Sanyo Electric Co., Ltd.

Other

Hitachi Maxell, Limited

Sanyo Electric., Ltd.

Yoshiharu Uchihara

Satoshi Sumi

Kenji Torazawa

Atsushi Yamaguchi

Toshiaki Hioki

Noboru Mamiya

Kenji Asano

Yoshihiro Hori

Kenji Tanase

Yoshihisa Suzuki

Kenji Nakao

Hisashi Matsuyama

Hitoshi Watanabe

Norio Ohta

Hiroyuki Awano

Naoyuki Takagi

Seiichiro Takahashi

Akiomi Kunisa

Nobuo Itoh

Hiroshi Shirai

Seiji Murata

Hiroshi Watanabe

Masahiro Higuchi

Sayoko Tanaka

Shigeki Hori

Sadao Sakamoto

Kenji Torasawa

A magneto-optical recording medium which includes a reproducing layer. When a laser beam is irradiated to the magneto-optical recording medium, a magnetic domain in a recording layer is transferred, through enlargement, to a reproducing layer increased in temperature. The magneto-optical recording medium further includes a calibration area that has a calibration magnetic domain recorded in a predetermined pattern in the recording layer. In a reproducing apparatus, a laser beam of an optical head is adjusted in output depending upon a reproduced signal obtained by reproducing the calibration magnetic domain.

Magneto-optical recording medium including a calibration magnetic domain recorded in a predetermined pattern in a recording layer

A magneto-optical record medium and a reproducing apparatus for the same allow data reproduction having good characteristics by a simple structure. The magneto-optical record medium includes a plurality of first grooves ( ) each having sidewalls, at least one of which is wobbled in accordance with address information; an address mark ( ) formed by changing a width of a land located between second grooves connected to the first grooves; and third grooves wobbled cyclically, formed in a data portion magnetically storing data and connected to the second grooves. The reproducing apparatus reproduces the data from the magneto-optical record medium.

Record medium and reproducing apparatus of the same for detecting an offset correction

An magneto-optical disc recording/reproducing apparatus includes an optical head ( ) to detect a wobble ( ) and an address mark ( to ) in an magneto-optical disc ( ) and output a wobble signal (WB , WB ) and an address mark signal (AML, AMG), a PLL circuit ( ) to generate a clock signal (CK) in response to wobble signal (WB ), an address mark synchronous signal generation circuit ( ) to generate an address mark synchronous signal (AM) in response to address mark signal (AML, AMG), a synchronizing circuit ( ) to synchronize clock signal (CK) with address mark synchronous signal (AM) and generate a synchronized clock signal (SCK), and a timing setting circuit ( ) to generate a timing pulse signal (TG ) to control a magnetic head driving circuit ( ) and a timing pulse signal (TG ) to control a laser driving circuit ( ). The recording/reproducing apparatus can detect a address mark ( to ), record la data signal on magneto-optical disc ( ) in synchronization with the detected address mark, and reproduce a data signal from magneto-optical disc ( ) in synchronization with the detected address mark, so that the data signal can be surely recorded/reproduced.

Information recording/reproducing apparatus to record/reproduce information on a recording medium recorded with an address mark

A meandering groove is formed in a digital disk (,) with a wobble signal that is wobbled to reproduce a clock signal. The wobble signal is read out by an optical head (,). An address detection circuit (,) detects an address signal that is multiplexed with the wobble signal. A PLL oscillation circuit (,) provides a clock signal in synchronization with the wobble signal. Data is modulated by a modulation circuit (,) according to the clock signal and a timing signal based on the address signal, and recorded on the digital disk (,). In reproduction, a RF signal in the wobble signal is converted into a digital signal by an A/D converter (,). The signal is demodulated by a demodulation circuit (,) for data output.

Digital disk recording and reproduction apparatus

Magneto-optical recording medium and recording/reproducing apparatus therefor in which recorded magnetic domains are transferred from the recording layer to the reproducing layer

A magneto-optic disk and a recording/reproduction device therefor adopt optical super-resolution to increase recording capacity. More specifically, the magneto-optic disk has an heat emitting layer (,) on a recording layer (,) and still preferably has an intermediate layer (,) between a reproduction layer (,) and the recording layer (,). The recording/reproduction device includes a circuit (,) for pulsing a laser beam to be radiated to the magneto-optic disk and still preferably includes a polarization rotating unit (,) and a polarizing filter (,) for blocking only the center of the laser beam in reproduction. The heat emitting layer (,) diffusing any heat generated by the laser beam, and the discontinuously radiated laser beam allow small recording domain. The laser beam having its center blocked forms smaller main lobe due to diffraction effect.

Recording and reproduction device for a magneto-optic recording medium capable of recording information according to optical super-resolution

Digital recording method, digital disk, digital disk recording device, and digital disk reproducing device

In magneto-optical recording medium, on a transparent substrate of polycarbonate resin, an SiN film having the thickness of 600 to 800 .ANG. and surface roughness Rmax of at most 10 nm is formed. On the SiN film, a GdFeCo reading layer having the thickness of 800 to 1200 .ANG. with Gd content of 30 to 36 at. % and Co content of 12 to 50 at. % is formed. On the reading layer, a TbFeCo recording layer of which Co content is 10 to 16 at. % is formed. The recording layer is a perpendicular magnetization film, and the reading layer is an in-plane magnetization film. At the time of reading, the reading and recording layers are heated, and the direction of magnetization of the recording layer is transferred to the reading layer only in the prescribed heated area. Information can be read only from the transferred portion, and thus a super resolution effect is obtained. When Kerr rotation angle .theta..sub.K is measured for the light reflected from the reading layer while the temperatures of the reading and recording layers are elevated, .theta..sub.K is approximately in proportion to Cth power of the elevated temperature t, wherein C is at least 8.0.

Magneto-optical recording medium and manufacturing method thereof

The method of manufacturing an optical disc related to the invention first forms warp prevention layer on one surface or the other surface of the disc substrate where information is recorded on one surface, and then, recording film covering the surface opposite from the surface having warp prevention layer or beam reflection film covering the information-recorded surface, and finally protection layer covering either the beam reflection film or the recording film, in this order. Thus the optical disc related to this invention can prevent damage and dust from incurring and adhering to the other surface of the disc substrate when forming these films on one surface so that the warp prevention layer can be perfectly level by suppressing swell of the layer itself. Since the warp prevention layer is formed on one surface before forming those films mentioned above on the other surface, the one surface maintains satisfactory wetness, and as a result, foam is rarely generated between the warp prevention layer and the disc substrate. Furthermore, the method of manufacturing an optical disc related to the invention introduces a system which measures the warp of the disc substrate coated with warp prevention layer before coating protection film, and then properly adjusts the thickness of the protection film to a specific thickness enough to fully cancel the warp. This effectively minimizes warping of the disc substrate itself.

Method of manufacturing optical disc

Growing community of inventors

Ogaki, Japan

Yoshiharu Uchihara