Mitsubishi Denki Kabushiki Kaisha

Mitsubishi Electric Corporation

Teac Corporation

Isao Watanabe

Kunimaro Tanaka

Osamu Ito

Kazuhiko Tsutsumi

Koichi Takeuchi

Kyosuke Yoshimoto

Masayoshi Shimamoto

Kazuhiko Nakane

Hajime Nakajima

Satoshi Komurasaki

Yoshihiro Kiyose

Teruo Furukawa

Keiji Nakamura

Kenjiro Kime

Keiji Nakatsu

Kyosuke Yosimoto

Kenichi Sato

Masaharu Ogawa

Yoshiyuki Nakaki

Kouichi Yamada

Koichi Yamada

Kenji Shimozawa

Masami Horita

Shigeo Hayashi

Yoshiyuki Nakai

Ryuichirou Aria

Hiroshi Konuma

Masaharu Yoshimura

Ryuichirou Arai

Osamu Itou

A magneto-optic recording system uses a unit recording medium having on a substrate a first magnetic layer whose Curie temperature is low and also having on the first magnetic layer a second magnetic layer whose Curie temperature is high. The system heats a spot on the medium with a heating device. The system may employ two such unit recording media, each having the second magnetic layer magnetized in one direction. The two unit recording media are superposed on each other and formed integrally so as to obtain a magneto-optic recording medium in which the amount of information recorded and the recording speed are doubled. In addition, a light-emitting device and a magnetic field generator are added to the magneto-optic recording medium to obtain a compact magneto-optic recording system with a low level of power consumption.

Magneto-optic recording system

A unit recording medium, having on a substrate a first magnetic layer whose Curie temperature is low and also having on the first magnetic layer a second magnetic layer whose Curie temperature is high, is heated by a heating device. After two such unit recording media each having the second magnetic layer magnetized in one direction are fabricated, and the fabricated two unit recording media are superposed on each other and formed integrally so as to obtain a magneto-optic recording recording medium in which the amount of information recorded and the recording speed are doubled. In addition, a light-emitting device and a magnetic field generator are added to the magneto-optic recording medium to obtain a compact magneto-optic recording system with a low level of power consumption.

Magneto-optic recording medium method of manufacturing the same and

An optical disc recording apparatus which records data with a second rotation frequency on an optical disc containing a preliminarily written recording condition in relation to a first rotation frequency. The optical disc recording apparatus preliminarily possesses recording condition in relation to the first and second rotation frequencies. The optical disc recording apparatus initially reads the recording condition in relation to the first rotation frequency, and then, in accordance with the read-out recording condition in relation to the first rotation frequency and the stored recording condition in relation to the first and second rotation frequencies, the recording apparatus computes the recording condition applicable to the optical disc in relation to the second rotation frequency. Finally, the optical disc recording apparatus records data on the optical disc by applying the computed recording condition. In consequence, even when the recording condition in relation to the second rotation frequency is not yet known, the apparatus can securely execute the data recording operation.

Optical disc recording apparatus

A magneto-optic recording medium has a cartridge provided with a magnetization direction indicating portion for indicating the direction of magnetization of a second magnetic layer. Alternatively, the direction of magnetization of the second magnetic layer is recorded in advance in the first magnetic layer. The direction of magnetization of the second magnetic layer indicated or recorded is detected and recognized. A magnetic field oriented in an opposite direction to the direction of magnetization detected is imparted to the magneto-optic recording medium. Alternatively, predetermined information is recorded in the first magnetic layer, the direction of magnetization of the second magnetic layer is detected on the basis of a signal reproducing that information, and the direction of a magnetic field to be applied to the magneto-optic recording medium is set on the basis of the direction of magnetization thus detected. In addition, the direction of the magnetic field to be applied to the magneto-optic recording medium is set and the output of a light beam is changed on the basis of the direction of the second magnetic layer detected.

Magneto-optic recording medium, magneto-optic recording system and

Methods and apparatuses are disclosed for improving accuracy of recording and reproducing information onto and from a magneto-optic recording information medium. In the first method, a width of a mark formed by a relatively low intensity light beam between two kinds of light beam intensities used for recording information is made larger than a sum of a track land width and the maximum track offset of the light beam, thereby the mark formed by the relatively low intensity light beam covers the track land portion in its full width. In the first apparatus, a reflected light beam from the magneto-optic recording information medium is split into a reflected beam for information reproducing and a reflected beam for tracking and focusing servos at the reproducing, thereby the apparatus can remove part being affected by the track groove portion from the reflected light beam for information reproducing. In the second method and apparatus, an intensity ratio of the two kinds of intensities of light beams used for information recording is controlled in such a manner that a mark width formed by the relative low intensity light beam is wider than a mark width formed by the relative high intensity light beam.

