Olympus Optical Company, Ltd.

Other

Nobuhide Matsubayashi

Kiichi Kato

Masaharu Sakamoto

Tsuneo Yanagida

Takeshi Maeda

Hitoshi Watanabe

Shigemi Maeda

Tetsu Watanabe

Satoshi Sumi

Masaaki Kurebayashi

Junichi Nakano

Mitsugu Sakai

Yasuhito Tanaka

Yasuhiro Miyazaki

Osamu Nakano

Hideyuki Kenjyo

Haruhiko Takemura

Hiroshi Ezawa

Ken Sugawara

Michio Matsuura

Yoichi Hosaka

A magneto-optical information recording/reproducing apparatus in which a magneto-optical information recording medium at least including a first magnetic film having perpendicular magnetic anisotropy, and a second magnetic film to which information recorded on the first magnetic film is transferred by irradiation of a laser beam, is used so that a readout laser beam is irradiated onto the second magnetic film to thereby readout the information transferred to the second magnetic film. The apparatus includes a 2-split detection circuit for receiving the readout laser beam reflected from the second magnetic film of the recording medium, and a subtraction circuit in which output signals of the two detection elements of the 2-split detection circuit are subtracted from each other to generate a differential signal. The apparatus further comprises a circuit for making a spot of the laser beam jump one track before readout of the information from the magneto-optical information recording medium, a positive/negative balance correction circuit for detecting an amplitude ratio between positive and negative side amplitudes in a track jump signal generated in the differential signal from the subtraction circuit in response to the track jump to thereby output a correction signal in accordance with the amplitude ratio, and an addition circuit for adding the correction signal to the differential signal to thereby generate a tracking error signal for tracking control used in readout of the magneto-optical information from the magneto-optical information recording medium.

Apparatus and method for recording/reproducing magneto-optical information

Write data, which has been modulated in a 4/11 mode and converted in an NRZI mode, is written on a sample servo type optical disk by means of a magnetic head and a laser diode in a pickup. A signal reproducer in an optical disk unit comprises a differentiating circuit for differentiating a reproduced signal originating from data recorded on the optical disk after detected by the pickup, an A/D converter for sampling a differential signal synchronously with a channel clock, and a difference detector for reproducing data by performing difference detection on results of A/D conversion. The difference detector includes a register, a selector, and a determiner.

Signal detector for an optical information reproducing apparatus

An optical head comprising a light source for emitting a light beam, an objective lens for focusing the light beam onto an optical record medium as a fine spot and a photodetector for receiving the light beam reflected by the optical record medium to derive an information signal, tracking error signal and focusing error signal. A Wollaston prism is arranged on an optical path along which both forward and return light beams propagate, so that the return light beam is separated from the forward light beam. The Wollaston prism is formed by cementing two wedge shaped-crystal plates having different directions of optic axes. The light source and photodetector may be arranged on a same substrate, and thus the optical head can be made small in size and less expensive in cost and can have a high reliability.

Optical head with forward and return light beam propagating along a

A photomagnetic signal detecting apparatus, in the reflected light path of a light beam reflected from a recording medium in which information is magnetically recorded, there is provided an optical element having a light beam dividing device transmitting one of two polarized lights intersecting at right angles with each other and reflecting the other polarized light and a light path converting device emitting by reflection or refraction the light beam reflected by this light beam dividing device in substantially the same direction as of the transmitted light transmitted through the above mentioned light beam dividing device so that the transmitted light and reflected light emitted from this optical element may be received by a photodetecting device.

Photomagnetic signal detecting device

An opto-magnetic pick-up device for use in an information recording and reproducing device is disclosed. The device comprises a phase difference correcting device capable of correcting the phase difference between the linearly polarized component of the reflected light from the recording medium and a polarized component vertical to the linearly polarized component.

Opto-magnetic pick-up device including phase difference correcting means

An optical recording/reproducing apparatus wherein a main beam is converged and projected onto a flat part between tracking guide groove parts adjacent to each other in an optical recording medium to record, reproduce or erase information, two sub-beams on both sides of the main beam are respectively converged and projected so as to cover the guide groove parts to form a tracking system for controlling tracking and one of the two sub-beams is utilized to discriminate the flat part.

