Optical: systems and elements – Single channel simultaneously to or from plural channels – By partial reflection at beam splitting or combining surface
Reissue Patent
2000-01-12
2002-04-23
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, C345S008000
Reissue Patent
active
RE037667
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an image display apparatus and, more particularly, to a portable head-mounted image display apparatus which can be retained on the user's head or face.
Helmet- and goggle-type head-mounted image display apparatuses, which are designed to be retained on the user's head or face, have heretofore been developed for the purpose of enabling the user to enjoy virtual reality or a wide-screen image by oneself.
Conventional head-mounted image display apparatuses, which are retained on the observer's head to project a virtual image in the air for observation, include one type in which a virtual image of a two-dimensional image display device, e.g., a liquid crystal display device, is formed by a combination of an optical path splitting device, e.g., a half-mirror or a beam splitter, and a concave ocular mirror, as disclosed, for example, in Japanese Patent Application Laid-Open (KOKAI) No. 03-191389 (1991). This type of head-mounted image display apparatus will be explained below with reference to the sectional view of
FIG. 18. A
beam splitter surface
4
is disposed in front of an eyeball position (eye point)
2
of an observer
1
so as to diagonally intersect the observer's visual axis
3
. A concave ocular mirror
5
is disposed below the beam splitter surface
4
so as to extend substantially parallel to the visual axis
3
, and a two-dimensional image display device
6
is disposed to face the concave ocular mirror
5
across the beam splitter surface
4
. A reference axis
8
which intersects the visual axis
3
at right angles is disposed to extend through the display center
7
of the two-dimensional image display device
6
and also through the center of the concave ocular mirror
5
. In this arrangement, light from the two-dimensional image display device
6
passes through the beam splitter surface
4
and is reflected by the concave ocular mirror
5
and then reflected by the beam splitter surface
4
to reach the eyeball position
2
. Thus, a virtual image of the image displayed on the two-dimensional image display device
6
is formed in the air by the action of the concave ocular mirror
5
, and the observer can view the displayed image. An outside, real world image can be viewed directly through the beam splitter surface
4
.
The conventional head-mounted image display apparatus arranged as described above suffers, however, from the problem that the substrate of the two-dimensional image display device
6
, e.g., a liquid crystal display device, is larger in size than the display screen thereof and hence interferes with the observer's head.
The problem of the conventional head-mounted image display apparatus will be explained below more specifically. The two-dimensional image display device
6
needs to raise the pixel density in the display screen thereof and to thereby increase the number of pixels per unit area in order to realize high-definition display. Therefore, it is necessary to achieve electrical connection by leading electric wirings for switching of the pixels to the outside of the display screen. When the number of pixels is 100,000, for example, the number of electrical connections required is 300. Therefore, the conventional practice is to fabricate, a switching circuit at the periphery of the display screen to thereby reduce the number of electrical connections, i.e., to ten-odd connections. For the above-described reason, the substrate of the two-dimensional display device needs an area for electrical connection of the pixels with switching elements in addition to the area for display and requires a substrate larger in size than the display screen.
Thus, the half-mirror or beam splitter surface
4
must be disposed at a predetermined distance from the observer's eye
2
in order to prevent the substrate of the two-dimensional image display device
6
from interfering with the observer's head. Accordingly, when it is intended to widen the field angle for observation, the size of the half-mirror or beam splitter surface
4
increases, resulting in an increase in the overall size of the apparatus. In the case of a head-mounted image display apparatus such as that shown in
FIG. 18
, the increase of the size and weight is a principal factor in making the user feel uncomfortable when wearing the display apparatus, which is a serious problem.
SUMMARY OF THE INVENTION
In view of the above-described problems of the background art, it is an object of the present invention to provide a head-mounted image display apparatus which is designed so that the field angle for observation can be widened without causing the substrate of a two-dimensional image display device to interfere with the observer's head and without increasing the overall size of the apparatus.
To attain the above-described object, the present invention first provides an image display apparatus including an image display device having a screen for displaying an image, a semitransparent reflecting surface disposed at an angle of inclination to an optical axis which is determined by a bundle of rays emitted from the display screen, the optical axis being defined as an image axis, and a magnifying reflecting mirror disposed so that an optical axis passing through the semitransparent reflecting surface goes to and returns from the magnifying reflecting mirror to form a turn-back optical path. In the image display apparatus, a straight line that connects an eye point and a position where the optical axis reflected by the magnifying reflecting mirror is reflected by the semitransparent reflecting surface is defined as a visual axis, and the semitransparent reflecting surface is disposed at a tilt to the image axis to change the angle of inclination of the semitransparent reflecting surface to the image axis so that the angle (&phgr;) made by intersection of the image axis extending from the image display device and the visual axis extending from the eye point is larger than 90° (&phgr;>90°).
Secondly, the present invention provides an image display apparatus including an image display device having a screen for displaying an image, a semitransparent reflecting surface disposed at an angle of inclination to an optical axis which is determined by a bundle of rays emitted from the display screen, the optical axis being defined as an image axis, and a magnifying reflecting mirror disposed so that an optical axis passing through the semitransparent reflecting surface goes to and returns from the magnifying reflecting mirror to form a turn-back optical path. In the image display apparatus, a straight line that connects an eye point and a position where the optical axis reflected by the magnifying reflecting mirror is reflected by the semitransparent reflecting surface is defined as a visual axis, and the magnifying reflecting mirror is disposed at a tilt to the image axis so that the angle (&phgr;) made by intersection of the image axis extending from the image display device and the visual axis extending from the eye point is larger than 90° (&phgr;>90°).
Thirdly, the present invention provides an image display apparatus including an image display device having a screen for displaying an image, a semitransparent reflecting surface disposed at an angle of inclination to an optical axis which is determined by a bundle of rays emitted from the display screen, the optical axis being defined as an image axis, and a magnifying reflecting mirror disposed so that an optical axis passing through the semitransparent reflecting surface goes to and returns from the magnifying reflecting mirror to form a turn-back optical path. In the image display apparatus, a straight line that connects an eye point and a position where the optical axis reflected by the magnifying reflecting mirror is reflected by the semitransparent reflecting surface is defined as a visual axis, and the magnifying reflecting mirror is shifted with respect to the image axis so that the angle (&phgr;) made by intersection of the image axis extend
Togino Takayoshi
Yasugaki Masato
Mack Ricky
Olympus Optical Co.
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