Zoom lens and image pickup apparatus

摘要

Disposing from an object side in the order of a positive first lens group which is fixed at the time of zooming, a negative second lens group which is moved at the time of zooming, an aperture stop, a positive third lens group which 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. The zoom lens is configured to simultaneously satisfy, when a focal length of the overall lens system at the telephoto end, an overall optical length, and an Abbe number of the second group first lens with respect to d-line are taken as ft, TL, and νd21 respectively, conditional expressions (1): 0.62

主权项

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:
0.62 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 νd21 is an Abbe number of the second group first lens with respect to d-line, wherein the second group second lens and second group third lens are cemented and the second lens group satisfies a conditional expression given below:
1.89 Nd22 is a refractive index of the second group second lens.