Zoom lens and imaging apparatus
To attain the above-described objective, a zoom lens according to the present invention includes sequentially from an object side, a front group which includes at least three lens groups and has positive refractive power as a whole, and a lens group disposed on an image side of the front group, a magnification is changed by a change of a distance on an optical axis between adjacent lens groups, the lens group includes sequentially from an image side, a lens component, a lens component, and a lens component, the lens group is moved to an object side at a time of changing a magnification from a wide-angle end to a telephoto end, focusing is obtained by movement of a part of lens groups in the front group along an optical axis, and a predetermined condition expression is satisfied.
1. A zoom lens comprising:
a front group that has positive refractive power as a whole; and
a lens group GB disposed on an image side of the front group, wherein
the front group and the lens group GB are arranged sequentially in a stated order from an object side,
a magnification is changed by a change of a distance on an optical axis between adjacent lens groups,
the front group includes at least three lens groups,
the lens group GB includes sequentially from the image side, a negative lens component Nb, a negative lens component Nf, and a positive lens component P,
an object-side surface of the negative lens component Nb is a concave surface,
the lens group GB is moved to the object side in zooming from a wide-angle end to a telephoto end,
focusing is obtained by movement of a part of the lens groups included in the front group, along the optical axis,
a following condition expression is satisfied:
−0.7≤( RNf+RNb )/( RNf−RNb )≤2.0 (1)
where
RNf represents a radius of curvature of a surface located closest to an image in the negative lens component Nf, and
RNb represents a radius of curvature of a surface located closest to an object in the negative lens component Nb,
the front group includes a negative lens group GF in a position closest to the image, and
a following condition expression is satisfied:
1.1≤β FBt/βFBw≤ 2.5 (2)
where
βFBt represents a synthetic lateral magnification of the lens group GF and the lens group GB at the telephoto end, and
βFBw represents a synthetic lateral magnification of the lens group GF and the lens group GB at the wide-angle end.
2. The zoom lens according to claim 1 , wherein focusing is obtained by movement of a lens group other than a lens group that is disposed closest to the object, out of the lens groups included in the front group, along the optical axis.
3. The zoom lens according to claim 1 , wherein the negative lens component Nb has a negative meniscus shape having a surface that is convex toward the image side.
4. The zoom lens according to claim 1 , wherein an air lens formed by an image-side surface of the positive lens component P and an object-side surface of the negative lens component Nf has a double concave shape, or a negative meniscus shape having a surface that is concave toward the object side.
5. The zoom lens according to claim 1 , wherein a following condition expression is satisfied:
0.4≤| fN|/Y≤ 2.7 (5)
where
fN represents a synthetic focal length of the negative lens component Nf and the negative lens component Nb, and
Y represents the largest image height of the zoom lens.
6. The zoom lens according to claim 1 , wherein a lens group that is disposed closest to the object in the front group is moved along the optical axis in zooming.
7. The zoom lens according to claim 1 , wherein a lens group that is disposed closest to the object in the front group has positive refractive power.
8. An imaging apparatus comprising:
the zoom lens recited in claim 1 ; and
an image sensor configured to convert an optical image that is formed on an image side of the zoom lens by the zoom lens, into an electrical signal.
9. A zoom lens comprising:
a front group that has positive refractive power as a whole; and
a lens group GB disposed on an image side of the front group, wherein
the front group and the lens group GB are arranged sequentially in a stated order from an object side,
a magnification is changed by a change of a distance on an optical axis between adjacent lens groups,
the front group includes at least three lens groups,
the lens group GB includes sequentially from the image side, a negative lens component Nb, a negative lens component Nf, and a positive lens component P,
an object-side surface of the negative lens component Nb is a concave surface,
the lens group GB is moved to the object side in zooming from a wide-angle end to a telephoto end,
focusing is obtained by movement of a part of the lens groups included in the front group, along the optical axis,
a following condition expression is satisfied:
−0.7≤( RNf+RNb )/( RNf−RNb )≤2.0 (1)
where
RNf represents a radius of curvature of a surface located closest to an image in the negative lens component Nf, and
RNb represents a radius of curvature of a surface located closest to an object in the negative lens component Nb, and
a following condition expression is satisfied:
0.657≤ BFw/Y≤ 1.5 (3)
where
BFw represents a back focus of the zoom lens at the wide-angle end, and
Y represents the largest image height of the zoom lens.
