Zoom lens and image pickup apparatus including the same
A zoom lens includes 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; and a rear lens group which includes at least one lens unit and has a positive refractive power as a whole. Distances between the adjacent lens units change during zooming. The rear lens group includes a lens P 1 that has a positive refractive power and moves at image stabilization so as to have a component perpendicular to the optical axis. The shape factor SFP 1 of the lens P 1 , a curvature radius R 1 P 1 of a lens surface of the lens P 1 on the object side, and a curvature radius R 2 P 1 of a lens surface of the lens P 1 on the image side are appropriately determined.
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; and
a rear lens group which includes at least one lens unit and has a positive refractive power as a whole,
wherein:
intervals between adjacent lens units are changed during zooming,
interval between the first lens unit and the second lens unit is longer at a telephoto end than at a wide angle end,
interval between the second lens unit and the rear lens group is a shorter at a telephoto end than a wide angle end,
the rear lens group includes a lens P 1 that has a positive refractive power and moves for image stabilization so as to have a component perpendicular to an optical axis,
a surface of the lens P 1 on the object side and a surface of the lens P 1 on the image side are both in contact with air,
the lens P 1 is a lens disposed at most object side in the rear lens group, and
the following conditional expression is satisfied:
−2.5< SFP 1≤−0.844
where SFP 1 is a shape factor of the lens P 1 which is expressed by SFP 1 =(R 2 P 1 +R 1 P 1 )/(R 2 P 1 −R 1 P 1 ), R 1 P 1 is a curvature radius of a lens surface of the lens P 1 on the object side while R 2 P 1 is a curvature radius of a lens surface of the lens P 1 on the image side,
wherein the rear 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 group having a positive refractive power; and a fifth lens group having a positive refractive power, and
wherein the third lens unit is composed of one positive lens, which is the lens P 1 .
2. The zoom lens according to claim 1 , wherein the following conditional expression is satisfied:
0.01<β st/βsw< 3.20
where βsw is a lateral magnification of a composite system of the second lens unit to the lens P 1 at a wide-angle end and βst is a lateral magnification of the composite system of the second lens unit to the lens P 1 at a telephoto end.
3. The zoom lens according to claim 1 , wherein
the following conditional expression is satisfied:
1.8< D 23 w/D 23 t< 20.0
where D 23 w is a distance between the second and third lens units on the optical axis at the wide-angle end and D 23 t is a distance between the second and third lens units on the optical axis at the telephoto end.
4. The zoom lens according to claim 1 , wherein
the following conditional expression is satisfied:
1.0<|−β Pw|< 25.0
where βfP is a lateral magnification of the lens P 1 at the wide-angle end.
5. The zoom lens according to claim 1 , wherein
the following conditional expression is satisfied:
1.1< fP/fRt <4.8
where fP is a focal length of the lens P 1 and fRt is a focal length of the rear lens group at the telephoto end.
6. The zoom lens according to claim 1 , wherein
the following conditional expression is satisfied:
0.7< fRt/fw <2.0
where fRt is a focal length of the rear lens group at the telephoto end and fw is 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:
0.5<(1−β Pt )□β Rt< 1.8
where βPt is a lateral magnification of the lens P 1 at the telephoto end and βRt is a lateral magnification of an optical system provided on the image side of the lens P 1 at the telephoto end.
8. The zoom lens according to claim 1 , wherein the following conditional expressions are satisfied:
1.45< nP< 1.75
45.0<ν P< 100.0
where nP and νP are a refractive power and an Abbe number of a material of the lens P 1 for the d-line, respectively.
9. An image pickup apparatus comprising a zoom lens and an image pickup element receiving an image formed by the zoom lens,
wherein the zoom lens includes 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; and at least one lens unit,
wherein the zoom lens includes a rear lens group having a positive refractive power as a whole, and distances between adjacent lens units change during zooming,
wherein:
interval between the first lens unit and the second lens unit is longer at a telephoto end than at a wide angle end,
interval between the second lens unit and the rear lens group is a shorter at a telephoto end than a wide angle end,
the rear lens group includes a lens P 1 that has a positive refractive power and moves at image stabilization so as to have a component perpendicular to an optical axis,
the lens P 1 is a lens disposed at most object side in the rear lens group, and
a surface of the lens P 1 on the object side and a surface of the lens P 1 on the image side are both in contact with air,
wherein the following conditional expression is satisfied:
−2.5< SFP 1≤−0.844
where SFP 1 is a shape factor of the lens P 1 which is expressed by SFP 1 =(R 2 P 1 +R 1 P 1 )/(R 2 P 1 −R 1 P 1 ), R 1 P 1 is a curvature radius of a lens surface of the lens P 1 on the object side while R 2 P 1 is a curvature radius of a lens surface of the lens P 1 on the image side,
wherein the rear 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 group having a positive refractive power; and a fifth lens group having a positive refractive power, and
wherein the third lens unit is composed of one positive lens, which is the lens P 1 .
