Zoom lens and image pickup apparatus including the same
A zoom lens includes, in order from an object side to an image side, a positive first lens unit, a negative second lens unit, a middle lens group including at least one lens unit, a negative N minus second lens unit, a negative N minus first lens unit, and a positive Nth lens unit, where N is an integer of six or more, in which distances between the adjacent lens units change during zooming, the first lens unit moves toward the object side during zooming from a wide-angle end to a telephoto end, the N minus second lens unit moves during focusing, and a total lens length at the wide-angle end, a backfocus at the wide-angle end, and a lateral magnification of a combined system of the N minus first lens unit and the Nth lens unit at the wide-angle end are set appropriately.
1. A zoom lens comprising, in order from an object side to an image side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a middle lens group including at least one lens unit, (N-2)th lens unit having a negative refractive power, an (N-1)th lens unit having a negative refractive power, and an Nth lens unit having a positive refractive power, where N is an integer of six or more, wherein
distances between the adjacent lens units change during zooming,
the first lens unit moves toward the object side during zooming from a wide-angle end to a telephoto end,
the (N-2)th lens unit moves during focusing, and
the following conditional expressions are satisfied:
8.0< Dw/skw< 20.0; and
0.8<β np< 3.0,
where Dw represents a total lens length at the wide-angle end, skw represents a backfocus at the wide-angle end, and βnp represents a lateral magnification of a combined system of the (N-1)th lens unit and the Nth lens unit at the wide-angle end.
2. The zoom lens according to claim 1 , wherein
the following conditional expression is satisfied:
0.1< f ( N− 2)/ f ( N− 1)<2.0,
where f(N−2) represents a focal length of the (N-2)th lens unit and f(N−1) represents a focal length of the (N-1)th lens unit.
3. The zoom lens according to claim 1 , wherein
the following conditional expression is satisfied:
−10.0<(1−β f 2 )×β rt 2 <−3.0,
where βf represents a lateral magnification of the (N-2)th lens unit at the telephoto end and βrt represents a lateral magnification of a combined system of the (N-1)th lens unit and the Nth lens unit at the telephoto end.
4. The zoom lens according to claim 1 , wherein
the following conditional expression is satisfied:
3.0< fN/skw< 40.0,
where fN represents a focal length of the Nth lens unit and skw represents a backfocus at the wide-angle end.
5. The zoom lens according to claim 1 , wherein
the following conditional expression is satisfied:
−5.0< f ( N− 2)/ fw<− 1.0,
where f(N−2) represents a focal length of the (N-2)th lens unit and fw represents a focal length of the zoom lens at the wide-angle end.
6. The zoom lens according to claim 1 , wherein
the following conditional expression is satisfied:
2.0< f 1/ fw< 8.0,
where f1 represents a focal length of the first lens unit and fw represents a focal length of the zoom lens at the wide-angle end.
7. The zoom lens according to claim 1 , wherein
the following conditional expression is satisfied:
−4.0< POw/fw<− 1.0,
where POw represents a distance from an image plane to an exit pupil position at the wide-angle end and fw represents a focal length of the zoom lens at the wide-angle end.
8. The zoom lens according to claim 1 , wherein
the following conditional expression is satisfied:
2.5< ft/fw< 50.0,
where ft represents a focal length of the zoom lens at the telephoto end and fw represents a focal length of the zoom lens at the wide-angle end.
9. The zoom lens according to claim 1 , wherein
fM represents a focal length of the zoom lens at a middle zoom position, and is defined as fM=√(fw×ft), where fw represents a focal length of the zoom lens at the wide-angle end and ft represents a focal length of the zoom lens at the telephoto end, and
the following conditional expression is satisfied:
0.3<| m ( N− 2)mid/ m ( N− 1)mid|<1.5,
where m(N−2)mid represents a movement amount of the (N-2)th lens unit during zooming from the wide-angle end to the middle zoom position, and m(N−1)mid represents a movement amount of the (N-1)th lens unit during zooming from the wide-angle end to the middle zoom position.
10. The zoom lens according to claim 1 , wherein
the following conditional expression is satisfied:
−7.0< m 1/ fw<− 1.0,
where m1 represents a movement amount of the first lens unit during zooming from the wide-angle end to the telephoto end and fw represents a focal length of the zoom lens at the wide-angle end.
11. The zoom lens according to claim 1 , wherein the Nth lens unit does not move during zooming.
12. The zoom lens according to claim 1 , wherein the (N-2)th lens unit includes a single lens or a cemented lens of two lenses cemented with each other.
13. The zoom lens according to claim 1 , wherein the middle lens group includes, in order from the object side to the image side, a third lens unit having a positive refractive power, a fourth lens unit having a positive refractive power, and a fifth lens unit having a positive refractive power.
14. The zoom lens according to claim 1 , wherein the middle lens group includes, in order from the object side to the image side, a third lens unit having a positive refractive power, a fourth lens unit having a negative refractive power, and a fifth lens unit having a positive refractive power.
15. The zoom lens according to claim 1 , wherein the middle lens group includes a third lens unit having a positive refractive power.
16. An image pickup apparatus comprising:
a zoom lens; and
a solid-state image pickup element that receives light of 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 having a positive refractive power, a second lens unit having a negative refractive power, a middle lens group including at least one lens unit, an (N- 2 )th lens unit having a negative refractive power, an (N- 1 )th lens unit having a negative regractive power, and an Nth lens unit having a positive refractive power, where N is an integer of six or more, wherein distances between the adjacent lens units change during zooming,
the first lens unit moves toward the object side during zooming from a wide-angle end to telephoto end,
the (N- 2 )th lens unit moves during focusing, and
the following conditional expressions are satisfied:
8.0< Dw/skw< 20.0; and
0.8<β np< 3.0,
where Dw represents a total lens length at the wide-angle end, skw represents a backfocus at the wide-angle end, and βnp represents a lateral magnification of a combined system of the (N-1)th lens unit and the Nth lens unit at the wide-angle end.