Zoom lens and imaging apparatus

摘要

A zoom lens includes first to fourth lens groups having negative, positive, negative, and positive refractive power, respectively, and arranged in order from an object side. The first lens group includes negative lenses. The fourth lens group is configured of one positive lens. A zooming operation from wide end to telephoto end allows the first to third lens groups to travel along an optical axis, and allows the fourth lens group to be fixed. A focusing operation allows the third lens group to travel along the optical axis. The conditional expressions 1<(R1a+R1b)/(R1a−R1b)<5 and 2<(R4a+R4b)/(R4a31 R4b)<7 are satisfied where R1a and R1b are curvature radii on the object side and on the image side of a most-object-sided negative lens in the first lens group, respectively, and R4a and R4b are curvature radii on the object side and on the image side of the positive lens in the fourth lens group, respectively.

主权项

1. A zoom lens comprising:
a first lens group having negative refractive power and including a plurality of negative lenses; a second lens group having positive refractive power; a third lens group having negative refractive power; and a fourth lens group having positive refractive power and configured of one positive lens, the first to fourth lens groups being arranged in order from an object side toward an image side, wherein a zooming operation from wide end to telephoto end allows the first to third lens groups to travel along an optical axis, and allows the fourth lens group to be fixed, a focusing operation allows the third lens group to travel along the optical axis, and the following conditional expressions are satisfied,
1<(R1a+R1b)/(R1a−R1b)<5  (1)2<(R4a+R4b)/(R4a−R4b)<7  (2)0.2<|f3/f4|<0.6  (4) where f4 is a focal length of the fourth lens group, R1a is a curvature radius on the object side of a most-object-sided negative lens in the first lens group, R1b is a curvature radius on the image side of the most-object-sided negative lens in the first lens group, R4a is a curvature radius on the object side of the positive lens in the fourth lens group, and R4b is a curvature radius on the image side of the positive lens in the fourth lens group.