Hitachi, Ltd.

Hitachi Maxell, Limited

Shigenori Okamine

Motoyasu Terao

Harukazu Miyamoto

Kiyoshi Matsumoto

Takeshi Maeda

Hisataka Sugiyama

Tetsuya Nishida

Norio Ohta

Masahiko Takahashi

Toshimitsu Kaku

Masaaki Futamoto

Yutaka Sugita

Yasushi Miyauchi

Fumiyoshi Kirino

Keikichi Andoo

Toshio Niihara

Yosuke Seo

Soichi Isono

Yasushi Fukuda

Takashi Tamura

Reiji Tamura

Hitoshi Komatsu

Yuji Yamane

Noriyuki Ogihara

Norio Murase

Kunihiko Kizaki

Nobuhiro Matsumura

A recording medium including a plurality of recording layers, including: an optional first recording layer on which a light spot at a diffraction limit is formed; and a second recording layer on which a mark string pattern is formed, said second recording layer being different from said first recording layer, wherein when said mark string pattern is formed on a light receiving plane, while information of said first recording layer is reproduced, assuming that an optical distance between said first and second recording layers is dm, an optical distance d between optional two recording layers among a plurality of said recording layers is different from said dm.

Three-dimensional recording and reproducing apparatus

In a three-dimensional recording and reproducing apparatus having a recording medium including a plurality of recording layers stacked on a substrate and an optical system for converging a light irradiated from the substrate side on each of the plurality of recording layers to three-dimensionally record and reproduce information, the following equation is satisfied:&#x3bb;/4&#x2266;(1/8)(1/&#x2212;1)where A light spot is focused on each layer of the multi-layer structured disc to record and reproduce highly reliable data in a high density.

In a magneto-optical disk for recording, reproduction or erasing with a laser beam, which comprises a film of four-layer structure consisting of a first dielectric layer, a magneto-optical recording layer, a second dielectric layer and a metallic layer, laid on a disk substrate provided with guide tracks, temperature distribution of the magneto-optical recording layer is controlled by controlling the thermal diffusivity of the metallic layer, and recording/reproduction/erasing repetition characteristics are improved thereby. In the disk of the present structure, the temperature is elevated in a broader area from the center of laser beam, and thus a thoroughly broad erasing domain width taking a track offset into account can be obtained and no recording domains remain after the erasing. The reproduced signal output is increased by 4 dB, as compared with that obtained by a disk of three-layer structure without any metallic layer, because the beam utilization efficiency is increased owing to both Kerr effect and Faraday effect. When the disk of the present structure is subjected to field modulation recording, tails of arrow-feather-shaped recording domains peculiar to the field modulation recording can be shortened and interbit interferences can be overcome, resulting in an increase in C/N (S/N) ratio and the high density recording can be made.

Magneto-optical disk

In a three-dimensional recording and reproducing apparatus having a recording medium including a plurality of recording layers stacked on a substrate and an optical system for converging a light irradiated from the substrate side on each of the plurality of recording layers to three-dimensionally record and reproduce information, the following equation is satisfied:

A wavelength-multiple optical memory is provided which is capable of performing high density recording/reading at room temperature. A large number of cylindrical recording members, each of which is made up of plural portions along a central axis of the cylinder and plural sizes which vary slightly in a direction perpendicular to the central axis, are formed on a substrate. The cylindrical recording members may be of circular cylindrical or elliptical cylindrical shape. It is preferable that recording material layers of the cylindrical recording members have complex refractive indexes which are different from each other. A difference in size of the recording material layers of the circular or elliptical cylinders having sizes closest to each other is preferably in a range of 1/5000 to 1/5 of an average of the sizes, are even more preferably in a range of 1/500 to 1/10. Wavelength-multiple recording is performed by changing a wavelength of a light beam emitted from a light source within a very narrow range.

Wavelength-multiple optical recording medium

By using an information recording medium comprising at least a substrate and an information recording film which is mounted on the above substrate and changes the physical property under irradiation of a recording energy beam, wherein the surface of the information recording area of the above substrate is uneven, both surfaces of the above recording film are also uneven, and an inorganic protective layer is provided in contact with the surface of the above recording film opposite to the above substrate, fine recording points can be formed stably without complicated control of the recording power and recording waveform so that an optical disk unit can record data simply in high density.

Information recording media, manufacturing method for the same, and

In a rotary type storage apparatus and a control method thereof, a plurality of concentric or spiral information tracks are set and also each of the plural information tracks is subdivided into a plurality of sectors along a circumferential direction, which constitute a plurality of information recording planes. Also, in this apparatus and method, there are provided a plurality of read/write heads employed at each of the information recording planes and accessible to the information tracks, and also a head drive mechanism for positioning these plural read/write heads to the information tracks. At least one of the plural information recording planes corresponds to such a recording plane where a substitution information track has been set, on which a substitution sector corresponding to a failed sector present at another information recording plane is recorded.

Rotary type storage apparatus and control method thereof

An optical read-out magnetic head of a single pole type having a main pole, an auxiliary pole, and a writing coil. The main pole consists of a high permeability film and a magneto-optical film, the magneto-optical film has an easy magnetization axis parallel to or in the extension direction of that film surface high permeability film. Writing is carried out magnetically by employing the coil, and reproduction is effected optically by employing the magneto-optic film.

Optical read-out magnetic head

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Kodaira, Japan

Shigenori Okamine