Patent ID: 8928991
Filing Date: 2015-01-06
Classification: G02B

Abstract:
1. A zoom lens comprising, in order from an object side to an image side: a first lens unit which does not move for zooming and has a positive refractive power; a second lens unit which moves during zooming and has a negative refractive power; a third lens unit which moves during zooming and has a positive refractive power; and a fourth lens unit which does not move for zooming and has a positive refractive power, wherein lenses forming the fourth lens unit are spaced at a first air interval and a second air interval in the fourth lens unit, and the fourth lens unit includes, in order from the object side to the image side, a 41 lens group having a positive refractive power, a 42 lens group having a negative refractive power, and a 43 lens group having a positive refractive power, wherein the 42 lens group includes one or more positive lenses and one or more negative lenses, and wherein the following conditions are satisfied: where β3w corresponds to a lateral magnification of the third lens unit at a wide-angle end when an infinite object is focused, f4 corresponds to a focal length of the fourth lens unit, Ld4 corresponds to a length on an optical axis from a most object side lens surface to a most image side lens surface of the fourth lens unit, Ld41 corresponds to an air interval between the 41 lens group and the 42 lens group, Ld42 corresponds to an air interval between the 42 lens group and the 43 lens group, f42 corresponds to a focal length of the 42 lens group, ν42p corresponds to an average value of Abbe constants of materials of the positive lenses included in the 42 lens group, θ42p corresponds to an average value of partial dispersion ratios of the materials of the positive lenses included in the 42 lens group, and ν42n corresponds to an average value of Abbe constants of materials of the negative lenses included in the 42 lens group, and θ42n corresponds to an average value of partial dispersion ratios of the materials of the negative lenses included in the 42 lens group.