Abstract: An opto-magnetic signal reproducing apparatus includes a light source unit for applying a linearly polarized light beam to a recording medium having magnetically recorded information, a splitter for splitting the light beam modulated, responding to the recorded information by a magneto-optic effect, into two light beams having different polarization directions from each other, and a reproducing device for differentially detecting the split light beams to reproduce the recorded information. The splitter imparts a phase different equal to an integer multiple of .pi. to each of the split light beams.

Abstract: A high-density information recording carrier such as an optical disk which is used for recording and/or playing back information carried on a plastic substrate by means of laser beams has an improved protective layer between a recording layer and the plastic substrate. The protective layer is made of inorganic glass made of alkali-free glass containing less than 1 wt % of alkali metal oxides. The resulting optical disk shows improved durability, higher C/N, lower BER and higher film forming rate.

Abstract: A hologram transducer using the Faraday effect in magnetic bubble devices for recording and reproducing the amplitude and phase distributions over a section of a beam of coherent light is disclosed. The transducer spatially modulates the intensity, by using linear polarization, and the phase, by using circular polarization, of light transmitted through a magnetic bubble device. Using linear polarization and a single magnetic bubble domain to traverse in a sequence the possible storage positions in the magnetic bubble device, the transducer samples at each of these positions the intensity of the transmitted light. Using in addition a coherent reference beam of light to interfere with the light being measured, the transducer samples the phase in the half range of 0 through .pi. radians at these positions. Further, using a quarter cycle phase shift in the reference beam, the transducer resolves the phase values over the full range of 0 through 2.pi. radians.

Abstract: In a method of recording, in the over-write mode, bivalent signals "0" and "1" on an opto-magnetic record medium having a ferrimagnetic material whose compensation temperature is higher than a room temperature, but is lower than a Curie temperature, an external magnetic field is applied to the record medium, and a laser light beam is modulated in accordance with the bivalent signals. When the bivalent signal "0" is to be recorded, the laser light beam is set to a lower power level and the ferrimagnetic material of the record medium is heated to a temperature higher than the room temperature, but lower than the compensation temperature so that the ferrimagnetic material is magnetized in the same direction as the external magnetic field.

Abstract: A magneto-optical recording medium made of a rare-earth-transition metal amorphous film provides a compensation temperature Tcomp of 50.degree.-200.degree. C. or 0.degree. C. or less. This compensation temperature decreases a saturation magnetization Ms during recording, thereby preventing the provision of inverted magnetic domains at the centers of recording domains resulting from the demagnetizing field generated by the strength distribution of laser light, and so improving a carrier-to-noise ratio during reading. In the case of using a Tb-Fe-Co system amorphous film, Tcomp of 50.degree.-200.degree. C. may be give by the composition comprising Tb of 24-30 atomic %, Co of 7-20 atomic % and Fe of the rest, and Tcomp of 0.degree. C. or less may be given by the composition comprising Tb of 18-21.5 atomic %, Co of 8-10 atomic % and Fe of the rest.

Abstract: A magneto-optical memory medium of a laminar structure comprising at least one non-magnetic layer, and a plurality of magneto-optical storage layers separated from each other by corresponding non-magnetic layers, and wherein information is read out from a selected one of the storage layers by detecting a change in the Kerr rotation angle of a corresponding one of light beams of different wavelengths applied to the memory medium, which change depends upon magneto-optical anisotropy of the storage layers. A thickness of one of the storage layers is determined so that the change in the Kerr rotation angle of each of the light beams repesents the anisotropy of the corresponding storage layer, irrespective of the anisotropy of the other storage layers. Also disclosed is a magneto-optical apparatus for writing and/or reading information on or from the desired magneto-optical layers.

Abstract: A magneto optic recording medium comprising a substrate, an amorphous magnetizable rare earth-transition metal alloy layer, a transparent dielectric layer on at least one side of the magnetizable layer, and a reflective surface located to reflect light through the magnetizable alloy layer. The dielectric layer is comprised of silicon carbide of the formula SiC.sub.x, wherein x, the molar ratio of carbon to silicon, is greater than 1. The dielectric layer is preferably deposited by direct current magnetron sputtering at low argon partial pressure from an electrically conductive mixture of silicon carbide and carbon. The medium exhibits similar or improved characteristics over media constructed with present dielectrics, for example, silicon suboxide (SiO.sub.y, y<2).

