Patent ID: 7009777

Claim:
A projection lens for forming an enlarged image of a pixelized panel on a screen, said projection lens having a long conjugate side, a short conjugate side, and an effective focal length f 0 , said lens, in order from the long conjugate side to the short conjugate side, comprising: (I) a first lens unit consisting in order from the long conjugate side to the short conjugate side of: (A) a first lens sub-unit having a negative power and comprising a negative lens element which (i) has a short conjugate surface which is concave towards the short conjugate side and (ii) comprises at least one aspheric surface; and (B) a second lens sub-unit; (II) an aperture stop; and (III) a second lens unit having a positive power, an effective focal length f U2 , and consisting in order from the long conjugate side to the short conjugate side of: (A) a first lens sub-unit having a positive power, an effective focal length f U2S1 and comprising a positive lens element and a negative lens element, the positive lens element having a lower dispersion than the negative lens element; and (B) a second lens sub-unit which, in order from the long conjugate side to the short conjugate side, comprises: a negative lens element having a focal length f neg and a lens element which comprises an aspherical surface which has a positive on-axis power; or a lens element having first and second optical surfaces,—where the first surface has a negative power θ neg , the second surface is an aspherical surface which has a positive on-axis power, and the first and second surfaces are separated by an axial distance t which satisfies the relationship: t/f 0 ≧0.05; wherein: (a) the first and second lens units are the only lens units of the projection lens; (b) f U2 /f 0 ≦1.5; (c) f U2S1 /f 0 ≦2.0; and (d) |f neg |≦2.0·f 0 or 1/|θ neg |≦1.5·f 0 .