Finder for single-lens reflex type digital cameras
First Claim
Patent Images
1. A finder for single-lens reflex type digital cameras, comprising:
- a reflecting plane constructed and arranged to split a light beam from an imaging optical system of a camera into two beams directed toward an image sensor and a finder system;
an image-erecting prism system; and
an ocular optical system,wherein said image-erecting prism system and said ocular optical system are arranged along a traveling direction of light in said finder system placed after a position of the image formed by said imaging optical system,wherein said prism system comprises, in order along the traveling direction of the light in one prism block, an entrance surface, a first reflecting surface consisting of one plane face, a second reflecting surface of roof shape, and an exit surface,wherein said first reflecting surface folds an optical path toward an opposite side of said ocular optical system in reference to said exit surface, andwherein the optical path between said entrance surface and said first reflecting surface intersects, inside the prism block, an optical path between said second reflecting surface and said exit surface.
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Abstract
A finder for single-lens reflex type digital cameras includes a reflecting plane for splitting a light beam from an imaging optical system of a camera into two beams directed toward an image sensor and a finder system, a prism system for erecting an image, and an ocular optical system. The prism system has an entrance surface, a reflecting surface consisting of one plane, a reflecting surface of roof shape, and an exit surface. An optical path between the entrance surface and the reflecting surface consisting of one plane is practically perpendicular to an optical path between the reflecting surface of roof shape and the exit surface in the prism block.
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Citations
18 Claims
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1. A finder for single-lens reflex type digital cameras, comprising:
- a reflecting plane constructed and arranged to split a light beam from an imaging optical system of a camera into two beams directed toward an image sensor and a finder system;
an image-erecting prism system; and an ocular optical system, wherein said image-erecting prism system and said ocular optical system are arranged along a traveling direction of light in said finder system placed after a position of the image formed by said imaging optical system, wherein said prism system comprises, in order along the traveling direction of the light in one prism block, an entrance surface, a first reflecting surface consisting of one plane face, a second reflecting surface of roof shape, and an exit surface, wherein said first reflecting surface folds an optical path toward an opposite side of said ocular optical system in reference to said exit surface, and wherein the optical path between said entrance surface and said first reflecting surface intersects, inside the prism block, an optical path between said second reflecting surface and said exit surface. - View Dependent Claims (2, 3, 4, 5, 6, 7)
- a reflecting plane constructed and arranged to split a light beam from an imaging optical system of a camera into two beams directed toward an image sensor and a finder system;
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8. A finder for single-lens reflex type digital cameras, comprising:
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a reflecting plane for splitting a light beam from an imaging optical system of a camera into two beams directed toward an image sensor and a finder system; a prism; and an ocular optical system, wherein said prism and said ocular optical system are arranged along a traveling direction of light in said finder system placed after a position of the image formed by said imaging optical system, wherein said prism comprises, in order along the traveling direction of the light, a first reflecting surface, a second reflecting surface, and a third reflecting surface, wherein a normal line to said first reflecting surface and a normal line to said second reflecting surface lie in a plane and intersect one another, wherein said plane intersects an optical axis of said imaging optical system, wherein an axial light beam from said imaging optical system is reflected by said third reflecting surface, to be substantially parallel with the optical axis of said imaging optical system, wherein said ocular optical system includes, in order from an object side, an object side surface of a biconvex lens that has a larger absolute value of curvature than an absolute value of curvature of a pupil-side surface thereof and a pupil side surface of a biconcave lens that has a larger absolute value of curvature than an absolute value of curvature of an object-side surface thereof, and wherein said finder satisfies the following conditions;
space="preserve" listing-type="equation">1<
l.sub.2 /l.sub.1 <
1.4
space="preserve" listing-type="equation">0.8<
L/L(np·
fE)<
1.6where l1 is an axial distance from said first reflecting surface to said second reflecting surface of said prism, l2 is an axial distance from said second reflecting surface to said third reflecting surface of said prism, L is an axial distance from an entrance surface to an exit surface of said prism, np is a refractive index of a medium of said prism, and fE is a combined focal length of said finder system on a pupil side of a position of the image formed by said imaging optical system. - View Dependent Claims (9, 10, 11, 12, 13)
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14. A finder for single-lens reflex type digital cameras, comprising:
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a reflecting plane for splitting a light beam from an imaging optical system of a camera into two beams directed toward an image sensor and a finder system; an image-erecting prism system; and an ocular optical system, wherein said prism system and said ocular optical system are arranged along a traveling direction of light in said finder system placed after a position of the image formed by said imaging optical system, wherein said ocular optical system includes, in order from an object side, an object side surface of a positive lens which is convex toward the object side and a pupil side surface of a negative lens which is concave toward the pupil side, and wherein said finder satisfies the following conditions;
space="preserve" listing-type="equation">-6<
(R.sub.31 +R.sub.32)/(R.sub.31 -R.sub.32)<
-0.1
space="preserve" listing-type="equation">0.1<
(R.sub.33 +R.sub.34)/(R.sub.33 -R.sub.34)<
15where R31 and R32 are radii of curvature of the object-side surface and the pupil-side surface, respectively, of said positive lens and R33 and R34 are radii of curvature of the object-side surface and the pupil-side surface, respectively, of said negative lens. - View Dependent Claims (15, 16, 17, 18)
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Specification