10. 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; and
a rear lens group which includes at least one lens unit and has a positive refractive power as a whole,
wherein:
intervals between adjacent lens units are changed during zooming,
interval between the first lens unit and the second lens unit is longer at a telephoto end than at a wide angle end,
interval between the second lens unit and the rear lens group is a shorter at a telephoto end than a wide angle end,
the rear 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 group having a positive refractive power; and a fifth lens group having a positive refractive power, or, the rear 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 group having a negative refractive power; and a fifth lens group having a positive refractive power, and
the third lens unit is composed of a lens P 1 that has a positive refractive power and moves for image stabilization so as to have a component perpendicular to an optical axis,
a surface of the lens P 1 on the object side and a surface of the lens P 1 on the image side are both in contact with air,
the lens P 1 is a lens disposed at most object side in the rear lens group, and
the following conditional expression is satisfied:
−2.5< SFP 1<−0.5
where SFP 1 is a shape factor of the lens P 1 which is expressed by SFP 1 =(R 2 P 1 +R 1 P 1 )/(R 2 P 1 −R 1 P 1 ), R 1 P 1 is a curvature radius of a lens surface of the lens P 1 on the object side while R 2 P 1 is a curvature radius of a lens surface of the lens P 1 on the image side.
11. 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; and
a rear lens group which includes at least one lens unit and has a positive refractive power as a whole,
wherein:
intervals between adjacent lens units are changed during zooming,
interval between the first lens unit and the second lens unit is longer at a telephoto end than at a wide angle end,
interval between the second lens unit and the rear lens group is a shorter at a telephoto end than a wide angle end,
the rear 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 group having a negative refractive power; and a fifth lens group having a positive refractive power, and
the third lens unit is composed of a plurality of lenses including a lens P 1 placed closest to the object, the lens P 1 having a positive refractive power and configured to move for image stabilization so as to have a component perpendicular to an optical axis,
a surface of the lens P 1 on the object side and a surface of the lens P 1 on the image side are both in contact with air,
the lens P 1 is a lens disposed at most object side in the rear lens group, and
the following conditional expression is satisfied:
−2.5< SFP 1<−0.5
where SFP 1 is a shape factor of the lens P 1 which is expressed by SFP 1 =(R 2 P 1 +R 1 P 1 )/(R 2 P 1 −R 1 P 1 ), R 1 P 1 is a curvature radius of a lens surface of the lens P 1 on the object side while R 2 P 1 is a curvature radius of a lens surface of the lens P 1 on the image side.
12. 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; and
a rear lens group which includes at least one lens unit and has a positive refractive power as a whole,
wherein:
intervals between adjacent lens units are changed during zooming,
interval between the first lens unit and the second lens unit is longer at a telephoto end than at a wide angle end,
interval between the second lens unit and the rear lens group is a shorter at a telephoto end than a wide angle end,
the rear lens group includes a lens P 1 that has a positive refractive power and moves for image stabilization so as to have a component perpendicular to an optical axis,
a surface of the lens P 1 on the object side and a surface of the lens P 1 on the image side are both in contact with air,
the lens P 1 is a lens disposed at most object side in the rear lens group, and
the following conditional expression is satisfied:
−2.5< SFP 1≤−0.844
where SFP 1 is a shape factor of the lens P 1 which is expressed by SFP 1 =(R 2 P 1 +R 1 P 1 )/(R 2 P 1 −R 1 P 1 ), R 1 P 1 is a curvature radius of a lens surface of the lens P 1 on the object side while R 2 P 1 is a curvature radius of a lens surface of the lens P 1 on the image side,
wherein the rear 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 group having a negative refractive power; and a fifth lens group having a positive refractive power, and
wherein the third lens unit is composed of one positive lens, which is the lens P 1 .
13. 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; and
a rear lens group which includes at least one lens unit and has a positive refractive power as a whole,
wherein:
intervals between adjacent lens units are changed during zooming,
interval between the first lens unit and the second lens unit is longer at a telephoto end than at a wide angle end,
interval between the second lens unit and the rear lens group is a shorter at a telephoto end than a wide angle end,
the rear lens group includes a lens P 1 that has a positive refractive power and moves for image stabilization so as to have a component perpendicular to an optical axis,
a surface of the lens P 1 on the object side and a surface of the lens P 1 on the image side are both in contact with air,
the lens P 1 is a lens disposed at most object side in the rear lens group, and
the following conditional expression is satisfied:
−2.5< SFP 1≤−0.844
where SFP 1 is a shape factor of the lens P 1 which is expressed by SFP 1 =(R 2 P 1 +R 1 P 1 )/(R 2 P 1 −R 1 P 1 ), R 1 P 1 is a curvature radius of a lens surface of the lens P 1 on the object side while R 2 P 1 is a curvature radius of a lens surface of the lens P 1 on the image side,
wherein the rear 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 group having a negative refractive power; and a fifth lens group having a positive refractive power, and
wherein the third lens unit is composed of a plurality of lenses including the positive lens P 1 placed closest to the object.