Abstract: Over Write Capable Magnetooptical Recording Medium, Recording Method and Apparatus Using the Same. The recording medium in which the direction of an initial field Hini. is the same as that of a bias field Hb (Classes 1, 2, and 8 in Table 1), and which satisfies predetermined formulas can allow an over-write operation if a jointing field Hjoint. is used which continuously changes from the initial field Hini. to the bias field Hb.

Abstract: An information-carrying medium with first, second and third ferromagnetic layers is enclosed in a housing, in which an initializing magnet is disposed. The second layer of the information-carrying medium is magnetized by the initializing magnet premagnetized in a uniform direction and is used as a bias layer.

Abstract: A magneto-optical recording medium comprises a recording layer formed of a magnetic material, and a protective layer composed of a combination of a dielectric material with a rare earth metal exhibiting a high oxygen absorptivity and formed on the recording layer by a simultaneous sputtering or a simultaneous deposition process, whereby free oxygen given rise to in the course of sputtering or deposition is absorbed on the protective layer side before being absorbed on the recording layer side.

Abstract: This device is an all-optical digital architecture for carrying out compuions. Residue number system addition and multiplication tables are produced on an optically-addressable plane composed of optically bistable material. The plane of optically bistable material devices represents a residue number system addition or multiplication tables and is addressed by two intersecting signal beams from the top and a bias beam from the bottom. A combination of two signal beams exceeds the material transmission threshold in the intersection region letting bias light emerge as a position encoded signal beam.

Abstract: Method and system for overwriting binary data values in microscopic storage regions of a thin film ferrimagnetic layer without using external magnetic bias aiding the recording process. The ferrimagnetic layer is selected having a compensation temperature at least a few tens of degrees above room temperature. In recording data, any previously recorded data is erased to establish a known state and magnetic domains of reverse magnetic polarity are recorded when the known state differs from the binary data state by temporarily heating an area on the ferrimagnetic layer above the compensation temperature in the absence of any external aiding magnetic bias.

Abstract: A magneto-optic information storage system is disclosed suitable for compensation point recording in the absence of an external bias field. The pulse of light used to erase imparts less energy than the pulse used to write. Also disclosed is a method for directly overwriting data recorded on a magneto-optic medium by applying lower energy erasing pulses of light and higher energy writing pulses.

Abstract: An opto-magnetic recording medium includes: a substrate; a first magnetic layer formed on the substrate, the first magnetic layer having the following composition:[(Tb.sub.1-x Dy.sub.x)(Fe.sub.1-y CO.sub.y)].sub.1-z M.sub.zwherein 0.ltoreq.x.ltoreq.1, 0.ltoreq.y.ltoreq.0.3, and 0.ltoreq.z.ltoreq.0.2, and M is one element selected from the group consisting of Cr and Al; and two second magnetic layers respectively formed on the two surfaces of the first magnetic layer, each of the second magnetic layers having a lower coercive force and a higher Curie temperature than those of the first magnetic layer, and being exchange-coupled to the first magnetic layer, and each of the magnetic layers having the following composition:(GdFeCo).sub.1-w M.sub.wwherein 0.ltoreq.w.ltoreq.0.2, and M is one element selected from the group consisting of Cr or Al.

Abstract: An apparatus for recording, reproducing and erasing data or information on a magneto-optical recording medium, for applying a steady magnetic field to the recording medium and for applying a variable magnetic field, a portion of the apparatus for applying the magnetic field being integrated into a recording head and and the record head being disposed on different sides of the recording medium, this results in the miniaturization of the means for applying the magnetic field to the recording medium and the apparatus presents an excellent recording/erasure property.

Abstract: An optical recording medium comprising a recording layer on a substrate is more durable when an intermediate layer of a composition comprising a rare earth element oxide, silicon oxide, and silicon nitride is formed between the substrate and the recording layer.

