Abstract: An improved read/write optical disk is disclosed which is capable of being rewritten more than 10.sup.6 times. The disk utilizes a storage medium in which data is stored by causing a localized region of the storage medium to assume one of two states. The two states can be converted from one to another by the application of electric fields to the localized region of the storage medium. The localized region in question is selected by illuminating an area on an addressing layer directly above the region in question with light. The preferred embodiment utilizes a lead lanthanum zirconate titanate material for the storage medium.

Abstract: An information recording and erasing method and apparatus of an optical memory medium including a substrate, a guard film, and an intermediate layer portion so disposed between said substrate and said guard film as to include at least a recording material layer having a phase changing with temperature and include at least one good conductor layer, comprising the steps of supplying magnetic flux varying relatively to said good conductor layer to generate eddy currents within said good conductor layer, and heating said recording material layer with heat generated in said good conductor due to the eddy current loss to effect information recording and erasing with respect to said recording material layer.

Abstract: A magneto-optical recording medium including a recording layer and a bias layer being stacked one upon the other to apply coupling interaction which is mainly magnetostatic interaction to each other, the bias layer having a magnetization-reversing temperature higher than that of the recording layer. The medium is irradiated with laser beam pulses having a recording level and an erasing level lower than the recording level, thereby recording and erasing the information. When the medium is irradiated with the laser beam pulse having the recording level and the irradiated region is cooled to the magnetization reversing temperature T.sub.rR, the magnetization of the beam-irradiated region of the recording layer is aligned with a direction of the leakage magnetic field leaking from the recording layer. When the medium is irradiated with the laser beam pulse having the erase level and the irradiated region is cooled to T.sub.

Abstract: An optical magnetic disk is disclosed having an anti-reflective layer thereon for enhancing the Kerr rotation angle (.theta.k) and the Faraday effect (.theta.f), which comprises a first anti-reflection layer and a second anti-reflective layer coating of an amorphous material forming a thin film layer coating composed of As.sub.40 Se.sub.50-x S.sub.x Ge.sub.10 on the upper and/or the lower surface of a recording layer, selectively, in which x is between 15 to 40, the reflective index (n) is in the range of 2.5 to 2.7, each of the thicknesses of the first and the second anti-reflective layers is between 600-660 .ANG. and 250-350 .ANG., and the Kerr rotation angle (.theta.k) of the amorphous thin film is 1.55.degree. at maximum.

Abstract: A magneto-optical recording apparatus records an information signal on a disk by illuminating a magnetic layer on the disk with a pulsed laser beam having a frequency at least twice the maximum frequency of the information signal, and applying a magnetic field with a polarity switched according to the information signal to the spot illuminated by the laser beam. To ensure erasure of old information, the apparatus can modify the peak power level, bottom power level, duty cycle, or frequency of the pulsed laser beam according to the radial position of the beam on the disk.

Abstract: A magnetic head position control apparatus for driving the magnetic head of a disc recording apparatus toward or away from the recording surface of a magneto-optical disc to effect position control of the magnetic head detects changes in the distance between the magnetic head and the magneto-optical disc by detecting changes in the capacitance between a capacitance detection electrode mounted on the magnetic head and a surface of the magnetic disc and generates a voltage to control the position of the magnetic head for maintaining it at a constant predetermined distance from the magneto-optical disc. Stray capacitance between the disc and the disc recording apparatus is based on the size of the disc, which is either detected directly or obtained from pre-recorded data on the disc, and is compensated by adding a bias voltage to the voltage generated using the capacitance detection electrode to provide further control of the position of the magnetic head.

