OBJECTIVE OPTICAL SYSTEM, OPTICAL PICKUP, AND OPTICAL DISC DRIVE

摘要

An objective optical system having at least a first optical element and being employed in an optical pickup, which at least performs reproduction and/or recording of information on a first optical information recording medium, having a protective substrate thickness (t1), using a first light flux having a first wavelength lambda1 emitted from a first light source, and performs reproduction and/or recording of information on a third optical information recording medium having a protective substrate thickness (t3) (t1<t3), using a third light flux having a third wavelength lambda3 (lambda1<lambda3) emitted from a third light source. The first optical element comprises a first member composed of a material (A) and a second member composed of a material (B) laminated in the direction of the optical axis. The material (A) and the material (B) have different Abbe numbers in d line, and a first phase structure is formed on the boundary surface of the first and second members. An optical pickup mounted with the objective optical system, and an optical disc drive are also provided.