Patent ID: 8437093

Claim:
A projection lens system that projects projection light from a light modulator onto a screen, comprising, in order from a screen side thereof, a first lens group with negative refractive power, a second lens group with positive refractive power, and a third lens group with positive refractive power, wherein the first lens group includes, in order from the screen side, a first negative meniscus lens that is made of resin and is convex on the screen side, a second negative meniscus lens that is made of glass and is convex on the screen side, and a negative biconcave lens made of resin, both surfaces of the first negative meniscus lens and of the negative biconcave lens being aspherical, the second lens group consists of a positive biconvex lens made of glass, and a combined focal length f 1 of the first lens group, a focal length f 12 of the second negative meniscus lens of the first lens group, a focal length f 13 of the negative biconcave lens of the first lens group, a refractive index n 12 of the second negative meniscus lens of the first lens group, a radius of curvature R 12 a of a surface on the screen side of the second negative meniscus lens of the first lens group, and a radius of curvature R 21 b of a surface on a light modulator side of the positive biconvex lens of the second lens group satisfy following conditions 1.0<| f 12/ f 1|<4.0, 5.0<| f 13/ f 1|<9.0, 1.74 <n 12<2.0, and 0.1 <R 21 b/R 12 a|< 0.8.