Patent ID: 6304389
Filing Date: 2001-10-16
Classification: G02B

Abstract:
A variable focal length lens system comprising, in order from an object side:a first lens group having negative refractive power;a second lens group having positive refractive power; anda third lens group having positive refractive power;wherein the first lens group includes, in order from the object side,a lens unit (1-1) having negative refractive power anda lens unit (1-2) having positive refractive power separated by predetermined air space; andwherein the second lens group includes, in order from the object side,a lens unit (2-1) having positive refractive power,a lens unit (2-2) having negative refractive power separated by predetermined air space, anda lens unit (2-3) having positive refractive power separated by predetermined air space;with the first and second lens groups being moved such that when a state of the lens group positions is changed from a wide-angle end state to a telephoto end state, a space between the first and second lens groups decreases and a space between the second and third lens groups increases while the third lens group is fixed;and wherein the following conditions are satisfied:0.7 < f2/.vertline.f1.vertline. < 1.5 (f1 < 0) 3 < f3/fw < 10 1 < f12/.vertline.f1.vertline. < 3 (f1 < 0) 1 < .vertline.f22.vertline./f2 < 5 (f22 < 0) 1.6 < (D1w - D1t)/fw < 6 1.6 < (d2t - D2w)/fw < 6where f1 denotes the focal length of the first lens group,f2 denotes the focal length of the second lens group,f3 denotes the focal length of the third lens group,fw denotes the focal length of the lens system in the wide-angle end state,f12 denotes the focal length of the lens unit (1-2),f22 denotes the focal length of the lens unit (2-2),D1w denotes the space between the first lens group and the second lens group at the wide-angle end state,D1t denotes the space between the first lens group and the second lens group in the telephoto end state,D2w denotes the space between the second lens group and the third lens group in the wide-angle end state, andD2t denotes the space between the second lens group and the third lens group at the telephoto end state.