Kabushiki Kaisha Toshiba

Masahiko Tanaka

Isao Hoshino

Toshihiro Sugaya

Kazuo Watabe

Yoshinori Honguh

Toyoki Taguchi

Shoko Wachi

Akihito Ogawa

Hisashi Yamada

Kazuto Kuroda

Mikio Yamamuro

Sumitaka Maruyama

Teruo Murakami

Yuichiro Yamamoto

Katsuo Iwata

Hiromichi Kobori

Hiroharu Satoh

Hideaki Ohsawa

Maho Kuwahara

Masaaki Matsumaru

Tamane Takahara

Kei Shimura

Sadanari Fujimoto

This invention relates to a focus control apparatus having a controller which generates a control signal and performs focus operation when the peak timing of a focus sum signal based on reflected light and the zero-crossing timing of a focus error signal are detected to substantially coincide with each other in supplying a control signal to a lens actuator driver for supplying a driving signal to a lens actuator for driving a lens. The invention also relates to an optical disk apparatus using the focus control apparatus. By detecting coincidence of the two timings, two reflected waves are discriminated, and stable focus operation is achieved.

Layer discriminating focus control apparatus, optical disk apparatus, and methods therefore

An optical head apparatus includes an objective lens which receives a light beam from a light source and condenses the light beam onto the optical recording medium. A photo-detector has plurality of photo-detecting planes disposed orthogonal to an optical axis of the reflected light beam and symmetrical with respect to the optical axis, and detects the light beam reflected by the optical recording medium. Each of the photo-detecting plane is divided into a plurality of divided areas by a plurality of dividing lines which are symmetrically divide the photo-detecting planes with respect to the optical axis. A diffractive optical element is disposed upstream to the photo-detector for diffracting the reflected light beam to diffract the reflected light beam such that the reflected light beam is divided at least in a direction parallel to a track of the optical recording medium, and a &plus;Nth order diffracted light beam and a &minus;Nth order diffracted light beam (N is 1 or an integer more than 1) in the photo-detecting plane are independently received by the divided areas which are disposed in positions symmetrically opposite with respect to the optical axis respectively. An arithmetic circuit calculates an error signal with respect to a position of the objective lens along the optical axis, by using outputs from the photo-detector of both the &plus;Nth order diffracted light beam and the &minus;Nth order diffracted light beam. A driver generates a signal for controlling the position of the objective lens based on an output from the arithmetic circuit.

Optical head apparatus for reproducing information from an optical recording medium

An optical information recording/reproducing apparatus for optically recording/reproducing information by irradiating a track on a recording medium with a light comprises: a detecting circuit, a tracking error signal producing circuit, and a tracking control circuit. The detecting circuit selectively detects a circular area having a diameter smaller than a diameter of a light beam reflected from the recording medium and obtains an output signal corresponding to the detected circular area. The tracking error signal producing circuit produces, from the output signal of the detecting circuit, a tracking error signal indicating a shift in a position of a light beam irradiated on the recording medium in a track width direction. The tracking control circuit controls an irradiation position of a light beam irradiated on the recording medium in the track width direction based on the tracking error signal.

Optical information recording/reproducing apparatus based on tracking control of irradiated light

Optical information recording/reproducing apparatus based on tracking

An optical head device adapted to be optically coupled to an optical disk includes a light-source laser and an objective lens optically coupled thereto. This lens receives an output light of the light source, and causes it to be projected onto the optical disk to form a focused spot thereon. Photodetectors are optically coupled to the lens in one optical path so that they are responsive to a light component which is reflected from the optical disk toward the photodetectors by way of the objective lens. A beam-shaping prism is located between the lens and a group of the light source and the photodetectors in the optical path. When the laser output light travels toward the lens, the prism reshapes the light into a predetermined isotropic beam profile. When the reflected light from the optical disk propagates reversely along the same optical path to enter the beam-shaping prism, this prism permits such an incident light to pass through itself toward the photodetectors.

Light beam shaping device to change an anisotropic beam to an isotropic

In a case where tracking control is carried out by a lens actuator in performing a tracking pull-in operation in which tracking control is started in the state where tracking control is out of operation, the tracking control circuit brings control into stable tracking control by moving the light spot onto a groove on the optical disc. After that, when tracking onto a land is needed, the tracking control circuit moves the light spot onto the land. This enables a pull-in action toward a stable tracking operation.

