Hitachi, Ltd.

Hitachi Media Electronics Co., Ltd.

Other

Hitachi-lg Data Storage, Inc.

Hitachi Consumer Electronics Co., Ltd.

Kunikazu Ohnishi

Masayuki Inoue

Tomoto Kawamura

Yukio Fukui

Takeshi Shimano

Shigeru Nakamura

Katsuhiko Izumi

Yoshio Suzuki

Takeshi Nakao

Shinji Fujita

Tohru Sasaki

Akira Arimoto

Kenichi Shimada

Takahiro Kurokawa

Kazuyoshi Yamazaki

Yasuyuki Sugi

Fumio Isshiki

Tooru Sasaki

Mitsuhiko Ota

Nobuyuki Maeda

Motoyasu Terao

Motoyuki Suzuki

Satoshi Ouchi

Hirofumi Sukeda

Toshimitsu Kaku

Kazuo Shigematsu

Norio Ohta

Michio Miura

Makoto Miyamoto

Yoshito Tsunoda

Toshiteru Nakamura

Shigeharu Kimura

Masaaki Kurebayashi

Masaji Ishigaki

Toshio Sugiyama

Yasuo Kitada

Akira Saito

Keikichi Ando

Hiroshi Yasuoka

Mitsuru Nagasawa

Nobuhiro Konuma

Norio Hosaka

Nobuo Imada

Toshiaki Ishibashi

Junji Nakajima

Hiromi Kita

Hisamitsu Tanaka

Hideo Onuki

Tesuya Nishida

The projection display system has a light source unit where a first light source and a second light source respectively emitting a first and second wavelength or wavelength range of light are juxtapositionally arranged; a third light source emitting a third wavelength or wavelength range of light; an optical combiner device for combining the three wavelengths or wavelength ranges of light from the light sources; an optical device for averaging distributions of the wavelengths or wavelength ranges of light; an image display device for receiving the light transmitted through the optical device and forming image light responsive to a video signal; and a projector lens for projecting the image light onto a screen. At least two of the optical axes of the first, second, and third wavelengths or wavelength ranges of light which are incident on the optical device are not coincident with each other.

Light source unit and projection display system using same

In a scanning image display device including a function to project and display a two-dimensional image on a projection screen using a deflecting unit that repeatedly operates a predetermined reflecting mirror surface to two-dimensionally scan a light beam, a large image distortion inevitably occurs, which is caused by the reflecting mirror surface that repeatedly and two-dimensionally operates for deflection. In order to solve the problem, a free-form surface lens or a wedge or trapezoid prism with a predetermined refractive index and a predetermined vertical angle is disposed in an optical path between the deflecting unit and the projection screen, thereby excellently correcting image distortion that occurs when scanning a light beam.

Optical beam scanning device and image display device using the same

Optical beams emitted by optical sources are incident on a mirror surface of a scan mirror in a substantially vertical direction and reflected in a substantially vertical direction by the scan mirror. The mirror surface of the scan mirror is driven to repeatedly rotate two-dimensionally by a predetermined scan angle by a scan mirror drive circuit. A polarized beam splitter causes the optical beam emitted by the optical source to be incident on the scan mirror through a quarter wave plate, and outputs the optical beam that has been reflected by the scan mirror and passed through the quarter wave plate toward the screen. A scan angle expander is arranged on the output side of the polarized beam splitter, whereby the scan angle of the optical beam is increased by N times.

Scan type image display device

An optical information device used with a grooveless multilayer disc including multiple recording layers used to record and reproduce information signals and a guide layer dedicated to detect tracking error signals (TES) can always stably detect the TESs when the distance between the recording layer and guide layer varies due to selection of a target recording layer. For example, a plurality of light spots for detecting the TESs are formed by a holographic grating on the guide layer, but are defocused with respect to each other. The TESs are detected individually from the respective light spots. The TESs are subjected to an addition operation to be a signal for tracking control, thereby extraordinarily increasing the defocus dynamic range of the TESs.

Optical information processing device and tracking control method thereof for use with grooveless multilayer optical disc

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

Undesired disturbance components leak eventually into various detection signals and reproduction signals as stray optical beams reflected from recording layers other than a reproduction layer overlap with signal beams on a light reception surface of an optical detector and interference occurs between them when an optical disc having multi-layered recording layers is reproduced. A diffraction grating having a specific grating groove pattern is arranged immediately ahead of an optical detector or in a return optical path. Such optical unit averages the disturbance components resulting from interference between a signal beam and a stray beam and can satisfactorily improve influences of leak.

Diffraction grating, optical pickup and optical disc device

In a multilayer disc has an increased number of recording layers) spaced by spacing from each other, a generation interval between focus error (FE) signals detected from the respective recording layers becomes small. This causes mutual interference between the FE signals and a resulting undesired offset and the like in the signals, leading to a significantly deteriorated quality of the FE signals. To avoid this, in an optical pickup device according to the present invention, detection surfaces are newly added at positions adjacent to the FE signal detection surfaces, a predetermined detection signal obtained from the newly-added detection surfaces is multiplied by a predetermined coefficient value depending on the spacing between the recording layers, and the multiplied signal is subtracted from the original FE signal. As a result, mutual interference between the FE signals can be remarkably reduced.

Optical pickup device

A rewritable optical disk apparatus, optical information recording and reproducing apparatus or the like is allowed to automatically and properly adjust the optical system to the optimum focal condition regardless of the readout signal detector's positional error and the residual aberration in the optical system. The spherical aberration and defocus are coarsely adjusted using the amplitude (PP amplitude) of the tracking error signal and then finely adjusted using the amplitude (RF amplitude) of the readout signal. Since the spherical aberration can properly be adjusted, it is possible to raise the reliability of the readout signal.

Optical information recording apparatus

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

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 pickup includes a diffraction grating partitioned into three areas, in which the phase of periodic grating groove structure in an area is successively shifted from that in the adjacent area by 90&#xb0;. In the generation of a differential push-pull signal, an amplification factor K for sub push-pull signals is varied depending on the type of the optical disk. By such composition of the optical pickup, amplitude deterioration of the tracking error signal accompanying displacement of the object lens is reduced.

Optical pickup and optical information recording apparatus using the same

An optical pickup module with enhanced aberration correctability is disclosed. This pickup includes more than two different types of laser light sources, an objective lens for collecting and focusing any one of the laser beams leaving the light sources onto an optical disc, and an aberration correction device of the liquid crystal (LC) type, which is disposed between the light sources and the objective lens. The aberration corrector has a surface on which multiple spaced-apart electrodes are patterned for enabling aberration correction relative to incident beams. The corrector controls the potential of a voltage being applied to each electrode in deference to incident beam properties and variations occurrable thereto, e.g., wavelength, effective beam diameter and relative incidence position offsets, thereby to optimally correct beam aberrations, such as coma aberration or wavefront aberration. An optical information reproduction apparatus using the pickup is also disclosed.

Optical pickup and optical information reproducing apparatus using same

Growing community of inventors

Yokosuka, Japan

Kunikazu Ohnishi