Hitachi Maxell, Limited

Other

Hitachi, Ltd.

Hitachi Maxwell, Ltd.

Masafumi Yoshihiro

Katsusuke Shimazaki

Norio Ohta

Satoru Ohnuki

Toshinori Sugiyama

Hiroyuki Awano

Osamu Ishizaki

Yukinori Yamada

Hiroki Takao

Manabu Tani

Hitoshi Watanabe

Hideo Fujiwara

Masaki Sekine

Susumu Imai

Tsuyoshi Maro

Akito Sakemoto

Kazuko Ishitsuka

Eiji Koyama

Masatoshi Hashimoto

Noriyuki Ogihara

Yoshinori Shirai

Hitoshi Furusho

Ryo Suzuki

Atsushi Yamaguchi

Fumiyoshi Kirino

Satoshi Sumi

Kouichirou Wakabayashi

Katsuji Nakagawa

Hiroshi Shirai

Akira Kashiwakura

Akiyoshi Itou

Junko Nakamura

Shin-Itsu Kinoshita

Norio Oota

Hisanori Sugiyama

Hiroshi Ido

Nobuyuki Nagai

Satoru Oonuki

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

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

When recording marks having various lengths are recorded to represent information on a magneto-optical recording medium, a mark length-correcting circuit is used to correct a mark length nT with a mark length correction amount Lc determined for each mark length so that the recording is performed with a shorter mark length nT&prime;&equals;nT&minus;Lc. When reproduction is performed on the magneto-optical recording medium, an appropriate reproducing light power and an appropriate reproducing magnetic field intensity can be easily selected for any recording mark having any length. Thus, the reproducing power margin is widened. The recording method is effective on a magneto-optical recording medium of the MAMMOS type comprising a recording layer and a reproducing layer, in which the light and the magnetic field are applied during the reproduction to transfer a magnetic domain from the recording layer to the reproducing layer in a magnified form.

Method for recording mark length shorter than channel bit length on magneto-optical medium

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

A compact recording and reproducing apparatus includes a floating-type head movable in a fan shape in parallel with the surface of a disk recording medium in order to make faster access to the tracks and to record information at a higher density. A slider and a head are secured to the tip of a swing arm capable of fan-shaped swing movement, and a solid immersion lens is used for the head, so that the light beam can be passed along the arm from the fulcrum at the rotating pivot of the swing arm member.

Recording and reproducing apparatus having a magneto-optical head with an objective lens and laser-beam-permeable member

A magneto-optical recording medium has, in order from the laser irradiation side, a second auxiliary magnetic film first auxiliary magnetic film and magneto-optical recording film First and second auxiliary magnetic films and change from in-plane magnetization to perpendicular magnetization when their respective critical temperatures T and T are exceeded. The Curie temperatures T , T and T of the magneto-optical recording film and the first and the second auxiliary magnetic films and their critical temperatures T and T satisfy the relationship: room temperature<T <T <T , T ,T . The first auxiliary magnetic layer has a film thickness greater than the thickness of the magnetic wall. In response to irradiation by the reproducing light beam, recording magnetic domain of magneto-optical recording film is transferred, with size reduction, to first auxiliary magnetic film and is then transferred, with magnification, to second auxiliary magnetic film This is ideal for reproduction of a high-density recording medium since an amplified reproduction signal is obtained from magnified magnetic domains

Magneto-optical recording media having an auxiliary magnetic layer

The magneto-optical recording medium has a magnetic domain magnification reproducing layer and an information recording layer. Clock marks are formed on the information recording layer, making it possible to generate a reproducing clock on the basis of these. The clock marks are detected either by irradiating directly with light of wavelength &lgr; (&lgr; &ne;&lgr; ), being different from the light of wavelength &lgr; which is used for reproducing the recording marks, or by applying a direct-current magnetic field, transferring and enlarging the clock marks on to the magnetic domain magnification reproducing layer, and detecting the reproduction signals from this magnetic domain magnification reproducing layer. Since the reproducing clock is in exact synchronisation with the recording marks, it is eminently suitable as a clock for pulse-modulated reproducing light and reproducing magnetic fields used when reproducing the reproducing layer.

