Patent ID: 7715111

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 or negative refractive power; a fourth lens group having a positive refractive power; a fifth lens group having a positive or negative refractive power; and a sixth lens group having a positive refractive power, wherein the projection zoom lens system is configured to be nearly telecentric on a reduction side, during zooming, four lens groups including the second to fifth lens groups are moved while the first and sixth lens groups remain stationary, the third lens group includes, at least, a positive lens L P having a convex surface directed to the magnification side, and a negative lens L N having a concave surface directed to the reduction side, the concave surface having a curvature larger than a magnification-side surface of the negative lens L N , and the following conditional expression (1A) is satisfied: 5.0≦| f G3 /R LN-2 | (1A) where f G3 denotes a focal length of the third lens group, and R LN-2 denotes a radius of curvature of the reduction-side surface of the negative lens L N .