Patent ID: 6999241

Claim:
A zoom lens comprising: a first lens group that is made of a lens having negative refractive power and a lens having positive refractive power, as well as a lens having positive refractive power, arranged in that order from an object side to an image plane side, the first lens group having an overall positive refractive power and being fixed with respect to an image plane; a second lens group having an overall negative refractive power, a zoom operation being carried out by shifting the second lens group on an optical axis; an aperture stop that is fixed with respect to the image plane; a third lens group that is made of a lens having positive refractive power, as well as a lens having a positive refractive power and a lens having negative refractive power, arranged in that order from the object side to the image plane side, the third lens group having an overall positive refractive power and being fixed with respect to the optical axis direction when zooming or focusing; and a fourth lens group that is made of a lens having positive refractive power, a lens having negative refractive power and a lens having positive refractive power, arranged in that order from the object side to the image plane side, the fourth lens group having an overall positive refractive power and being shifted on the optical axis so as to maintain the image plane that fluctuates when the second lens group is shifted on the optical axis and when the object moves, at a certain position from a reference plane; wherein the second lens group is made of a concave meniscus lens, a concave lens, a double convex lens and a concave lens, arranged in that order from the object side to the image plane side, and includes at least one aspheric surface; wherein the third lens group comprises a cemented lens having a cemented surface whose convex surface faces the image plane side, the third lens group can be shifted in a direction perpendicular to the optical axis in order to correct image fluctuations during camera shake, and includes at least one aspheric surface; wherein the fourth lens group comprises at least one aspheric surface; and wherein a condition of the following Expression (5) is satisfied when f 1 indicates a focal length of the first lens group, and f 11-12 indicates a combined focal length of a first lens and a second lens of the first lens group viewed from the object side 3.2<f 11-12 /f 1 <5.0 (5).