Patent ID: 9588323
Date: 2017-03-07
CPC Classifications: G02B

Claim:
1. A zoom lens comprising in order from an object side to an image side: a first lens unit having a positive refractive power which does not move for zooming; a second lens unit having a negative refractive power which moves during zooming; a third lens unit having a positive or negative refractive power which moves during zooming; an aperture stop; and a fourth lens unit having a positive refractive power which does not move for zooming, wherein, in the fourth lens unit, a front group is a lens system including a lens face which satisfies a relationship of among lenses in an optical path from the aperture stop to an image plane, and a rear group is a lens system other than the lens system of the front group, where h_i is an incidence height from an optical axis of an on-axis ray of an i-th lens, which is a thin lens, in paraxial tracking and h_bar_i is an incidence height from an optical axis of an off-axis main light beam of the i-th lens in the paraxial tracking, and wherein the zoom lens satisfies the following conditional expressions: where a partial dispersion ratio of a material of a positive lens Lm formed of a material having a highest partial dispersion ratio, which is contained in the rear group, is represented by θLm, a distance from the aperture stop to the image plane is represented by d, a distance from the aperture stop to the positive lens Lm is represented by dLm, an average value of Abbe constants of materials of positive lenses contained in the front group is represented by νRfp, an average value of partial dispersion ratios thereof is represented by θRfp, an average value of Abbe constants of materials of negative lenses contained in the front group is represented by νRfn, an average value of partial dispersion ratios thereof is represented by θRfn, a refractive power of the front group is represented by φRf, and a refractive power of the rear group is represented by φRb.