Nidec Sankyo Corporation

Sankyo Seiki Mfg. Co., Ltd

Tetsuro Okamura

Kenichi Hayashi

Yuji Fujita

Yoshifusa Miyasaka

Takahiro Azuma

A common objective lens typically used in reading data from different optical data storage media that are responsive to laser beams of different wavelengths, such as CD and DVD is provided. The lens has a refracting surface with inner and outer refracting surface regions. Diffraction gratings are provided in both the inner and outer refracting surface regions with each having a differential optical path function. The inner diffraction grating and at least a part of the outer diffraction grating emit an order of diffracted beams which have different polarities to cancel out any spherical aberrations caused by a change in temperature.

Lens, optical head apparatus, and objective lens for the optical head apparatus

An optical head device that converges first and second laser beams having different wavelengths on recording surfaces of first and second optical recording media through a single light converging optical system including an objective lens for recording or reproducing data on the recording surfaces. A refracting surface of the objective lens is divided into two regions, i.e., a central refracting surface region with an optical axis thereof being as a center and an outer circumferential refracting surface region that surrounds an outer circumference of the central refracting surface region. A diffraction grating is formed generally entirely over the central refracting surface region. When recording or reproducing data on the first optical recording medium using the first laser beam, a beam spot is formed with a diffracted beam obtained by the central refracting surface region. When recording or reproducing data on the second optical recording medium using the second laser beam, a beam spot is formed with a beam portion that passes the outer circumferential refracting surface region and a diffracted beam obtained by the central refracting surface region.

Growing community of inventors

Chino, Japan

Tetsuro Okamura