Information recording method for overwriting a magneto-optic recording

Magneto-optical disk recording and reproducing devices and actuators and distance detectors for use therewith are disclosed. The mageneto-optical disk device comprises, in addition to the usual elements, a bimorph type actuator or an electromagnetic actuator for driving the magnetic head of the magneto-optical disk device. The bimorph actuator has a metallic shim whose width varies with respect to the longitudinal distance inversely porportional to the normal function of the first or the second free natural vibration mode. Alternatively, the bimorph type actuator have a recess formed on a bimorph element to expose a piezoelectric crystal which outputs a voltage corresponding to the acceleration of the vibration of the actuator; the driver circuit of the actuator reduces the driving voltage when the frequency of the voltage generated at the recess comes into the neighborhood of a higher resonance frequency of the actuator. The optical distance detector comprises a light-emitting diode and a pair of photodiodes which detects the amount of light incident thereon after being reflected at a surface of an object the distance to which is measured. The geometric parameters of the photodiodes are selected in such a manner that the output of a first photodiode decreases as the measured distance increases while the output of a second photodiode increases as the measured distance increases. Thus, the normalized differential output of the two photodiodes, from which the measured distance is determined, varies substantially linearly with respect to the measured distance. In preferred forms, the photodetectors have stepped concentric configurations so that small distances can be measured accurately and efficiently.

Magneto-optical recording/reproducing system having an electromagnetic

Information recording method and information recording apparatus for

A laser power measuring jig is adapted for use in measuring a laser power of a laser beam which is emitted from an optical head of an optical disk unit which records and/or reproduces information on and/or from a medium. The laser power measuring jig supplies power information related to the laser power of the laser beam to a power meter which measures the laser power. The laser power measuring jig includes a main jig body which has a size and a shape which are approximately the same as those of the medium, and this main jig body is loaded into the optical disk unit. The laser power measuring jig also includes a mechanism for outputting the power information outside the optical disk unit and supplying the laser power information to the power meter when the main jig body is loaded into the optical disk unit.

Laser power measuring jig for optical disk unit

Magneto-optical disk recording and reproducing devices and actuators and distance detectors for use therewith are disclosed. The magneto-optical disk device includes a bimorph type actuator or an electromagnetic actuator for driving the magnetic head of the magneto-optical disk device. The bimorph actuator has a metallic shim having a width that varies with respect to the longitudinal distance in inverse proportion to the normal function of the first or the second free natural vibration mode. Alternatively, the bimorph type actuator has a recess formed on a bimorph element to expose a piezoelectric portion which outputs a voltage corresponding to the acceleration of the vibration of the actuator. The driver circuit of the actuator reduces the driving voltage when the frequency of the voltage generated at the recess comes into the neighborhood of a higher resonance frequency of the actuator. The optical distance detector comprises a light-emitting diode and a pair of photodiodes which detects the amount of light incident thereon after the light is reflected from a surface of an object the distance to which is measured. The geometric parameters of the photodiodes are selected such that the output of a first photodiode decreases as the measured distance increases while the output of a second photodiode increases as the measured distance increases. Thus, the normalized differential output of the two photodiodes, from which the measured distance is determined, varies substantially linearly with respect to the measured distance. In preferred forms, the photodetectors have stepped concentric configurations so that small distances can be measured accurately and efficiently.

Magneto-optical recording and reproducing disk device having a bimorph

In an optical disk apparatus for recording information in pits formed on an optical disk by projecting a light beam onto the optical disk and heating an area of the optical disk corresponding to the pulse pattern of the information, the pulse pattern of the information to be recorded is discriminated, and on the basis of the discriminated pulse pattern, the timing to start on and end the emission of the light beam from the light source to the optical disk is modified, or the number of emissions and the duration of each emission is controlled so that the pattern of the pits are corrected to the shapes that ensure accurate regeneration of the information.

Optical disk apparatus for shaping pits recorded on an optical disk

A magneto-optic recording apparatus which has a magnetic field generator that applies a magnetic field with a constant direction to a magneto-optic recording information medium for overwriting information to improve accuracy of recording and reproducing information onto and from magneto-optic recording information medium and further has an auxiliary magnetic field generator that compensates a variation of intensity of a magnetic field generated by the magnetic field generator and applied to the magneto-optic recording information medium is disclosed as the first invention. Also, a magneto-optic recording apparatus which performs synchronous wave detection of the reflected light signals from the magneto-optic recording information medium and controls A.C. voltages applied to an exciting coil of the magnetic field generator in response to the detected result of the synchronous wave detection, thus optimizing amplitudes of the reproducing signals from the magneto-optic recording information medium is disclosed as the second invention.

Magneto-optic recording apparatus with controlled magnetic field

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.

Magneto-optical recording apparatus for creating magnetic domains with

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.

Optical storage medium with provision for limitation of thermal

A device for driving and controlling an optical head by forming a spot of a light beam on an optical disk having a plurality of tracks and detecting light from the spot reflected on the optical disk by a pair of optical detectors disposed in the head. This device has: a head actuator for moving a movable portion of the optical head in the radial direction of the disk; a speed detector for detecting the track-crossing speed of the spot from outputs from the optical detectors; a reference speed generator for generating, while accessing to a target track, a reference moving speed signal in accordance with the distance to the target track obtained from the outputs from the optical detectors, the movable head portion being moved on the basis of the reference moving speed signal so that the speed of the movable portion decreases at a position near the target track before the light beam spot reaches this track; a speed error detector for obtaining the difference between outputs from the reference speed generator and the speed detector; and a magnification change circuit adapted for amplifying the outputs from the reference speed generator and the speed detector by a predetermined multiplying factor when the distance between the light beam spot and the target track, or the crossing speed of the spot, becomes smaller than a predetermined value, the magnification change circuit also being adapted for outputting the difference obtained by the speed error detector after multiplying it by the reciprocal of the multiplying factor. The head actuator is driven on the basis of the output from the error detector so as to control the speed of the movable head portion.

Growing community of inventors

Amagasaki, Japan

Isao Watanabe