Abstract: A method of overwriting information in a magneto-optical memory medium which includes a simultaneous writing and erasing step of continuously irradiating a written information-carrying area of the recording layer of the memory medium with two different pulses from a single laser beam head in accordance with information to be written, regardless of the presence or absence of written information. A variation includes irradiating the written information-carrying area with an erasing pulse from a laser beam head, regardless of the presence or absence of written information, and the then selectively irradiating the information-erased area with a writing pulse from another laser beam head in accordance with information to be written. According to these methods, it becomes possible to carry out a simple and high-speed overwriting with an increased and stabilized bit positioning accuracy.

Abstract: An optical information storage medium is used for recording optical information therein and reproducing optical information therefrom. The optical information storage medium includes parallel, concentric, or helical tracking guide grooves and information tracks defined between the tracking guide grooves. A preformat area composed of discrete pits is disposed on some of the information tracks. The tracking guide grooves and the preformat pits are defined in one surface of a transparent substrate, and a recording film capable of absorbing and reflecting light is disposed on said one surface of the transparent substrate. The ratio of the effective depth of the tracking guide grooves to the wavelength of a recording/reproducing laser beam within the transparent substrate is in a certain range, and the ratio of the effective depth of the preformat pits to the wavelength of the recording/reproducing laser beam within the transparent substrate is also in a certain range.

Abstract: A magneto-optical recording medium including a first magnetic layer (having film thickness t1 and saturation magnetization Ms1) and a second magnetic layer (having film thickness t2 and saturation magnetization Ms2) which are respectively made from a rare earth-transition metal alloy and sequentially laminated on a substrate to jointly make up a recording layer. Only the first magnetic layer or both the first and second magnetic layers contain a light rare earth element. At room temperature, a transition-metal sub-lattice magnetic moment is dominant in the first magnetic layer, whereas a rare earth sub-lattice magnetic moment is dominant in the second magnetic layer, respectively. Substantially, the directions to stabilize magnetization of the first and second magnetic layers are inverse from each other and the expression shown below is satisfied.t1.times.Ms 1-t2.times.Ms2.ltoreq.5 (.mu.m.times.emu/cm.sup.

Abstract: A magneto-optical storage medium and overwrite system comprises a first magnetic layer (reading/writing layer) (3), a second magnetic layer (auxiliary layer) (5) and a third magnetic layer (initializing layer) (7), each of which is a rare earth-transition metal alloy, and interface layers (4,6) for isolating magnetic exchange interaction between the magnetic layers, respectively. The second magnetic layer is initialized by the magnetization of the third magnetic layer (7) at room temperature. The first magnetic layer and/or the second magnetic layer is heated by a laser beam (P1) for demagnetization and remagnetization. The demagnetized portion of the second magnetic layer is remagnetized to the opposite direction by the demagnetizing field from the periphery. The demagnetized portion of the first magnetic layer is remagnetized to the same direction of the second magnetic layer.

Abstract: A photomagnetic recording apparatus comprises an optical pickup movable with reference to a photomagnetic recording medium to irradiate an optical beam toward a predetermined region of the photomagnetic recording medium, and a magnetic field-generating mechanism for applying a uniform magnetic field to that predetermined region of the optical magnetic recording medium which is irradiated with the optical beam. The magnetic field-generating mechanism includes a yoke, at least one arm portion supported by the yoke, a coil winding held by the at least one arm portion, and a recording medium-facing member supported by the at least one arm and having end portions extending from the coil winding in the direction in which the optical pickup is movable. The yoke, at least one arm portion, and the recording medium-facing member are made from a magnetic material.

Abstract: An optical memory device for recording, reproducing, or erasing information applies an optical beam such as a laser beam onto a recording medium. The optical memory device includes a recorded region detecting circuit for detecting information recorded region formed in the recording medium. In the optical memory device, a timing control for recording, reproducing, or erasing is performed with the use of a result obtained through detection of a synchronizing signal, such as a sector mark, indicative of a starting point of an information block and another result obtained through detection in the recorded region detecting circuit. The recorded region detecting circuit includes either at least one peak hold circuit for detecting a peak level of the playback signal or a low pass filter for smoothing the playback signal, and a comparator for comparing an output obtained through the peak hold circuit or through the low pass filter with a reference voltage.