10. A zoom lens comprising:
a front group that has positive refractive power as a whole; and
a lens group GB disposed on an image side of the front group, wherein
the front group and the lens group GB are arranged sequentially in a stated order from an object side,
a magnification is changed by a change of a distance on an optical axis between adjacent lens groups,
the front group includes at least three lens groups,
the lens group GB includes sequentially from the image side, a negative lens component Nb, a negative lens component Nf, and a positive lens component P,
an object-side surface of the negative lens component Nb is a concave surface,
the lens group GB is moved to the object side in zooming from a wide-angle end to a telephoto end,
focusing is obtained by movement of a part of the lens groups included in the front group, along the optical axis,
a following condition expression is satisfied:
−0.7≤( RNf+RNb )/( RNf−RNb )≤2.0 (1)
where
RNf represents a radius of curvature of a surface located closest to an image in the negative lens component Nf, and
RNb represents a radius of curvature of a surface located closest to an object in the negative lens component Nb, and
the positive lens component P has a double convex shape.
11. A zoom lens comprising:
a front group that has positive refractive power as a whole; and
a lens group GB disposed on an image side of the front group, wherein
the front group and the lens group GB are arranged sequentially in a stated order from an object side,
a magnification is changed by a change of a distance on an optical axis between adjacent lens groups,
the front group includes at least three lens groups,
the lens group GB includes sequentially from the image side, a negative lens component Nb, a negative lens component Nf, and a positive lens component P,
an object-side surface of the negative lens component Nb is a concave surface,
the lens group GB is moved to the object side in zooming from a wide-angle end to a telephoto end,
focusing is obtained by movement of a part of the lens groups included in the front group, along the optical axis,
a following condition expression is satisfied:
−0.7≤( RNf+RNb )/( RNf−RNb )≤2.0 (1)
where
RNf represents a radius of curvature of a surface located closest to an image in the negative lens component Nf, and
RNb represents a radius of curvature of a surface located closest to an object in the negative lens component Nb, and
a following condition expression is satisfied:
0.5≤ fP/Y≤ 2.7 (4)
where
fP represents a focal length of the positive lens component P, and
Y represents the largest image height of the zoom lens.
12. A zoom lens comprising:
a front group that has positive refractive power as a whole; and
a lens group GB disposed on an image side of the front group, wherein
the front group and the lens group GB are arranged sequentially in a stated order from an object side,
a magnification is changed by a change of a distance on an optical axis between adjacent lens groups,
the front group includes at least three lens groups,
the lens group GB includes sequentially from the image side, a negative lens component Nb, a negative lens component Nf, and a positive lens component P,
an object-side surface of the negative lens component Nb is a concave surface,
the lens group GB is moved to the object side in zooming from a wide-angle end to a telephoto end,
focusing is obtained by movement of a part of the lens groups included in the front group, along the optical axis,
a following condition expression is satisfied:
−0.7≤( RNf+RNb )/( RNf−RNb )≤2.0 (1)
where
RNf represents a radius of curvature of a surface located closest to an image in the negative lens component Nf, and
RNb represents a radius of curvature of a surface located closest to an object in the negative lens component Nb, and
a following condition expression is satisfied:
0.2≤ RP/fw≤ 2.5 (6)
where
RP represents a radius of curvature of an object-side surface of the positive lens component P, and
fw represents a focal length of the zoom lens at the wide-angle end.
13. A zoom lens comprising:
a front group that has positive refractive power as a whole; and
a lens group GB disposed on an image side of the front group, wherein
the front group and the lens group GB are arranged sequentially in a stated order from an object side,
a magnification is changed by a change of a distance on an optical axis between adjacent lens groups,
the front group includes at least three lens groups,
the lens group GB includes sequentially from the image side, a negative lens component Nb, a negative lens component Nf, and a positive lens component P,
an object-side surface of the negative lens component Nb is a concave surface,
the lens group GB is moved to the object side in zooming from a wide-angle end to a telephoto end,
focusing is obtained by movement of a part of the lens groups included in the front group, along the optical axis,
a following condition expression is satisfied:
−0.7≤( RNf+RNb )/( RNf−RNb )≤2.0 (1)
where
RNf represents a radius of curvature of a surface located closest to an image in the negative lens component Nf, and
RNb represents a radius of curvature of a surface located closest to an object in the negative lens component Nb, and
a following condition expression is satisfied:
23≤νP≤45 (8)
where
νP represents an Abbe number of a positive lens for a d line, the positive lens being included in the positive lens component P and having the smallest Abbe number.