Magneto-optical recording medium having clock-marks on recording layer and apparatus for recording and reproducing same

A magneto-optic recording medium includes a second auxiliary magnetic film, a first auxiliary magnetic film and a magneto-optic recording film on a substrate. The auxiliary magnetic films change from in-plane magnetization to vertical magnetization at critical temperatures T and T . Since they have the relation T >T , the magnetic domain transferred from the magneto-optic recording film to the first auxiliary magnetic film at the time of reproduction is expanded in diameter and is transferred to the second auxiliary magnetic film when the temperature profiles of the auxiliary magnetic films inside an optical spot are utilized. The magnetic domain of the magneto-optic recording film can be expanded and transferred, too, by means of magnetostatic coupling by using a non-magnetic film in place of the first auxiliary magnetic film. Pulse reproduction light subjected to power modulation in synchronism with a reproduction clock can be used at the time of reproduction. Even when a very small magnetic domain is recorded, the intensity of an amplified reproduction signal can be detected and excellent C/N can be obtained.

Magneto-optical recording medium and reproducing method for reproducing magnetic domain in enlarged form on a reproducing layer

A bit of binary information which is one of &ldquo;1&rdquo; and &ldquo;0&rdquo; is assigned to a domain pattern which is a combination of a recorded magnetic domain and a magnetic domain magnetized in the direction opposite to the direction in which the recording domain is magnetized. A bit of binary information which is the other of &ldquo;1&rdquo; and &ldquo;0&rdquo; is assigned to a domain pattern consisting of two magnetic domains magnetized in the same direction as the foregoing magnetic domain is magnetized. Consequently, two or more consecutive bits of record information are formed, on a recording layer, as a series of domain patterns each of which is a combination, as a record information unit, of a recorded magnetic domain and a magnetic domain magnetized in the direction opposite to the direction in which the recording domain is magnetized. Independent of the lengths of the magnetic domains recorded on the recording layer, the record information can be transferred to a reproducing layer. This makes it possible to reproduce high-density record information securely or reliably.

Magneto-optical recording method capable of adjusting the sizes magnetic domain

A magneto-optical recording medium comprises a protective layer having a self-lubricating property formed at an uppermost layer on a side opposite to a substrate wherein a recording or reproducing light beam comes into a side of the protective layer. The thickness and the refractive index of the protective layer are selected under predetermined conditions depending on whether or not evanescent light is transmitted through the protective layer. It is possible to perform high density recording and reproduction thereof by utilizing the evanescent light. A protective layer having a self-lubricating property may be also formed on a bottom surface of an optical head opposing to the optical recording medium. Even when the optical head contacts with the surface of the optical recording medium, the sliding scratch scarcely occurs, because the optical head smoothly glides on the recording medium surface. It is possible to reduce the influence of multiple interference of light which would be otherwise caused in an air layer existing between the optical recording medium and the optical head, and it is possible to suppress variation in reproduced signal intensity.

Optical recording medium with solid protective layer having self-lubricating property

On a surface of a transparent substrate,having a preformat pattern,formed thereon are laminated a first recording layer,in which a recording state exists in one different magnetic field region of an applied external magnetic field and a second recording layer,in which two recording states exist in magnetic field regions different from that for the first recording layer. As required, dielectric layers,and,, a reflecting layer,and a protection layer,can be laminated. The 4-valued recording of information becomes possible by assigning information signals &ldquo;1&rdquo;, &ldquo;0&rdquo;, &ldquo;3&rdquo;, and &ldquo;2&rdquo; to H,, H,, H,and H,, respectively.

Magneto-optical recording medium capable of recording multiple value signals

A magneto-optic recording medium includes a second auxiliary magnetic film, a first auxiliary magnetic film and a magneto-optic recording film on a substrate. The auxiliary magnetic films change from in-plane magnetization to vertical magnetization at critical temperatures T,and T,. Since they have the relation T,>T,, the magnetic domain transferred from the magneto-optic recording film to the first auxiliary magnetic film at the time of reproduction is expanded in diameter and is transferred to the second auxiliary magnetic film when the temperature profiles of the auxiliary magnetic films inside an optical spot are utilized. The magnetic domain of the magneto-optic recording film can be expanded and transferred, too, by means of magnetostatic coupling by using a non-magnetic film in place of the first auxiliary magnetic film. Pulse reproduction light subjected to power modulation in synchronism with a reproduction clock can be used at the time of reproduction. Even when a very small magnetic domain is recorded, the intensity of an amplified reproduction signal can be detected and excellent C/N can be obtained.

Magneto-optic recording medium and reproducing method for reproducing magnetic domain in enlarged form on a reproducing layer

Optical recording medium and optical recording device

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Kitasouma-gun, Japan

Masafumi Yoshihiro