Patent ID: 6185050
Filing Date: 2001-02-06
Classification: G02B

Abstract:
A zoom lens comprising:(a) a first lens group having positive refracting power; and(b) a second lens group provided on an image side of the first lens group, having negative refracting power,wherein the zooms lens has a variable power ratio of not less than 2.5 and a field angle of not less than 70.degree. at a wide angle end, and a magnification of the zoom lens is changed by changing a distance between the first lens group and the second lens group,wherein the following conditions are satisfied,1.25.ltoreq.Tw/Tt.ltoreq.1.80.6.ltoreq.fFc/fw.ltoreq.0.9where Tw represents a telephoto ratio at a wide angle end of the zoom lens, Tt represents a telephoto ratio at a telephoto end of the zoom lens, fw represents a focal length of the zoom lens at the wide angle end, and fFc represents a focal length of the first lens group, andwherein the first lens group has a first sub-unit and a second sub-unit, said second sub-unit includes one negative lens and one positive lens, or includes one negative lens and two positive lenses, wherein the first sub-unit has negative refracting power and the second sub-unit has positive refracting power both arranged in the order named from an object side across an air distance on an optical axis which is the longest in the first lens group, the first sub-unit includes two lenses one of which is a negative lens which is closer to an object, andwherein the second lens group includes two lenses.