Abstract: A magnetooptical recording medium provided with a first magnetic layer and a second magnetic layer having a higher Curie point and a lower coercive force than the first magnetic layer and being exchange coupled with the first magnetic layer satisfies the relation: ##EQU1## wherein H.sub.H is the coercive force of the first magnetic layer; H.sub.L is the coercive force of the second magnetic layer; M.sub.2 is the saturation magnetization of the second magnetic layer; h is the thickness thereof; and .sigma..sub.w is the magnetic wall energy between the first and second magnetic layers and a method of recording information on the same.

Abstract: Apparatus for recording opto-magnetically information on an opto-magnetic record medium in the form of the direction of the magnetization stored in a magnetic layer including an objective lens for projecting a laser light beam onto the magnetic layer of the opto-magnetic record medium, a device for generating a bias magnetic field which is applied to the magnetic layer in a direction perpendicular thereto, a supporting device for supporting the objective lens movably in a focusing direction parallel to an optical axis of the objective lens as well as in a tracking direction perpendicular both to the optical axis and an information track direction, and a driving device for moving the objective lens in the focusing and tracking directions to perform the focusing and tracking control.

Abstract: A multi-layered magnetooptical recording medium that satisfies predetermined formulas is over write capable when used, in a recording method and apparatus, with a jointing field, i.e., a magnetic field the intensity of which decreases continuously from an initial field to a bias field having the same direction as the initial field, permitting greater freedom in the choice of media compositions. In a two-layer structure including magnetically coupled recording and reference layers, recorded data may advantageously be reproduced from the reference layer.

Abstract: A floating head for use with a recording apparatus of magneto-optical memory type comprising a floating body which is provided in the vicinity of a rotating optical recording medium and which is made afloat by an air stream created by the rotation of the recording medium, an objective lens which is fitted in an optical path forming aperture in the floating body and which permits converging light from a light source to be focused on a focusing plane of the recording medium, and a coil which is installed in the vicinity of the optical path forming aperture in the floating body and which forms a magnetic field toward the focusing plane of the recording medium. The floating body is made of a soft magnetic material and is provided with a rim made of a soft magnetic material which is formed along the peripheral edge of the optical path forming aperture on the side closer to the optical recording medium and which projects toward the same.

Abstract: A magneto-optical recording and/or reproducing apparatus includes an optical head for providing a light spot for recording, reproducing and erasing of a magneto-optical disc, a magnetic head which is disposed at a position opposing the optical head with the magneto-optical disc therebetween and which provides a magnetic field for recording and erasing while maintaining a substantially constant distance from the magneto-optical disc by effecting a lift obtained by an air flow generated by the rotation of the disc, a loadbeam which has the magnetic head on its one end and serves to provide a force caused by elastic deformation to the magnetic head to thereby be balanced with the lift thus obtained, and a moving mechanism connected to the loadbeam. Approaching or evading the magnetic head to or from the magneto-optical disc can be realized by deforming the moving mechanism.

Abstract: Direct overwriting of encoded data along a track in a magneto-optic recording medium is described. A laser beam, not modulated by data, is directed at the active side of the medium to locally heat the width of one track for conditioning it for direct overwriting. A magnetic head comprising an inductor and a capacitance in parallel with the inductor is movable in an appropriate manner to a selectable track. While the head is in alignment with the beam, current of a preselected polarity is supplied from a current source to the inductor. The current source is disconnected to reverse the field of the magnetic head by reciprocation of energy between the inductor and capacitance. Once the magnetic field is reversed, current is supplied to the inductor for maintaining the field until the next field reversal, the reversal times being determined by the data to be written.

