Patent ID: 7535650

Claim:
A zoom lens, comprising: a first lens group having a negative refracting power; a second lens group having a positive refracting power, and including at least three positive lenses and two negative lenses in which at least one of the three positive lenses is an aspheric positive lens; and an aperture provided on an object side of the second lens group and which moves integrally with the second lens group, the first lens group and the second lens group being arranged in this order from the object side to an image side, and at least the first lens group and the second lens group being moved when zooming from a wide-angle end to a telephoto end is performed, such that an interval between the first lens group and the second lens group is reduced, and an interval between the second lens group and an image plane is increased, wherein an Abbe's number ν d and an anomalous dispersion Δθ g,F of a glass type of the at least one aspheric positive lens of the three positive lenses of the second lens group satisfy the following conditions, respectively: ν d >80.0 (1) Δθ g,F >0.025 (2) where n g is a refracting index to a g-line, n F is a refracting index to an F-line, n c is a refracting index to a c-line, ν d is the Abbe's number, and Δθ g,F is the anomalous dispersion, wherein a relative partial dispersion θ g,F is defined by a condition: θ g,F =( n g −n F )/( n F −n c ) wherein the anomalous dispersion Δθ g,F is defined as a deflection from a reference line on a two-dimensional coordinate surface, wherein the two-dimensional coordinate surface is defined by a plane including two perpendicular axes in which the relative partial dispersion θ g,F is a longitudinal axis and in which the Abbe's number ν d is a lateral axis thereof, and wherein the reference line is defined by a straight line connecting coordinate points (ν d =60.49, θ g,F =0.5432) of a reference glass type K7 and coordinate points (ν d =36.26, θ g,F =0.5830) of a reference glass type F2.