Patent ID: 8179606

Claim:
A zoom lens for projection comprising: a first lens group having a negative refractive power; a second lens group having a positive refractive power; a third lens group having a positive refractive power; a fourth lens group having a negative refractive power; a fifth lens group having a positive refractive power; and a sixth lens group having a positive refractive power, which are arranged from a magnification side of the zoom lens, wherein a reduction side of the zoom lens is telecentric, and wherein when the magnification of the zoom lens is changed, the first lens group and the sixth lens group are fixed, and each of the second lens group, the third lens group, the fourth lens group and the fifth lens group moves along the optical axis of the zoom lens, and wherein the fourth lens group is a negative lens having a concave surface facing the magnification side, and wherein the fifth lens group includes at least two positive lenses and at least two negative lenses, and wherein the following formula (1) is satisfied: −5.0 ≦f 4/ fw≦− 1.2 (1), where f4: the focal length of the fourth lens group; and fw: the focal length of the entire system of the zoom lens at a wide angle end.