Abstract: An optical type information record carrier is disclosed which includes an arrangement wherein the depth of the guide grooves is selected to be about (2N+1).lambda./8n (N=1, 2, 3, . . . ) and the inclination angle of the wall surface of the carrier is steep enough to ensure that the information recording medium will not adhere to the wall surface of the guide grooves, or will only adhere very weakly if it does adhere. Thermal conduction at the wall surface of the guide grooves is prevented so that extension of the recording bits is restricted.

Abstract: A control circuit for use in a magneto-optic data recording system is disclosed. The control circuitry includes proportional-integral-derivative (PID) circuitry for controlling the rotation position of a permanent magnet. Acceleration circuity is used in controlling the rotational movement of the permanent magnet. The outputs from the PID circuitry and the acceleration circuitry are selectively applied to drive circuity using a switch. The drive circuity supplies current to actuators for moving or controlling the position of the permanent magnet.

Abstract: An optical memory device has grooves for guiding a light spot and pits for serving as track number indicators. The width W.sub.1 and depth d.sub.1 of the grooves and the width W.sub.2 and depth d.sub.2 of the pits are so selected that 2D(W.sub.1, d.sub.1)=1+D(W.sub.2, d.sub.2) where D(W.sub.1, d.sub.1) and D(W.sub.2, d.sub.2) are respectively the reflectivity of the groove and the pit.

Abstract: A floating type magnetic head for magneto-optical recording, the magnetic head being positioned opposite to an optical head with a magneto-optical recording medium inserted therebetween. The magnetic head is supported out of contact with the magneto-optical recording medium and includes a slider and a head core. The head core has an end section located parallel to the magneto-optical medium. The end section is formed to be longer in the direction orthogonal to the tracks contained on the medium than in the direction parallel to the tracks.

Abstract: A track access operation system for an optical recording and reproducing apparatus using a medium having a plurality of guide grooves and ID sections utilized for identifying a particular guide groove. The intensity of reflected light and transmitted light from each of a plurality of light beams projected on the recording medium is monitored for determining the location of the beam on the disk. The system is designed such that at least either the plurality of light beams or the plurality of ID sections of the guide grooves are so arranged such that more than half of the light beams or more than half of the ID sections do not overlap in a parallel direction along the guide grooves whereby the number of light beams simultaneously projected on the ID sections is limited to less than half of the total number of light beams projected on the recording medium.

Abstract: A method of magneto-optically recording and erasing information which comprises irradiating pulse-like laser beam onto a magneto-optical information storage medium including recording and bias layers which has perpendicular magnetic anisotropy and which are stacked one upon the other to apply coupling interaction which is mainly magnetostatic interaction to each other, and magnetization-reversing temperature of the bias layer being higher than that of the recording layer. When the recording laser beam is irradiated onto the medium, the beam-irradiated portion of the medium is heated to form a reversed magnetic domain in the bias layer, magnetization of the recording layer is reversed by first leakage magnetic field applied to the recording layer when beam-irradiated portion is then cooled, and magnetization of the bias layer is directed in same direction as that under initial state by second leakage magnetic field, applied to the bias layer.

Abstract: Recording medium on which information is magneto-optically recorded is irradiated with a linearly polarized light beam. A light beam reflected from or passed through the recording medium is changed in phase by a wave plate. Through an analyzer the differently polarized components of the light beam from the wave plate are combined by aligning the polarizing directions of the light beam. The light intensities of the forward and backward parts of the moving direction of the recording medium in the far field of the light beam from the analyzer are detected by a photo detector. A difference between the detected signals of the forward and backward parts is generated to reproduce the information recorded on the recording medium. Furthermore, the light beam from the wave plate is splitted into two light beams linearly polarized in mutually orthogonal directions.

Abstract: An information read/write storage system for reading and writing data to and from a flexible magneto-optic media is shown to include a magnetic recording member, having a recording head positioned proximate the media, for recording information onto the media at a recording point, the recording point being defined as the area of the media wherein information is being recorded at any given time and an optical read/write assembly for providing focused light onto the media during reading and writing, for receiving reflected light from the media to read the information and for continuously providing focused light onto the media for heating the recording point while the magnetic recording member is recording.