Patent ID: 6999240
Filing Date: 2006-02-14
Classification: G02B

Abstract:
1. A zoom lens comprising: a first lens group that is made of a cemented lens including 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 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; a fourth lens group that is made of 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 negative refractive power and being fixed with respect to the image plane; and a fifth lens group that has an overall positive refractive power and that is shifted on the optical axis so as to maintain the image plane, which 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 four lenses, including a negative meniscus lens, a double concave lens, and a cemented lens made of a convex lens and a concave lens, arranged in that order from the object side to the image plane side; wherein the third lens group can be shifted in a direction perpendicular to the optical axis in order to correct image fluctuations during camera shake; wherein the fourth lens group is made of a cemented lens including a convex lens and a concave lens; wherein the fifth lens group is made of three lenses, including a cemented lens made of a double convex lens and a double concave lens, and a convex lens; and wherein, when φ