Real-image finder optical system and apparatus using the same
First Claim
1. In a real-image finder optical system comprising:
- an objective optical system for a finder;
an image-inverting optical system for erecting an object image formed by said objective optical system; and
an ocular optical system;
wherein an optical path for the finder is separate from an optical path for photography;
the improvement wherein said objective optical system has a plurality of lens units, wherein when zooming from a wide-angle end to a telephoto end is performed, a spacing between said plurality of lens units is changed, andsaid image-inverting optical system has a plurality of reflecting surfaces, wherein, of said plurality of reflecting surfaces, at least one reflecting surface that is placed closer to said ocular optical system than said object image is formed from a curved reflecting surface having a power, said image-inverting optical system having a rotationally asymmetric surface that corrects rotationally asymmetric decentration aberrations produced by said curved reflecting surface.
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Accused Products
Abstract
A real-image finder optical system having an objective optical system, an image-inverting optical system, and an ocular optical system, wherein a power is given to a reflecting surface of the image-inverting optical system that is closer to the observer side than an intermediate image, thereby achieving an increase in the finder magnification. The objective optical system has a plurality of lens units. When zooming from the wide-angle end to the telephoto end is performed, the spacing between the plurality of lens units is changed. The image-inverting optical system has a plurality of reflecting surfaces. Of the reflecting surfaces, at least one reflecting surface closer to the ocular optical system than the object image is formed from a curved reflecting surface that gives a power to a light beam. The image-inverting optical system has a rotationally asymmetric surface that corrects rotationally asymmetric decentration aberrations produced by the curved reflecting surface.
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Citations
26 Claims
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1. In a real-image finder optical system comprising:
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an objective optical system for a finder; an image-inverting optical system for erecting an object image formed by said objective optical system; and an ocular optical system; wherein an optical path for the finder is separate from an optical path for photography; the improvement wherein said objective optical system has a plurality of lens units, wherein when zooming from a wide-angle end to a telephoto end is performed, a spacing between said plurality of lens units is changed, and said image-inverting optical system has a plurality of reflecting surfaces, wherein, of said plurality of reflecting surfaces, at least one reflecting surface that is placed closer to said ocular optical system than said object image is formed from a curved reflecting surface having a power, said image-inverting optical system having a rotationally asymmetric surface that corrects rotationally asymmetric decentration aberrations produced by said curved reflecting surface. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26)
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2. In a real-image finder optical system comprising:
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an objective optical system for a finder; an image-inverting optical system for erecting an object image formed by said objective optical system; and an ocular optical system; wherein an optical path for the finder is separate from an optical path for photography; the improvement wherein said image-inverting optical system has a plurality of reflecting surface, wherein, of said plurality of reflecting surfaces, at least one reflecting surface that is placed closer to said ocular optical system than said object image is formed from a curved reflecting surface having a power, said image-inverting optical system having a rotationally asymmetric surface that corrects rotationally asymmetric decentration aberrations produced by said curved reflecting surface, and wherein the following conditions (3-1) and (3-2) are satisfied;
space="preserve" listing-type="equation">0<
|PXn/PX|<
5 (3-1)
space="preserve" listing-type="equation">0<
|PYn/PY|<
5 (3-2)where, when a light ray passing through a center of an object point and passing through a center of a stop or aperture of the objective optical system to reach a center of an intermediate image plane and further passing through the ocular optical system to enter a center of a pupil is defined as an axial principal ray, and axes are defined such that an axis defined by a straight line along which the axial principal ray travels until it intersects said rotationally asymmetric surface is defined as a Z-axis, and an axis perpendicularly intersecting said Z-axis in a decentration plane of said rotationally asymmetric surface is defined as a Y-axis, and further that an axis perpendicularly intersecting said Z-axis and also perpendicularly intersecting said Y-axis is defined as an X-axis, PXn and PYn are powers in X- and Y-axis directions of said reflecting surface having a power near the axial principal ray, and PX and PY are powers in the X- and Y-axis directions of the entire ocular optical system, which are determined such that parallel rays having a small height Δ
relative to the X- and Y-axis directions, respectively, are passed along the axial principal ray from the intermediate image toward an observer side, and a sine of a tilt angle with respect to the axial principal ray of each of said rays when emanating from a surface closest to the observer side is divided by said height Δ
, and resulting values are defined as the powers PX and PY, respectively.
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Specification