Zoom lens and image pickup apparatus including the same
Provided is a zoom lens including a plurality of lens units, in which an interval between each pair of adjacent lens units is changed during zooming, the plurality of lens units include a lens unit BR arranged closest to image side in zoom lens, which moves in optical axis direction during focusing and a lens element A arranged adjacent to lens unit BR on object side, having refractive power of sign opposite to that of lens unit BR, in which lens element A consists of a single lens or a cemented lens, and distance between surface closest to image side of lens element A and image plane at wide angle end, distance between surface closest to image side of lens element A and surface closest to object side of lens unit BR at wide angle end, and focal length of zoom lens at wide angle end are each appropriately set.
1. A zoom lens, comprising a plurality of lens units,
wherein an interval between each pair of adjacent lens units is changed during zooming,
wherein the plurality of lens units include:
a lens unit BR arranged closest to an image side in the zoom lens, which is configured to move in an optical axis direction during focusing; and
a lens element A arranged adjacent to the lens unit BR on an object side, having a refractive power of a sign opposite to a sign of a refractive power of the lens unit BR,
wherein the lens element A consists of one of a single lens and a cemented lens, and
wherein the following conditional expressions are satisfied:
0.2< di/fw< 1.4; and
0.2< df/fw< 1.2,
where di represents a distance between a surface closest to the image side of the lens element A and an image plane at a wide angle end, df represents a distance between the surface closest to the image side of the lens element A and a surface closest to the object side of the lens unit BR at the wide angle end, and fw represents a focal length of the zoom lens at the wide angle end.
2. A zoom lens according to claim 1 , wherein the lens unit BR has a positive refractive power.
3. A zoom lens according to claim 2 , wherein the following conditional expression is satisfied:
0.7<βw<1.0,
where βw represents a lateral magnification of the lens unit BR at the wide angle end.
4. A zoom lens according to claim 2 ,
wherein the lens unit BR consists of one of a single lens having a positive refractive power and a cemented lens having a positive refractive power, and
wherein the following conditional expression is satisfied:
−5.0<( rf+rr )/( rf−rr )<0.0,
where rf and rr represent curvature radii of the surface closest to the object side and a surface closest to the image side of the lens unit BR, respectively.
5. A zoom lens according to claim 2 , wherein the following conditional expression is satisfied:
1.0<− fa/fw< 4.0,
where fa represents a focal length of the lens element A.
6. A zoom lens according to claim 2 ,
wherein the zoom lens consists, in order from the object side to the image side, of a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, a fourth lens unit having a positive refractive power, a fifth lens unit having a negative refractive power, and a sixth lens unit having a positive refractive power, and
wherein the first lens unit to the sixth lens unit are configured to move along mutually different loci during zooming.
7. A zoom lens according to claim 2 ,
wherein the zoom lens consists, in order from the object side to the image side, of a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, a third lens unit having a positive refractive power, a fourth lens unit having a negative refractive power, a fifth lens unit having a positive refractive power, and
wherein the first lens unit to the fifth lens unit are configured to move along mutually different loci during zooming.
8. A zoom lens according to claim 2 ,
wherein the zoom lens consists, in order from the object side to the image side, of a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, a third lens unit having a negative refractive power, and a fourth lens unit having a positive refractive power, and
wherein the first lens unit to the fourth lens unit are configured to move along mutually different loci during zooming.
9. A zoom lens according to claim 1 , wherein the lens unit BR has a negative refractive power.
10. A zoom lens according to claim 9 , wherein the following conditional expression is satisfied:
1.0<βw<1.3,
where βw represents a lateral magnification of the lens unit BR at the wide angle end.
11. A zoom lens according to claim 9 ,
wherein the lens unit BR consists of one of a single lens having a negative refractive power and a cemented lens having a negative refractive power, and
wherein the following conditional expression is satisfied:
0.0<( rf+rr )/( rf−rr )<5.0,
where rf and rr represent curvature radii of the surface closest to the object side and a surface closest to the image side of the lens unit BR, respectively.
12. A zoom lens according to claim 9 , wherein the following conditional expression is satisfied:
1.0< fa/fw< 4.0,
where fa represents a focal length of the lens element A.
13. A zoom lens according to claim 9 ,
wherein the zoom lens consists, in order from the object side to the image side, of a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, a fourth lens unit having a negative refractive power, a fifth lens unit having a negative refractive power, and
wherein the first lens unit to the fifth lens unit are configured to move along mutually different loci during zooming.
14. A zoom lens according to claim 9 ,
wherein the zoom lens consists, in order from the object side to the image side, of a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, a third lens unit having a positive refractive power, a fourth lens unit having a negative refractive power, a fifth lens unit having a positive refractive power, and a sixth lens unit having a negative refractive power, and
wherein the first lens unit to the sixth lens unit are configured to move along mutually different loci during zooming.
15. A zoom lens according to claim 1 , further comprising an aperture stop, which determines an open f-number light beam,
wherein the following conditional expression is satisfied:
0.7<φ a/di< 1.4,
where φa represents an optically effective diameter of the surface closest to the image side of the lens element A.
16. An image pickup apparatus, comprising a zoom lens comprising a plurality of lens units and an image pickup element configured to receive light corresponding to an image formed by the zoom lens,
wherein an interval between each pair of adjacent lens units is changed during zooming,
wherein the plurality of lens units include:
a lens unit BR arranged closest to an image side in the zoom lens, which is configured to move in an optical axis direction during focusing; and
a lens element A arranged adjacent to the lens unit BR on an object side, having a refractive power of a sign opposite to a sign of a refractive power of the lens unit BR,
wherein the lens element A consists of one of a single lens and a cemented lens, and
wherein the following conditional expressions are satisfied:
0.2< di/fw< 1.4; and
0.2< df/fw< 1.2,
where di represents a distance between a surface closest to the image side of the lens element A and an image plane at a wide angle end, df represents a distance between the surface closest to the image side of the lens element A and a surface closest to the object side of the lens unit BR at the wide angle end, and fw represents a focal length of the zoom lens at the wide angle end.
17. An image pickup apparatus according to claim 16 , wherein the following conditional expression is satisfied:
ωw≧30°,
where ωw represents a photographing half angle of view at the wide angle end.