Hitachi, Ltd.

Hitachi Maxwell, Ltd.

Hitachi Maxell, Limited

Hitachi Cable, Inc.

Masahiro Ojima

Motoyasu Terao

Takeshi Nakao

Shigeru Nakamura

Atsushi Saito

Toshio Niihara

Keikichi Andoo

Yoshinori Miyamura

Yoshio Taniguchi

Harukazu Miyamoto

Kazuo Shigematsu

Seiji Yonezawa

Yasushi Tomioka

Toshimitsu Kaku

Tetsuya Nishida

Shuji Imazeki

Shinkichi Horigome

Hiroshi Yasuoka

Tsuyoshi Kato

Takeshi Maeda

Hirofumi Sukeda

Akira Arimoto

Takeshi Kato

Norio Ohta

Makoto Miyamoto

Kimio Tatsuno

Masaru Ito

Masuo Kasai

Susumu Saito

Yoshio Suzuki

Seiichi Mita

Tsuyoshi Toda

Yasushi Miyauchi

Hideo Fujiwara

Naoki Chinone

Kunio Harada

Yoshinori Takeuchi

Fumiyoshi Kirino

Hideaki Tsushima

Kyo Akagi

Shinji Tsuji

Hiroyuki Awano

Toshio Katsuyama

Yuzo Yamaguchi

Takashi Toyooka

Hiroaki Inoue

Toshinori Sugiyama

Masahiko Takahashi

Kenichi Mizuishi

Tsuneo Suganuma

Kazutaka Sato

Kunio Aiki

Kazuhiko Hosomi

Kiyoshi Matsumoto

Toshio Sugiyama

Masaya Horino

Akito Sakemoto

Yoshihiro Hamakawa

Misuzu Sagawa

Youichi Kawakubo

Eiichi Seya

Hirobumi Ouchi

Satoru Kikuchi

Keizo Kato

Manabu Yamamoto

Katuaki Chiba

Toyoji Okuwaki

Zenji Tsutsumi

Nobutaka Ohnuki

Norio Murase

Hideyuki Takashima

Makoto Horie

Sadatsugi Machida

Yoichi Yasuda

Young-kun Lee

The present invention aims to provide a dispersion compensator which is ultra small in size and low in cost and capable of controlling dispersion compensating values, and an optical transmission system using the dispersion compensator. A dispersion property of light that propagates through defects in a photonic crystal, is used to compensate for each wavelength dispersion. A dispersion compensator comprises a dispersion-compensating-waveguide array in which a plurality of dispersion compensating waveguides having dispersion compensating values different from one another are placed, a drive unit for driving the dispersion-compensating-waveguide array, and optical fibers for inputting/outputting a light signal. Each of the dispersion compensating waveguides comprises regular waveguides and a waveguide made of defects in photonic crystal. The lengths of the waveguides made of the defects in photonic crystal are changed one by one to make dispersion compensating values different from one another.

Dispersion compensator and optical transmission system using same

A light emitted from the supervisory light source is supplied to the input port of any one of a plurality of switching sections provided in the optical switching device. A light emitted from the output port of the switching section is converted into electric signals and then compared with the threshold value by a supervisory receiver. The supervisory control circuit discriminates the state of connection at each switching section in the optical switching device according to the compared result obtained by the supervisory receiver, whereby each switching section in the optical switching device is supervised.

Optical switching device and optical switching method

An optical fiber is held in a ferrule, and then the ferrule is located in a positioning groove formed in a substrate, thereby aligning the optical fiber with an optical device bonded to a surface of the substrate. Then, a lid is placed on the substrate in such a manner that the ferrule is located in a positioning groove formed in the lid and that the optical device is received in a cavity formed in the lid. The ferrule is thus held between the two grooves, and in this condition a resin is filled in the two grooves, thereby retaining the ferrule. Then, the lid is sealingly secured to the substrate. After these parts are thus assembled together, this assembly is put in dies, and then a package is molded.

