Patent ID: 7589905
Filing Date: 2009-09-15
Classification: G02B

Abstract:
1. An optical system comprising: a first negative lens element disposed nearest a front side; and a first positive lens element whose front surface resides within a distance 0.4 L from a surface nearest the front side toward a rear side of the optical system having a total lens length L, wherein the first negative lens element is composed of a material satisfying the following conditions: where Ndn1, νdn1, and θgFn1 denote a refractive index for the d-line, an Abbe number for the d-line, and a partial dispersion ratio for the g- and F-lines, respectively, of the material of the first negative lens element, and wherein the first positive lens element is composed of a material satisfying the following conditions: where Ndp, νdp, and θgFp denote a refractive index for the d-line, an Abbe number for the d-line, and a partial dispersion ratio for the g- and F-lines, respectively, of the material of the first positive lens element.