1. Field of the Invention
The present invention relates to a medium telephoto lens suitable for imaging devices, such as a single-lens reflex camera and the like, and particularly relates to a medium telephoto lens suitable for short-distance photography and to an imaging device including this medium telephoto lens.
2. Description of the Related Art
Medium telephoto lenses of this type, which substantially consist of a first lens group and a second lens group in this order from the object side and in which both the first lens group and the second lens group are moved while focusing, are conventionally known, as disclosed in Japanese Unexamined Patent Publication No. 2 (1990)-081015 and Japanese Unexamined Patent Publication No. 2004-212692. However, the medium telephoto lenses disclosed in Japanese Unexamined Patent Publication No. 2 (1990)-081015 and Japanese Unexamined Patent Publication No. 2004-212692 adopt floating mechanisms that move both the first lens group and the second lens group, which makes mechanisms for moving lenses complicated and causes an increase in the size and cost of the lenses.
As disclosed in Japanese Unexamined Patent Publication No. 2002-139668, medium telephoto lenses, in which only the first lens group is configured to move while focusing, are known. The medium telephoto lens disclosed in Japanese Unexamined Patent Publication No. 2002-139668 substantially consists of a first lens group having positive refractive power as a whole and a second lens group having positive refractive power as a whole in this order from the object side. In the medium telephoto lens, the first lens group substantially consists of a positive 1-1 lens having stronger positive power on the object side surface, a 1-2 lens which is a positive meniscus lens having positive power on the object side surface, a 1-3 lens which is a negative meniscus lens with a concave surface toward the image side, an aperture stop, a cemented lens formed by cementing a negative 1-4 lens with a concave surface toward the object side and a positive 1-5 lens, and a positive 1-6 lens in this order from the object side. The second lens group substantially consists of a 2-1 lens, which is a negative meniscus lens with a convex surface toward the object side, and a positive 2-2 lens in this order from the object side. Only the first lens group moves in the direction of the optical axis while focusing.
USPTO Backgrounds
USPTO Backgrounds