Hitachi, Ltd.

Hitachi Media Electronics Co., Ltd.

Other

Toshio Sugiyama

Yukio Fukui

Hideo Suenaga

Hidenori Shinohara

Nobuo Imada

Seiji Yonezawa

Hiroshi Ogasawara

Shozo Saegusa

Shinji Fujita

Masayoshi Watanabe

Yasuyuki Sugi

Takeshi Maeda

Katsuhiko Kimura

Masahiro Ojima

Kunikazu Ohnishi

Toshiteru Nakamura

Shigeharu Kimura

Seiichi Katou

Kazuyuki Fukuda

Ryoji Okada

Teruhisa Akashi

Yasuhiro Ishigaki

Yoshio Yamane

Hiromitsu Imamiya

When recording/reproducing an optical disc having a recording layer of multi-layer structure, an unwanted optical beam reflected from a recording layer other than a target layer for recording/reproduction is incident on a photodetector to cause an unwanted disturbance component to leak to a detection signal, giving rise to a degradation in the quality of a tracking control signal. In an optical pickup apparatus, for suppression of the degradation, an optical element is mounted having a diffraction area for diffracting part of the optical beam and light receiving planes for sub-optical beams are provided each of which has a light shielding zone or dead zone of a predetermined width on its central sectioning line.

Optical pickup and optical disc apparatus

An optical device wherein an optical component and a plurality of light emitting elements are mounted on an identical substrate, a level of a surface on which the optical component is mounted is different from that of a surface on which the light emitting elements are mounted by a step provided on the substrate, at least one plane vertical to the surface on which the optical component is mounted and located on a periphery of the substrate is opened, a reflecting surface, a transmitting surface or a diffraction grating surface of the optical component is provided along sides generated by the step provided in the substrate, optical axes of the plurality of light emitting elements of which polarization axes are in parallel with each other intersect with each other on the surface, and an exit light beam of the light emitting elements is emitted from the opened plane.

Optical device, optical pickup and optical disk apparatus

A dichroic mirror of a polarized beam splitter is installed between a mirror and an objective lens as a beam synthesize/split means, in an optical system corresponding to a second dick and an optical system corresponding to a first disk arranged so as to form a two-layer structure. The dimension of the optical head in the width, length, and thickness directions are designed moderately.

Compact optical head including two light emitters having parallel optical axes

The dichroic mirror or a polarized beam splitter is installed between a mirror and an objective lens as a beam synthesize/split means, in an optical system corresponding to a second disk and an optical system corresponding to a first disk arranged so as to form a two-layer structure. The dimension of the optical head in the width, length, and thickness directions are designed moderately.

Compact optical head including two light emitters having parallel

An optical disk apparatus comprises an optical pickup for directing a light beam onto pits formed in an optical disk and for receiving reflected light from the optical disk, an optical pickup supporting member including two guide rods for guiding the optical pickup in a radial direction of the optical disk, two first mounting members for mounting ends of one guide rod, and two second mounting members for mounting ends of the other guide rod, a chassis for mounting the first and second mounting members, an optical pickup driving mechanism including gears and a motor to move the optical pickup in a radial direction of the optical disk, a turntable on which the optical disk is located, and an optical disk drive motor for rotating the turntable. Each of the first fixing members includes a base fixed to the chassis, a guide rod supporting member for fixedly supporting the guide rod, and a flexible member located between the base and the guide rod supporting member for causing the guide rod supporting member to be displaced in a vertical direction with respect to a surface of the optical disk. A natural frequency of a system consisting of the one guide rod, the first mounting member, and the chassis is set to be less than that of the optical pickup, and of the optical disk.

Structure for supporting optical pickup

The present invention comprises an arrangement with removable optical element having a predetermined focal distance in the light path between a light source and an objective lens, so as to insert said optical element into the light path between the light source and the objective lens for playing back or recording onto one type of thickness of disk plates, as well as to remove it therefrom for playing back or recording onto another type of thickness of disk plates. Alternatively, by retaining variably the distance between the light source and the collimator lens, the distance between the light source and the collimator lens along with the light path is variably changed according to the thickness of the disk plate being inserted. Then by determining the type of the disk inserted and accordingly selectably inserting/removing the optical element, only one objective lens may be used to conform to the disk plates having different thicknesses.

