Patent ID: 7436597

Claim:
A projection lens comprising: a first lens group having a negative refractive power; and a second lens group having a positive refractive power, the first lens group and the second lens group being arranged in order from an enlargement side, wherein an interval between the first lens group and the second lens group is set to longest air spacing in the projection lens; each of the first lens group and the second lens group comprises at least one cemented triplet lens in which three lenses are cemented together; and conditional expression (1) through (4) provided below are satisfied −3.5 <f 1 /f <−1.2 (1) 8.0 ≦f 2 /f <12.0 (2) 6.0 <D G1G2 /f (3) 5.0 <Bf/f (4) where f: a focal length of the projection lens f 1 : a focal length of the first lens group f 2 : a focal length of the second lens group D G1G2 : air spacing between the first lens group and the second lens group Bf: an air equivalent length between a reduction-side lens surface of a lens, closest to the reduction side, of the second lens group and a reduction-side image-formation surface of the projection lens.