Patent ID: 6091691
Filing Date: 2000-07-18
Classification: G11B

Abstract:
An objective lens for use in an optical device compatible with different types of optical memory media, said objective lens having a plurality of portions having different optical characteristics, wherein one of said plurality of lens portions focuses said light onto one of said optical memory media independent of the type of said one optical memory medium;wherein said plurality of lens portions includea first portion to focus a light emitted from a light source onto said one optical memory medium independent of a thickness of said one optical memory medium,a second portion to focus said light emitted from the light source onto said one optical memory medium if said optical memory medium has a first predetermined thickness, anda third portion to focus said light emitted from said light source onto said one optical memory medium if said optical memory medium has a second predetermined thickness which is different from said first predetermined thickness; anda surface of the second portion forms a step difference with a surface of one of the first and third portions.