Optical disk apparatus and optical head thereof

An optical disk apparatus comprises an optical pickup for directing a light beam onto pits formed in an optical disk and for receiving reflected light from the optical disk, an optical pickup supporting member including two guide rods for guiding the optical pickup in a radial direction of the optical disk, two first mounting members for mounting ends of one guide rod, and two second mounting members for mounting ends of the other guide rod, a chassis for mounting the first and second mounting members, an optical pickup driving mechanism including gears and a motor to move the optical pickup in a radial direction of the optical disk, a turntable on which the optical disk is located, and an optical disk drive motor for rotating the turntable. Each of the first fixing members includes a base fixed to the chassis, a guide rod supporting member for fixedly supporting the guide rod, and a flexible member located between the base and the guide rod supporting member for causing the guide rod supporting member to be displaced in a vertical direction with respect to a surface of the optical disk. A natural frequency of a system consisting of the one guide rod, the first mounting member and the chassis is set to be less than that of the optical pickup and of the optical disk.

An optical reading/reproducing apparatus such as a compact disc (CD) player, and particularly a focusing system therefor, wherein the direction of one of the focal lines of the light spot on a light detector is set to be in parallel with the direction of track on the disc surface, a divide-into-four line of the light detector is set to be 45 degrees or a value close thereto with respect to the track direction, and an offset voltage is applied to a portion of the focus servo loop connected with the output unit of a focus error detector circuit. Owing to this structure, the optical parts can be easily mounted, a casing for containing them can be easily molded, and the apparatus can be mass-produced in small sizes.

Optical reading/reproducing apparatus

An optical disc apparatus arranged so that a light beam from a laser light source is focused by an object lens and irradiated on an optical recording medium having thereon a mirror surface and tracks of a plurality of pits for recording data, and that a reflected beam from the recording medium is irradiated on an optical detector from which a signal on the recording medium is reproduced for maintaining a position of said object lens at an optical center axis by a tracking servo. The optical detector includes at least two adjacent photoelectric transducers providing outputs indicative of the reflected beam incident thereon, a device for producing a signal indicative of a difference between the outputs from the transducers, and a position detector for detecting the position of the object lens in a direction perpendicular to the tracks in cooperation with said difference producing device. The position detector includes a sampling arrangement for sampling the difference signal when the light beam is irradiated only on a non-pit portion of said mirror surface. Further, the optical detector includes a feedback loop for positioning the object lens at the optical center axis when the tracking servo is not properly operated at the time of accessing or by external disturbance.

Optical disc apparatus with access system having object lens control

An optical scanning device for subjecting a light spot to a focussing operation and for causing the light spot to perform a tracking operation to reproduce information stored in a video or audio disc is disclosed in which a coil controlling a focussing optical system for forming the light spot and another coil causing the light spot to track the above-mentioned information are both placed in a magnetic gap included in a magnetic circuit formed by a permanent magnet and a magnetic member, and the magnetic circuit is arranged in a direction perpendicular to the direction of the tracking operation.

Two dimensional actuator for moving optical medium of scanning device

A method and apparatus is disclosed for reducing optical noise in an optical information processing system having a single longitudinal mode laser which is converged on a record medium for detecting information stored on the medium. A range from 1-10% of the total emitted light per facet of the laser is fed back to an emitting point of the laser to minimize the occurrence of optical noise present in the light emitted from the laser.

Method and apparatus for reducing semiconductor laser optical noise

A tracking system for optically tracking information tracks formed on a recording medium, comprising a comparator which generates a trigger signal when the light beam scanning the information track is located over an information pit, and a sample holding circuit which samples a deviation signal caused by the difference of reflection light intensities on two photo detectors at that time. The deviation signal obtained when the light beam is located over the information pit includes smaller error component caused by the displacement of the object lens during the tracking control, whereby the accurate tracking control can be achieved.

Optical tracking system

An optical system characterized in that a plano-convex lens for guiding onto a disk a light beam emitted from a semiconductor laser, and a prism for deriving reflected light from the disk are unitarily formed.

Optical system for reproducing information

In the case where the focus control or the tracking control of a light beam is performed by using the wobbling method in an optical information reproducing apparatus, the envelope of the reproduced signal obtained from the light reflected from the recording medium in a non-modulated state is diode-detected and the detected output is used as a focus control signal while the envelope of the reproduced signal obtained from the recording medium in a modulated state is diode-detected so as to be used as a tracking control signal.

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Toyokawa, Japan

Toshio Sugiyama