Abstract: A magnetooptical disc is initialized by reversing the direction of magnetization at fixed intervals and the direction of external magnetic field applied to it is reversed for each overwrite recording by exposure to laser light.

Abstract: A magnetooptical recording method for recording data using a bit having upward-magnetization and a bit having downward-magnetization on a recording layer of a magnetooptical recording medium comprises the steps of using, as the medium, a multilayered magnetic recording medium consisting of a first layer having a perpendicular magnetic anisotropy acting as a recording layer, and a second layer having a perpendicular magnetic anisotropy acting as a reference layer; moving the medium; applying an initial field so that, before recording, the direction of magnetization of the recording layer is left unchanged, and that of the reference layer is aligned either upward or downward; radiating two adjacent laser beams, i.e.

Abstract: A magneto-optical recording process is produced by irradiating a recording track of a recording medium, in the course of movement thereof, with a main light beam of intensity sufficient for heating the medium to a temperature at which the coercive force thereof is reduced to zero or a very small value in a continuous manner during the recording operation and irradiating a separating area with a subsidiary beam of a modulated intensity, thereby modulating the vertical magnetization of said separating area. A floating magnetic field generated by the thus modulated vertical magnetization generates magnetic fields of mutually different directions, thus forming a record bit on the recording track.

Abstract: A magnetooptical information recording apparatus is provided with a device for irradiating a magnetooptical recording medium with a light beam, and a device for applying a bias magnetic field to a portion, irradiated by the light beam, of the magnetooptical recording medium. The applying device is provided with a yoke member having a first projecting portion positioned in the vicinity of the irradiated portion and a second projecting portion spaced from the first projecting portion in a direction along the surface of the recording medium, wherein the distance of the second projecting portion from the first projecting portion at a closer side to the recording medium is smaller than that at a farther side to the recording medium.

Abstract: A magneto-optical information recording apparatus comprises an objective for condensing a light beam on a magneto-optical recording medium, a bias magnetic field producing device provided on the opposite side of the objective with respect to the magneto-optical recording medium and applying a magnetic field from outside to the magneto-optical recording medium near the condensed point of the light beam, and a protective outer frame containing the objective therein and having an opening for transmitting the light beam therethrough at a location opposed to the magneto-optical recording medium, at least a portion of the protective outer frame being formed of a ferromagnetic material.

Abstract: According to a disk-shaped magneto-optical recording medium of the invention, a transparent thin film serving as an interference layer is formed on a transparent substrate. The thin film is subjected to a plasma surface treatment, thereby decreasing the fused oxygen content in at least a surface portion thereof. A recording layer of a rare-earth-transition metal amorphous ferrimagnetic alloy thin film is formed on the plasma surface-treated film. Since the content of active, fused oxygen contained in at least the surface portion of the film decreases, rare-earth element oxide can hardly be formed in a boundary region between the recording layer and the transparent thin film. The content of the rare-earth element in this region is smaller than the average content in the overall recording layer.

Abstract: A magneto optical thin film recording medium is disclosed having very high carrier-to-noise ratios and high rotation angles. A transmission electron microscope photomicrograph (at 200,000 X) of one such medium is shown in FIG. 1. These are multi-phase amorphous materials having magnetic anisotropy perpendicular to the plane of the thin film. They are produced in a triode vacuum sputtering process at vacuums in the range of 4.times.10.sup.-3 to 6.times.10.sup.-4 Torr. By adjusting process parameters such as substrate temperature, anode bias and deposition rate, the properties of the thin film can be altered.

Abstract: An apparatus and a method for recording, reading and erasing information, which use, as a recording medium, a magnetic film having vertical magnetic anisotropy characteristics and record, read and erase information by means of a laser beam and an external magnetic field applied to the magnetic medium. These are characterized in that the application of the external magnetic field to the recording medium is controlled by controlling the magnetic field provided by a permanent magnet put at a predetermined distance from the recording medium. For controlling the magnetic field, means for applying an external magnetic field to a recording medium is employed, which comprises a permanent magnet, a magnetic core of a high magnetic permeability material comprising a pole piece attached to at least one pole of the permanent magnet and a lag piece integrally connected to the pole piece and having a wire wound therearound, and an electric current source supplying electric current to the wire wound of the core.

