Patent ID: 7161742

Claim:
A small zoom lens comprising: a first lens group that comprises a lens having a negative refractive power, a lens having a positive refractive power and a lens having a positive refractive power, arranged in that order from an object side, that has a positive refractive power as a whole, and that is fixed with respect to an image plane; a second lens group that has a negative refractive power as a whole, and that causes a zooming action when moved along an optical axis; an aperture stop that is fixed with respect to the image plane; a third lens group that comprises at least one aspherical surface, that comprises a meniscus negative lens whose concave surface faces the object side and a lens having a positive refractive power, arranged in that order from the object side, that has a positive or negative refractive power as a whole, and that is fixed with respect to a direction of the optical axis when zooming and when focusing; and a fourth lens group that comprises a lens having a positive refractive power, a lens having a negative refractive power and a lens having a positive refractive power, arranged in that order from the object side, that has a positive refractive power as a whole, and that moves along the optical axis such that the image plane, which is displaced by a movement of the second lens group along the optical axis and by a movement of the object, is maintained at a constant position with respect to a reference plane, wherein the following Condition (1) is satisfied: 4.01 <|f 3 /f 4|<60, (1) where f 3 : focal length of the third lens group, f 4 : focal length of the fourth lens group.