Patent ID: 8780453
Filing Date: 2014-07-15
Classification: G02B

Abstract:
1. A zoom lens comprising, in order from the object side, a first lens unit having a positive refractive power which does not move for varying magnification, a second lens unit having a negative refractive power which moves for varying magnification, a third lens unit having a negative refractive power which moves for varying magnification, and a fourth lens unit having a positive refractive power which does not move for varying magnification, wherein the first lens unit includes a positive lens which satisfies the following conditions: where Np is a refractive index of the positive lens, and νp is an Abbe constant of the positive lens, and wherein the following condition is satisfied: where fp is a focal length of the positive lens, wherein the first lens unit includes a plurality of negative lenses and fna is a combined focal length of negative lenses in the first lens unit defined by the following equation: where n is a number of the negative lenses included in the first lens unit, and fni is a focal length of the i-th negative lens.