Abstract: Magneto-optic recording media have been made more resistant to corrosion by incorporating small amounts of tantalum and/or yttrium into the rare earth-transition metal active layer of the recording media. This improvement should help make magneto-optic media more reliable in the long term storage and retrieval of information.

Abstract: A magneto-optical recording medium, which comprises a thin film constituted of an amorphous alloy (R.sub.x TM.sub.1-x).sub.1-y A.sub.y (where the element material R is at least one rare earth element, the element material TM at least one 3d transition metal and the element material A at least one semi-metal-semiconductor element) and having an easy axis of magnetization in a direction perpendicular to the film surface, the atomic ratio being 0.15.ltoreq.xx.ltoreq.0.35 and 0.00<y.ltoreq.0.20.

Abstract: Disclosed is a composite memory device which comprises a recording disc medium having a large number of recording tracks to and from which data is written and read, a housing for holding the recording disc medium, a rewritable semiconductor memory disposed within a portion of the housing, and pins disposed within a portion of the housing for transferring data between the semiconductor memory and an external device.

Abstract: An optical head for an optical disc or for a magneto-optical disc for reading out information recorded thereon, including a light source for emitting a beam of linearly polarized light toward the disc, at least one Faraday rotator for passing the emitted beam and rotating a plane of polarization of the beam by a predetermined angle, at least one beam splitter for either passing or reflecting the incident light depending upon the plane of polarization, and a light sensor for sensing a light reflected by the splitter. Some combinations and configurations of these beam splitters and Faraday rotators are exemplified. This head is designed to be easily assembled and to effectively detect a light reflected by the optical disc, thereby providing reliable detection of data recorded thereon.

Abstract: A magneto-optical recording medium comprises a substrate, a magneto-optical recording layer formed of a rare earth metal-transition metal alloy and a dielectric protective layer overlaid in this order on the substrate, and a rare earth metal layer overlaid on an edge face of the magneto-optical recording layer.

Abstract: A magneto-optical recording apparatus for writing information on a magneto-optical recording medium having at least one pair of magneto-optical storage layers each pair consisting of a first and a second storage layer which have at least one pair of corresponding recording segments, each pair of mutually corresponding recording segments consisting of a first recording segment provided on the first storage layer and a second recording segment provided on the second storage layer. The apparatus includes a first and a second writing/erasing head for writing and erasing information on the first and second storage layers, and a recording controller for activating one of the first and second writing/erasing heads to erase previous information already recorded on corresponding one of the first and second recording segments, while activating the other head to write first new information on the other of the first and second recording segments.

Abstract: In composition of Tb-Fe-Co type magnetooptic recording material, additional inclusion of specified amount of Be much improves corrosion resistance and Kerr rotation angle of a magnetooptic disc made therefrom.

Abstract: A magneto-optical recorder is disclosed in which an external magnetic field required for recording and erasing can be produced by a small-sized electromagnetic coil having a small magneto-motive force. The electromagnetic coil is made up of a magnetic core and a coil winding, and the outer peripheral portion of the coil winding other than that peripheral portion thereof which confronts a recording medium, is covered by a core material. A magnetic field emanating from the electromagnetic coil spreads in a narrow space, and can be applied to the recording medium with large intensity even when the electromagnetic coil has a small magneto-motive force. In the recorder, a magnetic body is disposed such that the electromagnetic coil and the magnetic body face each other, to concentrate the magnetic field generated by the electromagnetic coil, to the vicinity of that portion of the recording medium which is irradiated with a light spot.

Abstract: A magneto-optic recording medium including a transparent substrate and a non-oxide dielectric layer formed thereon is provided. The dielectric layer includes a first dielectric material of the type which exhibits cracks running in a generally radial direction when deposited on a surface and which is designated dielectric Group A and a second dielectric material which exhibits cracks running in a generally tangential direction when deposited on a surface and which is designated dielectric Group B. The dielectric layer may be separate layers or a mixture of the two dielectric materials.

