Patent ID: 7672066
Filing Date: 2010-03-02
Classification: G02B

Abstract:
1. A zoom lens, comprising, in order from an object to an image: a first lens group having positive refractive power; a second lens group having negative refractive power; a third lens group having positive refractive power; and a fourth lens group having positive refractive power; when varying a field angle from a wide-angle end to a telephoto end, the first lens group and the third lens group being moved to be located on the object side at the telephoto end rather than at the wide-angle end such that a distance between the first lens group and the second lens group increases, a distance between the second lens group and the third lens group decreases, and a distance between the third lens group and the fourth lens group increases, the first lens group including one negative lens and two positive lenses, at least one of the negative lens and the two positive lenses of the first lens group including an aspherical surface, and the first lens group satisfying the following conditional expressions, where, ν the abnormal dispersion Δθ ng, n