Aspherical zoom lens

摘要

The aspherical zoom lens of the invention includes sequentially from an object side: a first lens group which has a positive refractive power and is fixed relative to an image plane; a second lens group which has a negative refractive power and is movable on an optical axis of the aspherical zoom lens so as to have a magnification changing function; a third lens group which has a positive refractive power and is fixed relative to the image plane so as to have a light converging function; and a fourth lens group which has a positive refractive power and is movable on the optical axis so that the image plane displaceable in response to travel of the second lens group and movement of the object is fixed at a position spaced by a predetermined distance from a reference face. An air space is provided between the third and the fourth lens groups. When viewed sequentially from the object side, the first lens group includes a negative lens, a positive lens and a meniscus positive lens, the second lens group includes a meniscus negative lens, a double concave lens and a positive lens, the third lens group includes a single lens having at least one aspherical face and the fourth lens group includes a cemented doublet and a positive lens, at least one of which has at least one aspherical face.