Abstract: An optical system for use with an optical memory including an optical arrangement for separating light reflected from the surface of the optical memory into a plurality of different resultant beams. This optical mechanism comprising four reflecting surfaces each of which are inclined at a different angle relative the optical memory to direct the resultant beams of light each in a different direction nor normal or parallel to each other. Preferably, at least three of these reflective surface are contiguous to one another. The optical system further includes a photodetector having a plurality of photosensitive regions aligned to receive the resultant beams from the aforementioned reflective surfaces.

Abstract: The head comprises a light source (S), a polarizer (P), a parabolic mirror (MP1), a second parabolic mirror (MP2), a polarization converter grating (RCP), a reflector (M), a separating plate (LS) and a detector (D). The beam diffracted by (RCP) constitutes a reference beam and the beam which has passed through (RCP) an analysis beam. The interference state of these two beams is dependent upon the orientation of the magnetization of the support to be read.

Abstract: A device for producing a high frequency modulating magnetic field is disclosed. The device is especially useful to achieve real-time overwriting in magneto-optical recording. The device produces magnetic field modulated according to a signal to be recorded on a magneto-optical recording medium in which the signal is recorded in the form of magnetization direction on the magneto-optical recording medium under irradiation of a laser beam to raise the temperature of the medium. The device comprises a main magnetic pole formed of a low-loss soft magnetic material and having one end facing to the magnetic-optical recording medium and a sheathed conductor wound around the main magnetic pole and consisting of a parallel connection of a plurality of insulated elementary wires.

Abstract: A thermally written magnetic data storage medium retains desired domains of magnetization having field orientations representative of the data. A first magnetic layer retains one or more domains of desired magnetic field orientations. A second magnetic layer provides a biasing field for obtaining a predetermined magnetic field orientation in the first magnetic layer as a function of the temperature of the second magnetic layer. Disposed between the first and second layers is a thermal isolation layer which provides a thermal barrier for controlling the temperature of the second magnetic layer means. When the medium is heated for a short time, the fringe field from the first layer causes one direction of magnetic orientation to occur in a domain in the first layer. Upon cooling of the domain, the domain magnetization becomes stable with an orientation conforming to the orientation of the fringe field. The thermal isolation layer prevents significant heating of the second layer.

Abstract: In a magnetic recorder, magnetooptic, for example, the erasure dircetion for successive recording areas (sectors) are determined by the direction of magnetization of prior recording. A mark is placed in each sector for identifying its erasure direction.

Abstract: A reproducing apparatus for magneto-optical discs has a moving head portion and a fixed head portion. Light reflected from the disc is divided into two parallel light beam components having different planes of polarization. These light beam components are transmitted to corresponding light intensity detectors of the fixed head portion. The outputs of the detectors are unaffected by movement of the movable head portion relative to the fixed head portion radially of the disc and are unaffected by movement of the movable head portion in other directions due to inaccuracies in the slider mechanism that moves the movable head portion radially.

Abstract: A magneto-optical signal read-out system for a magneto-optical player in which the polarized plane of linearly polarized incident light is rotated when the incident light is reflected by or passes through a magneto-optical medium having tracks thereon and the rotation angle of the polarized plane is utilized as an information signal. The read-out system includes a first analyzer, a second analyzer and a photo detector divided into first and second photo detector sections. A differential amplifier receives output signals from the first and second photo detector sections and produces a detected signal representative of the difference between the first and second output signals to reduce in-phase noise in the detected signal.

Abstract: Disclosed herein are an improved method and apparatus for optically reading pre-recorded magnetic information on a magneto-optic recording element. The invention addresses the technical problem of minimizing the adverse effect of unpredictable variations in the state of polarization of the beam of radiation used for read-out. Such variations may be produced, for example, by birefringence variations in a transparent layer or substrate through which the recorded information is recovered. According to the invention, the undesired polarization variations are sensed from the system's output signal, and an error signal representative of such variations is produced. Such error signal is used to adjust the state of polarization of the read-out beam prior to detection by the system's detector elements. Preferably, the read beam is directed through the combination of a quarterwave plate and a Faraday rotator, and the error signal is used to control the magnetic field of the Faraday rotator.

