Patent ID: 6657792
Filing Date: 2003-12-02
Classification: G02B

Abstract:
A zoom lens system comprising a positive first lens group, a negative second lens group, a positive third lens group and a negative fourth lens group in this order from an object, wherein:zooming is performed by moving each of said first through fourth lens groups in the optical axis direction; and said zoom lens system satisfies the following conditions: 1.123T/f23W<1.8 0.223W/fW<0.45 0.01D23Wâˆ’D23T)/fT<0.05 0.1r1/fT|<0.25(r1<0) 6.0fT/f2|<12.0(f2<0) whereinf23W designates the combined focal length of said second and third lens groups at the short focal length extremity; f23T designates the combined focal length of said second and third lens groups at the long focal length extremity; LD23W designates the distance between the most object-side surface of said second lens group and the most image-side surface of said third lens group at the short focal length extremity; fw designates the focal length of aid entire zoom lens system at the short focal length extremity; D23W designates the axial air-distance between said second lens group and said third lens group at the short focal length extremity; D23T designates the axial air-distance between said second lens group and said third lens group at the long focal length extremity; fT designates the focal length of the entire zoom lens system at the long focal length extremity; r1 designates the radius of curvature of the most object-side surface of said first lens group; and f2 designates the focal length of said second lens group.