Patent ID: 8179610
Filing Date: 2012-05-15
Classification: G02B

Abstract:
1. A zoom lens comprising: a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power, which are disposed in order from an object side to an image side; and an aperture stop disposed at an object side of the third lens group, wherein when changing the magnification of the zoom lens from a wide angle end to a telephoto end, an interval between the first and second lens groups increases, an interval between the second and third lens groups decreases, and an interval between the third and fourth lens groups increases; the first lens group includes at least a negative lens, a positive lens, and a positive lens, which are disposed in order from the object side; and the following conditions are satisfied: where nd 11 is a refractive index of the negative lens of the first lens group for a d line, vd 11 is an Abbe number of the negative lens of the first lens group for the d line, and θ gF is a relative partial dispersion of the negative lens of the first lens group which is (n g −n F )/(n F −n C ) where n g is a refractive index for a g line, n F is a refractive index for a F line, and n C is a refractive index of the negative lens of the first lens group for a C line.