Hitachi Maxell, Limited

Hitachi, Ltd.

Other

Hitachi Maxwell, Ltd.

Sanyo Electric Co., Ltd.

Hiroyuki Awano

Norio Ohta

Katsusuke Shimazaki

Takeshi Shimano

Masafumi Yoshihiro

Hiroki Takao

Hitoshi Watanabe

Masaki Sekine

Kenchi Ito

Yooji Maruyama

Manabu Tani

Susumu Imai

Harukazu Miyamoto

Atsushi Yamaguchi

Atsushi Saito

Keikichi Andoo

Satoshi Sumi

Kouichirou Wakabayashi

Katsuji Nakagawa

Yuji Yamazaki

Hiroshi Shirai

Akiyoshi Itou

Takeshi Maeda

Hisataka Sugiyama

Hideki Saga

Nobuyuki Inaba

Junko Ushiyama

Osamu Ishizaki

Naoyuki Takagi

Osamu Komoda

Yoshiharu Uchihara

Yoshio Suzuki

Masaaki Futamoto

Yoshihiro Shiroishi

Tsuyoshi Toda

Makoto Miyamoto

Yoshibumi Matsuda

Yukio Honda

Mikio Suzuki

Fumiyoshi Kirino

Masahiro Ojima

Teruaki Takeuchi

Hiroaki Nemoto

Toshinori Sugiyama

Toshio Niihara

Satoshi Matsunuma

Tsuyoshi Maro

Akira Yano

Reiji Tamura

Tetsunori Koda

Harumi Hieida

Norio Ota

Masahumi Yoshihiro

Hiroshi Ido

Nobuyuki Nagai

Satoru Oonuki

In an apparatus for recording and reproducing a thin optical disc by using the same optical system as that of a CD, a DVD or the like, the invention provides a technique which can stably rotate the thin optical disc at a high speed. The structure can be made such that a turbulence of an airflow is not generated even if the thin optical disc on a turn table is rotated at a high speed, by employing a transparent turn table and arranging a recording and reproducing head or the like in an opposite side to a thin optical disc mounting surface of the turn table.

Recording and reproducing apparatus of thin optical disc

A magnetic recording medium comprises, on a substrate, a recording auxiliary layer, a recording holding layer, recording control layer, and a recording layer. The recording layer is constructed by using a ferri-magnetic material having perpendicular magnetization. The data can be recorded at a super high density by using the recording and reproducing head of the present invention, because the recording layer has the perpendicular magnetization. The disappearance of data, which would be otherwise caused by the thermomagnetic relaxation phenomenon, is suppressed after recording the data, because the recording layer has large coercive force at the room temperature. The data, which is recorded at the super high density on the magnetic recording medium, can be reproduced by using a magnetic resistance element carried on the recording and reproducing head.

Magneto-optical recording and reproducing method, using reproducing layer with high saturation magnetization

A magneto-optical recording medium has magneto-optical recording layers () and reproducing layers (). The information recorded in the reproducing layers are reproduced by means of reproducing light beams () of different wavelengths, respectively. In reproduction, magnetic domains () recorded in the recording layers are transferred in the reproducing layers formed on the respective recording layers, the transferred magnetic domains () are enlarged with an external magnetic field, and the information is reproduced. Since information is recorded and reproduced for each recording layer, the recording density is improved. Further since the reproduction signals are amplified by the magnetic domain enlargement, the C/N is improved.

Magneto-optical reproducing method using a plurality of different reproducing beams

A magnetic recording medium comprises an information-recording film and a ferromagnetic film on a substrate. The information-recording film is composed of, for example, an amorphous ferrimagnetic material having perpendicular magnetization. Further, the ferromagnetic film is composed of a magnetic material which has saturation magnetization larger than that of the information-recording film. Accordingly, the leak magnetic flux from the ferromagnetic film is larger than that from the information-recording film. The magnetic recording medium and a magnetic recording apparatus are obtained, which are excellent in thermal stability and which are preferred to perform super high density recording.

Magnetic recording medium with high thermal stability, method for producing the same, and magnetic recording apparatus

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 recording head comprises a magnetic coil formed on a lower surface of a transparent substrate opposed to a magneto-optical disk. A heat sink layer is provided at the outside of the magnetic coil on the lower surface. An objective lens is supported on an upper surface of the transparent substrate. The heat, which is generated by the magnetic coil, is released via the heat sink layer to the space between the magneto-optical disk and the substrate. The release of the heat is facilitated by the air stream which is generated by the rotation of the magneto-optical disk. The heat can be effectively released from the magnetic coil without inhibiting optical characteristics of the objective lens.

Magneto-optical head having heat sink layer

External magnetic fields H(x) or reproducing light beams L(x) having different intensity patterns are applied to an identical recording position on a magneto-optical recording medium so that different pieces of information corresponding to the patterns are reproduced from the identical recording position. A function H(x) or L(x) is a password for obtaining the information. Only a person, who knows the function, can access specified information recorded on the magneto-optical recording medium. The function H(x) or L(x) is a function in which the magnetic field intensity or the light intensity is modulated with respect to the recording position x so that magnetic domains may be thinned out to perform reproduction at a specified cycle from continuous magnetic domains in a recording area. Other than the use for the purpose of security, reproduced C/N can be remarkably improved by performing reproduction n times while radiating a reproducing light beam P /P which is power-modulated so that the high power P is applied at every cycle which is not less than n times the recording clock, to a specified magneto-optical recording medium capable of magnetic domain-magnifying reproduction.

