Patent ID: 7054074
Filing Date: 2006-05-30
Classification: G11B

Abstract:
1. An objective lens which is a doublet for converging a light beam emitted from a light source onto an optical recording medium, said objective lens comprising: a first lens made of a crown glass material having a refractive index of between 1.55 and 1.6, and an Abbe number of between 58 and 62, and having a first surface and second surface; a second lens made of a flint glass material having a refractive index of between 1.68 and 1.82, and an Abbe number of between 30 and 41, and having a third surface and a fourth surface, wherein a geometry of said third surface matches said second surface, wherein a glass transition point of said first lens is different from that of said second lens, and a difference of said glass transition points of said first and second lenses is 30° C. or higher.