Resin molded optical assembly

A magnetic head is supported with variable stiffness for loading onto the disk surface and unloading off the disk surface. The magnetic head is attached to an end of a thin leaf spring which has been curved in advance, and the leaf spring is interposed between two flat plates, with one of the flat plates being slidable. With the slidable flat plate being moved to the position where the plate overlies a fitting section of the magnetic head, a head support point is provided at a first position with respect to the magnetic head, the thin leaf spring takes an extending straightened state, and at the same time, the thin leaf spring, two flat plates, and magnetic head fitting section form a unitary member with a high stiffness for supporting the magnetic head thereby to load the magnetic head onto the disk surface. With the slidable plate being moved in the opposite direction so as to free the curved section of the thin leaf spring, a second head support point provided at a position further away from the magnetic head than the first position, and the magnetic head is supported flexibly with a lower stiffness by the thin leaf spring. Since the thin leaf spring curves in a free state at this moment, the magnetic head which is attached to the end of the leaf spring is unloaded off the disk surface as if it is whipped up.

Magnetic head load/unload device, method and a magneto-optical disk

A magneto-optical recording medium comprising, on a substrate, at least a first magnetic layer made of a rare earth amorphous alloy and a second magnetic layer made of a rare earth amorphous alloy having a relatively smaller coercivity Hc.sub.2 than that of the first magnetic layer, wherein the following relationship is satisfied at an operation temperature:

Magneto-optical recording media and mangeto-optical device using the

This invention provides a magneto-optical recording medium comprising at least an information storage layer and a readout layer disposed on the substrate, the information storage layer being used to record information by changing the magnetized state by raising the temperature thereof by light irradiation, and the readout layer being capable of copying information recorded on the above-mentioned information storage layer, located closer to the substrate than the above-mentioned information storage layer, and having a coercive force of 3 kOe or less at room temperature. By using this recording medium, a Signal to Noise ratio can be obtained in reproduction without deterioration of the information recording characteristics.

Magneto-optical recording media and magneto-optical recording device

Optical information recording/reproducing system including novel

In an optical recording method which utilizes hole burning, a plurality of sorts of light absorption centers having different properties are caused to coexist or to exist in the form of layers, thereby to remove the problem that, although the multiplicity of recording is high, the spacial recording density is low, so the overall recording density is low. Accordingly, the present invention can provide an optical recording method of very high recording density.

Optical recording method

A magnetic field of a polarity corresponding to information to be recorded is applied while a recording spot having a high energy is irradiated to a magneto-optical recording medium to record domains representing the information along a track. The recorded domains are read out by a reproducing spot having a lower energy than the recording spot and a high resolution power along the track. A recording head has an optical system for irradiating the recording spot having the high energy to the magneto-optical recording medium and a magnetic head for applying a magnetic field having a polarity thereof switched in accordance with the information to be recorded, to an irradiation area of the recording spot, a reproducing head has an optical system for irradiating the reproducing spot having the low energy by a laser beam having a wavelength of no larger than 600 nm and a magneto-optical signal detector for detecting a displacement of a polarization plane of a reflected light of the reproducing spot to read out the recording domains. The magneto-optical recording medium is made of a recording film having a multi-layer structure of alternate lamination of metal layers and dielectric layers.

Magneto-optical recording and reproducing method, magneto-optical memory

According to this invention, since the range of power necessary for erasing an overwritable magneto-optical recording medium is set to 2.5 mW or above, overwriting is possible without erase residue due to mark (magnetic domain) diameter difference, tracking offset, ambient temperature variation and characteristic dispersion between magneto-optical recording media and thus the magneto-optical recording medium has high reliability. Moreover, the rate of change, K of the switching field of the memory layer relative to temperature at around an erase start temperature can be controlled to be a constant value so that an erase power margin can be increased and that the tolerance to the reading light when the ambient temperature rises can be improved.