Abstract: A film of a crystal - crystal phase transformation type optical recording alloy is formed on an insulating substrate. Information is erased from the alloy film by heating it with an expedient other than a laser beam. Information is read by sensing reflected light of light projected on the alloy film.

Abstract: In an apparatus for generating a magnetic field, first and second electromagnetic coils are linearly arranged on a yoke. The coils face one surface of an optical disk. An optical head is positioned above the other surface of the optical disk. A track address for denoting a track on the optical disk is picked up from the optical disk by the optical head and an information signal processor. A first and/or second energizing signal is generated from a switching circuit in accordance with the track address. Thus, one or both of coil drive circuits are driven in response to the energizing signals, energizing one or both of the coils, so that a predetermined magnetic field is applied to the optical disk from the selected coil or coils.

Abstract: The present invention relates to an external magnetic field inverting apparatus for magneto-optical disc apparatus in which a permanent magnet (15) is used as external magnetic field generating means and a winding (25) is located so as to surround the permanent magnet (15), and the permanent magnet (15) can be half-rotated in a desired direction by a rotation force generated by a repulsive force by an external magnetic field Hm generated by this permanent magnet (15) and a magnetic field Hc resulting from supplying a current to the winding (25), whereby the apparatus of the invention can be reduced in cost, increased in reliability and miniaturized in size.

Abstract: An optical recording medium comprising a substrate, an optomagnetic recording layer made of a magnetic film where information can be recorded and reproduced by irradiation with a light beam, and an optical recording layer which can be modified in optical properties to form guide tracks when information is recorded in or reproduced from the optomagnetic recording layer.

Abstract: A method of making a magneto-optical recording medium comprises the steps of moving a rotating substrate along a first dielectric target, at least one rare earth metal target, and a second dielectric target which are disposed in this order from an upstream side toward the downstream side in an in-line sputtering apparatus, and carrying out simultaneous sputtering on the substrate in the course of the movement of the substrate by use of the first dielectric target and the rare earth metal target. Thereafter, sputtering is carried out on the substrate by use of the rare earth metal target. Then, simultaneous sputtering is carried out on the substrate by use of the rare earth metal target and the second dielectric target.

Abstract: A signal recording and reproducing device for use with an opto-magnetic disk having a number of concentric recording tracks. An optical head sweeps a given track at least twice during a time interval equal to a predetermined reproduction time for the track. Erasure signals and recording signals are supplied to the optical head during the first time sweeping and the second time sweeping, respectively, in order to effect signal erasure and recording. At the time of switching from the first time sweeping to the second time sweeping, the address data indicating the end point written on the terminal portion of the previously recorded signal area are sensed, and the recording is effected from the thus sensed recording end point.

Abstract: Method and apparatus for processing information on a recording member having a recording film capable of recording and erasing information in accordance with the change of a magnetizing direction, by utilizing a light induced thermo-magnetic effect, in which before the intensity of the laser light is switched at the high level eliminating the magnetization of the recording film in order to effect the recording and erasing operations by focusing the laser light on the recording film as a light spot, a magnetic field with the predetermined direction according to the recording and erasing operations is previously applied on the recording film, whereby the recording and erasing operations of the magnetized information can be effected with high speed and stably by applying the normal magnetic field in the direction according to the recording and erasing operations respectively.

Abstract: A magnetooptical recording element has a substrate bearing a magnetooptical recording layer. The recording layer is crystalline and comprises a compound of the formula R.sub.2 T.sub.14 B, wherein R is a rare earth metal or a combination of two or more rare earth metals, and T is a transition metal or a combination of two or more transition metals, in particular Fe or Co or a mixture thereof. A magnetooptical recording device comprises such a magnetooptical recording element.

Abstract: The optical recording and reproducing apparatus comprises a magnetic field applying section, a movable mechanism for moving the magnetic field applying section, a distance detecting section for detecting a distance between magnetic poles of the magnetic field applying section and the surface of a recording medium, and a distance control section for maintaining the above distance constant in response to an output of the distance detecting section. The distance between two magnetic pole ends of the magnetic field applying section can be minimized. Further, on the basis of the tracking control of either one of the recording and erasing light beams, it is possible to enable a high-precision tracking control to the other of the two light beams.