Zoom lens and image pickup apparatus

1. A zoom lens, comprising:

a first lens group having a positive refracting power;

a second lens group having a negative refracting power and serving as a movable group upon power variation of said zoom lens; and

a plurality of movable lens groups cooperable with said second group to form a macro lens group; wherein

said first lens group, second lens group and movable lens groups are disposed in order from an object side;

said movable lens groups include a single focusing group and an additional lens group disposed on the image side with respect to said single focusing group and having a negative refracting power; and

said zoom lens has a macro mode in which said zoom lens can be focused at a shorter distance than an ordinary region by moving said macro lens group integrally from a position at a telephoto end toward the object side while said first lens group is fixed at the telephotograph end;

wherein said ordinary region is a region where said single focusing group can focus on, upon power variations of said zoom lens; and

wherein, where the focal length of the entire lens system at the wide angle end is represented by fw and the back focus at the wide angle end is represented by Twbf, the expression 0.2<|Twbf/fw|<1.2 is satisfied.

2. The zoom lens according to claim 1 , wherein said plurality of movable lens groups include a third lens group having a positive refracting power, a fourth lens group having a positive refracting power and performing focusing when moved in a direction of an optical axis, a fifth lens group having a low refracting power and a sixth lens group having a negative refracting power, said second to sixth lens groups forming said macro lens group.

3. The zoom lens according to claim 1 , wherein, where the focal length of the entire lens system at the telephoto end is represented by fT, the focal length of said first lens group is represented by f1, the focal length of said macro lens group at the telephoto end is represented by fmgT the following expressions (1) and (2) are satisfied:

0.6< f 1 /fT <2.0  (1)

0.1< fmgT/tT 0.4  (2).

4. The zoom lens according to claim 1 , wherein, where the lateral magnification of the negative lenses included in said macro lens group at a macro position at which the magnifying power is highest is represented by βmgT, the following expression (4) is satisfied:

1.1 <βmgT <2.0  (4).

5. The zoom lens according to claim 1 , wherein, where the focal length of said focusing group is represented by ff and the focal length of said macro lens group at the telephoto end by fmgT, the following expression (5) is satisfied:

1.0< ff/fmgT <5.0  (5).

6. An image pickup apparatus, comprising:

a zoom lens; and

an image pickup element for converting an optical image formed by said zoom lens into an electric signal;

said zoom lens including a first lens group having a positive refracting power, a second lens group having a negative refracting power and serving as a movable group upon power variation of said zoom lens, and a plurality of movable lens groups cooperable with said second group to form a macro lens group, said first lens group, second lens group and movable lens groups being disposed in order from an object side, said movable lens groups including a single focusing group and an additional lens group disposed on the image side with respect to said single focusing group and having a negative refracting power;

said zoom lens having a macro mode in which said zoom lens can be focused at a shorter distance than an ordinary region by moving said macro lens group integrally from a position at the telephoto end toward the object side while said first lens group is fixed at a telephotograph end;

wherein said ordinary region is a region where said single focusing group can focus on, upon power variations of said zoom lens; and

wherein, where the focal length of the entire lens system at the wide angle end is represented by fw and the back focus at the wide angle end is represented by Twbf, the expression 0.2<|Twbf/fw|<1.2 is satisfied.

7. The image pickup apparatus according to claim 6 , wherein said plurality of movable lens group including a third lens group having a positive refracting power, a fourth lens group having a positive refracting power and performing focusing when moved in a direction of an optical axis, a fifth lens group having a low refracting power, and a sixth lens group having a negative refracting power, said second to sixth lens groups forming said macro lens group.