Zoom lens and image pickup apparatus equipped with same

1. A zoom lens consisting of, in order from the object side:

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; and

a fifth lens unit having a positive refractive power, wherein

the first lens unit and the fifth lens unit move during zooming from the wide angle end to the telephoto end, and

the following conditional expressions (1), (2), and (3) are satisfied:

f t / f w >6.0  (1),

Fno (T) <3.5  (2), and

Σ d/f t <0.6  (3),

where f t is the focal length of the entire zoom lens system at the telephoto end, f w is the focal length of the entire zoom lens system at the wide angle end, Fno( T ) is the F-number of the entire zoom lens system at the telephoto end, and Σd is the sum of the thicknesses of the first to fifth lens units, where the thickness of each lens unit refers to the distance on the optical axis from the lens surface closest to the object side to the lens surface closest to the image side in each lens unit.

2. A zoom lens according to claim 1 , wherein the second lens unit and the third lens unit move during zooming from the wide angle end to the telephoto end, and the following conditional expression (4) is satisfied:

2<Δ 2G /|Δ 3G |<5  (4)

where Δ 2G is the amount of shift of the second lens unit with zooming from the wide angle end to the telephoto end, Δ 3G is the amount of shift of the third lens unit with zooming from the wide angle end to the telephoto end, where the amounts of shift are calculated as the amounts of shift from the positions of the respective lens units at the wide angle end, and shifts toward the image plane are represented by positive values.

3. A zoom lens according to claim 1 , wherein the second lens unit moves during zooming from the wide angle end to the telephoto end, and the following conditional expression (5) is satisfied:

0.15≦Δ 2G /L t ≦0.5  (5),

where Δ 2G is the amount of shift of the second lens unit in the zoom lens during zooming from the wide angle end to the telephoto end, shifts toward the image plane being represented by positive values, and L t is the overall length of the entire zoom lens system at the telephoto end.

4. A zoom lens according to claim 1 , wherein the third lens unit moves during zooming from the wide angle end to the telephoto end, and the following conditional expression (6) is satisfied:

0.05≦|Δ 3G |/L t ≦0.2  (6),

where A 3G is the amount of shift of the third lens unit in the zoom lens during zooming from the wide angle end to the telephoto end, shifts toward the image plane being represented by positive values, and L t is the overall length of the entire zoom lens system at the telephoto end.

5. A zoom lens according to claim 1 , wherein the following conditional expression (7) is satisfied:

0.2<(β 2T /β 2w )/(f t /f w )<0.6  (7),

where β 2T is the lateral magnification of the second lens unit at the telephoto end of the focal length range of the zoom lens, and β 2w is the lateral magnification of the second lens unit at the wide angle end of the focal length range of the zoom lens.

6. A zoom lens according to claim 1 , wherein the following conditional expression (8) is satisfied:

0.1<(β 3T /β 3w )/(f t /f w )<0.3  (8),

where β 3T is the lateral magnification of the third lens unit at the telephoto end of the focal length range of the zoom lens, and β 3w is the lateral magnification of the third lens unit at the wide angle end of the focal length range of the zoom lens.

7. A zoom lens according to claim 1 , wherein the following conditional expression (9) is satisfied:

0.05<|f 2 |/f t <0.2  (9),

where f 2 is the focal length of the second lens unit.

8. A zoom lens according to claim 1 , wherein the following conditional expression (10) is satisfied:

0.05<f 3 /f t <0.3  (10),

where f 3 is the focal length of the third lens unit.

9. A zoom lens according to claim 1 , wherein the following conditional expression (11) is satisfied:

0.1<f 5 /f t <0.8  (11),

where f 5 is the focal length of the fifth lens unit.

10. A zoom lens according to claim 1 , wherein the fourth lens unit consists of one lens.

11. A zoom lens according to claim 1 , wherein the fourth lens unit moves during zooming.

12. An image pickup apparatus comprising:

a zoom lens according to claim 1 ; and

an image pickup element disposed on the image side of the zoom lens and having an image pickup element having an image pickup surface that receives an image formed by zoom lens.

13. A zoom lens consisting of, in order from the object side:

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; and

a fifth lens unit having a positive refractive power, wherein

the second lens unit consists of three lenses,

the fifth lens unit consists of one lens,

the first lens unit moves during zooming from the wide angle end to the telephoto end, and

the following conditional expressions (1) , (2), and (3) are satisfied,

f t f w >6.0  (1),

Fno (T) <3.5  (2), and

Σ d/f t <0.6  (3),

where f t is the focal length of the entire zoom lens system at the telephoto end, f w is the focal length of the entire zoom lens system at the wide angle end, Fno (T) is the F-number of the entire zoom lens system at the telephoto end, and Σd is the sum of the thicknesses of the first to fifth lens units, where the thickness of each lens unit refers to the distance on the optical axis from the lens surface closest to the object side to the lens surface closest to the image side in each lens unit.