Patent ID: 7440194

Claim:
A zoom lens for use in projection technology comprising, in this order from the magnification side to the minification side thereof, a first lens group having negative refraction of power, a second lens group having positive refraction of power, a third lens group having positive refraction of power, a fourth lens group having negative refraction of power, and a fifth lens group having positive refraction of power, wherein the zoom lens satisfies the formulas: −1.5<F 1 /Fw<−1.3, 1.5<F 2 /Fw<1.8, 1.8<F 3 /Fw<2.2, −10<F 4 /Fw<−5, and 2.3<F 5 /Fw<2.8, where F 1 , F 2 , F 3 , F 4 , F 5 , and Fw respectively represent the effective focal length of the first lens groups, the second lens group, the third lens group, the fourth lens group, the fifth lens group, and the shortest effective focal length of the zoom lens.