Patent Number: 7,613,098

Title: Objective optical system for optical recording media and optical pickup device using it

Abstract: An objective optical system focuses light from a light source onto at least two different types of optical recording media having different substrate thicknesses in order to record or reproduce information on the optical recording media by using a variable refractive power element and an objective lens. The variable refractive power element may be a liquid crystal element with concentric zones that serves as a transparent plate having no convergence effect when no voltage is applied when selecting an AOD, DVD, or CD and as a converging lens when a voltage is applied when selecting a BD. Alternately, the variable refractive power element may electrically vary the refractive index of a nanoparticle dispersion or at least one liquid of a two-liquid lens element. A diffractive optical element may be used to assist in focusing light to four recording media. An optical pickup device includes the objective optical system.

Inventors: Katsuma; Toshiaki (Tokyo, JP), Kitahara; Yu (Saitama, JP), Mori; Masao (Saitama, JP), Ori; Tetsuya (Koshigaya, JP)

Assignee: Fujinon Corporation

International Classification: G11B 7/00 (20060101)

Expiration Date: 1/03/02017