Patent ID: 6646815
Filing Date: 2003-11-11
Classification: G02B,G03B

Abstract:
A zoom lens system having an object side to face an object and an image side to face an image forming plane, comprising:a zoom lens consisting of three lens groups: a first lens group having a negative refracting power; a second lens group having a positive refracting power; and a third lens group having a positive refracting power arranged serially in this order from the object side, wherein the second lens group comprises a positive lens, a cemented lens including a positive lens and a negative lens and one lens arranged serially in this order from the object side, and when changing a magnification from a wide-angle side to a telephoto side, the first, second and third lens groups are moved on an optical axis so that a distance between the first lens group and the second lens group is reduced and a distance between the second lens group and the third lens group is increased for the magnification change, and wherein the following conditional expression is satisfied: 0.4<fw/f2<1.0 where f2 represents a focal length of the second lens group and fw represents a focal length of the total optical system at a wide-angle end.