Abstract: A head protection control for a magneto-optical recording/reproducing device, including an elastic arm for mounting a magnetic head at one end portion of the arm and biasing the magnetic head in a direction contacting a surface of a magneto-optical disk, which elastic arm is movable in a radial direction of the magneto-optical disk; a driver for driving the elastic arm in a direction moving away from the surface of the magneto-optical disk; a phase-locked loop (PLL) for generating a lock signal when the PLL circuit becomes synchronous with a clock signal in a reproduced signal from the magneto-optical disk; and a controller for controlling the driver so as to cause the driver, upon receipt of the lock signal, to lower the magnetic head to face the magneto-optical disk during rotation at the predetermined speed with a fine gap defined between the magnetic head and the magneto-optical disk by a flying force due to an air stream.

Abstract: A high density magnetooptical recording and playback method is disclosed. The magnetooptical recording medium comprises a recording hold magnetic layer and a playback magnetic layer magnetically coupled with each other. Prior to the playback operation, the playback magnetic layer is initialized by an external magnetic field. A laser light is irradiated to locally heat the medium and cause transfer of magnetization in the recording hold magnetic layer to the playback magnetic layer. The signal is read out by the interaction of the laser light and the transferred magnetization.

Abstract: An optical disk includes a substrate disk and an additional recording layer formed on a surface of the substrate disk. A series of pits and lands is formed on the surface of the substrate disk for recording basic information which includes address and data information along a basic recording track. The additional recording layer is for voluntarily and additionally recording additional information along an additional recording track positioned over the basic recording track. The basic and additional information can be reproduced by a basic information reproducing circuit and additional information recording and reproducing circuit, respectively. The additional information recording and reproducing circuit also records an additional information along the additional recording track so that the additional information is recorded over portions where the data information of the basic information is recorded.

Abstract: An opto-magnetic recording apparatus comprises a rotation device for rotating an opto-magnetic recording medium, an initial auxiliary magnetic field applying device, a laser beam source, a modulation device for pulse-modulating the beam intensity, in accordance with the binary information to be recorded, between a high level for magnetizing the recording medium to one of two states and a low level for magnetizing the same to the other state, and a recording magnetic field applying device. The apparatus further has a shifting device for shifting the initial auxiliary magnetic field applying device at least between two positions including a first position for over-write mode operation where the initial auxiliary magnetic field applying device applies the initial auxiliary magnetic field to the recording medium and a second position for non-over-write mode operation where the initial auxiliary magnetic field applying device does not apply the initial auxiliary magnetic field to the recording medium.

Abstract: A medium comprises a memory layer, a writing layer, a switching layer, and an initializing layer, these four layers consisting of perpendicularly magnetizable magnetic films being stacked in order, wherein the memory layer and the writing layer are exchange-coupled, a direction of magnetization of only the writing layer can be aligned in a predetermined direction without changing a direction of magnetization of the memory layer, and the writing layer and the initializing layer are exchange-coupled via the switching layer at a temperature equal to or lower than the Curie temperature of the switching layer. The writing layer is RE-rich at room temperature and has compensation temperature between room temperature and its Curie temperature, and the initializing layer is RE-rich at room temperature and has no compensation temperature between room temperature and its Curie temperature.

Abstract: The invention relates to a magneto-optical recorder with magnetic-field modulation. It comprises a laser (8) for producing a light beam (6), an optical focussing system (9) for forming a focal spot (12), and a servo device (10) for maintaining the focal spot (12) in focus on the surface of a thermo-magnetic record carrier (4), and for supplying a correction signal (V.sub.c) which is representative of the position of the surface of said carrier. A current modulator modulates the current through a coil (15) of a magnetic head. A compensation device (7) is responsive to said correction signal (V.sub.c) to change a parameter influencing the field of the coil, in such a way that the field strength at the surface of said carrier (4) is substantially independant of the position of said surface.

Abstract: A method for recording a signal on a magneto-optical recording medium comprising a first magnetic layer exhibiting a vertical magnetic anisotropy and a second magnetic layer exchange-coupled to the first magnetic layer and having a higher Curie point and a lower coercive force at a room temperature than those of the first magnetic layer, exchange forces acting on the first and second magnetic layers being lower than the coercive force of the second magnetic layer by applying to the medium a biasing magnetic field having polarity and magnitude thereof modulated in predetermined states depending on the signal while a light beam having a power to heat the medium to the vicinity of the Curie point of the first magnetic layer is irradiated to the medium.

