Abstract: A magneto-optic disk drive includes a magneto-optic disk and a rotary arm for positioning a focus/bias field switching assembly adjacent bit positions on the disk. A bias field switching assembly includes an annular permanent magnet mounted within a guide for movement between write and erase positions and an objective lens. The magnet has central and pole surfaces generally parallel to the disk. Coils on the guide are energized to drive the magnet between the write and erase positions. In its erase position the magnet impinges a first polarity erase magnetic field on the disk. In its write position the magnet impinges a second polarity write magnetic field upon the disk. The magnet is releasably latched in both its write and erase positions by ferro-magnetic elements mounted to the guide.

Abstract: An optical analyzer for determining changes of the polarization plane in a light beam (4) comprises a substrate (20) supporting a photodetector array (21) and a system of imaging mirrors (22-24) underneath a parallel plate (25) of high-quality optical glass. The lower surface of the glass plate is covered by a system (26) of dielectric multilayers which acts as a polarizing beam splitter over a large range of angles of incidence. The optical beam (4) enters the analyzer through the glass plate to impinge under an oblique angle of incidence on a first mirror (24) which rotates the plane of polarization in the beam by 45 degrees with respect to the polarizing beam splitter, which then generates two beams partial (202,203) to be eventually directed to photodetector array (21). The beam analyzer is used in magneto-optical storage system to extract an information signal and to generate servo control signals for the focus and track positions of the beam.

Abstract: An opto-magnetic recording apparatus for sequentially driving an optical head driver and a biasing magnetic field generator. The apparatus includes a biasing magnetic field generator for applying a biasing magnetic field to an opto-magnetic recording medium, an optical head for irradiating a light beam spot onto a portion of the medium while the biasing magnetic field is applied, thereby to record or erase information, an optical head driver to drive an optical head by an electromagnetic force to make the light beam spot access desired positions on the medium, and a controller for deactivating the magnetic field generator when the driver is activated and activating the magnetic field generator after the drive by the driver is completed.

Abstract: In a system of alternately operating a plurality of disk players, when the pickup of a first one of the disk players comes near the last address of the last address of the last of the pieces of music recorded, as data signals on a data recording disk, a second disk player is activated so that it is in standby state at the beginning of a piece of music which is the first in the order of pieces of music to be played by the second disk player. Immediately after the last address of the last piece of music is read by the first disk player, the second disk player is caused to play the piece of music.

Abstract: An optical disc memory for optically storing and retrieving information formed of a substrate and a recording layer supported on the substrate. The recording layer has a chemically stable dielectric material and a semiconductor which has an optical property that changes reversibly as a function of the intensity of a laser beam applied through the substrate. A multilayered optical disc memory having a substrate, a recording layer formed on the substrate and a metallic layer formed on the recording layer, and a method of optically storing and retrieving information by using the above-described optical disc memory, are also disclosed.

Abstract: An optical mass storage device for use in data processing systems. Two or more lasers provide separate read and write laser beams having different wavelengths. The read and write laser beams can be orthogonally polarized. A polarizing beam splitter combines the read and write beams along a common optical path to an optical head. The head directs the combined beam to a magneto-optic storage medium. A read beam is reflected back by the medium to the common path through the head. A dichroic beam splitter disposed in the common path between the head and the polarizing splitter reflects the read beam to an optical detector. If more than one write laser is necessary, a second dichroic splitter can be used to combine the multiple write beams and the read beam.

Abstract: A magneto-optic data recording system and actuating device therefor comprises a permanent magnet mounted adjacent to a magneto-optic disk medium. The permanent magnet is rotatable about its longitudinal axis to change the polarity of the magnetic field which supplied to the medium. Rotation of the magnet is achieved by activation of electromagnet actuators located laterally adjacent to the permanent magnet. Rotation of the magnet through 180.degree. is preferably achieved within less than 1 period of revolution of the disk, preferably less than 1/2 the period of revolution of the disk.

Abstract: A magnetooptical recording apparatus is disclosed which is capable of performing real-time overwrite operation. The apparatus comprises a laser beam and focusing parts thereof, and a pulse magnetic field generator device, procided on both sides of a magnetooptical recording medium, respectively. The laser beam and focusing parts thereof are formed of an objective lens connected to a moving coil which is provided with a magnet, thus the objective lens is movable relative to a magnetic layer of the magnetooptical recording medium by the interaction between the magnet and the moving coil. The magnet generates and applies a D.C. magnetic field of one polarity perpendicular to the magnetic thin film around a point where the laser beam is focused, while the pulse magnetic field generator device generates pulse magnetic field of the opposite polarity modulated by information signal around the point where the laser beam is focused. Thus one and opposite polarity magnetic field pulse row obtained by a sum of the D.C.

Abstract: A record carrier body is disclosed which is, provided with sector addresses and servo-track portions. The maximum width of the servo-track portions is at least 60% of the track period, in a direction transverse to the track direction, and is at least of the order of twice the maximum width of the sector-address areas. This makes it possible to obtain an improved tracking signal in addition to a satisfactory address signal. An improved information signal can be obtained by recording the information in the lands between the servo tracks. An apparatus is disclosed for recording sector addresses and servo track portions on the record carrier body.

