Optical: systems and elements – Single channel simultaneously to or from plural channels – By partial reflection at beam splitting or combining surface
Reexamination Certificate
2000-03-20
2001-01-30
Mack, Ricky (Department: 2873)
Optical: systems and elements
Single channel simultaneously to or from plural channels
By partial reflection at beam splitting or combining surface
C359S631000, C359S637000
Reexamination Certificate
active
06181475
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a compact imaging optical system and ocular optical system which have favorable aberration correction performance, a wide field angle and high resolution. The present invention also relates to an image display apparatus which uses the ocular optical system.
In recent years, helmet- and goggle-type head- or face-mounted image display apparatuses have been developed for virtual reality or for the purpose of enabling the user to enjoy a wide-screen image personally.
For example, Japanese Patent Application Laid-Open ( KOKAI) No. 2-297516 discloses an-image display apparatus including, as shown in
FIG. 48
, a two-dimensional display device
21
for displaying an image, an objective collimator lens
22
, and a parallel transparent plate
23
having off-axis parabolic mirrors at both ends thereof. Display light emanating from the two-dimensional display device
21
is formed into parallel rays through the objective collimator lens
22
. Thereafter, the light rays are successively subjected to first transmission by one of the parallel surfaces of the parallel transparent plate
23
, reflection by the first parabolic mirror, some total reflections in the parallel transparent plate
23
, reflection by the second parabolic mirror and second transmission by the other of the parallel surfaces (a total of 8 reflections and a total of 2 transmissions), thereby forming an intermediate image at the point F and projecting the intermediate image into an observer's eyeball
24
.
U.S. Pat. No. 4,026,641 discloses an image display apparatus in which, as shown in
FIG. 49
, an object image displayed by an image display device
25
is converted into a curved object image by a transfer optical element
26
, and the object image is projected into an observer's eyeball by a toric reflecting surface
27
.
In head-mounted image display apparatuses, it is important to lead an image of an image display device to an observer's eyeball without using a relay optical system and without forming an intermediate image in the optical path, as shown for example in Japanese Patent Application Laid-Open (KOKAI) No. 6-308424.
However, in Japanese Patent Application Laid-Open (KOKAI) No. 6-308424, the optical path is formed with a half-mirror interposed therein. Therefore, there is a loss of light quantity, and it is not easy to perform bright display.
European Patent No. 0,583,116A2 discloses a head-mounted image display apparatus which is capable of displaying a bright image without using a half-mirror. In this case, however, a relay optical system is used, which causes the size of the apparatus to increase unfavorably.
In an image display apparatus of the type in which an image of an image display device is relayed, as shown in
FIG. 48
, a relay optical system is needed in addition to an ocular optical system. Consequently, the entire optical system increases in both size and weight, and an amount by which the optical system projects from the observer's face or head also increases. Therefore, this type of image display apparatus is not suitable for use as a head- or face-mounted image display apparatus.
In the optical system that focuses parallel rays to form an intermediate image, and also in the optical system that projects an intermediate image into an observer's eyeball, only the parabolic mirror has power. Therefore, exceedingly large aberrations are produced in these optical systems.
When a concave mirror alone is used as an ocular optical system as shown in
FIG. 49
, even if the concave mirror is a toric surface as in the case of
FIG. 49
, the ocular optical system produces exceedingly large aberrations, causing the image quality to be degraded. Accordingly, it is necessary to use a transfer optical element
26
such as a fiber plate for correcting field curvature produced by the ocular optical system. However, comatic and other aberrations cannot satisfactorily be corrected even if the transfer optical element
26
and the toric reflecting surface
27
are used.
SUMMARY OF THE INVENTION
In view of the above-described problems of the conventional techniques, an object of the present invention is to provide an optical system of the type having at least three surfaces and in which a space formed by the at least three surfaces is filled with a medium having a refractive index larger than 1. The optical system according to the present invention is compact, lightweight and satisfactorily corrected for aberrations and may be suitably used as an imaging optical system or an ocular optical system and also for an image display apparatus which uses the ocular optical system.
To attain the above-described object, the present invention provides an optical system having an optical member and a diffraction optical element which is adjacent to the optical member. The optical member has at least three adjacent optical surfaces which are decentered with respect to each other. At least one of the three optical surfaces is a curved surface, and the three optical surfaces are arranged such that at least two reflections take place between them.
In addition, the present invention provides an image display apparatus having an image display device for displaying an image, an ocular optical system for leading the image displayed by the image display device to an observer's eyeball without forming an intermediate real image, and a device for retaining both the image display device and the ocular optical system on an observer's head or face. The ocular optical system includes an optical member having a first surface disposed to face the image display device, a second surface disposed on an observer's visual axis to face an observer's pupil at a tilt to the observer's visual axis, and a third surface disposed on the observer's visual axis between the second surface and the observer's pupil. The second surface is a reflecting surface. Light rays emitted from the image display device enter the optical member through the first surface, and the light rays are reflected by the second surface and led to the observer's eyeball through the third surface. In addition, a correction optical element is disposed at a position between the image display device and the observer's pupil. The correction optical element produces aberrations which are opposite in sign to aberrations produced by the transmitting surfaces of the optical member.
In addition, the present invention provides an image display apparatus having an image display device for displaying an image, an ocular optical system for leading the image displayed by the image display device to an observer's eyeball without forming an intermediate real image, and a device for retaining both the image display device and the ocular optical system on an observer's head or face. A light-blocking member is provided between the ocular optical system and the observer's eyeball.
In addition, the present invention provides an image display apparatus having an image display device for displaying an image, an ocular optical system for leading the image displayed by the image display device to an observer's eyeball without forming an intermediate real image, and a device for retaining both the image display device and the ocular optical system on an observer's head or face. A numerical aperture limiting member is disposed between the image display device and the ocular optical system to limit the numerical aperture of a bundle of light rays emitted from the image display device.
In addition, the present invention provides an image display apparatus having an image display device for displaying an image, an ocular optical system for leading the image displayed by the image display device to an observer's eyeball without forming an intermediate real image, and a device for retaining both the image display device and the ocular optical system on an observer's head or face. The image display device is a transmission type liquid crystal display d
Nakaoka Masaya
Togino Takayoshi
Mack Ricky
Olympus Optical Co,. Ltd.
Pillsbury Madison & Sutro LLP
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