Masahiro Ojima has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).
Abstract: The present invention relates to a handover method of a mobile IPv6 communication network capable of reducing the handover interrupt time, the packet loss rate, and the load of the home agent. The mobile station is a single or a multimode physical access terminal, and monitors a link situation to obtain a network handover initiation. After obtaining initiation information, the mobile station sends handover information including link information of a new access router to a current access router and the current access router returns network information of the new access router, and the mobile station starts a network layer handover of the mobile IPv6 before the link layer handover. Data sent from the communication end to the mobile station is directly sent to a new care-of address of the mobile station. In order to reduce the packet loss, the new access router stores data sent to the mobile station before the mobile station and the new access router establish their connection.
July 1, 2004
March 3, 2005
Masashi Yano, Nie Ya Ling, Masahiro Ojima, Niu Zhisheng
Abstract: 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.
Abstract: 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.
Abstract: 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.
July 19, 2000
Date of Patent:
October 8, 2002
Hideaki Tsushima, Masahiro Ojima, Masaya Horino, Kazutaka Sato
Abstract: 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.
Abstract: 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.
Abstract: 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:Hw.sub.1 -Hexc.sub.1 >Hc.sub.2 -Hexc.sub.2where Hw.sub.1 represents the magnetic domain wall coercivity of the first magnetic layer, Hexc.sub.1 represents the magnitude of the exchange magnetic field exerted on the first magnetic field and Hexc.sub.2 represents the magnitude of the exchange magnetic field exerted on the second magnetic layer is used, to obtain a magneto-optical recording medium with no increase in the noises by overwriting, and without reduction of C/N ratio after repeating recording for a number of cycles, a recording method and overwriting method using the media and a magneto-optical recording device.
Abstract: 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.
Abstract: An optical information recording/reproducing system is disclosed in which optical information having guide grooves for tracking and information pits beforehand provided thereon is irradiated with a main light beam for the recording/reproduction of information and a pair of subsidiary light beams for the detection of tracking and the scanning loci of the centers of the subsidiary light beams are arranged on the optical information carrier on opposite sides of the scanning locus of the center of the main light beam, respectively, first and second means for generating electric signals having their amplitudes corresponding to the respective intensities of the subsidiary light beams reflected by the optical information carrier, third means for detecting a difference in amplitude between the electric output signals of the first and second means, fourth means for detecting Ac components of the electric output signals of the first and second means to detect a difference in amplitude between the AC components, and fif
Abstract: 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.
Abstract: 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.
Abstract: 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.
Abstract: 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.
Abstract: 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.theta.k/2.+-.n.multidot.45.degree.where.theta.k/2.+-. : the Kerr rotation angle of a magnetic recording film of the recording medium,N= 0, 1, 2, . . . .
Abstract: 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.
Abstract: 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.
Abstract: 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.
November 21, 1990
Date of Patent:
November 3, 1992
Atsushi Saito, Masahiro Ojima, Masaru Ito
Abstract: According to the present invention, the apparatus is provided with a single laser light source and arranged so that light from the laser light source is divided into a plurality of beams by a grating and the plurality of beams are converged to form a plurality of light spots on a recording film by an optical system, whereby in writing information onto a recording film, overwriting to perform erasing and writing at the same time is carried out and an error check on the recorded information is performed in real time while a magnetic field which is polarity-inverted or intensity-modulated in accordance with the recording information is applied to the recording film.
Abstract: A magneto-optical memory apparatus has an optical head for applying a light to a substrate of a recording medium such as a magneto-optical disk having a magneto-optical recording film formed on the substrate and continuously applying a high power laser beam in a record mode, and a floating magnetic head arranged on the opposite side of the recording medium to the side of the optical head and adapted to be kept at a substantially constant distance from the recording medium by an air pressure created between the magnetic head and the recording medium by the movement of the recording medium, for applying, in the record mode, a magnetic field which is polarity-inverted or intensity-modulated according to information to be recorded, to the magneto-optical recording film.
Abstract: In a two-laser beam optical head including first and second signal detectors for guiding emitting beams from first and second laser sources as two spots to an information medium and detecting the reflected beams from the two spots, the optical head of the present invention has the construction wherein the two laser sources are stored in one package, the emitting beams from two laser sources can be rotated together with a collimate lens with the optical axis of the collimate lens being the center in order to enable the two spots around the optical axis of a focusing lens as the center and the direction of the center line between the two spots can be changed so that the center line between the two spots is always perpendicular to the radial direction of the track on the information medium.