Patent ID: 7289270

Claim:
A projection lens comprising: in order from a magnification side thereof, a first lens group having a negative refractive power, the first lens group consisting of an aspheric lens and a double-concave lens in this order from the magnification side; a second lens group having a positive refractive power, the second lens group comprising one positive lens or comprising one positive lens and one negative lens; and a third lens group having a positive refractive power, the third lens group comprising three to five lenses including at least a cemented lens portion and a positive lens portion in this order from the magnification side, the three to five lenses including a surface closest to the magnification side as an aspheric surface, wherein the projection lens has a substantially telecentricity on a reduction side thereof; the third lens group has a magnification-side focal position located in an air space between the third lens group and the second lens group; the projection lens has a space between the first lens group and the second lens group, the space being the longest air space in the projection lens; and the projection lens satisfies conditional expressions (1) to (7): −3.5 <f 1 /f<− 1.2 (1) 2.5 <f 3 /f< 8.0 (2) 3.5 <D 12 /f< 15.0 (3) 2.0 <Bf/f< 8.0 (4) 7.5 <|ASf 1 /f| (5) |FFd/f|< 3.0 (6) 75 degrees<2ω (7) wherein f designates a focal length of the projection lens; f 1 designates a focal length of the first lens group; f 3 designates a focal length of the third lens group; D 12 designates an air space between the first lens group and the second lens group; Bf designates an air-basis length between a reduction-side lens surface of a lens closest to the reduction side in the third lens group and a reduction-side image plane; ASf 1 designates a focal length of the aspheric lens of the first lens group; FFd designates a magnification-side focal position of the third lens group; and 2ω designates a magnification-side view angle.