Variable magnification optical system and imaging apparatus

摘要

A variable magnification optical system consists of a negative first lens group, a stop that is fixed relative to an image plane during magnification change, and a positive second lens group, which are in this order from an object side. A distance between the first lens group and the second lens group in an optical axis direction becomes shorter when magnification is changed from a wide-angle end to a telephoto end. The first lens group consists of a positive lens having a convex object-side surface and two negative lenses, in this order from the object side. The variable magnification optical system satisfies the following formula (1) about Abbe number νd1 of the positive lens in the first lens group for d-line:
25.5<νd1<50  (1).

主权项

1. A variable magnification optical system consisting of:
a first lens group having negative refractive power; a stop; and a second lens group having positive refractive power, which are in this order from an object side, wherein a distance between the first lens group and the second lens group in an optical axis direction becomes shorter when magnification is changed from a wide-angle end to a telephoto end, and wherein the stop is fixed relative to an image plane during magnification change, and wherein the first lens group consists of a positive lens having a convex object-side surface and two negative lenses in this order from the object side, and wherein the second lens group consists of a double-convex lens, a negative meniscus lens, a double-convex lens, a double-concave lens and a positive lens, which are in this order from the object side, wherein the following formula (1) is satisfied:
25.5<νd1<50  (1), where νd1: an Abbe number of the positive lens in the first lens group for d-line.