Reproducing method and reproducing apparatus for magneto-optical recording medium

While a magneto-optical recording medium is irradiated with a laser beam, the medium is rotated relative to the beam at a controlled speed in such a manner that a high temperature region of a heat spot produced on the basis of the light intensity distribution of the beam is formed outside the associated light spot. A magnetic field source includes a magnetic field generator which is narrow in the direction along the track of the medium. The field source is positioned with the field generator at the heat center outside the light spot to apply a narrow recording magnetic field to the high temperature region. This forms a recording magnetic domain in the high temperature region. The magnetic domain is rectangular and narrow in the direction along the track. Rectangular recording magnetic domains adjoining in the direction along the track hardly interfere with each other even if they are closely spaced. This results in high density recording.

Recording method, reproducing method and recording and reproducing apparatus for magneto-optical recording medium

An optical head comprises a laser light source, detectors, a reflecting mirror, a magnetic coil, and a driving circuit which are formed in a monolithic manner on a surface of a substrate. A diffraction grating is formed on the reflecting mirror. A reflected light beam can be divided into those directed to the detectors. Optical paths from the reflecting mirror to the respective detectors are disposed in directions along the substrate. Accordingly, the thickness of the optical head can be made thin. The substrate can be also processed into a slider. The optical head is capable of high speed access and high speed data transfer, in which a miniaturized size and a light weight are realized.

Optical head and apparatus provided therewith

A magneto-optical recording medium has magneto-optical recording layers ( ) and reproducing layers ( ). The information recorded in the reproducing layers are reproduced by means of reproducing light beams ( ) of different wavelengths, respectively. In reproduction, magnetic domains ( ) recorded in the recording layers are transferred in the reproducing layers formed on the respective recording layers, the transferred magnetic domains ( ) are enlarged with an external magnetic field, and the information is reproduced. Since information is recorded and reproduced for each recording layer, the recording density is improved. Further since the reproduction signals are amplified by the magnetic domain enlargement, the C/N is improved.

Magneto-optical reproducing method using a plural of different reproducing beams

A reproducing apparatus for a magneto-optical recording medium has, at one end of a swing arm, a magneto-optical head provided with a slider and a solid immersion lens. A reproducing light beam-detecting system is installed to the other end of the swing arm. During reproduction on a magneto-optical recording medium, an alternating magnetic field is applied while radiating a reproducing light beam which is power-modulated to have a low power and a high power in synchronization with a reproducing clock. The reproducing light beam having the low power causes transfer of a magnetic domain in the information-recording layer to the reproducing layer and magnification thereof. The reproducing light beam having the high power extinguishes the magnified magnetic domain. Minute magnetic domains can be individually reproduced at high C/N.

Reproducing method and reproducing apparatus using plural light beam powers for transferring a magnetic domain

An optical head including a semiconductor laser source, a condenser lens, a photodiode for detecting a laser light emitter from said semiconductor laser source, and an optical coupler unit for collecting the laser light to the photodiode. A chromatic aberration W of condenser lens is satisfied by an expression W(h, NA)&equals;&lcub;(NA) &Dgr;&lgr;/4&lgr;&rcub;h, where h is a height of incident light from an optical axis on a hologram, NA is a numerical aperture, &Dgr;&lgr; is a wavelength fluctuation, and a &lgr; is a wavelength at recording. The height h is determined so that the chromatic aberration W becomes equal to or less than &lgr;/4.

Flying type optical head integrally formed with light source and photodetector and optical disk apparatus with the same

A recording method for recording information on a recording layer of a magneto optical recording medium by radiating a recording light beam onto the medium while applying a magnetic field in a recording direction to the medium. The method includes applying a magnetic field having a magnetic field strength H1 in the recording direction when recording a record mark having a mark length A on the recording layer, and applying a magnetic field have a magnetic field strength H2 in the recording direction when recording a record mark having a mark length B (B&ne;A) on the recording layer. Independent of the lengths of the magnetic domains recorded on the recording layer, the record information can be transferred to a reproducing layer making it possible to reproduce high density record information.

Magneto-optical recording apparatus using multiple magnetic field strengths for recording different mark lengths

Reproducing method and reproducing apparatus for magneto-optical recording medium using different radiation patterns

Disclosed are a reproducing method and a reproducing apparatus capable of performing reproduction with a wide power margin, as well as a recording method and a recording apparatus preferably used for super high density recording. A recording and reproducing apparatus principally comprises a magnetic field-applying unit, a laser beam-radiating section, and a signal processing system. A magnetic coil which is provided for the magnetic field-applying unit, is arranged so that its axis of magnetic field generation is oblique to a surface of an information-recording medium A reproducing magnetic field is applied in an oblique direction to the surface of the information-recording medium by using the magnetic coil while radiating a reproducing light beam to the medium by using the laser beam-radiating section. Accordingly, the leak magnetic field in the in-plane direction from a recording magnetic domain in a recording layer is amplified. The inversion of magnetization in a reproducing layer tends to occur, and the reproducing power margin is widened. The recording and reproducing apparatus is also capable of recording information. An extremely minute recording magnetic domain can be formed in the recording layer of the information-recording medium.

METHOD AND APPARATUS FOR RECORDING AND REPRODUCING INFORMATION BY APPLYING FIELD IN A DIRECTION OTHER THAN THE DIRECTION OF MAGNETIZATION OR THE DIRECTION TO A SURFACE OF AN INFORMATION RECORDING MEDIUM

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Noda, Japan

Hiroyuki Awano