Patent ID: 7230770
Filing Date: 2007-06-12
Classification: G02B

Abstract:
1. A projection lens for forming an enlarged image of a pixelized panel on a screen, said projection lens having an optical axis, 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 which, in order from the long conjugate side to the short conjugate side, comprises: (A) a lens element L (B) at least one other lens element; and (II) a second lens unit having a positive power, said lens unit, in order from the long conjugate side to the short conjugate side, comprising: (A) a first color-correcting doublet which, from the long conjugate side to the short conjugate side, has a positive-followed-by-negative form; (B) a first positive lens element; and (C) a second color-correcting doublet which, from the long conjugate side to the short conjugate side, has a negative-followed-by-positive form; wherein: (a) the first and second lens units are the only lens units of the projection lens; (b) the projection lens has an aperture stop that is located between the first and second lens units; (c) the projection lens has a field of view in the direction of the long conjugate which is greater than or equal to 75 degrees; (d) the projection lens is telecentric on the short conjugate side; (e) the projection lens has an effective back focal length BFL which satisfies the relationship: (f) the projection lens has a mechanical spacing S between two of its lens elements which satisfies the relationship: where the mechanical spacing is the smaller of the center-to-center distance and the edge-to-edge distance between the elements for an unfolded optical axis.