Patent ID: 7529034

Claim:
A zoom lens comprising, in order from a magnifying side, a first lens group having a negative refractive power as a whole, a second lens group having a positive or negative refractive power as a whole, a third lens group having a positive refractive power as a whole and a fourth lens group having a positive refractive power as a whole, wherein a variable power as a whole lens system thereof is established by configuring such that the fourth lens group is left fixed while a variable power is effected, the first lens group and the second lens group are made to move on an optical axis in such a manner as to move in a direction from a magnifying side to a contracting side over a range from a wide angle end to an intermediate area and to move in a direction from the contracting side to the magnifying side over a range from the intermediate area to a telephoto end, and the third lens group is made to move on the optical axis in such a manner as to move in a direction from the contracting side to the magnifying side over a range from the wide angle end to the telephoto end, and wherein the following conditional expression (1) is satisfied with respect to a power set at the first lens group and the second lens group, the following conditional expression (2) is satisfied with respect to a power set at the third lens group, and the following conditional expression (3) is satisfied with respect to a positional relationship between the third lens group and the fourth lens group at the wide angle end: −0.9 <f w /f I-II <−0.5 (1) 0.3 <f w /f III <0.55 (2) 1.7 <d wIII /f w (3) where f w : composite focal length of the whole lens system at the wide angle end (focused at a magnifying side object distance of 1700 mm from a lens surface of the first lens group which is situated closest to the magnifying side); f I-II : composite focal length of the first lens group and the second lens group at the wide angle end (focused at a magnifying side object distance of 1700 mm from a lens surface of the first lens group which is situated closest to the magnifying side); f III : composite focal length of the third lens group; d wIII : airspace between the third lens group and the fourth lens group at the wide angle end.