Patent ID: 8922906
Filing Date: 2014-12-30
Classification: G02B

Abstract:
1. A zoom lens, substantially consisting of four lens groups, composed of a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a negative refractive power, and a fourth lens group having a positive refractive power, disposed in order from the object side, wherein: upon zooming from the wide angle end to the telephoto end, the first lens group and the fourth lens group are fixed in an optical axis direction, the second lens group is moved to the image side, and the third lens group is moved so as to correct an image plane variation due to the movement of the second lens group; the first lens group is substantially consists of three lens groups, composed of a first lens group front group having a negative refractive power, a first lens group middle group having a positive refractive power, and a first lens group rear group having a positive refractive power, disposed in order from the object side; the first lens group front group substantially consists of three lenses, composed of two negative lenses and one positive lens, disposed in order from the object side; the first lens group middle group is composed of a cemented lens in which a negative lens and a positive lens are cemented; the zoom lens is configured such that focusing is performed by moving only the first lens group middle group in an optical axis direction; and the zoom lens satisfies a conditional expression (2) given below: where: t1: the distance from the most object side surface of the first lens group to the most image side surface of the first lens group on the optical axis; and fw: the focal length of the entire system at the wide angle end.