Hitachi Media Electronics Co., Ltd.

Other

Katsuhiko Izumi

Kunikazu Ohnishi

Masayuki Inoue

Michio Miura

Kenichi Shimada

Tomoto Kawamura

Shinro Inui

Naomitsu Kuroda

Ryuichiro Mizuno

Naohiko Otoshi

Shinji Fujita

Kazuyoshi Yamazaki

Fumio Isshiki

For use with a multi-layer optical disc, an optical pickup can eliminate a problem of causing a focus error signal and a tracking error signal to fluctuate due to interference of a signal light beam with a return light beam from another recording surface of a multi-layer optical disc during reproduction with an optical pickup that produces a tracking error signal and a focus error signal from a difference signal based on polarized reflected light.

Optical pickup and optical disc unit

An optical pickup free from tracking error signal variation when playing back a double-layered disc, and coping with incompatible optical discs, such as BDs and HD DVDs, includes a laser light source, a first polarization rotation element for rotating a polarization direction of an optical beam from the source, an optical branching element disposed in a position after the polarization rotation element to reflect or transmit an optical beam according to polarization of the beam, first and second object lenses for focusing the reflected and transmitted optical beams onto first and second optical discs, respectively, a photodetector for sensing reflected light from the first and second optical discs, and a second polarization rotation element disposed after reflection or transmission of the reflected light from the first and second optical discs conducted by the branching element, to rotate a polarization direction of the reflected light.

Optical pickup and optical disc apparatus

Provided are an optical pick up and an optical component used for the optical pickup which are capable of preventing or restraining occurrence of deviation and unbalance which are caused by assembly errors during manufacturing of optical components, a temperature variation or the like. The optical pickup comprises a laser, a polarization changeover element for changing over a direction of polarization of an optical beam emitted from the laser, a beam splitting element for splitting the laser beam into a plurality of optical paths in accordance with a direction of a polarization, a plurality of objective lenses for focusing laser beams onto a recording layer of the optical disc, a rise-up mirror, and a plurality of coupling lenses arranged respectively intermediate of the plurality of optical paths led to the plurality of objective lenses. The rise-up mirror is arranged intermediate of the plurality of optical paths led to the plurality of objective lenses and adapted to be used common to respective optical beams on the plurality of optical paths. The plurality of the coupling lenses are coupled to and held on one and the same drive portion.

Optical disc drive, optical pickup and optical component used therefor

The present invention provides a photodetector capable of generating highly accurate tracking and focusing error signals free of variations in light quantity caused by interference, in an optical pickup with a two-wavelength multilaser. The photodetector comprises first three light receiving areas arranged linearly to receive three light beams respectively resulting from splitting of a light beam emitted from a laser light source of a first wavelength and second three light receiving areas arranged linearly to receive three light beams respectively resulting from splitting of a light beam emitted from a laser light source of a second wavelength longer than the first wavelength. The distance between both-end light receiving areas out of the first three light receiving areas is longer than the distance between both-end light receiving areas out of the second three light receiving areas.

Photodetector, diffraction grating, optical pickup and optical disc apparatus

An optical system is disclosed including an optical pickup having a wavefront aberration-correcting element capable of correcting coma aberration and astigmatism, and an optical disc apparatus which uses the optical pickup. The optical pickup includes a laser light source for irradiating an optical disc with a light beam; an objective lens for focusing the light beam on the optical disc; a lens for correcting astigmatism; a second lens for correcting coma aberration; and a photodetector for receiving the light beam reflected from the optical disc. The astigmatism and the coma aberration are corrected independently of each other.

An optical pickup has a semiconductor laser having two laser sources of different wavelengths disposed in the same package, one diffraction grating and one optical detector. A plurality of light reception areas each having four divisional light reception planes of a-character shape are disposed at positions where light beams reflected from an optical disc are applied. A focus error signal is generated by an astigmatism method by using independently these light reception areas and a tracking error signal is generated by a differential phase detection method by using one or both the light reception areas.

Optical detector, optical pickup and optical information reproducing apparatus using optical pickup for detecting at least three light beams separated from one or more light sources

It is an object to perform a thin and compact design of the objective lens driving device. In order to achieve the above object, optical beam is passed through a space surrounded by a tracking coil and a focusing coil which are adjacent to each other and fixed in a holder. Further, it is another object to position the objective lens with high precision in an objective lens driving device for switching a plurality of objective lenses in accordance with the type of an optical disc. In order to achieve this object, magnetic substances which are radially extended with the sliding shaft at the center are provided in the lens holder, and the magnetic substances are located within a plane perpendicular to the plane constituting the magnetic gap and at the outside of the magnetic gap. Still further, in an objective lens driving device it is another object to prevent the occurrence of positional displacement of the objective lens due to resistance force of current supply means such as FPC. To achieve this object, a first objective lens and a second objective lens are arranged so that the objective lens arrangement angle at which the first and second objective lenses are arranged with respect to the shaft center of the sliding shaft is displaced, by a predetermined amount, from the magnetic circuit arrangement angle at which the magnetic substances and the magnets are arranged with respect to the shaft center of the sliding shaft.

Growing community of inventors

Kamakura, Japan

Katsuhiko Izumi