Patent ID: 9069155
Filing Date: 2015-06-30
Classification: G02B

Abstract:
1. A zoom lens, consisting of a first lens group which has a positive power and is fixed at the time of zooming, a second lens group which has a negative power and is moved along an optical axis at the time of zooming, an aperture stop, a third lens group which has a positive power and is fixed at the time of zooming, and a fourth lens group which is moved along the optical axis at the time of zooming to correct a change in image plane position arising from the zooming for focusing, disposed in this order from an object side, wherein: the first lens group is consisted of a first group first lens having a negative power, a first group second lens having a positive power, a first group third lens having a positive power, and a first group fourth lens having a positive power, disposed in this order from the object side; the second lens group is consisted of a second group first lens having a negative power, a second group second lens having a negative power, a second group third lens having a positive power, and a second group fourth lens having a positive or negative power with at least one surface being aspheric, disposed in this order from the object side; and the zoom lens is configured to simultaneously satisfy conditional expressions (1) and (2) given blow: where: ft is a focal length of the overall lens system at a telephoto end; TL is a distance from an object side surface of the first group first lens to an image forming plane on the optical axis; and νd wherein the second group second lens and second group third lens are cemented and the second lens group satisfies a conditional expression given below: where: Nd