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.

Abstract: A magnetic recording apparatus including a magnetic head having a core formed of a magnetic material is disclosed. If the size of a cross section of the core is A.times.B (A.gtoreq.B), the distance d between a core end surface and a recording layer of the recording medium is selected so as to satisfy the relationship:0.1.times.B<d<0.4.times.A.The magnetic field applied to the recording layer facing the core end surface is thereby made uniform. A method of applying a magnetic field to a magnetic recording carrier using such an apparatus also is disclosed.

Abstract: An apparatus for generating a magnetic biasing field for recording in a magneto-optical medium, including a coil mounted on a core and connected in parallel with a capacitor and a first switch, and a control circuit for generating a first pulse for opening and closing of the first switch upon each transition of an information signal to be recorded, thereby to produce magnetic flux inversions in the core. A second coil is mounted on the same core as the first coil. Second and third switches are connected in series between positive and negative voltages, and a series connection point between the second and third switches is connected to the second coil, the other end of which is connected to ground. Second and third pulses of fixed duration are applied to the second and third switches based on the trailing and leading edges of the information signal to be recorded, respectively. Monostables are used to generate the first, second and third pulses. The control circuit includes the monostables.

Abstract: A pickup apparatus for a magneto-optical recording medium comprises a waveguide for receiving a light beam reflected by a magneto-optical recording medium, and first and second focusing grating couplers disposed side by side on the waveguide for introducing the reflected light beam into the waveguide in a TE or TM guided mode and converging the thus guided optical waves at two positions spaced from each other. First and second photodetectors are mounted on the waveguide for detecting the optical waves converged by the first and second focusing grating couplers. Tracking error and focusing error are detected based on the outputs of the first and second photodetectors, and recorded signals are detected based on the output of the first photodetector and/or the output of the second photodetector. In another embodiment, three focusing grating couplers are disposed on two waveguides.

Abstract: A magneto-optic recording and regenerating process and the device using it in accordance with the present invention are intended to magnetize the magnetic, or magnet, film of a disk parallel to the plane of the magnetic film to record or erase information. When regenerating information, light beams whose incident plane is substantially perpendicular to the direction of magnetization of the recording medium is applied to the disk, so that the recorded information is regenerated dependent on the light intensity of reflected light obtained in response to the direction and magnitude of magnitization of the disk. Additionally, the magneto-optic disk includes a magnetic film having a coercive force smaller than the saturated magnetization at room temperature, so that irradiating light beams elevate the temperature of the magnetic film but not up to its Curie temperature. Information is then recorded on or erased from the magnetic film with its coercive force decreased by the elevated temperature.

Abstract: A magneto-optical disc apparatus comprising a distance sensor detecting the distance optically between a magneto-optical disc and a magnetic head, a circuit sample-holding the detected output of the distance sensor, and a controlling mechanism controlling the distance between the magneto-optical disc and the magnetic head in the case where the detected output of the distance sensor is changed suddenly, responsive to a sample-held detected output immediately before the sudden change. Even when the detected output of the distance sensor changes suddenly by receiving a reflected light from a sector mark of the magneto-optical disc, the distance between the magneto-optical disc and the magnetic head does not change suddenly according to the sudden change, since the distance between the both is controlled responsive to the detected output having been sample-held immediately before the sudden change.

Abstract: By performing a recording operation and an erasing operation while oscillating a position of a laser beam irradiation on an optical recording medium in a direction perpendicular to the track direction, an improvement in the S/N ratio during reproduction and a reduction of jitter in the detecting signal are attained. As an element for oscillating the laser beam irradiation position in the direction perpendicular to the track direction, an acousto-optical deflector or an electro-optical deflector is used.