Magneto-optical recording media and overwrite recording method using the

A magneto-optical recording apparatus including a magnetic head applying a magnetic field to a magneto-optical recording medium in a region wider than a minimum bit record area thereby forming a magnetic field region, a beam source and an optical system forming on the magneto-optical recording medium a laser beam spot defining the minimum bit record area, a modulation unit for modulating at least one of the magnetic field and the laser beam thereby forming the laser beam spot within the range of the magnetic field region, and a mechanical unit for moving the magnetic field region and the laser beam spot relative to each other on the magneto-optical recording medium while the modulation unit is under operation, the magnetic head being floated to be spaced apart from the surface of the magneto-optical recording medium by a distance not smaller than 10 .mu.m while the mechanical unit is under operation. The slider rails (11) each have a width of at least 2 mm, so as to increase the flying height of the slider (1017) over the medium.

Magneto-optical recording apparatus having a magnetic slider with

An optical fiber type magneto-optical head is capable of realizing satisfactory reductions in size and weight of a movable portion of an optical head. An extinction-type form of the optical fiber type magneto-optical head comprises a first optical device for condensing a polarized light beam and leading the light beam into a polarization-maintaining optical fiber, a second optical device for focusing light emerging from the optical fiber into a beam spot on a magnetic recording medium, a detector for detecting via the optical fiber light reflected from the magnetic recording medium with a change in polarized state, and an azimuth rotator disposed between the second optical device and the optical fiber, wherein the azimuth rotator is designed so that the angle of optical rotation upon one pass therethrough is

Magneto-optical head employing optical fiber connected stationary and

A separation type optical head according to the present invention includes at least a light source portion for emitting collimated beams, a focusing device (a focusing lens) for focusing the collimated beams onto an information recording surface of an optical disc medium, a focal point control mechanism for the position of the spot on the information recording surface, and a photo-detection portion for receiving beams reflected by the information recording surface. The structure is divided into a fixed portion including the light source portion and the photo-detection portion and a movable portion including the focusing device (focusing lens) and the focal point control mechanism. At least the movable portion of the separation type optical head is movably accommodated n a frame (sealing case) for the optical head so as to prevent irregular vibrations of the movable portion due to high speed air flows or turbulence. Furthermore, a focal point control mechanism of an air float type may be employed in the movable portion of the separation type optical head so as to actively utilize the high speed air flow generated due to the rotation of the disc medium to perform a rough adjustment of the focal point of the focusing device.

Stack type optical disc apparatus, sealed and separate type optical head

A semiconductor laser device comprises a semiconductor laser which oscillates a fundamental wave, and a transparent waveguide which is installed substantially in parallel to a direction of a cavity of the semiconductor laser and integral with the semiconductor laser, where second harmonics of the fundamental wave travel through the transparent waveguide and are emitted therefrom. The semiconductor laser and the transparent waveguide have a refractive index in a prescribed range respectively, and an output of second harmonics being significantly high in comparison to the prior art can be obtained.

Semiconductor laser device having a transparent waveguide and a large

A record carrier for recording, reproducing and erasing information. A circular disc-like substrate has a recording layer thereon such that information is written onto the recording layer by changing the direction of magnetization. A guide groove of a plurality of tracks is formed in advance and extends in the radial direction with intervals therebetween. Each track of the guide groove is divided into a plurality of sectors, each of which includes a header portion in which a header signal containing an address for distinguishing at least said sector is formed in advance with pits of a phase structure and a data portion adjacent to said header portion. The guide groove serves as an optical guide for a light beam which records, reproduces and erases information onto the data portion. A first detection system for detecting the light intensity of the reflected light from the record carrier and a second detection system for detecting the direction of polarization of the reflected light from the record carrier, and a level adjustment circuit for adjusting the levels of the header signal detected by the first detection system and the data signal detected by the second detection system are incorporated in this apparatus, whereby recording, reproducing and erasing information of any number of sectors are enabled.

Magneto-optical disc memory apparatus including a header signal and

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Tokyo, Japan

Masahiro Ojima