Multi-beam optical recording/reproducing apparatus for

A magneto-optic player for reading an information signal stored in a magneto-optical record medium in the form of vertical magnetization including a semiconductor laser emitting a linearly polarized laser light beam, a beam splitter for transmitting the laser light beam, an objective lens for projecting the laser light beam transmitted through the beam splitter onto the record medium and for directing light reflected by the record medium, the light being subjected to Kerr rotation the rotational direction of which is dependent upon the direction of the vertical magnetization. A first quarter-wavelength plate arranged between the objective lens and the beam splitter for converting the linearly polarized light reflected by the record medium into an elliptically polarized light the rotational direction of which is determined by the direction of the vertical magnetization. A second quarter-wavelength plate arranged to receive the elliptically polarized light reflected by the beam splitter for converting it into elliptically polarized light the direction of the major axis of which is aligned with P-polarization or S-Polarization depending upon the rotational direction, a polarization beam splitter for splitting the elliptically polarized light into P-polarized and S-polarized components, two photodetectors for receiving the P-polarized and S-polarized components, respectively, and a differential amplifier for deriving a difference between outputs of the two photodetectors as a reproduced information signal.

Magneto-optic player with improved C/N ratio

In an apparatus for reproducing information recorded in an opto-magnetic record medium, a linearly polarized light beam is made incident upon the record medium, a light beam reflected by the record medium is made incident upon a quarter wavelength plate whose principal axis is inclined with respect to the polarization direction of the incident linearly polarized light beam and is converted into one of elliptically polarized light beams having major axes perpendicular to each other depending upon the direction of magnetization in the record medium. The elliptically polarized light beam is made incident upon a polarization beam splitter for separating major and minor axis components from each other, and the thus separated major and minor axis components are received by first and second photodetectors, respectively. Output signals from the photodetectors are supplied to a differential amplifier to drive a difference therebetween representing a reproduced information signal. The information signal having a high C/N ratio can be reproduced without being influenced by a phase difference caused by the optomagnetic record medium and/or optical elements constituting of an optical system of the apparatus.

Apparatus for reproducing information from opto-magnetic record medium

This invention relates to an optical pickup device using a semiconductor light emitting element provided with a light emitting mode change detecting means or the like.

Optical pickup device having a detector for detecting the light emitting

A linearly polarized light is projected upon a recording medium of a photomagnetic type; the reflected light is rotated by an appropriate angle through a halfwave plate and split into a reflected light and a transmitted light through a beam splitter having reflection factors of 0 or 100% for p- or s-polarized light in such a way that the beam splitter functions as an analyzer for one of the reflected and transmitted lights. The other of the reflected and transmitted lights is passed through an analyzer. The two lights passed through the beam splitter and the analyzer are detected by two photodetectors separately and applied to a differential amplifier to generate a reproduction signal of high S/N ratio without the use of a half mirror R.sub.p =R.sub.s =50% which is very difficult to manufacture.

Photomagnetic differential reproducing system

Optical pickup for use in optical discs

An optical disk apparatus has an optical head. The optical head emits a light beam onto an optical disk and forms pits in the optical disk, thereby recording a signal. A detector detects the relative inclination between the optical head and the optical disk and generates a signal corresponding to this relative inclination. A beam intensity correction circuit corrects the intensity of the light beam in accordance with the relative inclination to form proper pits. In one embodiment, the intensity of the light beam is increased when the relative inclination is increased.

Optical disk apparatus with beam energy correction for deviations in

An optical recording/reproducing apparatus has a beam emitting device adapted to emit at least two light beams in directions at a minute angle to each other. The light beams are condensed by a condensing member onto slightly separated two points on a disk and reflected by the disk. The light beams from the disk are polarized to a prism by a polarizing device. The prism refracts the light beams from the polarizing device, thereby increasing the relative angle between the light beams. The refracted light beams are converged by a converging lens on a detector.

Growing community of inventors

Hachioji, Japan

Nobuhide Matsubayashi