Patent ID: 9128275
Filing Date: 2015-09-08
Classification: G02B

Abstract:
1. A variable magnification optical system, consisting essentially of a first lens group having a negative refractive power, a stop, and a second lens group having a positive refractive power in order from the object side, and being configured such that the distance in an optical axis direction between the first lens group and the second lens group is reduced when magnification is changed from the wide angle end to the telephoto end, wherein: the stop is fixed with respect to an image plane when magnification is changed; the first lens group is composed of a positive lens, a negative lens, a negative lens, and a positive meniscus lens with a convex surface on the object side in order from the object side; the second lens group is composed of a biconvex lens, a negative lens, a biconvex lens, a negative lens, and a positive lens in order from the object side; and the variable magnification optical system satisfies conditional expressions (1) and (2) given below: where, νdp: average Abbe number of the most object side positive lens and the most image side positive meniscus lens in the first lens group at the d-line, fw: focal length of the entire system at the wide angle end, and f2: focal length of the negative lens disposed second from the object side in the first lens group.