Patent ID: 7733576

Claim:
A two-group zoom projection lens comprising: in order from a magnification side, a first lens group having a negative refractive power; and a second lens group having a positive refractive power, the second lens group comprising a front group and a rear group in order from the magnification side, the front group comprising a group having at least two positive lenses and a group having at least one negative lens in order from the magnification side, the rear group comprising a group having at least one negative lens and a group having at least two positive lenses in order from the magnification side, wherein the at least one negative lens in the front group comprises a lens having a concave surface directed toward the magnification side, the at least one negative lens in the rear group comprises a lens having a concave surface directed toward a reduction side, and the two-group zoom projection lens satisfies conditional expressions (1) to (4): n 2i >1.75 (1) 0.8 <D 2 /f 2 <1.2 (2) 0.6 <f w /f 2 <0.8 (3) 0.6 <f w /|f 1 |<0.9 (4) wherein f 1 represents a focal length of the first lens group, n 2i represents a refractive index with respect to a d-line of a glass material comprising the negative lenses in the second lens group and i is a lens number of at least 2 counted from the magnification side, D 2 represents an overall length of the second lens group, f 2 represents a focal length of the second lens group, and f w represents a focal length at a wide-angle end of the overall system of the two-group zoom projection lens.