Computer graphics processing and selective visual display system – Image superposition by optical means
Reexamination Certificate
1999-03-26
2002-01-29
Saras, Steven (Department: 2675)
Computer graphics processing and selective visual display system
Image superposition by optical means
C345S008000, C359S631000, C359S630000
Reexamination Certificate
active
06342871
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to image display apparatus and, more particularly, to a head- or face-mounted image display apparatus that can be retained on the observer's head or face.
In recent years, image display apparatus, particularly head- or face-mounted image display apparatus, have been developed actively for the purpose of enabling the user to enjoy a wide-screen image personally.
There has heretofore been known a head-mounted image display apparatus in which an image displayed on an image display device, e.g. a liquid crystal display (LCD) or a CRT, is once formed in the air by a relay optical system, and then the image is led to an observer's eyeball through an ocular optical system including a semitransparent mirror and a concave mirror [for example, see Japanese Patent Application Unexamined Publication Numbers (hereinafter referred to as “JP(A)”) 3-39925 and 7-151993]. There has also been known a head-mounted image display apparatus in which an image displayed on an image display device is once formed in the air by an optical system including a semitransparent mirror and a concave mirror, and then the image is led to an observer's eyeball through an ordinary ocular optical system [see Published Japanese Translation of PCT International Publication No. 10-504115].
Incidentally, the above-described image display apparatus, which has an optical system wherein a first image is formed by using a relay optical system and the first image is led to an observer's eyeball through an ocular optical system including a semitransparent mirror and a concave mirror, is superior to image display apparatus having no relay optical system in the following points:
{circle around (1)} Aberrations produced in the ocular optical system can be corrected by the relay optical system.
{circle around (2)} An image of a small LCD is formed as an enlarged image on an intermediate image plane by the relay optical system. This is equivalent to using a large LCD panel in combination with an ocular optical system including a semitransparent mirror and a concave mirror. Thus, a wide viewing field angle can be obtained even if a small LCD is used. To attain a wide viewing field angle with an image display apparatus using only an ocular optical system including a semitransparent mirror and a concave mirror, without using a relay optical system, it is necessary to shorten the focal length of the concave mirror to thereby increase the magnification. However, if the power of the concave mirror is made excessively strong, aberrations are aggravated.
Incidentally, JP(A) 7-333551 and 8-234137 propose a technique whereby the optical system of an image display apparatus can be made compact in size and light in weight while maintaining high optical performance (brightness, field angle, resolution, etc.) by using a decentered optical system.
SUMMARY OF THE INVENTION
In view of the above-described circumstances of the prior art, an object of the present invention is to provide an image display apparatus including a relay optical system that forms an intermediate image of an image display device, and an ocular optical system having a semitransparent mirror and a concave mirror, wherein a decentered optical system is used in the relay optical system to fold an optical path, thereby making the optical system even more compact, and further the intermediate image magnifying power of the relay optical system is increased to thereby realize a wide field angle while keeping the power of the concave mirror part of the ocular optical system at a small value.
To attain the above-described object, the present invention provides an image display apparatus having an image display device and a viewing optical system that leads an image formed by the image display device to the position of an observer's eyeball.
The viewing optical system has at least the following three surfaces. That is, the viewing optical system has an image source-side reflecting surface having a decentered curved surface configuration that gives a power to a light beam emitted from the image display device when the light beam is reflected by the decentered curved surface. The image source-side reflecting surface also has a rotationally asymmetric surface configuration that corrects decentration aberrations produced by reflection at the decentered curved surface. The viewing optical system further has a semitransparent reflecting surface with half-mirror coating that transmits or reflects the light beam reflected from the image source-side reflecting surface, and a concave reflecting surface that forms a folded optical path between the concave reflecting surface and the semitransparent reflecting surface. The concave reflecting surface has a concave surface directed toward the semitransparent reflecting surface. An enlarged intermediate image of the image displayed on the image display device is formed between the image source-side reflecting surface and the semitransparent reflecting surface.
In this case, the viewing optical system may have at least two surfaces, which are a first surface and a second surface that face each other across a medium having a refractive index larger than 1. The first surface is an entrance surface through which a light beam emitted from the image display device enters the medium. The second surface serves as the image source-side reflecting surface. The first and second surfaces are placed between the intermediate image and the image display device.
The viewing optical system may have a third surface that faces the first and second surfaces across the medium whose refractive index is larger than 1. The third surface is formed from at least a reflecting surface having a rotationally asymmetric curved surface configuration that gives a power to a light beam when reflecting it and corrects decentration aberrations. Moreover, the third surface is placed in an optical path between the first surface and the semitransparent reflecting surface.
The reasons for adopting the above-described arrangements in the present invention, together with the functions thereof, will be described below.
An image display apparatus according to the present invention has an image display device and a viewing optical system that leads an image formed by the image display device to the position of an observer's eyeball. The viewing optical system has at least the following three surfaces. That is, the viewing optical system has an image source-side reflecting surface having a decentered curved surface configuration that gives a power to a light beam emitted from the image display device when the light beam is reflected by the decentered curved surface. The image source-side reflecting surface also has a rotationally asymmetric surface configuration that corrects decentration aberrations produced by reflection at the decentered curved surface. The viewing optical system further has a semitransparent reflecting surface with half-mirror coating that transmits or reflects the light beam reflected by the image source-side reflecting surface, and a concave reflecting surface that forms a folded optical path between the concave reflecting surface and the semitransparent reflecting surface. The concave reflecting surface has a concave surface directed toward the semitransparent reflecting surface. The viewing optical system forms an enlarged intermediate image of the image of the image display device between the image source-side reflecting surface and the semitransparent reflecting surface. Thus, a part of the viewing optical system that acts as a relay optical system has at least the image source-side reflecting surface. Therefore, the optical path can be folded, and the relay optical system can be made more compact than the conventional relay optical system using an axially symmetric optical system. Furthermore, because the relay optical system enlarges the intermediate image while correcting aberrations, it is possible to realize a wide field angle while keeping the power of the
Anyaso Uchendu O.
Olympus Optical Co,. Ltd.
Pillsbury & Winthrop
Saras Steven
LandOfFree
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