Optical: systems and elements – Single channel simultaneously to or from plural channels – By partial reflection at beam splitting or combining surface
Reexamination Certificate
1999-06-18
2001-10-30
Epps, Georgia (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
Reexamination Certificate
active
06310728
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image viewing apparatus and, more particularly, to the image viewing apparatus suitably applicable to an image viewing system such as a viewfinder of a camera, a so-called head-mounted display, a goggle type display, or the like and to an image pickup device such as a camera.
2. Related Background Art
Downsizing of the whole apparatus has been demanded for image viewing apparatuses such as the head-mounted displays (HMDs), goggle type displays, etc. A variety of optical systems for meeting this demand have been suggested heretofore.
Applicant of the present application suggested in Japanese Laid-open Patent Application No. 7-333551, No. 8-50256, No. 8-160340, and No. 8-179238 the image viewing apparatus using an LCD (liquid crystal display) as display means for displaying image information and a small prism as a viewing optical system while achieving the downsizing of the whole apparatus.
The above applications describe that light emitted from the LCD displaying the image information is made incident into the small prism and then is guided via a refracting surface and a total reflection surface having curvature, formed in the small prism, and then via a reflecting surface out of the small prism toward a viewer. This causes an enlarged virtual image of the image information displayed on the display means (LCD) to be formed ahead of the viewer, whereby the viewer can view the virtual image.
In an image viewing apparatus such as an HMD etc., it is a significant challenge to decrease the overall size and weight of apparatus, because the apparatus is mounted on the head part of viewer. Another important challenge is to broaden the viewing angle in order to provide the viewing of the image information displayed on the display means with strong appeal.
SUMMARY OF THE INVENTION
An object of the present invention is, therefore, to provide an image viewing apparatus that permits the viewing of image information in a wide viewing field and with good image quality while achieving the downsizing of the whole apparatus, by properly setting the structure of an optical system for guiding light from the display means to the eye of the viewer, e.g. an optical element or the like comprised of a prism body having the refracting action, on the occasion of the image information viewing the image information displayed on the display means, such as a liquid crystal display or the like, in the wide viewing field.
In order to accomplish the above object, the image viewing apparatus of the present invention is characterized by comprising the following constituent elements:
a stop for limiting light from an original image; and
a viewing optical system for guiding the light from the original image, limited by the stop, to the eye of a viewer, said viewing optical system having an optical element of a transparent optical material, wherein said optical element comprises an entrance surface into which the light from said original image is incident, a reflecting surface for reflecting the light incident into the entrance surface, and an exit surface from which the light reflected by the reflecting surface is emergent and wherein at least one of the entrance surface, reflecting surface, and exit surface is a curved surface, the curved surface being a rotationally asymmetric, aspherical surface.
When a reference optical axis is defined by a ray emitted from the center of the original image and passing the center of the pupil of the viewer via the viewing optical system, the image viewing apparatus of the present invention further satisfies at least one of the following conditions (a) to (d):
3.5
<Epy/Ly
(a)
where Ly is a width of the original image in an extending direction of an intersecting line between a plane including the reference optical axis, and the original image, and Epy is a distance from an intersecting point on the viewer side, of two rays emitted from two edges of the original image in the extending direction of the intersecting line, passing edges of an aperture of the stop corresponding to the respective edges of the image, and passing through the viewing optical system, to the optical element;
1<
Epx/Epy
(b)
where Epy is a distance to the optical element from an intersecting point on the viewer side, of two rays emitted from two edges of the original image in an extending direction of an intersecting line between a plane including the reference optical axis, and the original image, passing edges of an aperture of the stop corresponding to the respective edges of the image, and passing through the viewing optical system, and Epx is a distance to the optical element from an intersecting point on the viewer side, of two rays emitted from two edges of the original image in a direction perpendicular to the intersecting line, passing edges of the aperture of the stop corresponding to the respective edges of the image, and passing through the viewing optical system;
23°<&agr;h (C)
where &agr;h is an angle at an intersection on the viewer side between two rays emitted from two edges of the original image in a direction perpendicular to an intersecting line between a plane including the reference optical axis, and the original image, passing edges of an aperture of the stop corresponding to the respective edges of the image, and passing through the viewing optical system;
D
(tan
2
&agr;y
)/
Ly
2
<1/1000 (d)
where
&agr;
y
=(&agr;
u−&agr;b
)/2,
where Ly is a width of the original image in an extending direction of an intersecting line between a plane including the reference optical axis, and the original image, &agr;u is an angle at an intersection on the viewer side between a ray emitted from one edge of the original image in the extending direction of said intersecting line, passing an edge of the aperture of the stop corresponding thereto, and passing through the viewing optical system, and the reference optical axis, &agr;b is an angle at an intersection on the viewer side between a ray emitted from another edge of the original image in the extending direction of the intersecting line and passing an edge of the aperture of the stop corresponding thereto, and the reference optical axis, and D is an air-reduced amount between the stop and the original image.
In another aspect, the image viewing apparatus of the present invention is also characterized by comprising the following:
a liquid crystal display device, the liquid crystal display device comprising a liquid crystal element for changing a polarization property of light incident thereto and emitting the incident light with the changed polarization property, a light source for illuminating the liquid crystal element, and a viewing angle improving element for substantially equalizing polarization properties of the liquid crystal element varying according to angles of incidence of the illumination light; and
a viewing optical system for guiding light from the liquid crystal display device to the eye of a viewer, the viewing optical system comprising an optical element of a transparent optical material, wherein the optical element comprises an entrance surface into which the light from the liquid crystal display device is incident, a reflecting surface for reflecting the light incident into the entrance surface, and an exit surface from which the light reflected by the reflecting surface is emergent and wherein at least one of the entrance surface, reflecting surface, and exit surface is a curved surface, the curved surface being a rotationally asymmetric, aspherical surface.
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Kuramochi Junko
Okuyama Atsushi
Canon Kabushiki Kaisha
Epps Georgia
Fitzpatrick ,Cella, Harper & Scinto
Spector David N.
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