Patent ID: 7706079

Claim:
A projection zoom lens system comprising, in order from a magnification side: 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 positive refractive power; and a fifth lens group having a positive refractive power, wherein the first lens group has an aspheric surface, a lens closest to the magnification side in the fourth lens group has an aspheric surface, and the fifth lens group consists of one positive lens, wherein during zooming, the first and fifth lens groups remain stationary, while the second, third, and fourth lens groups are movable respectively, and during zooming from a wide-angle end to a telephoto end, the second, third, and fourth lens groups moves toward the magnification side along an optical axis, and wherein the following conditional expression (1) is satisfied: 0.8< d 34/ fw (1), where fw denotes a focal length of the whole system at the wide-angle end, and d34 denotes an air space between the third lens group and the fourth lens group at the wide-angle end.