Sanyo Electric Co., Ltd.

Other

Hitachi Maxell, Limited

Naoyuki Takagi

Atsushi Yamaguchi

Hiroshi Watanabe

Shuichi Ichiura

Koichi Tada

Ken Hirose

Kenichiro Mitani

Shinichi Ohe

Satoshi Sumi

Hitoshi Noguchi

Hitoshi Watanabe

Norio Ohta

Hiroyuki Awano

Kazushi Mori

Katsutoshi Hibino

Yoshiharu Uchihara

Hiroshi Shirai

Hiroki Ishida

Kenji Nagatomi

Morio Nakatani

Kenji Asano

Osamu Ota

Shogo Suzuki

An optical element is disposed on an optical path between a beam branching element and a photodetector. The optical element is disposed at a focal position of a stray light beam reflected by a recording layer except a target recording layer, and shields or attenuates the light beam in a region where the stray light beam converges.

Optical pick-up capable of eliminating stray beams

A diffraction element is disposed between a beam branching element (such as a beam splitter) and a photodetector. The diffraction element further segment an interference fringe introduced into stray light by a diffraction grating which divides a laser beam emitted from a laser beam source into a main beam and two sub-beams.

Optical pickup device

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 medium includes a recording layer and a reproducing layer respectively formed by magnetic layers on a substrate. A record magnetic domain is formed within the recording layer by using a magnetic head, which is transferred into a reproducing layer by irradiating a laser beam upon reproduction. The physical length in recording a unit bit is taken as a unit domain length. Where the unit domain length is 1T and &ldquo;1&rdquo; is recorded in 1T, &ldquo;1&rdquo; is recorded in a former half 1T/2 and &ldquo;0&rdquo; is in a latter half 1T/2 by applying one period of an alternating magnetic field to the unit domain length.

Method and apparatus for recording with a magneto-optical recording medium

A reproducing apparatus reproduces a signal recorded in a magneto-optical disk. The magneto-optical disk includes a layered structure having a recording layer, an intermediate layer and a reproducing layer. Laser light is illuminated from an optical head to the magneto-optical disk in such an intensity that no magnetic domain is transferred from the recording layer to the reproducing layer only by the laser light. In this state, alternating magnetic field is applied through a magnetic head to the magneto-optical disk, thereby concurrently causing transfer and expansion of a magnetic domain to the reproducing layer. As a result, transfer of the magnetic domain is effected with expansion.

Method and apparatus for determining power level of laser beam in magneto-optical recording device

Method and apparatus for recording with a magneto-optical recording medium applying one period of an alternating magnetic field to a unit domain length

A magneto-optical recording medium of magnetic domain enlarging/reproducing system including a recording layer and a reproducing layer, a gate layer selectively extracting each magnetic domain within the recording layer is formed on the recording layer, a magnetic field reinforcement layer reinforcing a leakage magnetic field reaching the reproducing layer is formed on the gate layer, and a blocking layer blocking an exchange coupling force from the magnetic field reinforcement layer to the reproducing layer is formed on the magnetic field reinforcement layer.

Magneto-optical recording medium with intermediate layer having a controlled saturation magnetization

A magnetic head is configured of a core and a coil wound around the core and passing current through the coil in a variable direction allows the core to have an edge generating an alternating magnetic field Hex and another edge generating an alternating magnetic field Hex . Alternating magnetic fields Hex and Hex are applied to the respective edges. Furthermore, a laser beam LB is directed such that its optical axis L matches the edge receiving the alternating magnetic field Hex , and a laser beam LB is directed such that its optical axis L matches the edge receiving the alternating magnetic field Hex . A first magneto-optical signal detected through the alternating magnetic field Hex and the laser beam LB and a second magneto-optical signal detected through the alternating magnetic field Hex and the laser beam LB are composited together. As such, an alternating magnetic field can be applied to a magneto-optical recording medium at a predetermined angle to an in-plane direction of the recording medium to accurately enlarge a magnetic domains for reproduction.

Magneto-optical disk apparatus capable of accurately enlarging and reproducing a magnetic domain and method of reproducing the same

In order to reproduce signals from a double-layer optical disc having two signal recording surfaces, a focus jump that the focusing of an objective lens from the one signal recording surface to the other signal recording surface is quickly achieved, is necessary. When a focus error signal (FE) from a pickup ( ) reaches a predetermined threshold value (Vcomp), a deceleration signal for decelerating the objective lens ( ) is supplied to an actuator ( ). Preferably, a deceleration pulse voltage is lowered step by step. The deceleration pulse voltage is determined in accordance with the maximum value (DFEmax) of a differential focus error signal (DFE) generated by differentiating the focus error signal (FE). Preferably, the address seeking is done simultaneously with the focus jump. The focus jump is performed in accordance with the layer-to-layer distance which is measured beforehand. The focus jump is performed by using a lens ( ) having a controllable focal distance. Preferably, whether the layer is the first layer or the second layer is judged based on the reflected luminous power. If the focus error signal (FE) from the other layer is not obtained even when a certain time passages after the focus jump is started, the objective lens ( ) is moved in the reverse direction.

Optical disk device

A laser beam is directed from an optical head ( ) while an alternating magnetic field is applied from a magnetic head ( ). A reproduced signal from the optical head ( ) is input to a reproduced signal detecting circuit ( ) through a reproduced signal amplifying circuit ( ). The detected signal (CK) of discontinuous regions provided at prescribed intervals in the groove of a magneto-optical recording medium ( ) is input to an external synchronous signal generating circuit ( ) and, in response, an external synchronous signal (SYN) is generated. In synchronization with the external synchronous signal (SYN), the reproduced signal detecting circuit ( ) calculates a difference between the reproduced signal generated when a magnetic field for magnetic domain magnification is applied and the reproduced signal generated when a magnetic field for magnetic domain erasure is applied. The difference is detected as a reproduced signal (RF). Accordingly, low frequency &ldquo;winding&rdquo; included in the reproduced signal from the optical head ( ) is offset, resulting in a correct reproduced signal (RF).

Apparatus and method for reproducing information from a magneto optical recording medium by the magnetic domain magnification method

Reproducing method for magneto-optic recording medium, and magneto-optic disk device

An optical pickup device for an AS-MO disk, a DVD and a CD includes a dual wavelength semiconductor laser with first and second oscillation devices, a polarization plane rotary unit selectively rotating a plane of polarization of a laser beam 90&deg;, and a polarization selective diffraction grating passing a laser beam straight forward or dividing a laser beam into three beams depending upon the direction of polarization. The optical pickup device operates by the DPP tracking system where three laser beams are directed for an AS-MO disk, and by the DPD tracking system where a single laser beam is directed for a DVD or a CD. As a result, a signal can be reproduced from an AS-MO disk, a DVD, or a CD having different tracking systems.

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Gifu, Japan

Naoyuki Takagi