Patent ID: 7215485

Claim:
A rear focus type zoom lens for an image capturing element, comprising, in the order from the object side: a first lens group having a positive refracting power; a second lens group having a negative refracting power and movable for variable magnification; a third lens group having a positive refracting power; and a fourth lens group having a positive refracting power and movable for correcting positional change of an image plane in variable magnification; wherein the first lens group includes, in the order from the object side, a negative lens (L 11 ), a positive lens (L 12 ) and a positive lens (L 13 ), the second lens group includes, in the order from the object side, a negative lens (L 21 ), a negative lens (L 22 ) and a positive lens (L 23 ), the third lens group includes a single lens (L 31 ) having a positive refracting power and having at least one aspheric surface and the fourth lens group has at least one aspheric surface or more and includes, in the order from the object side, a negative lens (L 41 ), a positive lens (L 42 ) and a positive lens (L 43 ), and when ν 1 represents Abbe's number of at least one piece of positive lenses of the first lens group, ν 31 represents Abbe's number of the single lens (L 31 ), fi represents a focal length of an i th lens group and f 4 —represents a focal length of the negative lens (L 41 ) in the fourth lens group, the following conditional expressions are satisfied: 75.0<ν1 (1) 40.0>ν31 (2) 0.8 <f 4 /|f 4−|<1.5 (3) 3.0 <|f 1 /f 2|<6.0 (4).