Zoom lens and image pickup apparatus equipped with zoom lens
A zoom lens includes, in order from an object side to an image side, a first lens unit of a negative refractive power, a second lens unit of a positive refractive power, and a third lens unit of a positive refractive power, each lens unit being moved during zooming, wherein the second lens unit includes two positive lenses, a negative lens, a positive lens in order from the object side to the image side, and an average refractive index Nd 2 p for d-line of materials of the positive lenses in the second lens unit and a refractive index Nd 2 n for d-line of a material of the negative lens in the second lens unit are appropriately set.
1. A zoom lens comprising, in order from an object side to an image side, a first lens unit of a negative refractive power, a second lens unit of a positive refractive power, and a third lens unit of a positive refractive power, each lens unit being moved during zooming,
wherein the second lens unit includes two positive lenses, a negative lens, and a positive lens in order from the object side to the image side, and
wherein the following conditions are satisfied:
1.73 <Nd 2 p <1.92,
1.90 <Nd 2 n <2.40, and
1.90 <Dd 2/ Dd 21<4.00,
where Nd 2 p denotes an average refractive index for d-line of materials of the positive lenses in the second lens unit, Nd 2 n denotes a refractive index for d-line of a material of the negative lens in the second lens unit, Dd 2 denotes a thickness of the second lens unit on an optical axis, and Dd 21 denotes a thickness of a positive lens closest to the object side of the second lens unit on the optical axis.
2. The zoom lens according to claim 1 , wherein the following condition is satisfied:
0.15 <f 2/√( fw·ft )<1.15,
where f 2 denotes a focal length of the second lens unit, fw denotes a focal length of the entire zoom lens at a wide-angle end, and ft denotes a focal length of the entire zoom lens at a telephoto end.
3. The zoom lens according to claim 1 , wherein the following condition is satisfied:
0.75 <f 21/ f 2<1.60,
where f 2 denotes a focal length of the second lens unit, and f 21 denotes a focal length of a positive lens in the second lens unit closest to the object side.
4. The zoom lens according to claim 1 , wherein the following condition is satisfied:
0.95 <m 2/ f 21<2.20,
where f 21 denotes a focal length of a positive lens in the second lens unit closest to the object side, and m 2 denotes a movement amount in an optical axis direction of the second lens unit during zooming from a wide-angle end to a telephoto end, a sign of the movement amount being positive when the second lens unit moves towards the image side.
5. The zoom lens according to claim 1 , wherein the following condition is satisfied:
1.65 <Nd 2 min<1.85,
where Nd2 min denotes a refractive index of a material having the lowest refractive index for d-line out of materials of lenses in the second lens unit.
6. The zoom lens according to claim 1 , wherein the following condition is satisfied:
0.90 <f 2 p/f 2<4.00,
where f 2 denotes a focal length of the second lens unit, and f 2 p denotes an average focal length of the positive lenses in the second lens unit.
7. The zoom lens according to claim 1 , wherein the following condition is satisfied:
−1.30<( R 21 a+R 21 b )/( R 21 a−R 21 b )<−1.00,
where R 21 a denotes a radius of curvature of an object-side lens surface of a positive lens closest to the object side in the second lens unit, and R 21 b denotes a radius of curvature of an image-side lens surface thereof.
8. The zoom lens according to claim 1 , wherein the following condition is satisfied:
0.90 <f 2/| f 1|<1.20,
where f 1 denotes a focal length of the first lens unit, and f 2 denotes a focal length of the second lens unit.
9. The zoom lens according to claim 1 , wherein the following condition is satisfied:
1.50 <f 2/ fw< 2.60,
where f 2 denotes a focal length of the second lens unit, and fw denotes a focal length of the entire zoom lens at a wide-angle end.
10. The zoom lens according to claim 1 , wherein the first lens unit includes one negative lens and one positive lens.
11. The zoom lens according to claim 1 , wherein the third lens unit includes one positive lens.
12. The zoom lens according to claim 1 , wherein the zoom lens is configured to form an image on a solid-state image sensor.
