Sankyo Seiki Mfg. Co., Ltd

Kabushiki Kaisha Sankyo Seiki Seisakusho

Ken Ishikawa

Tadashi Takeda

Yoshio Hayashi

Hideo Takezoe

Takaaki Suzuki

Satoru Nakao

Atsuo Fukuda

An optical pickup head apparatus for reading information signals from a recording medium having a laser beam light source, an objective lens and a photodetector, the improvement comprises a holographic optical element constructed of a pair of diffraction gratings having different diffractive conditions wherein the element is split into two by a split line near its optical axis as a border and a diffraction generation prevention device for preventing the generation of unwanted diffracted beams from a recording medium. The optical pickup head apparatus irradiates a laser beam emitted from the light source onto a recording medium via the holographic optical element and the objective lens. Beams reflected from the recording medium are guided to the photodetector via the objective lens and the holographic optical element.

Optical pickup head apparatus

A polarizing beam-splitter comprises an optically isotropics crystalline substrate and a birefringent material layer made of an oriented polydiacetylene film formed on the optically isotropic crystalline substrate. A periodic grating photo-mask is formed in the birefringent material layer by an area that is changed into a different color phase when an ultra violet light is irradiated in a predetermined pattern on the birefringent material layer and by an area in which the color remains unchanged. The periodic grating photo-mask has a diffraction efficiency for the orientation of the oriented polydiacetylene film in the area that is changed into a different color phase which is lower than that in the area in which the color is unchanged.

Polarizing beam splitter and method for manufacturing same

A polarizing beam splitter includes: an optically isotropic substrate; a layer of birefringent material formed on top of said optically isotropic substrate; and a periodic pattern of ridges and grooves formed on a surface of said optically isotropic substrate to make a grating; and a refractive index equal to either the refractive index of the birefringent material for ordinary light or the index for extraordinary light, said grooves being filled with the material.

Polarizing beam splitter and optical head assembly

Growing community of inventors

Nagano, Japan

Ken Ishikawa