Optical disc apparatus for recording and reproducing data onto and from

A primary optical disk recording apparatus comprises a first light source for recording a signal on a primary optical disk, an objective lens for converging a light beam from the first light source on the primary optical disk, a second light source for detecting a focus error between the objective lens and the primary optical disk, and a controller for detecting a reflection light beam from the first light source, which is reflected from the primary optical disk, while the signal is being recorded on the primary optical disk, and for subjecting a signal of the reflection beam to an arithmetic operation process, thereby detecting a first focus error signal and controlling the focus error on the basis of the first focus error signal.

Apparatus for recording information on a primary optical disk to

An optical head has a first light source for emitting a first light beam having a first wavelength, a second light source for emitting a second light beam having a second wavelength larger than the first wavelength, and an optical system for guiding the first and second light beams to an optical disc and guiding light beams reflected by the optical disc to an optical detector. The optical system comprises an objective lens, a beam splitter for reflecting the first light beam and the S-polarized component of the second light beam and transmitting the P-polarized component of the second light beam, and a quarter wavelength plate. When a high density medium is set against the optical hend, recording is performed by the second light beam and reproduction is performed by the first light beam. When a low density medium is set against the optical head, recording and reproduction are carried out by the second light beam. A single optical head provides read/write compatibility with optical discs of different densities, and recording and reproduction can be made on a high density optical disc.

Optical recording and reproducing apparatus

An optical head device adapted to be optically coupled to an optical disk includes a light-source laser and an objective lens optically coupled thereto. This lens receives an output light of the light source, and causes it to be projected onto the optical disk to form a focused spot thereon. Photodetectors which are arranged near the light-source laser are optically coupled to the lens in one optical path so that they are responsive to a light component which is reflected from the optical disk toward the photodetectors by way of the objective lens. A beam-shaping prism is located between the lens and a group of the light source and the photodetectors in the optical path. When the laser output light travels toward the lens, the prism reshapes the light into a predetermined isotropic beam profile. When the reflected light from the optical disk propagates reversely along the same optical path to enter the beam-shaping prism, this prism permits such an incident light to pass through itself toward the photodetectors.

An optical head has a first light source for emitting a first light beam having a first wavelength, a second light source for emitting a second light beam having a second wavelength larger than the first wavelength, and an optical system for guiding the first and second light beams to an optical disc and guiding light beams reflected by the optical disc to an optical detector. The optical system, includes an objective lens, a beam splitter for reflecting the first light beam and the S-polarized component of the second light beam and transmitting the P-polarized component of the second light beam, and a quarter wavelength plate. When a high density medium is set against the optical head, recording is performed by the second light beam and reproduction is performed by the first light beam. When a low density medium is set against the optical head, recording and reproduction are carried out by the second light beam. A single optical head provides read/write compatibility with optical discs of different densities, and recording and reproduction can be made on a high density optical disc.

An optical disk apparatus includes a semiconductor laser for emitting a light beam, and an automatic power control or APC circuit for driving the laser. A compound prism structure is optically coupled to the laser in an optical head section, and defines a first optical path for causing a front laser light to be projected onto a rotating optical disk and guiding a reflected light therefrom toward a first photodetector, and a second optical path for guiding a part of the reflected light toward a second photodetector. An output signal of the first photodetector is used to generate a reproduced information signal. An output signal of the second photodetector is fed back to the APC circuit as a front light monitor signal. A part of a laser control signal internally generated in the APC circuit is supplied through a wiring line to a noise reduction circuit as a laser noise monitor signal. The noise reduction circuit subtracts this noise monitor signal from the reproduced information signal to provide a noise-suppressed information signal.

Noise reduction system for optical record and reproduction apparatus

First and second beam splitters are arranged on the optical path of a light beam emerging from a recording surface, and such that the phases and amplitudes of the respective polarized light components of a light beam incident thereon are changed to equal extends. As a result of this arrangement, the state of polarization beam of the light beam emerging from the recording surface is maintained when a light beam is outputted through the two beam splitters. Stable reproduction signals and servo control signals for focusing, tracking, and the like can be reliably supplied by utilizing an apparatus of this invention.

Growing community of inventors

Yokohama, Japan

Masahiko Tanaka