Optics: image projectors – Reflector
Reexamination Certificate
2001-10-04
2002-10-15
Dowling, William (Department: 2851)
Optics: image projectors
Reflector
C353S099000, C353S122000, C353S030000, C359S637000, C359S629000, C359S633000, C359S631000
Reexamination Certificate
active
06464361
ABSTRACT:
This application claims benefit of Japanese Application No. 2000-306013 filed in Japan on Oct. 5, 2000, the contents of which are incorporated by this reference.
BACKGROUND OF THE INVENTION
The present invention relates to image display apparatus having a three-dimensionally decentered optical path. More particularly, the present invention relates to a head- or face-mounted image display apparatus that can be retained on an observer's head or face.
Image display apparatus designed to observe the image of a single image display device with two eyes have heretofore been known in Japanese Patent Application Unexamined Publication Nos. [hereinafter referred to as “JP(A)”] Hei 6-110013, Hei 7-287185, Hei 9-61748, Hei 9-181998, and Hei 9-181999, Published Japanese Translation of PCT International Publication No. Hei 10-504115, etc.
Among them, the image display apparatus of JP(A) Hei 6-110013 splits and folds light rays by using a prism in the shape of an isosceles triangular prism and a mirror. Therefore, correction of various aberrations is performed by using a lens placed in front of the pupil. This makes it difficult to correct aberrations, and at the same time, causes the apparatus to become large in size.
JP(A) Hei 7-287185 uses a plurality of mirrors and performs image formation with a single convex lens. Therefore, it is very difficult to perform assembly adjustment. In addition, appropriate performance cannot be attained. Although the image display device is placed three dimensionally, left and right optical systems are in bilateral symmetry with each other. Therefore, left and right images are in oppositely rotated relation to each other.
In JP(A) Hei 9-61748, display light from an LCD (Liquid Crystal Display) is split by using a half-mirror so as to be observed with two eyes. Because the display light is distributed to the left and right eyeballs, the image for observation is weak in light intensity and hence dark.
JP(A) Hei 9-181998 and Hei 9-181999 have an arrangement using only one reflecting surface and are not sufficiently corrected for decentration aberrations. Therefore, these image display apparatus cannot be applied to recent compact and high-definition image display devices. Further, the field angle is very narrow.
The image display apparatus of Published Japanese Translation of PCT International Publication No. Hei 10-504115 has a very large number of components and requires a very complicated assembling operation. Further, in this case, the image for observation is weak in light intensity and hence dark because a half-mirror is used.
In addition, with the recent achievement of small-sized image display devices, it has also become necessary to reduce the focal length of the viewing optical system. Further, in order to ensure a wide field angle, the focal length needs to be reduced. Consequently, it is difficult to ensure the required back focus, and it is impossible to increase the optical path length within the prism. As a result, it is impossible to increase the number of reflecting surfaces and hence impossible to correct decentration aberrations satisfactorily.
Further, recent image display devices are becoming higher in definition year by year.
SUMMARY OF THE INVENTION
The present invention was made in view of the above-described problems with the prior art. An object of the present invention is to provide a wide-field angle and low-cost image display apparatus, e.g. a head-mounted image display apparatus, in which an image from a single image display device is led to two eyes without using a half-mirror, thereby allowing observation of a bright image, and in which at least four reflecting surfaces having curved surfaces are used to form an optical system, thereby facilitating correction of various aberrations to obtain compatibility with recent compact and high-definition image display devices. Another object of the present invention is to further widen the field angle of an image display apparatus such as that proposed previously in Japanese Patent Application No. 2000-48750.
An image display apparatus having a three-dimensionally decentered optical path according to the present invention provided to attain the above-described objects includes an image display device for forming an image for observation on an image display area. The image display apparatus further includes a viewing optical system for leading the image formed by the image display device to a pupil corresponding to a position where an eyeball of an observer is to be placed.
The image display device is a single image display device having a plurality of pixels juxtaposed on a single substrate.
Each pixel located at least in the central portion of the single image display device is arranged to emit an image light beam at such an exit angle that the light beam can be led to the left and right eyes of the observer.
The viewing optical system includes, at least, a left ocular part for leading the light beam to the left eye of the observer; a right ocular part for leading the light beam to the right eye of the observer; and an optical path distributing part for distributing the image light beam emitted from the image display device at the above-described exit angle to the left and right ocular parts.
The left ocular part has at least two reflecting surfaces. At least one of the at least two reflecting surfaces is formed from a rotationally asymmetric curved reflecting surface having the function of correcting decentration aberrations.
The right ocular part has at least two reflecting surfaces. At least one of, the at least two reflecting surfaces is formed from a rotationally asymmetric curved reflecting surface having the function of correcting decentration aberrations.
The left and right ocular parts are arranged so that the plane of a decentered optical path of an axial principal ray formed by the at least two reflecting surfaces of the left ocular part (the plane being a YZ-plane, which is the vertical direction of the observer) and the plane of a decentered optical path of an axial principal ray formed by the at least two reflecting surfaces of the right ocular part (the plane being a YZ-plane, which is the vertical direction of the observer) are approximately parallel to each other (YZ-plane).
The optical path distributing part has optical surfaces arranged in bilaterally rotational symmetry to form left and right optical paths that are not in plane symmetry with each other but in 180-degree rotational symmetry with respect to only a normal line passing through the center of the image display device. The optical path distributing part has at least two pairs of reflecting surfaces for the left and right optical paths as the optical surfaces.
The reasons for adopting the above-described arrangement in the present invention, together with the function thereof, will be described below.
In general, the distance between the human pupils is said to be approximately 64 millimeters on the average and differs among individuals. Therefore, it is preferable that the pupil of the viewing optical system for observation with both eyes should be set long sideways in advance with a view to absorbing the difference in interpupillary distance among individuals in the viewing optical system. In other words, it is preferable that the pupil of the viewing optical system should be an elliptical (or rectangular, etc.) pupil that is long in the horizontal direction of the observer.
In that case, if the longitudinal direction of the pupil and the decentration direction of the ocular part are set in the same direction, it becomes unavoidably necessary to decenter the ocular part to a considerable extent in order to ensure the required effective area. Consequently, the amount of decentration aberrations produced becomes extremely large. To minimize the amount of decentration, the overall size of the optical system has to be increased. In addition, because the human interpupillary distance restricts the extent to which the size of the optical system can be made large sideways, it is impossible to achi
Nagata Tetsuo
Togino Takayoshi
Dowling William
Olympus Optical Co,. Ltd.
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