13. An image pickup apparatus comprising:
a zoom lens; and
a solid-state image sensor configured to receive an image formed by the zoom lens,
wherein the zoom lens comprises, in order from an object side to an image side, a first lens unit of a negative refractive power, a second lens unit of a positive refractive power, and a third lens unit of a positive refractive power, each lens unit being moved during zooming,
wherein the second lens unit includes two positive lenses, a negative lens, and a positive lens in order from the object side to the image side, and
wherein the following conditions are satisfied:
1.73 <Nd 2 p <1.92,
1.90 <Nd 2 n <2.40, and
1.90 <Dd 2/ Dd 21<4.00,
where Nd 2 p denotes an average refractive index for d-line of materials of the positive lenses in the second lens unit, Nd 2 n denotes a refractive index for d-line of a material of the negative lens in the second lens unit, Dd 2 denotes a thickness of the second lens unit on an optical axis, and Dd 21 denotes a thickness of a positive lens closest to the object side of the second lens unit on the optical axis.
14. A zoom lens comprising, in order from an object side to an image side, a first lens unit of a negative refractive power, a second lens unit of a positive refractive power, and a third lens unit of a positive refractive power, each lens unit being moved during zooming,
wherein the second lens unit includes two positive lenses, a negative lens, and a positive lens in order from the object side to the image side, and
wherein the following conditions are satisfied:
1.73 <Nd 2 p <1.92,
1.90 <Nd 2 n <2.40, and
1.65 <Nd 2 min<1.85,
where Nd 2 p denotes an average refractive index for d-line of materials of the positive lenses in the second lens unit, Nd 2 n denotes a refractive index for d-line of a material of the negative lens in the second lens unit, and Nd2 min denotes a refractive index of a material having the lowest refractive index for d-line out of materials of lenses in the second lens unit.
15. A zoom lens comprising, in order from an object side to an image side, a first lens unit of a negative refractive power, a second lens unit of a positive refractive power, and a third lens unit of a positive refractive power, each lens unit being moved during zooming,
wherein the second lens unit includes two positive lenses, a negative lens, and a positive lens in order from the object side to the image side, and
wherein the following conditions are satisfied:
1.73 <Nd 2 p <1.92,
1.90 <Nd 2 n <2.40, and
1.50 <f 2/ fw< 2.60,
where Nd 2 p denotes an average refractive index for d-line of materials of the positive lenses in the second lens unit, Nd 2 n denotes a refractive index for d-line of a material of the negative lens in the second lens unit, f 2 denotes a focal length of the second lens unit, and fw denotes a focal length of the entire zoom lens at a wide-angle end.
16. An image pickup apparatus comprising:
a zoom lens; and
a solid-state image sensor configured to receive an image formed by the zoom lens,
wherein the zoom lens comprises, in order from an object side to an image side:
a first lens unit of a negative refractive power, a second lens unit of a positive refractive power, and a third lens unit of a positive refractive power, each lens unit being moved during zooming,
wherein the second lens unit includes two positive lenses, a negative lens, and a positive lens in order from the object side to the image side, and
wherein the following conditions are satisfied:
1.73 <Nd 2 p <1.92,
1.90 <Nd 2 n <2.40, and
1.65 <Nd 2 min<1.85,
where Nd 2 p denotes an average refractive index for d-line of materials of the positive lenses in the second lens unit, Nd 2 n denotes a refractive index for d-line of a material of the negative lens in the second lens unit, and Nd2 min denotes a refractive index of a material having the lowest refractive index for d-line out of materials of lenses in the second lens unit.
17. An image pickup apparatus comprising:
a zoom lens; and
a solid-state image sensor configured to receive an image formed by the zoom lens,
wherein the zoom lens comprises, in order from an object side to an image side:
a first lens unit of a negative refractive power, a second lens unit of a positive refractive power, and a third lens unit of a positive refractive power, each lens unit being moved during zooming,
wherein the second lens unit includes two positive lenses, a negative lens, and a positive lens in order from the object side to the image side, and
wherein the following conditions are satisfied:
1.73 <Nd 2 p <1.92,
1.90 <Nd 2 n <2.40, and
1.50 <f 2/ fw< 2.60,
where Nd 2 p denotes an average refractive index for d-line of materials of the positive lenses in the second lens unit, Nd 2 n denotes a refractive index for d-line of a material of the negative lens in the second lens unit, and f 2 denotes a focal length of the second lens unit, and fw denotes a focal length of the entire zoom lens at a wide-angle end.