Patent ID: 6404562
Filing Date: 2002-06-11
Classification: G02B

Abstract:
A zoom lens to form an image of an object with variable magnification, comprising:a first lens group having a positive refracting power, and a second lens group positioned closer to the image than the first lens group and having a negative refracting power, wherein, when the magnification is changed, a distance between the first lens group and the second lens group is changed, wherein the first lens group consists of a 1-1 lens, a 1-2 lens, and a 1-3 lens aligned in this order from the object and the second lens group comprises a 2-1 lens and a 2-2 lens aligned in this order from the object, wherein the zoom lens comprises at least two plastic lenses, and wherein the 1-1 lens is a plastic lens, the 1-3 lens has a positive refracting power and the 2-2 lens has a negative refracting power, and wherein the 1-2 lens is a plastic lens, at least four surfaces of the lenses in the entire system of the zoom lens are an aspherical surface, and a following formula is satisfied: 1.50&lE;n2-2&lE;1.90 where n2-2 is a refractive index of the 2-2 lens, wherein the 1-1 lens has a positive refracting power and has at least one aspherical surface, the 2-1 lens is a plastic lens and has at least one aspherical surface, and a following formula is satisfied: âˆ’5&lE;(&phgr;P+&phgr;4)Â·fT2/FT&lE;5 where &phgr;P is a power of a plastic lens of the first lens group, &phgr;4 is a power of the 2-1 lens, fT is a focal length of the zoom lens at a telephoto end and FT is an F-number of the zoom lens at a telephoto end.