Zoom lens and image pickup apparatus using the same

1. A zoom lens comprising:

a first lens unit that has a positive refractive power;

a second lens unit that has a negative refractive power;

a third lens unit that has a positive refractive power;

a fourth lens unit that has a negative refractive power; and

a fifth lens unit that has a positive refractive power,

wherein the first to fifth lens units are arranged sequentially from an object side to an image side,

wherein, in comparison with a wide-angle end, at a telephoto end, a distance between the first lens unit and the second lens unit is increased, a distance between the second lens unit and the third lens unit is decreased, a distance between the third lens unit and the fourth lens unit is increased, and a distance between the fourth lens unit and the fifth lens unit is increased,

wherein, in comparison with the wide-angle end, at the telephoto end, each lens unit moves so that the first lens unit is positioned closer to the object side,

wherein the first lens unit and the second lens unit each consist of a single positive lens element and a single negative lens element, and

wherein, when the distance between the third lens unit and the fourth lens unit at the wide-angle end is defined as D 34 w , the distance between the third lens unit and the fourth lens unit at the telephoto end is defined as D 34 t , and a focal length of the entire zoom lens at the wide-angle end is defined as fw, the following conditional expression is satisfied:

0.2<( D 34 t−D 34 w )/ fw< 1.2.

2. The zoom lens according to claim 1 ,

wherein, when a moving distance of the first lens unit in zooming from the wide-angle end to the telephoto end is defined as M 1 , the following conditional expression is satisfied:

−5.0< M 1/ fw<− 2.0.

3. The zoom lens according to claim 1 ,

wherein, when a focal length of the fourth lens unit is defined as f 4 , the following conditional expression is satisfied:

3.0<| f 4|/ fw< 6.0.

4. The zoom lens according to claim 1 ,

wherein, when a focal length of the positive lens element of the first lens unit is defined as f 1 p and a focal length of the first lens unit is defined as f 1 , the following conditional expression is satisfied:

0.3< f 1 p/f 1<0.9.

5. The zoom lens according to claim 1 ,

wherein, when a focal length of the negative lens element of the second lens unit is defined as f 2 n and a focal length of the second lens unit is defined as f 2 , the following conditional expression is satisfied:

0.3< f 2 n/f 2<0.9.

6. The zoom lens according to claim 1 ,

wherein, when a focal length of the first lens unit is defined as f 1 , the following conditional expression is satisfied:

4.0< f 1/ fw< 10.0.

7. The zoom lens according to claim 1 ,

wherein, when a focal length of the second lens unit is defined as f 2 , the following conditional expression is satisfied:

0.8<| f 2|/ fw< 2.0.

8. The zoom lens according to claim 1 ,

wherein, when lateral magnifications of the third lens unit, the fourth lens unit, and the fifth lens unit at the wide-angle end are respectively defined as β 3 w , β 4 w , and β 5 w , the lateral magnifications of the third lens unit, the fourth lens unit, and the fifth lens unit at the telephoto end are respectively defined as β 3 t , β 4 t , and β 5 t , and the focal length of the entire zoom lens at the telephoto end is defined as ft, the following conditional expression is satisfied:

0.2<{(β3 t×β 4 t×β 5 t )/(β3 w×β 4 w×β 5 w )}/( ft/fw )<0.5.

9. The zoom lens according to claim 1 ,

wherein, when Abbe numbers of materials of the positive lens element and the negative lens element of the first lens unit are respectively defined as ν 1 p and ν 1 n , the following conditional expression is satisfied:

0.03<1/ν1 n− 1/ν1 p< 0.05.

10. The zoom lens according to claim 1 ,

wherein, when Abbe numbers of materials of the positive lens element and the negative lens element of the second lens unit are respectively defined as ν 2 p and ν 2 n , the following conditional expression is satisfied:

0.02<1/ν2 p− 1/ν2 n< 0.04.

11. The zoom lens according to claim 1 ,

wherein, when a focal length of the third lens unit is defined as f 3 , the following conditional expression is satisfied:

1.0< f 3/ fw< 3.0.

12. The zoom lens according to claim 1 ,

wherein, when a focal length of the fifth lens unit is defined as f 5 , the following conditional expression is satisfied:

3.0< f 5/ fw< 6.0.

13. The zoom lens according to claim 1 ,

wherein, when a radius of curvature of a lens surface of the first lens unit, the lens surface being a lens surface closest to the object side, is defined as R 1 a , and a radius of curvature of a lens surface of the first lens unit, the lens surface being a lens surface closest to the image side, is defined as R 1 b , the following conditional expression is satisfied:

−1.5<( R 1 a+R 1 b )/( R 1 a−R 1 b )<−0.5.

14. The zoom lens according to claim 1 ,

wherein the negative lens element and the positive lens element of the second lens unit are arranged in this order from the object side to the image side, and

wherein, when a distance between the positive lens element and the negative lens element of the second lens unit is defined as L, and a focal length of the second lens unit is defined as f 2 , the following conditional expression is satisfied:

0.2< L/|f 2|<0.5.

15. An image pickup apparatus comprising:

the zoom lens according to claim 1 ; and

a solid-state image pickup device that receives an image formed by the zoom lens.