Abstract: Thermomagnetic recording method using a thermomagnetic recording medium having a superposed layer of magnetically coupled first and second magnetic thin films is disclosed. The magnetic thin film includes a portion where the respective magnetic moments of the first and second thin films are coupled in opposite directions to each other. The method comprises heating the superposed layer in a first heating state in which the superposed layer is heated at a temperature T.sub.1 which is higher than the Curie temperature T.sub.C1 of the first magnetic thin film and will not cause the inversion of the magnetic moment of the second magnetic thin film or in a second heating state in which the superimposed layer is heated at a temperature T.sub.2 which is higher than the Curie temperature T.sub.

Abstract: A magneto-optic disk reading head system including an external semiconductor laser resonator. A magneto-optic disk forms a part of the external resonator. In the external resonator, orthogonal two mode oscillations are established to produce a beat signal used for reading data stored in the magneto-optic disk. The magneto-optic disk reading head system is a floating type reading head.

Abstract: In an optical system for recording information on an erasable recording medium, first and second pulse recording laser beams can be emitted from a laser unit. The first laser beam is converged by an objective lens onto a recording layer of an optical disk to form a permanent recorded region on the recording layer. The second laser beam, which has a lower intensity than that of the first laser beam, is also converged onto the recording layer by the objective lens onto the recording layer to form an erasable recorded region on the recording layer. Thus, the erasable and permanent recorded regions are formed in the recording layer.

Abstract: In an optomagnetic recording/reproducing apparatus, an objective lens is actuated by a lens actuator having focusing and tracking magnetic circuits so that a light beam is focused on an optical disk and is directed to a predetermined area of the optical disk. The lens actuator is mounted on a pickup body which is driven in a radial direction of the disk by a driving magnetic circuit. The optical disk is clamped on a turntable by a magnetic clamp mechanism. First leakage magnetic fields produced from each of the focusing and tracking magnetic circuits, second leakage magnetic fields are produced from the driving magnetic circuit and the magnetic clamp mechanism, and the first and second magnetic fields are directed in mutually opposite directions relative to the optical disk.

Abstract: A method of recording at least ternary data on an optomagnetic recording medium having at least a first magnetic layer, and a second magnetic layer whose Curie temperature is higher than that of the first magnetic layer and which is capable of being magnetization inverted independently of the first magnetic layer, the method including the steps of aligning directions of magnetization of the first and second magnetic layers of the medium in a predetermined direction; and radiating a single light beam whose power is adjusted in accordance with the data so as to obtain one of a first level, a second level higher than the first level, and a third level lower than the first and second levels, while applying a bias magnetic field in a direction opposite to the predetermined direction, wherein only the direction of the first magnetic layer of the medium is inverted when a power of the light beam is in the first level, the directions of the first and second magnetic layers are inverted when the power of the light bea

Abstract: An optical magnetic memory device includes an optical magnetic recording medium such as a disc having recording magnetic film at least on one side thereof and initialized in a certain direction in advance, a recording section for recording data in such a manner that data-recorded portions and non-recorded portions are alternately formed, and a reproducing section for reproducing data from the recording medium by detecting the interval between the recorded or non-recorded portions. The reproducing section comprises a detector for detecting positive and negative peaks of signals reproduced from the recorded or non-recorded portion and a selector for selecting either of the detection outputs from the detector according to a control signal.

Abstract: In a magneto-optical recording and reproducing apparatus for effecting the recording of information, etc. by irradiating a magnetic recording layer of a magneto-optical disk with a laser beam focued by an objective lens and applying a magnetic field to a portion of the magnetic recording layer irradiated with the laser beam, the strength of the magnetic field is controlled by a signal to drive the objective lens for focusing the laser beam onto the magnetic recording layer.

Abstract: In method of operating a magnetic recorder, magnetooptic, for example, the erasure direction for successive recording areas (sectors) are determined by the direction of magnetization of prior recording. When the erasure direction is reversed, the direction of remanent magnetiaztion indicating a "non-erasure", record or information representing direction is also reversed. A mark is placed in each sector for identifying its erasure direction.

Abstract: A magnetic head drive circuit for driving a coil of the magnetic head performing opto-magnetic recording, is disclosed. According to the present invention, the switching elements are actuated on the basis of driving signals for commutatingly connecting three power sources presenting three different potentials to both ends of a coil of the magnetic head such that the potential difference across both ends of the coil at the time of magnetic field inversion is larger than that at the time of generation of the stationary magnetic field to render the rise time of the current flowing in the coil sufficiently short.

Abstract: A beam controller for controlling a semiconductor laser provided in an optical recording/playback apparatus includes first and second current sources for driving the semiconductor laser at a low level (play-back mode) and/or at a high level (recording or erasing mode). The first and second current sources are controlled to have stable power automatically by a first and second auto-power circuits, respectively. The first and second auto-power control circuits include a sample-hold circuit which stores an output signal from a low-pass filter. This enables the beam controller to avoid the transition response problems of the low-pass filter. A switching circuit is also included to select either the stored low-pass filter signal on the present low-pass filter signal.

Abstract: A protective carrying case for an electronic device, especially a video cassette recorder, having upper and lower carrying case halves of high impact material with the video cassette recorder positioned therebetween. The upper and lower carrying case halves are integrally coupled to each other. First and second cover members rotatably connected to the upper and lower case halves are provided for affording access to the video cassette recorder cassette door and electrical connections respectively, the electrical connections passing through an integral barrier between the upper and lower carrying case halves for protectively isolating the video cassette recorder from a user thereof. A control panel allows a user access to at least a portion of the video cassette recorder's manual controls.