further has a top frame 34 joined at both ends
thereof to the other ends of the left and right rear frames 33,
respectively, such that the top frame 34 supports the top of the
observer's head.
[0183] A rear plate 35 is joined to one front frame 32 near the
joint to the rear frame 33. The rear plate 35 is formed from an
elastic member, e.g. a metal leaf spring. In the case of FIG. 22, a
rear cover 36, which constitutes a part of the support member, is
joined to the rear plate 35 such that the rear cover 36 can support
the apparatus at a position behind the observer's ear in a region
extending from the back part of the head to the base of the neck. A
speaker 39 is mounted inside the rear plate 35 or the rear cover 36
at a position corresponding to the observer's ear.
[0184] A cable 41 for transmitting external image and sound signals
is led out from the display apparatus body unit 31. In the case of
FIG. 22, the cable 41 extends through the top frame 34, the rear
frames 33, the front frames 32 and the rear plate 35 and projects
to the outside from the rear end of the rear cover 36. In the case
of FIG. 21, the cable 41 projects from the rear end of the rear
plate 35. The cable 41 is connected to a video reproducing unit 40.
It should be noted that reference numeral 40a denotes a switch and
volume control part of the video reproducing unit 40.
[0185] The cable 41 may have a-jack and plug arrangement attached
to the distal end thereof so that the cable 41 can be detachably
connected to an existing video deck. The cable 41 may also be
connected to a TV signal receiving tuner so as to enable the user
to enjoy watching TV. Alternatively, the cable 41 may be connected
to a computer to receive computer graphic images or message images
or the like from the computer. To eliminate the bothersome cord,
the image display apparatus may be arranged to receive external
radio signals through an antenna connected thereto.
[0186] Further, the ocular optical system of the image display
apparatus according to the present invention can be used as an
image-forming optical system. For example, as shown in FIG. 23, the
ocular optical system may be used in a finder optical system
F.sub.i of a compact camera C.sub.a in which a photographic optical
system O.sub.b and the finder optical system F.sub.i are provided
separately in parallel to each other. FIG. 24 shows the arrangement
of an optical system in a case where the ocular optical system
according to the present invention is used as such an image-forming
optical system. As illustrated, the ocular optical system DS
according to the present invention is disposed behind a front lens
group GF and an aperture diaphragm D, thereby constituting an
objective optical system L.sub.t. An image that is formed by the
objective optical system L.sub.t is erected by a Porro prism P, in
which there are four reflections, provided at the observer side of
the objective optical system L.sub.t, thereby enabling an erect
image to be observed through an ocular lens O.sub.c.
[0187] Although the prism optical element, image observation
apparatus and image display apparatus according to the present
invention have been described above by way of some, examples, it
should be noted that the present invention is not necessarily
limited to these examples, and that various modifications may be
imparted thereto without departing from the scope of the present
invention.
[0188] As will be clear from the foregoing description, the present
invention makes it possible to provide an image display apparatus
usable as an image observation apparatus which has an extremely
thin and compact ocular optical system and yet suffers from minimal
unwanted light and provides an observation image that is clear even
at a wide observation field angle.
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