Patent ID: 7002753

Claim:
A retrofocus 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 having a negative power, said lens unit, in order from the long conjugate side to the short conjugate side, comprising: (A) a first lens element L 1 composed of an optical material having an Abbe number v L1 , said element having at least one aspherical surface and an on-axis optical power φ L1 ; and (B) a second lens element L 2 composed of an optical material having an Abbe number v L2 , said element having at least one aspherical surface and an on-axis optical power φ L2 ; and (II) a second lens unit having a positive power; wherein: (a) the first and second lens units are the only lens units of the retrofocus lens; (b) the first lens element L 1 has a generally meniscus shape which is convex towards the long conjugate; (c) the second lens element L 2 has a biconcave shape when its surface configurations are described by best fit spherical curves; (d) φ L1 , v L1 , φ L2 , and v L2 satisfy the relationships: (i) φ L1 <0; (ii) |φ L1 |>|φ L2 |; (iii) v L2 <v L1 ; and (iv) v L2 ≦55; and (e) the at least one aspherical surface of the second lens element L 2 is configured so that the element has an optical power φ L2/0.7CA at 0.7 of the clear aperture of its short conjugate surface which satisfies the relationships: φ L2/0.7CA <0, and |φ L2/0.7CA |>|φ L2 |.