Patent ID: 7280285

Claim:
A projection lens having a magnification side and a reduction side opposite the magnification side and comprising three lens groups, arranged in order from the magnification side, as follows: a first lens group having negative refractive power; a second lens group having positive refractive power; and a third lens group having positive refractive power; wherein said first lens group includes, arranged in order from the magnification side, a first lens element of negative refractive power and meniscus shape with its convex surface on the magnification side and with at least one surface aspheric, a second lens element of negative refractive power and meniscus shape with its concave surface on the reduction side, and a third lens element of negative refractive power, having surfaces of different curvature, with its surface of greater absolute value of refractive power being concave and on the reduction side; said second lens group includes a fourth lens element having positive refractive power, a meniscus shape, and a convex surface on the magnification side; said third lens group includes a fifth lens element having positive refractive power, a meniscus shape, a convex surface on the reduction side, and an aspheric surface on the magnification side, and a lens component formed by cementing two or more lens elements together; the on-axis distance between said first lens group and said second lens group provides a space for placement of a mirror for deflecting the optical path between said first lens group and said second lens group; the projection lens is telecentric on the reduction side; and the following conditions are satisfied: | f 1 /D G1G2 |<0.5 8 <|f 1 ·D G1G2 |/f 2 <13 0.35 <D G1G2 /DL− 0.55 where f 1 is the focal length of said first lens group; D G1G2 is the on-axis distance between said first lens group and said second lens group; f is the focal length of the projection lens; and DL is the total length of the projection lens.