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
2001-09-18
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
C359S630000, C359S637000, C345S008000
Reexamination Certificate
active
06292301
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical system and, more particularly, to an optical system suitably applicable to use in image viewing apparatuses, such as viewfinders of cameras, so-called head-mounted displays, or the like, and in image pickup apparatuses, such as camera or the like.
2. Related Background Art
For the head-mounted display etc., various optical systems have been devised heretofore for making compact the overall apparatus.
For example, Japanese Laid-open Patent Application No. 58-78116 discloses an optical apparatus for a viewer to view an object image on a primary image plane, obtained by a photographing optical system, through an optical element of a prism shape having a concave, spherical reflecting surface inclined with respect to the eye of the viewer.
Since in this conventional example the reflecting surface is an inclined, spherical surface, it is difficult to correct optical aberrations such as astigmatism etc. occurring thereat into good order. The above Japanese application describes the necessity for addition of a new lens system for improving the aberrations.
Japanese Laid-open Patent Application No. 5-303055 (the Japanese counterpart of U.S. Pat. No. 5,594,588) discloses an apparatus additionally including such a lens system (relay lens system). The addition of such a relay lens system, however, involves the disadvantages of increasing the total length of the optical system and degrading the compactification of the optical system.
In order to improve the compactification and the aberrations of the optical system, Japanese Laid- open Patent Applications No. 5-303054, No. 5-303056 (the Japanese counterpart of USP No. 5,594,588), and No. 5-323229 disclose optical systems in which the reflecting surface is one reflecting surface comprised of a general, rotationally asymmetric surface having higher-order aspherical terms, a paraboloid of revolution or an ellipsoid of revolution according to a conical function defined by a conical coefficient, or a toric, aspherical surface (or an anamorphic, aspherical surface) represented by different aspherical functions on the orthogonal coordinate axes respectively and is inclined with respect to the optical axis of the viewer's eye.
The optical systems of the structures having the reflecting surface of such one aspherical surface, however, had the drawback of incapability of sufficiently correcting all of deformation of image (distortion), curvature of field, and difference between foci in orthogonal directions (astigmatism).
In the case of the so-called decentering optical systems with the reflecting surface thus inclined, optical performance will vary greatly if focus adjustment (diopter adjustment) of the optical system is effected by moving the optical system. Therefore, a desired method for the focus adjustment is one for adjusting the focus by moving the focal plane of the optical system (an image display element or an image pickup element). For that, it is desirable to make the optical system telecentric with respect to the focal plane.
Let us check the conventional examples described above from these viewpoints. In Japanese Laid-open Patent Application No. 5-303054 correction is made for astigmatism and distortion but curvature of field still remains without being corrected.
In Japanese Laid-open Patent Application No. 5-323229, correction is made for curvature of field, astigmatism, and distortion, but angles of rays are inclined largely with respect to the focal plane. If a display element or an image pickup element such as a liquid crystal panel, a CCD, or the like is placed on the focal plane there will arise a drawback of considerable degradation of performance due to angular dependence of characteristics of these elements.
In the optical systems suggested in these applications, though distortion is corrected, deformation of the image is of a level in which is can be discriminated at a glance and thus the correction is not sufficient.
As described above, the structures with the reflecting surface of one aspherical surface had the drawback of incapability of sufficiently correcting all the aberrations.
Further, Japanese Laid-open Patent Application No. 3-180810 discloses an optical system in which distortion of the image plane is corrected by an aspherical surface having cross terms (xy etc.) of the orthogonal coordinate system (x, y, z) while the visual point of the viewer is moved away from the optical system to increase FNo to the optical system and increase the depth of focus of the optical system.
This optical system, however, is based on the method for viewing the image from the distant visual point and, therefore, cannot be constructed in a wide angle or large screen configuration. Although the optical system is constructed in the telephoto type by combining a convex mirror with a concave mirror, the overall size is large. Therefore, the optical system had the drawback of incapability of being constructed in compact structure.
SUMMARY OF THE INVENTION
An object of the present invention is, therefore, to provide an image viewing optical system that is corrected well for various aberrations and has a high angle of view while being constructed in very simple structure and that permits good viewing of information of an image displayed on a display surface of image display means when used as a viewing system.
For accomplishing the above object, optical systems of various aspects according to the present invention are characterized by comprising the following in an optical path between a focal plane and a stop:
a first optical acting surface; and
a second optical acting surface,
wherein, in an optical path traced from said focal plane to said stop, light emitted from said focal plane is reflected by said second optical acting surface and thereafter reflected by said first optical acting surface to reach said stop.
Here, a ray connecting a center of said focal plane with a center of said stop via said first optical acting surface and second optical acting surface is defined as a reference axis ray, said center of the stop is defined as an origin, an axis including a line segment extending from said origin, out of said reference axis ray traced from the origin to the center of said focal plane, is defined as a Z-axis (a positive direction of which is a direction extending from said origin to said optical system), and an axis perpendicular to said Z-axis in a plane including said reference axis ray is defined as a Y-axis (a positive direction of which is a direction including a component of a direction in which said reference axis ray traced from said origin to the center of said focal plane is bent by said first optical acting surface).
In one aspect of the present invention, the second optical acting surface is of a rotationally asymmetric, aspherical shape only one symmetry plane of which is a plane including said reference axis ray, and satisfies at least one of the following conditions (A), (B), and (C).
1.0≦
r
2
Lui/r
2
Lvi≦
12.0 (A)
where an azimuth direction in which an absolute value of a local curvature radius is maximum, out of local curvature radii in all azimuth directions in a tangent plane around a normal to the tangent plane on an arbitrary point i in a ray effective range of said second optical acting surface, is defined as a ui axis, an azimuth direction normal to the ui axis is defined as a vi axis, a local curvature radius in the direction of said ui axis at said arbitrary point i is defined as r2Lui, and a local curvature radius in the direction of said vi axis as r2Lvi.
(B) When an angle of the ui axis with respect to said symmetry plane is &thgr;2i, absolute values of the &thgr;2i increase monotonically from the near side to the far side with respect to said symmetry plane at arbitrary points on an intersecting line between the second optical acting surface and a plane being normal to said symmetry plane and including said Z-axis or being parallel to said Z-axis.
(C) The &thgr;2i satisfies the followi
Kuramochi Junko
Okuyama Atsushi
Canon Kabushiki Kaisha
Epps Georgia
Fitzpatrick ,Cella, Harper & Scinto
Spector David N.
LandOfFree
Optical viewing system for use in head-mounted display does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Optical viewing system for use in head-mounted display, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical viewing system for use in head-mounted display will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2496551