Patent ID: 7333273
Filing Date: 2008-02-19
Classification: G02B

Abstract:
1. A zoom lens system comprising, in order from an object: a first lens group having negative refractive power; a second lens group having positive refractive power; a third lens group having negative refractive power; and a fourth lens group having positive refractive power; wherein upon zooming from a wide-angle end state to a telephoto end state, each lens group moves along an optical axis such that a distance between the first lens group and the second lens group decreases, a distance between the second lens group and the third lens group increases, and the distance between the third lens group and the fourth lens group decreases; and the first lens group includes a negative lens, at least one lens in the negative lens includes an aspherical surface, and the negative lens satisfies the following conditional expressions: when 30≦νd1<36, when 36≦νd1<41, when 41≦νd1<51, when 51≦νd1<61, when 61≦νd1≦71, where nd1 denotes refractive index of a material of the negative lens in the first lens group at d-line, which has a wavelength λ=587.6 nm, and νd1 denotes Abbe number of a material of the negative lens in the first lens group at d-line, which has a wavelength λ=587.6 nm.