Optical: systems and elements – Single channel simultaneously to or from plural channels – By partial reflection at beam splitting or combining surface
Reexamination Certificate
1999-12-13
2001-08-21
Ben, Loha (Department: 2873)
Optical: systems and elements
Single channel simultaneously to or from plural channels
By partial reflection at beam splitting or combining surface
C359S633000, C359S627000, C359S730000, C396S352000
Reexamination Certificate
active
06278556
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a prism optical system, and more specifically to a prism optical system having power, which comprises a decentered reflecting surface.
2. Background of Related Art
Among reflecting decentered optical systems of compact size known in the art, there is a one-dimensional light receiving lens system comprising a cylindrical reflecting surface as disclosed in JP-A-59-84201. However, this system can never take two-dimensional images. JP-A-62-144127 describes a system using an identical surface for two reflections, thereby reducing spherical aberration produced in the system described in JP-A-59-84201.
JP-A-62-205547 shows the use of an aspheric form of reflecting surface, but fails to refer exactly to the configuration of the reflecting surface. U.S. Pat. Nos. 3,810,221 and 3,836,931 disclose examples of a lens system comprising a rotationally symmetric aspheric mirror and a surface having only one symmetric plane, which is used for a finder optical system for reflex cameras. Note that the surface having only one symmetric plane is used for the purpose of correcting the tilt of the image to be observed.
JP-A-1-257834 (corresponding to U.S. Pat. No. 5,274,406) discloses an example of using a surface having only one symmetric plane for a reflector to make correction for image distortion in a rear projection type television, wherein a projection lens system is used for projection onto a screen, and the surface having only one symmetric plane is used for correcting image distortion.
JP-A-7-333551 discloses an example of a back-surface type of decentered optical system which comprises an anamorphic surface and a toric surface, and is designed as a viewing optical system. However, this system is still less than satisfactory in terms of correction of aberrations inclusive of image distortion, and so cannot be applied to a phototaking optical system.
However, none of these prior systems is a system having only one symmetric plane and using a back-surface mirror for a turn-back optical path.
Also, all these prior systems are directed to a sort of rotationally symmetric optical system wherein a refracting lens forming part of the optical system is constructed of a plane rotationally symmetric with respect to an optical axis.
One problem with such prior systems is that unless a formed real image is well corrected for aberrations and distortion, an image pattern or the like will be distorted, ending up with a failure in recording an exact form thereof. Another problem is that since the optical path is in a linear form, the optical system becomes long in the optical axis direction, resulting in an increase in phototaking device size.
SUMMARY OF THE INVENTION
In view of such problems associated with the prior art, it is an object of the present invention to provide a prism optical system which has an image-forming action, and can form a clear yet substantially undistorted image even at a wide field angle.
Another object of the present invention is to provide a prism optical system which can act as both an inverting prism and an ocular optical system, and can form a clear yet substantially undistorted image even at a wide field angle.
According to one aspect of the present invention, the aforesaid objects are achievable by the provision of a prism optical system comprising an aperture and having an action on erecting an image formed by an objective, characterized by comprising a reflecting surface for erecting said image,
said reflecting surface being constructed of a curved surface having a power, and
said curved surface being of an irrotationally symmetric surface shape having no rotationally symmetric axis both within and outside said curved surface so that decentering aberration produced by reflection of light at said curved surface can be corrected.
Preferably in this aspect, the irrotationally symmetric surface shape comprises only one symmetry plane, and a three-dimensional surface configuration defined by
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(
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where C
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According to the first aspect of the present invention, there is also provided a prism optical system comprising a reflecting surface for image inversion, characterized in that:
said reflecting surface is located in said prism optical system such that incident and exit optical paths for a beam or pencil of light differ to produce irrotationally symmetric decentering aberration, and at least one surface of said reflecting surface, another reflecting surface, and a transmitting surface is of an irrotationally symmetric shape that can make correction for said irrotationally symmetric decentering aberration.
Preferably in this case, the prism optical system comprises at least four reflecting surfaces, and at least two transmitting surfaces.
According to the first aspect of the present invention, there is further provided a prism optical system comprising an aperture and a roof prism constructed of a curved surface, characterized in that:
said curved surface comprises at least one surface of an irrotationally symmetric shape having no rotationally symmetric axis both within and outside said surface.
According to the first aspect of the present invention, there is still further provided a prism optical system comprising an aperture and a Porro prism constructed of a curved surface, characterized in that:
said curved surface comprises at least one surface of an irrotationally symmetric shape having no rotationally symmetric axis both within and outside said surface.
According to another aspect of the present invention, the aforesaid objects are achievable by the provision of a prism optical system for image inversion, characterized in that:
said inverting prism optical system comprises at least two prisms, at least one of which is constructed of a curved surface having at least two surfaces of a rotationally asymmetric shape, each having no rotationally symmetric axis both within and outside the surface, at least one of said at least two rotationally asymmetric surfaces acting as a reflecting surface having a reflecting action and said rotationally asymmetric shape making correction for rotationally asymmetric aberration produced due to decentering, and
said inverting prism optical system has a finite focal length so as to act as an ocular optical system.
In this case, the prism optical system may be designed to have substantially the same optical path as a Schmidt prism, and may be designed such that one of the two prisms has a substantially intersecting optical path and comprises a roof surface, whereas the other prism has an optical path that does not intersect. Alternatively, the prism optical system may be designed such that a prism having a substantially intersecting optical path and comprising a roof surface is located on an objective side of said system, and a prism having an optical path that does not intersect is located on a viewer's pupil side of said system.
According to the second aspect of the present invention, there is also provided a prism optical system for image inversion, characterized in that:
said inverting prism optical system comprises at least two prisms, at least one of which is constructed of a curved surface having at least two sur
Ben Loha
Olympus Optical Co,. Ltd.
Pillsbury & Winthrop LLP
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